Cells.

Characteristics of a Living Thing
In order for something to be considered living, it has to meet the following criteria: Have order Regulation Growth and development Process energy Response to the environment Reproduction Evolutionary adaptation

Characteristics of a Living Thing
(1) Order (2) Regulation (3) Growth and development (4) Energy processing (5) Response to the environment (6) Reproduction (7) Evolutionary adaptation

Robert Hooke 1665 First to observe cells using a microscope
Looked at cork under the microscope and saw little “cells”

Antoni van Leeuwenhoek
1600s Examined pond water with a single lens microscope he made and saw many organisms. He called them “animalcules” He saw bacteria moving! He also observed blood cells from fish, birds, frogs, dogs, and humans. Therefore, it was known that cells are found in animals as well as plants.

The Cell Theory Complete
3 Basic Components of the Cell Theory – 1. All organisms are composed of one or more cells. (Schleiden & Schwann)( ) 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)( ) 3. All cells are produced by the division of preexisting cells. (Virchow)(1858)

Most Cells are Microscopic
Most cells cannot be seen without a microscope Bacteria are the smallest of all cells and require magnifications up to 1,000X Plant and animal cells are 10 times larger than most bacteria

10 m 1 m 100 mm Unaided eye (10 cm) 10 mm (1 cm) 1 mm 100 µm
Human height 1 m Length of some nerve and muscle cells 100 mm (10 cm) Unaided eye Chicken egg 10 mm (1 cm) Frog egg 1 mm 100 µm Most plant and animal cells Light microscope 10 µm Nucleus Most bacteria Mitochondrion 1 µm Figure 4.2A The sizes of cells and related objects. Mycoplasmas (smallest bacteria) Electron microscope 100 nm Viruses Ribosome 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms

Prokaryotic versus Eukaryotic Cells
Bacteria and archaea = prokaryotic cells All other forms of life = eukaryotic cells Both prokaryotic and eukaryotic cells have a plasma membrane one or more chromosomes ribosomes Eukaryotic cells have a membrane-bound nucleus and a number of other organelles Prokaryotes have a nucleoid and no true organelles

A thin section through the bacterium Bacillus coagulans (TEM)
Pili Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule Figure 4.3 A structural diagram (left) and electron micrograph (right) of a typical prokaryotic cell. Module 4.3 mentions how antibiotics can specifically target prokaryotic but not eukaryotic cells. This might be a good time to discuss the evolution of antibiotic resistance. Teaching tips and ideas for related lessons can be found at A thin section through the bacterium Bacillus coagulans (TEM) A typical rod-shaped bacterium Flagella

Prokaryotic Cells Pili – attachment structures on the surface of some prokaryotes Nucleoid – region where the cell’s DNA is located Ribosomes – structures that make proteins Plasma membrane – encloses the cytoplasm Cell wall – rigid structure surrounding the cell membrane Capsule – jellylike outer coating Flagella – used for movement

Eukaryotic Cells Has a membrane bound nucleus that contains chromosomes Has many organelles (little organs) found in the cytoplasm

There are four life processes in eukaryotic cells that depend upon structures and organelles
Manufacturing - nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus Breakdown of molecules - lysosomes, vacuoles, and peroxisomes Energy processing - mitochondria in animal cells and chloroplasts in plant cells Structural support, movement, and communication - cytoskeleton, plasma membrane, and cell wall

Plant versus Animal Cells
Plant cells DO NOT have lysosomes or centrioles (help with cell division) Animal cells DO NOT have cell walls, central vacuoles, or chloroplasts

NUCLEUS: Nuclear envelope Chromosomes Smooth endoplasmic reticulum
Nucleolus Rough endoplasmic reticulum Lysosome Centriole Ribosomes Figure 4.4A An animal cell. Peroxisome Golgi apparatus CYTOSKELETON: Microtubule Plasma membrane Intermediate filament Mitochondrion Microfilament

NUCLEUS: Rough endoplasmic reticulum Nuclear envelope Chromosome
Ribosomes Nucleolus Smooth endoplasmic reticulum Golgi apparatus CYTOSKELETON: Central vacuole Microtubule Chloroplast Intermediate filament Cell wall Plasmodesmata Microfilament Figure 4.4B A plant cell. Mitochondrion Peroxisome Plasma membrane Cell wall of adjacent cell

Plasma Membrane Boundary between the cell and its surroundings
Controls what goes in and out of the cell – selective permeability The membrane is very thin. Made up of phospholipids, proteins and some carbohydrates. Phospholipid – has a negative charged hydrophilic head and two nonpolar hydrophobic fatty acid tails

