Ch. 3 Cells Cell Theory 1.Cells are the basic units of life 2.All organisms are made of one or more cells 3.Cells arise from other cells

Figure 6.8a ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Nuclear envelope Nucleolus Chromatin Plasma membrane Ribosomes Golgi apparatus Lysosome Mitochondrion Peroxisome Microvilli Microtubules Intermediate filaments Microfilaments Centrosome CYTOSKELETON: Flagellum NUCLEUS

Cell Membrane Cell membrane – gate, controlling what comes in and out of the cells Phospholipid bilayer – phosphate head and two fatty acid tailsPhospholipid bilayer – phosphate head and two fatty acid tails Phosphate head – hydrophilic (water loving)Phosphate head – hydrophilic (water loving) Fatty tails – hydrophobic (water hating)Fatty tails – hydrophobic (water hating) Selectively permeableSelectively permeable Cholesterol – stability at high temperatures, flexibility at low temps.Cholesterol – stability at high temperatures, flexibility at low temps.

Proteins 1.Recognition proteins – identify the cell - glycoproteins 2.Channel proteins – passage of small, hydrophilic substances in and out of the cell 3.Adhesion proteins – form junctions with other cells 4.Transport pumps – sodium/potassium pump 5.Receptor proteins – G-protein linked 6.Ion channels – Na/K channels 7.Carrier proteins – move specific substances through membrane

Prokaryote Cell – Bacterial Cells

Prokaryote vs. Eukaryote  Prokaryotes – bacterial cells Do not have a nucleusDo not have a nucleus Have fewer parts, smaller ribosomesHave fewer parts, smaller ribosomes Have DNA and reproduceHave DNA and reproduce No membrane around organellesNo membrane around organelles  Eukaryotes – plants, animals Have a nucleusHave a nucleus Have more partsHave more parts Membrane bound organellesMembrane bound organelles

Cytoplasm  Cytosol and organelles  Cytosol is mostly water  Organelles – nucleus and other parts floating in cytosol

Organelles  Ribosomes – On the rough endoplasmic reticulum and free in the cytoplasm  make proteins (manufacturer)  Smooth endoplasmic reticulum  detoxification and making lipids and carbohydrates

Nucleus  The control center – “brain”  Nuclear envelope – covered in pores – send proteins out  Contains DNA coiled around histone proteins (nucleosome)  DNA coils into chromatin and chromatin condenses into chromosomes (blueprint)

Nucleolus  Dark structure inside the nucleus  Make ribosomes  Disappears during mitosis (cell division)

Golgi and Lysosomes  Golgi apparatus  stack of pancakes  Packages things and sends them out of the cell  Lysosome  digestion of food particles  contain enzymes  Low pH

Mitochondria  Powerhouse of the cell  ATP – energy is created

Cell Shape  Cytoskeleton – internal framework in an animal cell that helps maintain cell shape.  Microtubules – hollow tubes made of protein - help maintain cell shape and serve as tracks for transport throughout the cell.  Cillia and Flagella are made of microtubules.  Microfilaments – smaller proteins that help maintain cell shape.

Euglena

Paramecium

Vacuoles and vesicles  Transport vesicles – move materials within the cells and through the endomembrane system  Food vacuoles – temp. food storage, merge with lysosomes for digestive purposes  Contractile vacuole – in some organisms for pumping water  Central vacuole – in plants, fills with water creating turgor pressure

Figure 6.32 Tight junctions prevent fluid from moving across a layer of cells Tight junction TEM 0.5  m TEM 1  m TEM 0.1  m Extracellular matrix Plasma membranes of adjacent cells Space between cells Ions or small molecules Desmosome Intermediate filaments Gap junction

Plant Cells  Plant cells have a cell wall – made of cellulose  They also have chloroplasts – where photosynthesis occurs  Chlorophyll – pigment that absorbs sunlight energy  Other functions of central vacuole – pg. 35

Plant Cells

Cell Transport  Semipermeable membrane – small, lipid-soluble particles can pass, but large, charged particles cannot  Diffusion – net movement of particles from high to low concentration  Concentration gradient – the difference in concentration between one area and another

Cell Membrane

Diffusion

Osmosis  Diffusion of water through aquaporins  Moves from high water potential to low water potential.  Hypertonic solution – higher solute concentration  Hypotonic solution – lower solute conc.  Isotonic soln. – solute conc. Equal on both sides and equilibrium.

Osmosis

Figure 36.9 Plasmolyzed cell at osmotic equilibrium with its surroundings 0.4 M sucrose solution: Initial flaccid cell: Pure water: Turgid cell at osmotic equilibrium with its surroundings (a) Initial conditions: cellular   environmental  (b) Initial conditions: cellular   environmental  PP  0 PP  0 SS  PP  0 SS  PP  0.7 SS  0.9   0.9 MPa  SS   0.9  0.9 MPa      0.7 MPa SS  0.7  PP 0  0 0 MPa    MPa 

Facilitated Diffusion  Passive transport – no Energy required  Moves down concentration gradient  Moves through a carrier or channel protein  Ex. Glucose  Lipid-insoluble substances

Facilitated Diffusion

Active Transport  Not passive  Goes up or against the concentration gradient (needs energy)  Na + out/K + in  Involves specific carrier proteins  Important in muscle contractions, nerve impulses – maintains resting potential  Ex. Plant roots, ion pumps

Active Transport – Sodium/Potassium Pump

Endocytosis  Enodcytosis – cell taking materials in  Pinocytosis – cell drinking  Phagocytosis – cell eating

Endocytosis

Receptor-mediated endocytosis

Exocytosis  Releasing molecules into the extracellular matrix  Bulk flow – passage of substances through vessels or xylem/phloem

Exocytosis

Countercurrent exchange  Movement of materials in bulk flow in opposite direction  Ex. Fish gills and capillaries  Water(with fresh dissolved oxygen) entering gills encounter capillaries deficient in oxygen  Diffusion of oxygen is enhanced

Cell Junctions  Plasmodesmata – tunnels between plant cells  Junctions in animal cells – tight, anchoring, communicating