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1 © 2015 Pearson Education, Inc.

2 Cells Cells are the structural units of all living things
The human body has 50 to 100 trillion cells © 2015 Pearson Education, Inc.

3 Four Concepts of the Cell Theory
A cell is the basic structural and functional unit of living organisms. The activity of an organism depends on the collective activities of its cells. According to the principle of complementarity, the biochemical activities of cells are dictated by the relative number of their specific subcellular structures. Continuity of life has a cellular basis. © 2015 Pearson Education, Inc.

4 Chemical Components of Cells
Most cells are composed of four elements: Carbon Hydrogen Oxygen Nitrogen Cells are about 60% water © 2015 Pearson Education, Inc.

5 Anatomy of a Generalized Cell
In general, a cell has three main regions or parts: Nucleus Cytoplasm Plasma membrane © 2015 Pearson Education, Inc.

6 Figure 3.1a Anatomy of the generalized animal cell nucleus.
Cytoplasm Plasma membrane (a)

7 The Nucleus Control center of the cell Three regions:
Contains genetic material known as deoxyribonucleic acid, or DNA DNA is needed for building proteins DNA is necessary for cell reproduction Three regions: Nuclear envelope (membrane) Nucleolus Chromatin © 2015 Pearson Education, Inc.

8 Figure 3.1b Anatomy of the generalized animal cell nucleus.
Nuclear envelope Chromatin Nucleus Nucleolus Nuclear pores Rough ER (b)

9 The Nucleus Nuclear envelope (membrane)
Consists of a double membrane that bounds the nucleus Contains nuclear pores that allow for exchange of material with the rest of the cell Encloses the jellylike fluid called the nucleoplasm © 2015 Pearson Education, Inc.

10 The Nucleus Nucleoli Nucleus contains one or more nucleoli
Sites of ribosome assembly Ribosomes migrate into the cytoplasm through nuclear pores to serve as the site of protein synthesis © 2015 Pearson Education, Inc.

11 The Nucleus Chromatin Composed of DNA and protein
Present when the cell is not dividing Scattered throughout the nucleus Condenses to form dense, rod-like bodies called chromosomes when the cell divides © 2015 Pearson Education, Inc.

12 Plasma Membrane Transparent barrier for cell contents
Contains cell contents Separates cell contents from surrounding environment © 2015 Pearson Education, Inc.

13 Plasma Membrane Fluid mosaic model is constructed of: Phospholipids
Cholesterol Proteins Sugars © 2015 Pearson Education, Inc.

14 Figure 3.2 Structure of the plasma membrane.
Extracellular fluid (watery environment) Glycoprotein Glycolipid Cholesterol Sugar group Polar heads of phospholipid molecules Bimolecular lipid layer containing proteins Channel Nonpolar tails of phospholipid molecules Proteins Filaments of cytoskeleton Cytoplasm (watery environment)

15 Concept Link © 2015 Pearson Education, Inc.

16 Plasma Membrane Fluid mosaic model Phospholipid arrangement
Hydrophilic (“water-loving”) polar “heads” are oriented on the inner and outer surfaces of the membrane Hydrophobic (“water-hating”) nonpolar “tails” form the center (interior) of the membrane © 2015 Pearson Education, Inc.

17 Plasma Membrane Fluid mosaic model Phospholipid arrangement
The hydrophobic interior makes the plasma membrane impermeable to most water-soluble molecules © 2015 Pearson Education, Inc.

18 Plasma Membrane Fluid mosaic model Proteins
Responsible for specialized functions Roles of proteins Enzymes Receptors Transport as channels or carriers © 2015 Pearson Education, Inc.

19 Plasma Membrane Fluid mosaic model Sugars
Glycoproteins are branched sugars attached to proteins that abut the extracellular space Glycocalyx is the fuzzy, sticky, sugar-rich area on the cell’s surface © 2015 Pearson Education, Inc.

20 Plasma Membrane Junctions
Cells are bound together in three ways: Glycoproteins in the glycocalyx act as an adhesive or cellular glue Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion Special membrane junctions are formed, which vary structurally depending on their roles © 2015 Pearson Education, Inc.

21 Plasma Membrane Junctions
Tight junctions Impermeable junctions Bind cells together into leakproof sheets Prevent substances from passing through extracellular space between cells © 2015 Pearson Education, Inc.

22 Plasma Membrane Junctions
Desmosomes Anchoring junctions that prevent cells from being pulled as a result of mechanical stress Created by buttonlike thickenings of adjacent plasma membranes © 2015 Pearson Education, Inc.

23 Plasma Membrane Junctions
Gap junctions Allow communication between cells Hollow cylinders of proteins (connexons) span the width of the abutting membranes Molecules can travel directly from one cell to the next through these channels © 2015 Pearson Education, Inc.

24 Tight (impermeable) junction
Figure 3.3 Cell junctions. Microvilli Tight (impermeable) junction Desmosome (anchoring junction) Plasma membranes of adjacent cells Connexon Underlying basement membrane Extracellular space between cells Gap (communicating) junction

25 Cytoplasm The material outside the nucleus and inside the plasma membrane Site of most cellular activities © 2015 Pearson Education, Inc.

26 Cytoplasm Contains three major elements Cytosol Organelles Inclusions
Fluid that suspends other elements Organelles Metabolic machinery of the cell “Little organs” that perform functions for the cell Inclusions Chemical substances, such as stored nutrients or cell products © 2015 Pearson Education, Inc.

27 Figure 3.4 Structure of the generalized cell.
Chromatin Smooth endoplasmic reticulum Nuclear envelope Nucleolus Nucleus Plasma membrane Cytosol Lysosome Mitochondrion Rough endoplasmic reticulum Centrioles Ribosomes Golgi apparatus Secretion being released from cell by exocytosis Microtubule Peroxisome Intermediate filaments

28 Cytoplasmic Organelles
Specialized cellular compartments Many are membrane-bound Compartmentalization is critical for organelle’s ability to perform specialized functions © 2015 Pearson Education, Inc.