Hydrophilic head Phosphate group Symbol Hydrophobic tails
Figure 4.5A Phospholipid molecule. Hydrophobic tails

Phospholipids form a two-layer sheet called a phospholipid bilayer
Hydrophilic heads face outward, and hydrophobic tails point inward Hydrophilic heads are exposed to water, while hydrophobic tails are shielded from water Proteins are attached to the surface and some are embedded into the phospholipid bilayer Proteins also have hydrophilic and hydrophobic portions

Outside cell Hydrophilic heads Hydrophobic region of protein
tails Inside cell Proteins Figure 4.5B Phospholipid bilayer with associated proteins. Hydrophilic region of protein

Nonpolar molecules can pass easily through the membrane
Oxygen Carbon Dioxide

CELL STRUCTURES INVOLVED IN MANUFACTURING AND BREAKDOWN
Copyright © 2009 Pearson Education, Inc.

Nucleus Genetic control center Contains DNA
DNA is copied within the nucleus prior to cell division Controls the cell’s activities Eukaryotic chromosomes are made up if chromatin (proteins and DNA)

Nuclear envelope – double membrane that surrounds the nucleus.
The envelope is attached to the endoplasmic reticulum Nuclear pores – holes in the membrane that allows molecules to move in and out of the nucleus Nucleolus – darkened center of the nucleus where ribosomes are made

Two membranes of nuclear envelope
Nucleus Nucleolus Chromatin Pore Figure 4.6 TEM (left) and diagram (right) of the nucleus. Endoplasmic reticulum Ribosomes

Ribosomes Perform protein synthesis Can be found as
Free ribosomes – found in the cytoplasm Bound ribosomes – attached to the endoplasmic reticulum Can go back and forth as free and bound Cells that must synthesize large amounts of protein have a large number of ribosomes

Endoplasmic reticulum (ER)
Ribosomes Cytoplasm ER Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Figure 4.7 Ribosomes. Small subunit TEM showing ER and ribosomes Diagram of a ribosome

Endomembrane System The membranes within a eukaryotic cell are physically connected and compose the endomembrane system. It includes – Nuclear envelope Endoplasmic reticulum (ER) Golgi apparatus Lysosomes Vacuoles Plasma membrane

Some parts of the endomembrane system are connected to each other.
Some parts use vesicles (sacs of membranes) to transfer material. This communication allows for the synthesis, storage, and export of molecules.

Endoplasmic Reticulum
The membrane of the ER is continuous with that of the nuclear membrane. Two types – Smooth ER Rough ER Both the Smooth and Rough ERs are connected

Smooth ER Has no ribosomes attached to it
Have enzymes here that make lipids (oils, steroids, phospholipids) Stores calcium

Nuclear envelope Ribosomes Smooth ER Rough ER
Figure 4.9A Smooth and rough endoplasmic reticulum.

Rough ER Has ribosomes attached to it Helps to make more membranes
Bound ribosomes make proteins that will be inserted into the ER and then transported to other organelles by vesicles.

Secretory Proteins – Polypetides that are made by bound ribosomes
This protein moves through a pore into the ER Sugars are added to the proteins to make glycoproteins The glycoproteins get packaged into a transport vesicle and get exported from the ER Vesicles bud off from the ER and go to the Golgi

4 3 1 2 Transport vesicle buds off Ribosome Secretory protein
inside transport vesicle 3 Sugar chain 1 Figure 4.9B Synthesis and packaging of a secretory protein by the rough ER. Glycoprotein 2 Polypeptide Rough ER

Golgi Apparatus Made up of flattened sacs stacked on top of each other
The sacs are not connected and the amount of sacs varies The Golgi receives and modifies products from the ER. One side of the Golgi receives the vesicles from the ER and the other side gives rise to vesicles which bud off and travel to other sites.

As proteins move from one side of the Golgi to the other, they get modified and tagged so they know where they are going. The finished products usually become part of the membrane or another organelle.

Golgi apparatus “Receiving” side of Golgi Golgi apparatus apparatus
Transport vesicle from ER New vesicle forming Figure 4.10 The Golgi apparatus. You might tell your students that the Golgi apparatus looks like a stack of pita bread. Transport vesicle from the Golgi “Shipping” side of Golgi apparatus

Lysosomes Are membranous sacs that contain digestive enzymes.
Are made by the RER and modified by the Golgi The inside of the lysosomes are acidic. Help to break down food and damaged organelles. The damaged organelle is first enclosed in a membrane vesicle Then a lysosome fuses with the vesicle, dismantling its contents and breaking down the damaged organelle.

