Chapter 4 Cell Structure and Function Nucleolus Nucleus Nuclear envelope Ribosome (attached) Ribosome (free) Cell Membrane Rough endoplasmic reticulum Golgi apparatus Mitochondrion Smooth endoplasmic reticulum Centrioles

A CELL is... made of MOLECULES _______  ___________  ___________ ATOMS MOLECULESORGANELLES

WHICH IS BIGGER? _________ > _____________ > ___________ Plant cellAnimal cell bacteria

ALL LIVING THINGS ARE MADE OF CELLS PROKARYOTES Lack nucleus Lack membrane bound organelles EUKARYOTES Have nucleus Have membrane bound organelles Bacterial Cell

CYTOPLASM (Between nucleus and cell membrane) ORGANELLE- small structure with a specific function (job) Organelles suspended in gel-like goo

CELL WALL Supports and protects cell Outside of cell membrane Made of carbohydrates & proteins Plant cell walls are mainly cellulose

CELL MEMBRANE (also called plasma membrane) Made mainly of phospholipids & proteins Controls what enters and leaves the cell Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

PHOSPHOLIPID Phospholipid has 2 main regions: Head  negative charge, hydrophilic 2 fatty acid Tails  nonpolar, hydrophobic HYDROPHILIC  HYDROPHOBIC 

PHOSPHOLIPID BILAYER They form a two-layered sheet called the phospholipid bilayer. Hydrophilic heads face out Hydrophobic tails tucked inward. Proteins are embedded on the membrane, or attached to the surface.

CELL MEMBRANE Proteins are embedded on the membrane, or attached to the surface. Proteins that stick on the surface = PERIPHERAL (either inside or outside of cell) Proteins that stick INTO membrane = Integral (can go part way in or all the way through)

Permeability Nonpolar molecules such as O 2 and CO 2 can easily pass through the hydrophobic interior. Proteins in the membrane form channels that allow specific molecules to cross.

Recognize “self” GLYCOPROTEINS GLYCOPROTEINS are PROTEINS with carbohydrates attached. Play a role in cell-cell interactions.

TRANSPORT PROTEINS help move substances across the cell membrane

Cell membranes MOVE! Molecules in cell membranes are constantly moving and changing

WHAT DOES IT DO? Acts as a boundary Controls what enters and leaves cell

Nucleoid The DNA of a prokaryotic cell is coiled into a region called the nucleoid. Unlike the eukaryotic nucleus, it has no membrane that surrounds the DNA. Also, the ribosomes of prokaryotic cells are smaller. Antibiotics are designed to target (smaller) ribosomes of prokaryotic cells (bacteria), interrupting protein synthesis. –Antibiotics do not harm eukaryotic cells.

NUCLEUS Contains cell’s genetic material (DNA) Controls cell’s activity by directing protein synthesis. Largest organelle in animal cells

Genetic material (DNA) Chromatin – thin fibers of DNA and proteins that look like a diffuse mass. As the cell prepares to divide, the DNA is copied and the chromatin coils up (becoming visible with a light microscope) into the structure we know as chromosomes.

NUCLEUS Surrounded by NUCLEAR ENVELOPE It is a double membrane perforated with protein lined pores. (also called NUCLEAR MEMBRANE)

NUCLEUS NUCLEAR PORES Openings that control the flow of materials into and out of the nucleus

NUCLEOLUS Dark spot in nucleus Site where ribosomal RNA (rRNA) is synthesized according to the instructions of DNA. Proteins brought in through the nuclear pores are assembled with the rRNA to build a subunit of ribosomes. These subunits exit through the nuclear pores where they will be joined to form functional ribosomes. Large subunit Small subunit Diagram of a ribosome

Another type of RNA The nucleus directs protein synthesis with messenger RNA (mRNA). mRNA is a short transcription (copy) of DNA that exits through the nuclear pores where it is translated by ribosomes into amino acid sequences of proteins. 

