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Cell Physiology Ch. 2. Objectives Understand what the Cell Theory states Identify organelles and state their function Know how Mitochondria produce ATP.

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Presentation on theme: "Cell Physiology Ch. 2. Objectives Understand what the Cell Theory states Identify organelles and state their function Know how Mitochondria produce ATP."— Presentation transcript:

1 Cell Physiology Ch. 2

2 Objectives Understand what the Cell Theory states Identify organelles and state their function Know how Mitochondria produce ATP

3 The Cell Theory All living things are composed of cells Cell are the smallest unit of life All cells come from pre-existing cells The cell is the structural and functional unit of life

4 Cells Cells vary in size Small size of cells makes them efficient Focus on eukaryotic cells

5 Two major kinds of cell Eukaryotic cell – Complex organization – True nucleus present Stores DNA – Many membrane bound organelles Specialized for a particular function Not all membrane bound – Cell wall present in some organisms – Size: 10 – 100 μm

6 Eukaryotic Cell Structure Nucleus – Control center of the cell – Bound by nuclear membrane – Stores hereditary information Nucleolus – Within nucleus – Responsible for making rRNA Ribosome subunits Ribosomes – Sites of protein synthesis in a cell Two subunits – Three binding sites where mRNA and tRNA interact – Free floating or attached to membranes

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8 Eukaryotic Cell Structure Endoplasmic reticulum (ER) – Two types Rough ER – Synthesis of proteins for export and membrane construction – Ribosomes present Smooth ER – Synthesis of lipids – Detoxification of drugs and poisons – p roduces vesicles for transport

9 Eukaryotic Cell Structure Golgi Complex – UPS of the cell – Receive molecules from the ER Modify, sort, and deliver – Vesicles do the delivering – Vesicles are specific in the cargo they carry

10 Specificity of Vesicles Finished proteins contain sorting signals – Bind to specific recognition sites Coatomers bind to vesicle membrane surface – Cause bulging to occur – Eventually buds off V-SNARE bind to t-SNARE on plasma membrane – Ensures that content of vesicle is secreted out of the cell

11 Eukaryotic Cell Structure Lysosomes – Digestive compartments Hydrolysis Breakdown old or damaged organic matter – Autophagy Foreign material – Endocytosis » Phagocytosis » Pinocytosis » Receptor-mediated – Also function in programmed cell death – Defects may lead to storage disorders Pompe’s disease Tay-Sachs disease

12 Eukaryotic Cell Structure Peroxisomes – Contain oxidative enzymes – Enzymes remove H from various substrates and add it to O, producing hydrogen peroxide catalase – Have many functions Metabolism of fatty acids Detoxification

13 Mitochondria and ATP Production Mitochondria – The powerhouse of the cell – Site of cellular respiration and ATP production Endosymbiotic theory – Believed to have been prokaryotes that formed a symbiotic relationship with precursor eukaryotic cells Cellular respiration – Glycolysis – Acetyl CoA production – Citric acid cycle – Electron transport chain

14 Overview of ATP Production Glucose Glucose 6-phosphate Glycogen Fat Fructose 6-phosphate Fructose 1,6-diphosphate 2 PGAL 2 2 NAD + 2 NADH + 2 H + 2 2 H2O 2 2 2 pyruvic acid 2 NADH + 2 H + 2 NAD + O2 lacking O2 present 2 2 lactic acid 2 2 Aerobic respirationAnaerobic fermentation 5 Dephosphorylation 1 Phosphorylation 2 Priming 3 Cleavage 4 Oxidation Pi ATP 2 ADP 2 Key Carbon atoms Phosphate groups Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. End-products of glycolysis are: 2 pyruvic acid + 2 NADH + 2 ATP + 2 H +

15 Aerobic Respiration Most ATP generated in mitochondria – Oxygen required as final electron acceptor Pyruvate decarboxylated – Combines with coenzyme A to enter matrix Occurs in two principal steps: – Matrix reactions – controlling enzymes are in the fluid of the mitochondrial matrix – Membrane reactions - controlling enzymes are bound to the membranes of the mitochondrial cristae

16 Mitochondrial Matrix Reactions 10 7 6 Pyruvic acid (C3) CO2 NAD + NADH + H + Acetyl group (C2) Acetyl-Co A Coenzyme A H2O Citric acid (C6) Oxaloacetic acid (C4) H2O (C6) CO2 FAD FADH2 H2O NADH + H + NAD + 11 14 15 17 18 GTPGDP 12 13 16 Occurs in mitochondrial matrix ADP 9 8 Pi Citric acid cycle H2O NAD + NADH + H + (C4) (C5) NAD + NADH + H + CO2 (C4) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATP

17 Membrane Reactions Membrane reactions have two purposes: – to further oxidize NADH and FADH 2 and transfer their energy to ATP – to regenerate NAD + and FAD and make them available again to earlier reaction steps Mitochondrial electron-transport chain – series of compounds that carry out this series of membrane reactions

18 Members of the Transport Chain Flavin mononucleotide (FMN) – derivative of riboflavin similar to FAD – bound to a membrane protein FMN accepts electrons from NADH Iron-sulfur (Fe-S) centers – complexes of iron and sulfur atoms bound to membrane proteins Coenzyme Q (CoQ) – accepts electrons from FADH 2 – small mobile molecule that moves about in the membrane Copper (Cu) ions – bound to two membrane proteins Cytochromes – five enzymes with iron cofactors – brightly colored in pure form – in order of participation in the chain, b, c 1, c, a, a 3

19 Electron Transport hydrogen atoms are spilt apart as they transfer from coenzymes to the chain protons pumped into the intermembrane space electrons travel in pairs (2 e - ) along the transport chain each electron carrier becomes reduced when it receives an electron pair and oxidized again when it passes the electrons along to the next carrier oxygen is the final electron acceptor – each oxygen atom accepts two electrons from cytochrome a 3 and two protons from the mitochondrial matrix forming water body’s primary source of metabolic water – water synthesized in the body – this reaction explains the body’s oxygen requirement – no oxygen, cell produces too little ATP to sustain life

20 50 40 30 20 10 Enzyme complex 1 Relative free energy (kcal/mole) 0 NADH + H + NAD + FADH2 FAD Enzyme complex 2 Reaction progress Enzyme complex 3 ½ O2 + 2 H + H2O 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Electron Transport Chain

21 Chemiosmotic Mechanism electron transport chain energy fuels respiratory enzyme complexes – pump protons from matrix into space between inner and outer mitochondrial membranes – creates steep electrochemical gradient for H + across inner mitochondrial membrane inner membrane is permeable to H + at channel proteins called ATP synthase chemiosmotic mechanism - H + current rushing back through these ATP synthase channels drives ATP synthesis

22 Chemiosmotic ATP Synthesis Figure 26.6 Matrix Inner membrane NADH + H + NAD + 2 H + H2O 3 ADP + 3 Pi 6 H + 2e – Matrix Cristae Outer membrane CoQ Cyt c ATP synthase 2 3 Enzyme complex 1 Intermembrane space Inner membrane Intermembrane space Outer membrane 2 H + Enzyme complex Enzyme complex ½ O2 + 2 H + Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 ATP

23 Overview of ATP Production NADH releases an electron pair to electron transport system and H + to prime pumps – enough energy to synthesize 3 ATP FADH 2 releases its electron pairs further along electron-transport system – enough energy to synthesize 2 ATP complete aerobic oxidation of glucose to CO 2 and H 2 O produces 36-38 ATP – efficiency rating of 40% - 60% is lost as heat

24 ATP Generated by Oxidation of Glucose Figure 26.7 2 NADH + 2 H + 2 pyruvate Cytosol Mitochondria Glucose 2 NADH + 2 H + 6 NADH + 6 H + Citric acid cycle 2 FADH2 Electron-transport chain H2OO2 Glycolysis Total 36–38 ATP 2 2 4 (net) 28–30 CO2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATP

25 Vaults and Cytosol Vaults – May function as cellular transporters – True function unknown Cytosol – Gel-like semiliquid that occupies most of the cell volume – involved with Intermediary metabolism Ribosomal protein synthesis Inclusions

26 The Cytoskeleton Structural support of the cell Composed of three types of protein fibers – Microtubules Tubulin Maintain shape of asymmetrical cells Also functions in cellular locomotion and movement – Microfilaments Actin Cellular contractile systems Mechanical stiffeners – microvilli – Intermediate filaments Resist mechanical stress

27 The Cytoskeleton

28 Centrioles – Assembly of microtubules – Function in cell divison Other functions – Cellular movement Cilia and flagella – Transport of materials Dynein-kinesin motor proteins

29 The Plasma Membrane Surrounds all living cells Composed of a phospholipid bilayer – Polar hydrophilic heads on the outside, nonpolar hydrophobic tails on the inside Fluid mosaic model – Proteins and cholesterol embedded

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31 Beyond the Plasma Membrane Extra Cellular Matrix – Surrounds plasma membrane of animal cells Protection and regulation


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