Digestive enzymes Lysosome Plasma membrane
Figure 4.11A Lysosome fusing with a food vacuole and digesting food.

Digestive enzymes Lysosome Plasma membrane Food vacuole

Digestive enzymes Lysosome Plasma membrane Digestion Food vacuole

damaged mitochondrion
Lysosome Figure 4.11B Lysosome fusing with vesicle containing damaged organelle and digesting and recycling its contents. Vesicle containing damaged mitochondrion

damaged mitochondrion
Lysosome Digestion Figure 4.11B Lysosome fusing with vesicle containing damaged organelle and digesting and recycling its contents. Vesicle containing damaged mitochondrion

Vacuole Are membranous sacs that are found in a variety of cells and possess an assortment of functions Central vacuole – In plants Helps with cell growth and storage of chemicals and wastes. Contractile vacuoles – help to pump out excess water.

Chloroplast Nucleus Central vacuole
Figure 4.12A Central vacuole in a plant cell. Ask your students to identify organelles in animal cells that are not involved in the synthesis of proteins (other than mitochondria). (Vacuoles and peroxisomes are not involved in protein synthesis.)

Nucleus Contractile vacuoles
Figure 4.12B Contractile vacuoles in Paramecium, a single-celled organism. Contractile vacuoles

Nucleus Nuclear membrane Rough ER Smooth ER Transport vesicle
Figure 4.13 Connections among the organelles of the endomembrane system. Golgi apparatus Lysosome Vacuole Plasma membrane

Peroxisomes Not part of the endomembrane system
Contain enzymes that transfer H to O Makes peroxide as a by product which is converted into water Helps to break down fatty acids Also helps to detoxify alcohol

ENERGY-CONVERTING ORGANELLES

Mitochondria Cellular respiration occurs here
Cellular respiration involves conversion of chemical energy in foods to chemical energy in ATP Has 2 membranes, each with a phospholipid bilayer

Has 2 internal components
Intermembranal space – region between the inner and outer membrane Mitochondrial matrix – contains DNA, ribosomes and enzymes Cristae – folds of the inner membrane

Mitochondrion Outer membrane Intermembrane space Inner membrane
Figure 4.14 The mitochondrion. Inner membrane Cristae Matrix

Chloroplasts Photosynthesis happens here
Photosynthesis is the conversion of light energy to chemical energy of sugar molecules Has an inner and outer membrane with an intermembranal space between them. Stroma – fluid found here Contains the DNA, ribosomes and enzymes

Thylakoids – interconnected sacs
Granum (a) – stacks of thylakoids The grana contains the chlorophyll. Chlorophyll – pigment that allows for photosynthesis

Chloroplast Stroma Inner and outer membranes Granum Intermembrane
Figure 4.15 The chloroplast. Granum Intermembrane space

Evolution of Mitochondria and Chloroplasts
Believe mitochondria and chloroplasts came about by endosymbiosis The hypothesis of endosymbiosis proposes that mitochondria and chloroplasts were formerly small prokaryotes that began living within larger cells Symbiosis benefitted both cell types Believe mitochondria evolved before chloroplasts because all eukaryotic cells have mitochondria

Evidence – DNA in mitochondria and chloroplasts is similar to DNA of prokaryotes The ribosomes found there are similar to ribosomes on prokaryotes Both organelles have a double membrane Both organelles reproduce in the same splitting process as prokaryotes

Mitochondrion Engulfing of photosynthetic prokaryote Some cells
of aerobic prokaryote Chloroplast Host cell Figure 4.16 Endosymbiotic origin of mitochondria and chloroplasts. Mitochondrion Host cell

INTERNAL AND EXTERNAL SUPPORT: THE CYTOSKELETON AND CELL SURFACES

Cytoskeleton Protein fibers found throughout the cytoplasm
Acts like a skeleton by providing support and motility Scientists believe that motility and cellular regulation result when the cytoskeleton interacts with proteins called motor proteins Made up of Microfilaments Intermediate filaments Microtubules