RIBOSOMES Can be attached to: Nucleus Rough ER OR Free in cytoplasm

ENDOPLASMIC RETICULUM Two kinds: SMOOTH or ROUGH Network of flattened sacs and tubules “endoplasmic” – within the cell “reticulum” – little net

Smooth ER NO ribosomes attached Has enzymes for special tasks: Example: Cells of ovaries & testes synthesize the steroid sex hormones. –Enzymes synthesize lipids (oils, phospholipids, & steroids)

Another example (pg.60) Liver cells help process drugs and other harmful substances. Cells exposed to drugs cause the amount of smooth ER (w/ detoxifying enzymes) to increase This increases the rate of detoxification. Causing increasing tolerance to the drug. Now, dose must be increased to be effective. Another complication is that enzymes often cannot distinguish among related drugs. So an increase in tolerance in one drug, may cause one in another drug. –Ex: barbiturate use can decrease effectiveness of antibiotics.

Another example (pg.60) In muscle cells, smooth ER membrane pumps calcium ions into the interior of the ER. When a nerve signal stimulates a muscle, calcium ions rush from the smooth ER into the cytoplasm….triggering a contraction of the cell.

Rough ER Rough ER membrane enlarges. Phospholipids made by enzymes of the ER are inserted into the membrane. Some of this membrane is passed onto other membranes in vesicles.

Rough ER Ribosomes attached. (rough) These ribosomes make proteins, which are inserted into the ER membrane, where they are modified and transported to other organelles. Example: Insulin. Secreted by cells in the pancreas. Ribosome

After leaving the ER, many transport vesicles travel to the Golgi apparatus… Transport vesicle from ER Golgi apparatus Rough ER

GOLGI APPARATUS (BODY) Discovered by Camillo Golgi with a light microscope. Confirmed later with an electron microscope. Electron micrograph Flattened sacs stacked on top of each other. Sacs are NOT interconnected like ER. Number of Golgi stacks correlates with how active the cell is in secreting proteins.

GOLGI APPARATUS (BODY) Molecular warehouse & finishing factory. Receives & modifies products from ER. One side is receiving dock for transport vesicles Other side is shipping dock giving off vesicles. “maturation model” entire sacs mature as they move from the receiving end to the shipping end, carrying and modifying their cargo as they go. Exiting vesicles move to the cell membrane for export form the cell.

LYSOSOMES Membrane bound sacs that contain digestive enzymes. Made by rough ER & transferred to Golgi body.  Serves as a recycling center. Damaged organelles are dismantled, releasing organic molecules for reuse. * Found in animal cells only!

LYSOSOMES Protists engulf food particles into vacuoles… White blood cells ingest bacteria into vacuoles… Lysosomes fuse with these vacuoles and empties its digestive enzymes into them. Plasma membrane Lysosome Digestive enzymes Food vacuole Digestion

Lysosomal storage disease Lack one or more lysosomal enzymes. Lysosomes become engorged with undigested material. Example: Tay-Sachs disease Lipid digesting enzyme is missing Brain cells become impaired by accumulation of lipids. A child with Tay-Sachs disease will die within a few years.

Peroxisome Vesicle that neutralizes dangerous oxygen compounds –contains catalase that breaks down H 2 O 2 –Detoxification of alcohol Also breaks down fatty acids to be used as fuel.

Zellweger Syndrome Defective genes reduce or eliminate the presence of peroxisomes Results in build up of iron and copper in blood and tissue Symptoms include an enlarged liver; facial deformities, and neurological abnormalities such as mental retardation and seizures. Most infants do not survive past the first 6 months, and usually succumb to respiratory distress, gastrointestinal bleeding, or liver failure.