29 Cytoplasmic Organelles
Mitochondria “Powerhouses” of the cell Change shape continuously Mitochondrial wall consists of a double membrane with cristae on the inner membrane Carry out reactions where oxygen is used to break down food Provides ATP for cellular energy © 2015 Pearson Education, Inc.

30 Cytoplasmic Organelles
Ribosomes Bilobed dark bodies Made of protein and ribosomal RNA Sites of protein synthesis Found at two locations: Free in the cytoplasm As part of the rough endoplasmic reticulum © 2015 Pearson Education, Inc.

31 Cytoplasmic Organelles
Endoplasmic reticulum (ER) Fluid-filled cisterns (tubules or canals) for carrying substances within the cell Two types: Rough ER Smooth ER © 2015 Pearson Education, Inc.

32 Cytoplasmic Organelles
Endoplasmic reticulum (ER) Rough endoplasmic reticulum Studded with ribosomes Synthesizes proteins Transport vesicles move proteins within cell Abundant in cells that make and export proteins © 2015 Pearson Education, Inc.

33 Figure 3.5 Synthesis and export of a protein by the rough ER.
Slide 1 Ribosome mRNA Rough ER As the protein is synthesized on the ribosome, it migrates into the rough ER cistern. 1 2 1 3 2 In the cistern, the protein folds into its functional shape. Short sugar chains may be attached to the protein (forming a glycoprotein). Protein Transport vesicle buds off 4 The protein is packaged in a tiny membranous sac called a transport vesicle. 3 The transport vesicle buds from the rough ER and travels to the Golgi apparatus for further processing. 4 Protein inside transport vesicle

34 Cytoplasmic Organelles
Endoplasmic reticulum (ER) Smooth endoplasmic reticulum Functions in lipid metabolism Detoxification of drugs and pesticides © 2015 Pearson Education, Inc.

35 Cytoplasmic Organelles
Golgi apparatus Appears as a stack of flattened membranes associated with tiny vesicles Modifies and packages proteins arriving from the rough ER via transport vesicles Produces different types of packages Secretory vesicles (pathway 1) In-house proteins and lipids (pathway 2) Lysosomes (pathway 3) © 2015 Pearson Education, Inc.

36 Lysosome fuses with ingested substances. Membrane
Figure 3.6 Role of the Golgi apparatus in packaging the products of the rough ER. Rough ER Cisterns Proteins in cisterns Lysosome fuses with ingested substances. Membrane Transport vesicle Golgi vesicle containing digestive enzymes becomes a lysosome. Pathway 3 Pathway 2 Golgi vesicle containing membrane components fuses with the plasma membrane and is incorporated into it. Golgi apparatus Secretory vesicles Pathway 1 Proteins Golgi vesicle containing proteins to be secreted becomes a secretory vesicle. Plasma membrane Secretion by exocytosis Extracellular fluid

37 Cytoplasmic Organelles
Lysosomes Membranous “bags” packaged by the Golgi apparatus Contain enzymes produced by ribosomes Enzymes can digest worn-out or nonusable cell structures House phagocytes that dispose of bacteria and cell debris © 2015 Pearson Education, Inc.

38 Cytoplasmic Organelles
Peroxisomes Membranous sacs of oxidase enzymes Detoxify harmful substances such as alcohol and formaldehyde Break down free radicals (highly reactive chemicals) Free radicals are converted to hydrogen peroxide and then to water Replicate by pinching in half or budding from the ER © 2015 Pearson Education, Inc.

39 Cytoplasmic Organelles
Cytoskeleton Network of protein structures that extend throughout the cytoplasm Provides the cell with an internal framework Three different types of elements: Microfilaments (largest) Intermediate filaments Microtubules (smallest) © 2015 Pearson Education, Inc.

40 (b) Intermediate filaments (c) Microtubules
Figure 3.7 Cytoskeletal elements support the cell and help to generate movement. (a) Microfilaments (b) Intermediate filaments (c) Microtubules Tubulin subunits Fibrous subunits Actin subunit 10 nm 25 nm 7 nm Microfilaments form the blue batlike network. Intermediate filaments form the purple network surrounding the pink nucleus. Microtubules appear as gold networks surrounding the cells’ pink nuclei.

41 Cytoplasmic Organelles
Centrioles Rod-shaped bodies made of microtubules Generate microtubules Direct the formation of mitotic spindle during cell division © 2015 Pearson Education, Inc.

42 Table 3.1 Parts of the Cell: Structure and Function (1 of 5).

43 Table 3.1 Parts of the Cell: Structure and Function (2 of 5).

44 Table 3.1 Parts of the Cell: Structure and Function (3 of 5).

45 Table 3.1 Parts of the Cell: Structure and Function (4 of 5).

46 Table 3.1 Parts of the Cell: Structure and Function (5 of 5).

47 Cell Extensions Surface extensions found in some cells
Cilia move materials across the cell surface Located in the respiratory system to move mucus Flagella propel the cell The only flagellated cell in the human body is sperm Microvilli are tiny, fingerlike extensions of the plasma membrane Increase surface area for absorption Nucleus Flagellum Sperm (g) Cell of reproduction © 2015 Pearson Education, Inc.

48 Cell Diversity The human body houses over 200 different cell types
Cells vary in length from 1/12,000 of an inch to over 1 yard (nerve cells) Cell shape reflects its specialized function © 2015 Pearson Education, Inc.

49 Cell Diversity Cells that connect body parts Fibroblast
Secretes cable-like fibers Erythrocyte (red blood cell) Carries oxygen in the bloodstream Rough ER and Golgi apparatus No organelles Nucleus Fibroblasts Erythrocytes (a) Cells that connect body parts © 2015 Pearson Education, Inc.