Receptor for motor protein
Vesicle ATP Receptor for motor protein Motor protein (ATP powered) Microtubule of cytoskeleton (a) Microtubule Vesicles 0.25 µm Campbell, Neil, and Jane Reece, Biology, 8th ed., Figure 6.21 Motor proteins and the cytoskeleton. (a) Motor proteins that attach to receptors on vesicles can “walk” the vesicles along microtubules or, in some cases, microfilaments; Vesicles containing neurotransmitters migrate to the tips of nerve cell axons via the mechanism in (a). (b)

Microfilaments Also known as actin filaments
Are solid rods made up of actin (globular protein) arranged in a twisted double chain These proteins can assemble and reassemble to help with movement and shape Muscle contractions

7 nm Actin subunit Microfilament
Figure 4.17 Fibers of the cytoskeleton: microfilaments are stained red. Actin subunit 7 nm Microfilament

Intermediate Filaments
Made up of proteins Have a ropelike structure Reinforce cell shape and anchor organelles More of a permanent fixture

10 nm Nucleus Fibrous subunits Intermediate filament
Figure 4.17 Fibers of the cytoskeleton: intermediate filaments are stained yellow-green. Fibrous subunits 10 nm Intermediate filament

Microtubules Are straight hollow tubes made up of globular proteins called tubulins Grow out from the centrosome (cytoplasm surrounding centrioles) Help with shape, support and acts as tracks for motor proteins to move Can help guide movement of chromosomes when cells divide

25 nm Nucleus Tubulin subunit Microtubule
Figure 4.17 Fibers of the cytoskeleton: microtubules are stained green. Tubulin subunit 25 nm Microtubule

Cilia and Flagella Are locomotor appendages that protrude from the cell Cilia – short and usually there are tons attached to the cell Flagella – longer and usually there are only a few attached to the cell A flagellum propels a cell by a whiplike motion Cilia work more like the oars of a crew boat

Cilia Figure 4.18A Cilia on cells lining the respiratory tract.

Flagellum Figure 4.18B Undulating flagellum on a sperm cell.

Both are made up of microtubules
A ring of nine microtubule doublets surrounds a central pair of microtubules This is known as a arrangement The cilia and flagella are anchored in a basal body with nine microtubule triplets arranged in a ring

Cross sections: Outer microtubule doublet Central microtubules
Radial spoke Dynein arms Flagellum Plasma membrane Figure 4.18C Structure of a eukaryotic flagellum or cilium. Triplet Basal body Basal body

Cilia and flagella move by bending motor proteins called dynein arms
These attach to and exert a sliding force on an adjacent doublet The arms then release and reattach a little further along and repeat this time after time This “walking” causes the microtubules to bend Energy is needed for this to occur

Extracellular Matrix Cells synthesize and secrete the extracellular matrix (ECM) that is essential to cell function Helps with support, movement and regulation Helps to hold cells together in tissues and also protects and supports the membrane It is made up of strong fibers of collagen, which holds cells together and protects the plasma membrane

ECM attaches through connecting proteins that bind to membrane proteins called integrins
Integrins span the plasma membrane and connect to microfilaments of the cytoskeleton

EXTRACELLULAR FLUID CYTOPLASM Glycoprotein complex with long
polysaccharide EXTRACELLULAR FLUID Collagen fiber Connecting glycoprotein Integrin Plasma membrane Figure 4.20 The extracellular matrix (ECM) of an animal cell. Microfilaments CYTOPLASM

Cell Junctions Neighboring cells can communicate through junctions
Types 1. Tight Junctions – membranes of neighboring cells are tightly pressed against each other They prevent leakage of extracellular fluid across a layer of epithelial cells

2. Anchoring junctions – fasten cells together into sheets
Found in skin and heart 3. Gap junctions – channels that allow small molecules to flow through protein-lined pores between neighboring cells. In heart muscle to coordinate contractions

Tight junctions Anchoring junction Gap junctions Plasma membranes
Figure 4.21 Three types of cell junctions in animal tissues. Plasma membranes of adjacent cells Extracellular matrix

Cell Walls Found in plants Very rigid Offer support and protection
Made up of cellulose Has a primary cell wall that is thin and flexible so that the cell can enlarge

Then can have a secondary wall.
This is what makes up wood! Plasmodesmata (cell junctions) – channels between plant cells used for circulatory and communication systems (water, nourishment, messages)

Walls of two adjacent plant cells Vacuole Plasmodesmata
Primary cell wall Figure 4.22 Plant cell walls and cell junction. Secondary cell wall Cytoplasm Plasma membrane

Table 4.23 Eukaryotic Cell Structures and Functions.

a. l. b. c. k. j. i. h. d. g. e. f.

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