Apoptosis Programmed cell death Lysosomes help digest unwanted cells Cells in developing hands and feet creates the spaces between fingers & toes. Apoptosis Dead cell engulfed and digested by adjacent cell

Apoptosis plays a role in: Embryonic development Normal body cell maintenance Immune system responses Cancer AIDS infection Transplant rejection

VACUOLES Membrane sacs used for storage

VACUOLES Storage space for WATER, salts, proteins (enzymes), carbohydrates, and waste Maintains internal pH Largest structure in plant cells Small in animal cells No vacuoles in bacteria cells

Contractile vacuoles Paramecium (unicellular organism, protists) Collect excess water from cell, and expels it to the outside of cell. Without vacuole, cell fluid would become too diluted to support life, & cell would eventually swell & burst. Nucleus Contractile vacuoles

Central vacuole Found in plant cells. Can take up more than half the cells volume Holds large amounts of water, food & waste Plays an important role in plant structure. Vacuoles in flower petals contain pigments to attract insects!

Food Vacuole capture and digestion of food particles Fuse with lysosomes to digest food And release nutrients. phagocytosis - the ingestion of particulate matter

Mitochondrion Mitochondria (plural) cellular respiration - converts food energy into a molecule energy. ATP (adenosine triphosphate). –The main energy source for cellular work.

Enclosed by 2 membranes. The inner membrane is highly folded, and contains proteins that make ATP. The folds (cristae) increase membrane surface area, enhancing ability to produce ATP. Has 2 internal compartments 1.Internal membrane space – narrow region between inner and outer membrane. 2.Mitochondrial matrix – contains the mitochondrial DNA, ribosomes, & enzymes. Mitochondrion’s structure

Found in plant & animal cells!

MITOCHONDRIA You inherit your mitochondria from your mother!

WHAT DOES IT DO? Converts glucose to ATP “Powerplant of cell” 

Chloroplasts Photosynthesizing organelles - Use energy from sunlight to make own food (glucose)

Chloroplasts Has an inner and outer membrane. Inside inner membrane is a thick fluid called stroma. Stroma contains the chloroplast DNA & ribosomes.

Chloroplasts Thylakoids (a network of connected sacs) are stacked inside the chloroplast. The stacks of thylakoids are called grana Grana are the solar power packs – site where green chlorophyll molecules trap solar energy.

Endosymbiosis Mitochondria & chloroplasts were formerly small prokaryotes that began living within larger cells. May have occurred as undigested prey or internal parasites. Forming symbiotic relationship. –Host cell uses nutrients released from photosynthetic endosymbionts. –Endosymbionts are provided protection by host cell. Over time, they would become more interdependent, eventually becoming a single organism.

Evidence of Endosymbiosis Mitochondria & chloroplasts both contain their own DNA & ribosomes. Their ribosomes are more similar to prokaryotic ribosomes. Both reproduce by a splitting process similar to that of prokaryotes. Both are surrounded by two membranes.

Fig Engulfing of photosynthetic prokaryote Chloroplast Mitochondrion Some cells Host cell Mitochondrion Host cell Engulfing of aerobic prokaryote

CYTOSKELETON Helps cell maintain shape Help move organelles around Network of protein fibers, found throughout the cytoplasm. Three main types of fibers make up the cytoskeleton: 1. Microfilaments (the thinnest) 2. Microtubules (the thickest) 3. Intermediate filaments (in between)

Microfilaments Solid rods made of the protein actin, in a twisted double chain Supports the cell’s shape & involved in cell movement. –Ex: Actin and another protein myosin interact to cause contraction of muscle cells. Microfilament Actin subunit

Microtubules Straight hollow tubes made of the protein tubulin. Easily disassembled & subunits reused elsewhere. Give shape and support to the cell & acts as tracks along which organelles with motor proteins can move. –Ex: lysosomes move along track to reach a food vacuole. –Ex: guide chromosomes during cell division The main component of cilia & flagella Tubulin subunit Microtubule Nucleus

Intermediate filaments Made of various proteins, and has a ropelike structure. Reinforce cell shape & anchors organelles. –Ex: Nucleus is held in place by a cage of intermediate filaments. –Ex: Our outer layer of skin consists of dead cells containing intermediate filaments made of keratin proteins. Nucleus Intermediate filament