50 Cell Diversity Cells that cover and line body organs Epithelial cell
Packs together in sheets Intermediate fibers resist tearing during rubbing or pulling Nucleus Intermediate filaments Epithelial cells (b) Cells that cover and line body organs © 2015 Pearson Education, Inc.

51 Cell Diversity Cells that move organs and body parts
Skeletal muscle and smooth muscle cells Contractile filaments allow cells to shorten forcefully Nuclei Contractile filaments Skeletal muscle cell Smooth muscle cells (c) Cells that move organs and body parts © 2015 Pearson Education, Inc.

52 Cell Diversity Cell that stores nutrients Fat cells
Lipid droplets stored in cytoplasm Lipid droplet Nucleus Fat cell (d) Cell that stores nutrients © 2015 Pearson Education, Inc.

53 Cell Diversity Cell that fights disease Macrophage (a phagocytic cell)
Digests infectious microorganisms Lysosomes Macrophage (e) Cell that fights disease Pseudo- pods © 2015 Pearson Education, Inc.

54 Cell Diversity Cell that gathers information and controls body functions Nerve cell (neuron) Receives and transmits messages to other body structures Processes Rough ER Nucleus (f) Cell that gathers information and controls body functions Nerve cell © 2015 Pearson Education, Inc.

55 Cell Diversity Cells of reproduction Oocyte (female) Sperm (male)
Largest cell in the body Divides to become an embryo upon fertilization Sperm (male) Built for swimming to the egg for fertilization Flagellum acts as a motile whip Nucleus Flagellum Sperm (g) Cell of reproduction © 2015 Pearson Education, Inc.

56 Cell Physiology Cells have the ability to: Metabolize Digest food
Dispose of wastes Reproduce Grow Move Respond to a stimulus © 2015 Pearson Education, Inc.

57 Membrane Transport Solution—homogeneous mixture of two or more components Solvent—dissolving medium; typically water in the body Solutes—components in smaller quantities within a solution © 2015 Pearson Education, Inc.

58 Membrane Transport Intracellular fluid Interstitial fluid
Nucleoplasm and cytosol Solution containing gases, nutrients, and salts dissolved in water Interstitial fluid Fluid on the exterior of the cell Contains thousands of ingredients, such as nutrients, hormones, neurotransmitters, salts, waste products © 2015 Pearson Education, Inc.

59 Membrane Transport The plasma membrane is a selectively permeable barrier Some materials can pass through while others are excluded For example: Nutrients can enter the cell Undesirable substances are kept out © 2015 Pearson Education, Inc.

60 Membrane Transport Two basic methods of transport Passive processes
No energy (ATP) is required Active processes Cell must provide metabolic energy (ATP) © 2015 Pearson Education, Inc.

61 Passive Processes Diffusion
Particles tend to distribute themselves evenly within a solution Driving force is the kinetic energy (energy of motion) that causes the molecules to move about randomly © 2015 Pearson Education, Inc.

62 Passive Processes Diffusion
Molecule movement is from high concentration to low concentration, or down a concentration gradient Size of molecule and temperature affects the speed of diffusion The smaller the molecule, the faster the rate of diffusion The warmer the molecule, the faster the rate of diffusion © 2015 Pearson Education, Inc.

63 Passive Processes Example of diffusion:
Pour a cup of coffee and drop in a cube of sugar Do not stir the sugar into the coffee; leave the cup of coffee sitting all day, and it will taste sweet at the end of the day. Molecules move by diffusion and sweeten the entire cup © 2015 Pearson Education, Inc.

64 Passive Processes Molecules will move by diffusion if any of the following applies: The molecules are small enough to pass through the membrane’s pores (channels formed by membrane proteins) The molecules are lipid-soluble The molecules are assisted by a membrane carrier © 2015 Pearson Education, Inc.

65 Passive Processes Types of diffusion Simple diffusion
An unassisted process Solutes are lipid-soluble or small enough to pass through membrane pores © 2015 Pearson Education, Inc.

66 Passive Processes Types of diffusion (continued)
Water molecules Lipid bilayer (d) Osmosis, diffusion of water through a specific channel protein (aquaporin) or through the lipid bilayer Types of diffusion (continued) Osmosis—simple diffusion of water Highly polar water molecules easily cross the plasma membrane through aquaporins Water moves down its concentration gradient © 2015 Pearson Education, Inc.

67 Passive Processes Osmosis—A Closer Look
Isotonic solutions have the same solute and water concentrations as cells and cause no visible changes in the cell Hypertonic solutions contain more solutes than the cells do; the cells will begin to shrink Hypotonic solutions contain fewer solutes (more water) than the cells do; cells will plump (a) RBC in isotonic solution (b) RBC in hypertonic solution (c) RBC in hypotonic solution © 2015 Pearson Education, Inc.

68 Passive Processes Types of diffusion (continued) Facilitated diffusion
Lipid- insoluble solutes Small lipid- insoluble solutes (b) Carrier-mediated facilitated diffusion via protein carrier specific for one chemical; binding of substrate causes shape change in transport protein (c) Channel- mediated facilitated diffusion through a channel protein; mostly ions, selected on basis of size and charge Types of diffusion (continued) Facilitated diffusion Transports lipid- insoluble and large substances Glucose is transported via facilitated diffusion Protein membrane channels or protein molecules that act as carriers are used © 2015 Pearson Education, Inc.

69 Passive Processes Filtration
Water and solutes are forced through a membrane by fluid, or hydrostatic pressure A pressure gradient must exist Solute-containing fluid (filtrate) is pushed from a high- pressure area to a lower-pressure area Filtration is critical for the kidneys to work properly © 2015 Pearson Education, Inc.

70 Active Processes Sometimes called solute pumping
Requires protein carriers to transport substances that: May be too large to travel through membrane channels May not be lipid-soluble May have to move against a concentration gradient ATP is used for transport © 2015 Pearson Education, Inc.

71 Active Processes Active transport
Amino acids, some sugars, and ions are transported by protein carriers known as solute pumps ATP energizes solute pumps In most cases, substances are moved against concentration (or electrical) gradients © 2015 Pearson Education, Inc.

72 Active Processes Example of active transport is the sodium- potassium pump Sodium is transported out of the cell Potassium is transported into the cell Na+-K+ pump 2 3 1 Na+ Extracellular fluid K+ P ATP ADP Binding of cytoplasmic Na+ to the pump protein stimulates phosphorylation by ATP, which causes the pump protein to change its shape. The shape change expels Na+ to the outside. Extracellular K+ binds, causing release of the phosphate group. Loss of phosphate restores the original conformation of the pump protein. K+ is released to the cytoplasm, and Na+ sites are ready to bind Na+ again; the cycle repeats. Cytoplasm Slide 1 © 2015 Pearson Education, Inc.

73 Active Processes Vesicular transport: substances are moved without actually crossing the plasma membrane Exocytosis Endocytosis Phagocytosis Pinocytosis © 2015 Pearson Education, Inc.

74 Active Processes Vesicular transport (continued) Exocytosis
Moves materials out of the cell Material is carried in a membranous sac called a vesicle Vesicle migrates to plasma membrane Vesicle combines with plasma membrane Material is emptied to the outside Refer to Pathway 1 in Figure 3.6 (b) Electron micrograph of a secretory vesicle in exocytosis (190,000×) © 2015 Pearson Education, Inc.

75 Lysosome fuses with ingested substances. Membrane
Figure 3.6 Role of the Golgi apparatus in packaging the products of the rough ER. Rough ER Cisterns Proteins in cisterns Lysosome fuses with ingested substances. Membrane Transport vesicle Golgi vesicle containing digestive enzymes becomes a lysosome. Pathway 3 Pathway 2 Golgi vesicle containing membrane components fuses with the plasma membrane and is incorporated into it. Golgi apparatus Secretory vesicles Pathway 1 Proteins Golgi vesicle containing proteins to be secreted becomes a secretory vesicle. Plasma membrane Secretion by exocytosis Extracellular fluid

76 Active Processes Vesicular transport (continued) Endocytosis
Extracellular substances are engulfed by being enclosed in a membranous vescicle Vesicle typically fuses with a lysosome Contents are digested by lysosomal enzymes In some cases, the vesicle is released by exocytosis on the opposite side of the cell © 2015 Pearson Education, Inc.

77 Figure 3.13a Events and types of endocytosis.
Slide 1 Extracellular fluid Cytosol Plasma membrane Vesicle Lysosome 1 Vesicle fusing with lysosome for digestion Release of contents to cytosol 2 Transport to plasma membrane and exocytosis of vesicle contents Detached vesicle Ingested substance Membranes and receptors (if present) recycled to plasma membrane 3 Pit (a)

78 Active Processes Vesicular transport (continued) Types of endocytosis
Phagocytosis—“cell eating” Cell engulfs large particles such as bacteria or dead body cells Pseudopods are cytoplasmic extensions that separate substances (such as bacteria or dead body cells) from external environment Phagocytosis is a protective mechanism, not a means of getting nutrients Pseudopod Bacterium or other particle Extracellular fluid Cytoplasm © 2015 Pearson Education, Inc.

79 Active Processes Vesicular transport (continued) Types of endocytosis
Pinocytosis—“cell drinking” Cell “gulps” droplets of extracellular fluid containing dissolved proteins or fats Plasma membrane forms a pit, and edges fuse around droplet of fluid Routine activity for most cells, such as those involved in absorption (small intestine) © 2015 Pearson Education, Inc.

80 Active Processes Vesicular transport (continued) Types of endocytosis
Receptor-mediated endocytosis Method for taking up specific target molecules Receptor proteins on the membrane surface bind only certain substances Highly selective process of taking in substances such as enzymes, some hormones, cholesterol, and iron © 2015 Pearson Education, Inc.

81 Active Processes Vesicular transport (continued) Types of endocytosis
Receptor-mediated endocytosis Both the receptors and target molecules are in a vesicle Contents of the vesicles are dealt with in one of the ways shown in the next figure Membrane receptor © 2015 Pearson Education, Inc.

82 Cell Life Cycle Cell life cycle is a series of changes the cell experiences from the time it is formed until it divides Cycle has two major periods Interphase Cell grows Cell carries on metabolic processes Longer phase of the cell cycle Cell division Cell replicates itself Function is to produce more cells for growth and repair processes © 2015 Pearson Education, Inc.

83 DNA Replication KEY: Adenine Thymine Cytosine Guanine Old (template) strand Newly synthesized strand New strand forming DNA of one chromatid Genetic material is duplicated and readies a cell for division into two cells Occurs toward the end of interphase © 2015 Pearson Education, Inc.

84 DNA Replication DNA uncoils into two nucleotide chains, and each side serves as a template Nucleotides are complementary Adenine (A) always bonds with thymine (T) Guanine (G) always bonds with cytosine (C) For example, TACTGC bonds with new nucleotides in the order ATGACG © 2015 Pearson Education, Inc.

85 Events of Cell Division
Mitosis—division of the nucleus Results in the formation of two daughter nuclei Cytokinesis—division of the cytoplasm Begins when mitosis is near completion Results in the formation of two daughter cells © 2015 Pearson Education, Inc.

86 Stages of Mitosis Prophase First part of cell division
Chromatin coils into chromosomes Chromosomes are held together by a centromere A chromosome has two strands Each strand is called a chromatid © 2015 Pearson Education, Inc.