Centrioles Appear during cell division to guide chromosomes apart

Centrioles

Cilia & Flagella Both consist of microtubules wrapped in an extension of the cell membrane. Ring of 9 microtubule “doublets” surrounds a central pair of microtubules. –(called pattern) Outer microtubule doublet Central microtubules Plasma membrane

Cilia – short numerous appendages that propel cell forward. –Found on cells lining the human windpipe, which sweeps mucus & trapped debris out of our lungs. Cilia

Flagella – longer, and limited to one or a few per cell. –Sperm have flagella for movement. Flagellum Bacteria

Extracellular matrix (ECM) Helps hold cells together in tissues. Protects and supports the plasma membrane. Main component: glycoproteins (ex: collagen) Integers - membrane proteins that interconnects the ECM to the cytoskeleton.

Fig EXTRACELLULAR FLUID Microfilaments Collagen fiber Connecting glycoprotein Integrin Plasma membrane Glycoprotein complex with long polysaccharide CYTOPLASM

Three types of cell junctions Tight junction – membranes of neighboring cells are very tightly pressed against each other. Prevent leakage of extracellular fluid Tight junctions –Example: tissue lines the digestive tract, preventing the contents from leaking into surrounding tissues.

Three types of cell junctions Anchoring junction – functions like rivets, fastening cells together into strong sheets. Common in tissue subject to stretching or mechanical stress. –Skin & heart muscle Anchoring junction

Three types of cell junctions Gap junctions – channels that allow small molecules to flow through protein lined pores between neighboring cells. –Ex: flow of ions through gap junctions in the cells of heart muscle coordinates their contraction. Gap junctions

Fig Tight junctions Anchoring junction Gap junctions Plasma membranes of adjacent cells Extracellular matrix

Plasmodesmata Channels between adjacent plant cells, form a circulatory and communication system connecting the cells in plant tissue. Cell membrane & cytoplasm extend through the plasmodesmata, so water and molecules can pass cell to cell.

Fig Vacuole Walls of two adjacent plant cells Cytoplasm Primary cell wall Plasma membrane Plasmodesmata Secondary cell wall

DIFFERENCES IN ANIMAL CELLS, PLANT CELLS, AND BACTERIA ANIMAL CELLPLANT CELLBACTERIA Eukaryotes Prokaryotes Cell membrane Nuclear membrane NO nuclear membrane NO cell wallCell wall made of CELLULOSE Cell wall made of PEPTIDOGLYCAN Has ribosomes DNA in multiple chromosomes DNA is a single circular ring CYTOSKELETON Small vacuolesReally big vacuoleNO vacuoles Has lysosomesNO lysosomes Has centriolesNO centrioles Has mitochondria No mitochondria NO chloroplastsChloroplastsNO chloroplasts SMALLERSMALLSMALLEST

USE WORDS FROM THE WORD BANKS TO COMPLETE THE VENN DIAGRAM COMPARISON

Fig. 4-4b Smooth endoplasmic reticulum Rough endoplasmic reticulum CYTOSKELETON: NUCLEUS: Nuclear envelope Chromosome Nucleolus Ribosomes Golgi apparatus Plasma membrane Mitochondrion Peroxisome Cell wall Central vacuole Microtubule Intermediate filament Microfilament Cell wall of adjacent cell Chloroplast Plasmodesmata

Fig. 4-4a Smooth endoplasmic reticulum Rough endoplasmic reticulum CYTOSKELETON: NUCLEUS: Nuclear envelope Chromosomes Nucleolus Ribosomes Golgi apparatus Plasma membrane Mitochondrion Peroxisome Centriole Lysosome Microtubule Intermediate filament Microfilament

Fig. 4-3b Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella Bacterial chromosome Pili

Fig. 4-UN3 a. b. c. d. e. f. g. h. i. j. k. l.