87 Stages of Mitosis Prophase (continued)
Centrioles migrate to the poles to direct assembly of mitotic spindle fibers Mitotic spindles are made of microtubules Spindle provides scaffolding for the attachment and movement of the chromosomes during the later mitotic stages Nuclear envelope breaks down and disappears © 2015 Pearson Education, Inc.

88 Stages of Mitosis Metaphase
Chromosomes are aligned in the center of the cell on the metaphase plate Metaphase plate is the center of the spindle midway between the centrioles Straight line of chromosomes is now seen © 2015 Pearson Education, Inc.

89 Stages of Mitosis Anaphase Centromere splits
Chromatids move slowly apart and toward the opposite ends of the cell Anaphase is over when the chromosomes stop moving © 2015 Pearson Education, Inc.

90 Stages of Mitosis Telophase Reverse of prophase
Chromosomes uncoil to become chromatin Spindles break down and disappear Nuclear envelope reforms around chromatin Nucleoli appear in each of the daughter nuclei © 2015 Pearson Education, Inc.

91 Stages of Mitosis Cytokinesis Division of the cytoplasm
Begins during late anaphase and completes during telophase A cleavage furrow forms to pinch the cells into two parts Cleavage furrow is a contractile ring made of microfilaments © 2015 Pearson Education, Inc.

92 Stages of Mitosis Two daughter cells exist at the end of cell division
In most cases, mitosis and cytokinesis occur together In some cases, the cytoplasm is not divided Binucleate or multinucleate cells result Common in the liver Mitosis gone wild is the basis for tumors and cancers © 2015 Pearson Education, Inc.

93 Figure 3.15 Stages of mitosis.
Slide 1 Centrioles Chromatin Centrioles Spindle microtubules Centromere Forming mitotic spindle Centromere Plasma membrane Nuclear envelope Chromosome, consisting of two sister chromatids Fragments of nuclear envelope Spindle pole Nucleolus Interphase Early prophase Late prophase Metaphase plate Nucleolus forming Cleavage furrow Nuclear envelope forming Spindle Sister chromatids Daughter chromosomes Metaphase Anaphase Telophase and cytokinesis

94 Protein Synthesis DNA serves as a blueprint for making proteins
Gene: DNA segment that carries a blueprint for building one protein or polypeptide chain Proteins have many functions Fibrous (structural) proteins are the building materials for cells Globular (functional) proteins act as enzymes (biological catalysts) © 2015 Pearson Education, Inc.

95 Protein Synthesis DNA information is coded into triplets Triplets
Contain three bases Call for a particular amino acid For example, a DNA sequence of AAA specifies the amino acid phenylalanine © 2015 Pearson Education, Inc.

96 Protein Synthesis Most ribosomes, the manufacturing sites of proteins, are located in the cytoplasm DNA never leaves the nucleus in interphase cells DNA requires a decoder and a messenger to build proteins, both are functions carried out by RNA (ribonucleic acid) © 2015 Pearson Education, Inc.

97 Protein Synthesis How does RNA differ from DNA? RNA:
Is single-stranded Contains ribose sugar instead of deoxyribose Contains uracil (U) base instead of thymine (T) © 2015 Pearson Education, Inc.

98 Role of RNA Transfer RNA (tRNA) Ribosomal RNA (rRNA)
Transfers appropriate amino acids to the ribosome for building the protein Ribosomal RNA (rRNA) Helps form the ribosomes where proteins are built Messenger RNA (mRNA) Carries the instructions for building a protein from the nucleus to the ribosome © 2015 Pearson Education, Inc.

99 Role of RNA Protein synthesis involves two major phases:
Transcription Translation We will detail these two phases next © 2015 Pearson Education, Inc.

100 Protein Synthesis Transcription
Transfer of information from DNA’s base sequence to the complementary base sequence of mRNA Only DNA and mRNA are involved Triplets are the three-base sequence specifying a particular amino acid on the DNA gene Codons are the corresponding three-base sequences on mRNA © 2015 Pearson Education, Inc.

101 Protein Synthesis Example of transcription: DNA triplets AAT-CGT-TCG
mRNA codons UUA-GCA-AGC © 2015 Pearson Education, Inc.

102 Protein Synthesis Translation
As the ribosome moves along the mRNA, a new amino acid is added to the growing protein chain. Released tRNA reenters the cytoplasmic pool, ready to be recharged with a new amino acid. mRNA specifying one polypeptide is made on DNA template. mRNA leaves nucleus and attaches to ribosome, and translation begins. Incoming tRNA recognizes a complementary mRNA codon calling for its amino acid by binding via its anticodon to the codon. mRNA Nuclear membrane 2 1 3 4 5 Nuclear pore Nucleus (site of transcription) DNA Amino acids Cytoplasm (site of translation) Synthetase enzyme Correct amino acid attached to each species of tRNA by an enzyme Growing polypeptide chain Peptide bond tRNA “head” bearing anticodon Large ribosomal subunit Codon Portion of mRNA already translated Small ribosomal subunit Direction of ribosome advance; ribosome moves the mRNA strand along sequentially as each codon is read. Met Gly Ser Phe Ala Translation Base sequence of nucleic acid is translated to an amino acid sequence Amino acids are the building blocks of proteins © 2015 Pearson Education, Inc.

103 Protein Synthesis Translation (continued)
Steps correspond to Figure 3.16 (step 1 covers transcription) mRNA leaves nucleus and attaches to ribosome, and translation begins Incoming tRNA recognizes a complementary mRNA codon calling for its amino acid by binding via its anticodon to the codon. © 2015 Pearson Education, Inc.

104 Protein Synthesis Translation (continued)
Steps correspond to Figure 3.16 As the ribosome moves along the mRNA, a new amino acid is added to the growing protein chain. Released tRNA reenters the cytoplasmic pool, ready to be recharged with a new amino acid. © 2015 Pearson Education, Inc.

105 Body Tissues Tissues Groups of cells with similar structure and function Four primary types: Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue © 2015 Pearson Education, Inc.

106 Epithelial Tissues Locations: Functions: Body coverings Body linings
Glandular tissue Functions: Protection Absorption Filtration Secretion © 2015 Pearson Education, Inc.

107 Epithelium Characteristics
Cells fit closely together and often form sheets The apical surface is the free surface of the tissue The lower surface of the epithelium rests on a basement membrane Avascular (no blood supply) Regenerate easily if well nourished © 2015 Pearson Education, Inc.

108 Classification of Epithelia
Number of cell layers Simple one layer Stratified more than one layer Basal surface Apical surface Simple Stratified (a) Classification based on number of cell layers © 2015 Pearson Education, Inc.

109 Classification of Epithelia
Shape of cells Squamous Flattened, like fish scales Cuboidal Cube-shaped, like dice Columnar Column-like Squamous Cuboidal Columnar (b) Classification based on cell shape © 2015 Pearson Education, Inc.

110 Figure 3.17c Classification and functions of epithelia.
Number of layers One layer: simple epithelial tissues More than one layer: stratified epithelial tissues Cell shape Squamous Diffusion and filtration Secretion in serous membranes Protection Cuboidal Secretion and absorption; ciliated types propel mucus or reproductive cells Protection; these tissue types are rare in humans Columnar Secretion and absorption; ciliated types propel mucus or reproductive cells Transitional Protection; stretching to accommodate distension of urinary structures (c) Function of epithelial tissue related to tissue type

111 Simple Epithelia Simple squamous Single layer of flat cells
Location—usually forms membranes Lines air sacs of the lungs Forms walls of capillaries Forms serous membranes (serosae) that line and cover organs in ventral cavity Functions in diffusion, filtration, or secretion in membranes © 2015 Pearson Education, Inc.

112 Nucleus of squamous epithelial cell
Figure 3.18a Types of epithelia and their common locations in the body. Air sacs of lungs Nucleus of squamous epithelial cell Nuclei of squamous epithelial cells Basement membrane Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (275×). (a) Diagram: Simple squamous

113 Simple Epithelia Simple cuboidal Single layer of cube-like cells
Locations: Common in glands and their ducts Forms walls of kidney tubules Covers the surface of ovaries Functions in secretion and absorption; ciliated types propel mucus or reproductive cells © 2015 Pearson Education, Inc.

114 Nucleus of simple cuboidal epithelial cell
Figure 3.18b Types of epithelia and their common locations in the body. Nucleus of simple cuboidal epithelial cell Simple cuboidal epithelial cells Basement membrane Basement membrane Connective tissue Photomicrograph: Simple cuboidal epithelium in kidney tubules (250×). (b) Diagram: Simple cuboidal

115 Simple Epithelia Simple columnar Single layer of tall cells Location:
Goblet cells secrete mucus Location: Lines digestive tract from stomach to anus Mucous membranes (mucosae) line body cavities opening to the exterior Functions in secretion and absorption; ciliated types propel mucus or reproductive cells © 2015 Pearson Education, Inc.

116 Nucleus of simple columnar epithelial cell
Figure 3.18c Types of epithelia and their common locations in the body. Mucus of a goblet cell Nucleus of simple columnar epithelial cell Simple columnar epithelial cells Basement membrane Basement membrane Photomicrograph: Simple columnar epithelium of the small intestine (575×). (c) Diagram: Simple columnar

117 Simple Epithelia Pseudostratified columnar
All cells rest on a basement membrane Single layer, but some cells are shorter than others giving a false (pseudo) impression of stratification Location: Respiratory tract, where it is ciliated and known as pseudostratified ciliated columnar epithelium Functions in absorption or secretion © 2015 Pearson Education, Inc.

118 Pseudo- stratified epithelial layer
Figure 3.18d Types of epithelia and their common locations in the body. Cilia Pseudo- stratified epithelial layer Pseudo- stratified epithelial layer Basement membrane Basement membrane Connective tissue Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (560×). (d) Diagram: Pseudostratified (ciliated) columnar

119 Stratified Epithelia Stratified squamous
Named for cells present at the free (apical) surface, which are flattened Functions as a protective covering where friction is common Locations—lining of the: Skin (outer portion) Mouth Esophagus © 2015 Pearson Education, Inc.

120 Stratified squamous epithelium Stratified squamous epithelium
Figure 3.18e Types of epithelia and their common locations in the body. Nuclei Stratified squamous epithelium Stratified squamous epithelium Basement membrane Basement membrane Photomicrograph: Stratified squamous epithelium lining of the esophagus (140×). Connective tissue (e) Diagram: Stratified squamous

121 Stratified Epithelia Stratified cuboidal—two layers of cuboidal cells; functions in protection Stratified columnar—surface cells are columnar, and cells underneath vary in size and shape; functions in protection Stratified cuboidal and columnar Rare in human body Found mainly in ducts of large glands © 2015 Pearson Education, Inc.

122 Stratified Epithelia Transitional epithelium
Composed of modified stratified squamous epithelium Shape of cells depends upon the amount of stretching Functions in stretching and the ability to return to normal shape Locations: urinary system organs © 2015 Pearson Education, Inc.

123 Transi- tional epithelium
Figure 3.18f Types of epithelia and their common locations in the body. Basement membrane Transi- tional epithelium Transitional epithelium Basement membrane Connective tissue Photomicrograph: Transitional epithelium lining of the bladder, relaxed state (270×); surface rounded cells flatten and elongate when the bladder fills with urine. (f) Diagram: Transitional

124 Glandular Epithelium Gland
One or more cells responsible for secreting a particular product Secretions contain protein molecules in an aqueous (water-based) fluid Secretion is an active process © 2015 Pearson Education, Inc.

125 Glandular Epithelium Two major gland types Endocrine gland
Ductless; secretions diffuse into blood vessels All secretions are hormones Examples include thyroid, adrenals, and pituitary © 2015 Pearson Education, Inc.

126 Glandular Epithelium Two major gland types Exocrine gland
Secretions empty through ducts to the epithelial surface Include sweat and oil glands, liver, and pancreas Includes both internal and external glands © 2015 Pearson Education, Inc.

127 Connective Tissue Found everywhere in the body
Includes the most abundant and widely distributed tissues Functions: Provides protection Binds body tissues together Supports the body © 2015 Pearson Education, Inc.

128 Connective Tissue Characteristics
Variations in blood supply Some tissue types are well vascularized Some have a poor blood supply or are avascular Extracellular matrix Nonliving material that surrounds living cells © 2015 Pearson Education, Inc.

129 Extracellular Matrix Two main elements
Ground substance—mostly water along with adhesion proteins and polysaccharide molecules Fibers Produced by the cells Three types: Collagen (white) fibers Elastic (yellow) fibers Reticular fibers (a type of collagen) © 2015 Pearson Education, Inc.

130 Connective Tissue Types
From most rigid to softest, or most fluid: Bone Cartilage Dense connective tissue Loose connective tissue Blood © 2015 Pearson Education, Inc.

131 Connective Tissue Types
Bone (osseous tissue) Composed of: Osteocytes (bone cells) sitting in lacunae (cavities) Hard matrix of calcium salts Large numbers of collagen fibers Functions to protect and support the body © 2015 Pearson Education, Inc.

132 Figure 3.19a Connective tissues and their common body locations.
Bone cells in lacunae Central canal Lacunae Lamella (a) Diagram: Bone Photomicrograph: Cross-sectional view of ground bone (165×)

133 Connective Tissue Types
Cartilage Less hard and more flexible than bone Found in only a few places in the body Chondrocyte (cartilage cell) is the major cell type © 2015 Pearson Education, Inc.

134 Connective Tissue Types
Hyaline cartilage Hyaline cartilage is the most widespread type of cartilage Composed of abundant collagen fibers and a rubbery matrix Locations: Larynx Entire fetal skeleton prior to birth Epiphyseal plates Functions as a more flexible skeletal element than bone © 2015 Pearson Education, Inc.

135 Figure 3.19b Connective tissues and their common body locations.
Chondrocyte (cartilage cell) Chondrocyte in lacuna Lacunae Matrix (b) Diagram: Hyaline cartilage Photomicrograph: Hyaline cartilage from the trachea (400×)

136 Connective Tissue Types
Elastic cartilage (not pictured) Provides elasticity Location: Supports the external ear Fibrocartilage Highly compressible Forms cushionlike discs between vertebrae of the spinal column © 2015 Pearson Education, Inc.

137 Figure 3.19c Connective tissues and their common body locations.
Chondrocytes in lacunae Chondro- cytes in lacunae Collagen fiber Collagen fibers (c) Diagram: Fibrocartilage Photomicrograph: Fibrocartilage of an intervertebral disc (150×)

138 Connective Tissue Types
Dense connective tissue (dense fibrous tissue) Main matrix element is collagen fiber Fibroblasts are cells that make fibers Locations: Tendons—attach skeletal muscle to bone Ligaments—attach bone to bone at joints and are more elastic than tendons Dermis—lower layers of the skin © 2015 Pearson Education, Inc.

139 Figure 3.19d Connective tissues and their common body locations.
Ligament Tendon Collagen fibers Collagen fibers Nuclei of fibroblasts Nuclei of fibroblasts (d) Diagram: Dense fibrous Photomicrograph: Dense fibrous connective tissue from a tendon (475×)

140 Connective Tissue Types
Loose connective tissue types Areolar tissue Most widely distributed connective tissue Soft, pliable tissue like “cobwebs” Functions as a universal packing tissue and “glue” to hold organs in place Layer of areolar tissue called lamina propria underlies all membranes All fiber types form a loose network Can soak up excess fluid (causes edema) © 2015 Pearson Education, Inc.

141 Figure 3.19e Connective tissues and their common body locations.
Mucosa epithelium Elastic fibers Lamina propria Collagen fibers Fibers of matrix Fibroblast nuclei Nuclei of fibroblasts (e) Diagram: Areolar Photomicrograph: Areolar connective tissue, a soft packaging tissue of the body (270×)

142 Connective Tissue Types
Loose connective tissue types Adipose tissue Matrix is an areolar tissue in which fat globules predominate Many cells contain large lipid deposits with nucleus to one side (signet ring cells) Functions Insulates the body Protects some organs Serves as a site of fuel storage © 2015 Pearson Education, Inc.

143 Figure 3.19f Connective tissues and their common body locations.
Nuclei of fat cells Vacuole containing fat droplet Nuclei of fat cells Vacuole containing fat droplet (f) Diagram: Adipose Photomicrograph: Adipose tissue from the subcutaneous layer beneath the skin (570×)

144 Connective Tissue Types
Loose connective tissue types Reticular connective tissue Delicate network of interwoven fibers with reticular cells (like fibroblasts) Locations: Forms stroma (internal framework) of organs, such as these lymphoid organs: Lymph nodes Spleen Bone marrow © 2015 Pearson Education, Inc.

145 Figure 3.19g Connective tissues and their common body locations.
Spleen White blood cell (lymphocyte) Reticular cell Reticular fibers Blood cell Reticular fibers (g) Diagram: Reticular Photomicrograph: Dark-staining network of reticular connective tissue (400×)

146 Connective Tissue Types
Blood (vascular tissue) Blood cells surrounded by fluid matrix known as blood plasma Soluble fibers are visible only during clotting Functions as the transport vehicle for the cardiovascular system, carrying: Nutrients Wastes Respiratory gases © 2015 Pearson Education, Inc.

147 Figure 3.19h Connective tissues and their common body locations.
Blood cells in capillary Neutrophil (white blood cell) White blood cell Red blood cells Monocyte (white blood cell) Red blood cells (h) Diagram: Blood Photomicrograph: Smear of human blood (1290×)

148 Muscle Tissue Function is to contract, or shorten, to produce movement
Three types: Skeletal muscle Cardiac muscle Smooth muscle © 2015 Pearson Education, Inc.

149 Muscle Tissue Types Skeletal muscle
Voluntarily (consciously) controlled Attached to the skeleton and pull on bones or skin Produces gross body movements or facial expressions Characteristics of skeletal muscle cells Striations (stripes) Multinucleate (more than one nucleus) Long, cylindrical shape © 2015 Pearson Education, Inc.

150 (a) Diagram: Skeletal muscle Photomicrograph: Skeletal muscle (195×)
Figure 3.20a Type of muscle tissue and their common locations in the body. Nuclei Part of muscle fiber (a) Diagram: Skeletal muscle Photomicrograph: Skeletal muscle (195×)

151 Muscle Tissue Types Cardiac muscle Involuntarily controlled
Found only in the heart Pumps blood through blood vessels Characteristics of cardiac muscle cells Striations Uninucleate, short, branching cells Intercalated discs contain gap junctions to connect cells together © 2015 Pearson Education, Inc.

152 (b) Diagram: Cardiac muscle Photomicrograph: Cardiac muscle (475×)
Figure 3.20b Type of muscle tissue and their common locations in the body. Intercalated discs Nucleus (b) Diagram: Cardiac muscle Photomicrograph: Cardiac muscle (475×)

153 Muscle Tissue Types Smooth (visceral) muscle Involuntarily controlled
Found in walls of hollow organs such as stomach, uterus, and blood vessels Peristalsis, a wavelike activity, is a typical activity Characteristics of smooth muscle cells No visible striations Uninucleate Spindle-shaped cells © 2015 Pearson Education, Inc.

154 (c) Diagram: Smooth muscle
Figure 3.20c Type of muscle tissue and their common locations in the body. Smooth muscle cell Nuclei (c) Diagram: Smooth muscle Photomicrograph: Sheet of smooth muscle (285×)

155 Nervous Tissue Composed of neurons and nerve support cells
Function is to receive and conduct electrochemical impulses to and from body parts Irritability Conductivity Support cells called neuroglia insulate, protect, and support neurons © 2015 Pearson Education, Inc.

156 Nuclei of supporting cells Spinal cord
Figure 3.21 Nervous tissue. Brain Nuclei of supporting cells Spinal cord Nuclei of supporting cells Cell body of neuron Cell body of neuron Neuron processes Neuron processes Diagram: Nervous tissue Photomicrograph: Neurons (320×)

157 Summary of Tissues Figure 3.22 summarizes the tissue types and functions in the body © 2015 Pearson Education, Inc.

158 Nervous tissue: Internal communication
Figure 3.22 Summary of the major functions and body locations of the four tissue types: epithelial, connective, muscle, and nervous tissues. Nervous tissue: Internal communication • Brain, spinal cord, and nerves Muscle tissue: Contracts to cause movement • Muscles attached to bones (skeletal) • Muscles of heart (cardiac) • Muscles of walls of hollow organs (smooth) Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters • Lining of GI tract organs and other hollow organs • Skin surface (epidermis) Connective tissue: Supports, protects, binds other tissues together • Bones • Tendons • Fat and other soft padding tissue

159 Tissue Repair (Wound Healing)
Tissue repair (wound healing) occurs in two ways: Regeneration Replacement of destroyed tissue by the same kind of cells Fibrosis Repair by dense (fibrous) connective tissue (scar tissue) © 2015 Pearson Education, Inc.

160 Tissue Repair (Wound Healing)
Whether regeneration or fibrosis occurs depends on: Type of tissue damaged Severity of the injury Clean cuts (incisions) heal more successfully than ragged tears of the tissue © 2015 Pearson Education, Inc.

161 Events in Tissue Repair
Inflammation Capillaries become very permeable Clotting proteins migrate into the area from the bloodstream A clot walls off the injured area Granulation tissue forms Growth of new capillaries Phagocytes dispose of blood clot and fibroblasts Rebuild collagen fibers © 2015 Pearson Education, Inc.

162 Events in Tissue Repair
Regeneration of surface epithelium Scab detaches Whether scar is visible or invisible depends on severity of wound © 2015 Pearson Education, Inc.

163 Regeneration of Tissues
Tissues that regenerate easily Epithelial tissue (skin and mucous membranes) Fibrous connective tissues and bone Tissues that regenerate poorly Skeletal muscle Tissues that are replaced largely with scar tissue Cardiac muscle Nervous tissue within the brain and spinal cord © 2015 Pearson Education, Inc.

164 Development Aspects of Cells and Tissues
Growth through cell division continues through puberty Cell populations exposed to friction (such as epithelium) replace lost cells throughout life Connective tissue remains mitotic and forms repair (scar) tissue With some exceptions, muscle tissue becomes amitotic by the end of puberty Nervous tissue becomes amitotic shortly after birth. © 2015 Pearson Education, Inc.

165 Developmental Aspects of Cells and Tissues
Injury can severely handicap amitotic tissues The cause of aging is unknown, but chemical and physical insults, as well as genetic programming, have been proposed as possible causes © 2015 Pearson Education, Inc.

166 Developmental Aspects of Cells and Tissues
Neoplasms, both benign and cancerous, represent abnormal cell masses in which normal controls on cell division are not working Hyperplasia (increase in size) of a tissue or organ may occur when tissue is strongly stimulated or irritated Atrophy (decrease in size) of a tissue or organ occurs when the organ is no longer stimulated normally © 2015 Pearson Education, Inc.


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