Cell Membranes: Structure and Function Overview

1. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • 1. phospholipids POLAR END (react with water) NON-POLAR END (hyrophobic)

2. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • 2. proteins and carbohydrates

3. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • B. Membrane Function • 1. semi-permeable barrier Aqueous Solution (outside cell) dissolved ions dissolved polar molecules suspended non-polar (lipid soluble) Aqueous Solution (inside cell) dissolved ions dissolved polar molecules suspended non-polar (lipid soluble)

4. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • B. Membrane Function • 1. semi-permeable barrier • 2. transport Net diffusion Net diffusion equilibrium

5. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • B. Membrane Function • 1. semi-permeable barrier • 2. transport – facilitated diffusion

6. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • B. Membrane Function • 1. semi-permeable barrier • 2. transport - osmosis

7. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • B. Membrane Function • 1. semi-permeable barrier • 2. transport – active transport

8. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • B. Membrane Function • 1. semi-permeable barrier • 2. transport • 3. metabolism (enzymes nested in membrane) • 4. signal transduction

9. Cell Biology • Overview • II. Membranes – How Things Get in and Out of Cells • A. Membrane Structure • B. Membrane Function • 1. semi-permeable barrier • 2. transport • 3. metabolism (enzymes nested in membrane) • 4. signal transduction • 5. cell-cell binding • 6. cell recognition • 7. cytoskeleton attachment

10. Cellular Respiration

11. III. Cellular Respiration Overview: Proteins, Carbohydrates, Fats, Nucleic Acids Organic Molecules: C—C—C—C Break C—C bonds release E Some trapped in bonds between ADP + P ATP NAD + H+ NADH Some E lost (heat) C C C C (These are CO2 molecules)

12. III. Cellular Respiration Overview: Proteins, Carbohydrates, Fats, Nucleic Acids Organic Molecules: C—C—C—C Break C—C bonds release E Some trapped in bonds between ADP + P ATP NAD + H+ NADH Some E lost (heat) C C C C (These are CO2 molecules) Break NADH ADP + P Make ATP NAD, H+

13. III. Cellular Respiration Overview: Focus on core process… Glucose metabolism GLYCOLYSIS

14. III. Cellular Respiration Overview: 1. Glycolysis: - All cells do this! (very primitive pathway) - Occurs in the cytoplasm of all cells - Occurs in presence OR absence of oxygen gas. Glucose C6H12O6 2 pyruvate 2 C3

15. III. Cellular Respiration Overview: 1. Glycolysis: - Energy in 2 ATP is used to ‘activate’/start reaction 2 ATP 2 ADP + P Glucose C6H12O6 2 pyruvate 2 C3

16. III. Cellular Respiration Overview: 1. Glycolysis: - Energy in 2 ATP is used to ‘activate’/start reaction - breaking the C-C bond in glucose releases e- /Energy - electrons accepted by NAD NAD- +H+ NADH NAD NADH 2 ATP 2 ADP + P Glucose C6H12O6 2 pyruvate 2 C3 4 ADP + P 4 ATP

17. III. Cellular Respiration Overview: GLYCOLYSIS PYRUVATE METABOLISM Oxygen Absent? Oxygen Present? Anaerobic Respiration Or Fermentation Aerobic Respiration MORE ATP SOME ATP

18. III. Cellular Respiration • Overview: • Glycolysis • Anaerobic Respiration C3 C2-CoA + CO2 Pyruvate Acetyl-CoA NAD NADH

19. III. Cellular Respiration • Overview: • Glycolysis • Anaerobic Respiration C3 C2-CoA + CO2 CoA NAD NADH NAD NADH C6 C4 Incomplete Citric Acid Cycle C5 + CO2

20. 2. Anaerobic Respiration Electron Transport Chain across a membrane to convert energy harvested in NADH into bonds in ATP. OUTER Intermembrane (periplasmic) space INNER e- NADH NAD + H+ STEP 1: NADH gives up electron to an electron acceptor protein in the membrane, splitting into NAD and H+ ions. NAD is RECYCLED at this step, so GLYCOLYSIS can continue!

21. 2. Anaerobic Respiration Electron Transport Chain across a membrane to convert energy harvested in NADH into bonds in ATP. OUTER Intermembrane (periplasmic) space H+ H+ e- INNER e- NADH NAD + H+ H+ Step 2: The electron is passed from protein to protein, across the inner membrane. This movement of negative charge draws H+ ions across through protein channels… H+ build up in the intermembrane space, creating a CHARGE DIFFERENTIAL.

22. 2. Anaerobic Respiration Electron Transport Chain across a membrane to convert energy harvested in NADH into bonds in ATP. OUTER Intermembrane (periplasmic) space H+ H+ H+ e- INNER ATP synthase e- NADH NAD ADP + P ATP Step 3: The charge differential is electric potential energy. Eventually, the differential is so great that H+ ions flow back through the membrane. The energy in this ‘current’ of charged particles is used to add P + ADP  ATP.

23. 2. Anaerobic Respiration Electron Transport Chain across a membrane to convert energy harvested in NADH into bonds in ATP. OUTER Intermembrane (periplasmic) space e- INNER ADP + P ATP e- NADH NAD S- H2S S H+ H+ Step 4: The electron(s) are accepted by a ‘final electron acceptor’. In anaerobic respiration, this is CO2, NO3, Fe, or S. And the anion formed reacts with H+ ions. THUS, ENERGY IN NADH IS USED TO MAKE BONDS IN ATP.

24. III. Cellular Respiration • Overview: • Glycolysis • Anaerobic Respiration Ethanol Fermentation: Some bacteria, plants, yeasts Lactate Fermentation: Some bacteria, animals

25. III. Cellular Respiration Overview: GLYCOLYSIS PYRUVATE METABOLISM Oxygen Absent? Oxygen Present? Anaerobic Respiration Or Fermentation Aerobic Respiration MORE ATP SOME ATP

26. III. Cellular Respiration • Overview: • Glycolysis • Anaerobic Respiration • Aerobic Respiration Occurs in: Aerobic bacteria Aerobic Archaea All Eukaryotes (in the mitochondria descended from aerobic bacteria!) GLYCOLYSIS OCCURS IN THE CYTOPLASM. THAT’S WHERE THE PYRUVATES ARE PRODUCED.

27. III. Cellular Respiration • Overview: • Glycolysis • Anaerobic Respiration C3 C2-CoA + CO2 Pyruvate Acetyl-CoA NAD NADH “Gateway Step” In Eukaryotes

28. REVIEW – ANAEROBIC RESPIRATION Incomplete Citric Acid Cycle CoA CoA – C2 NAD NADH (oxaloacetate) C6 C4 C5 + CO2 NAD NADH NAD FAD FADH2 NADH C4 + CO2 ADP + P ATP

29. Aerobic Respiration Citric Acid (“Krebs”) Cycle CoA CoA – C2 NAD NADH (oxaloacetate) C6 C4 C5 + CO2 NAD NADH NAD FAD FADH2 NADH C4 + CO2 ADP + P ATP The C5 molecule is recycled into oxaloacetate (C4), with the release of even MORE ENERGY trapped in ATP, NADH, and FADH

30. 2. Aerobic Respiration Electron Transport Chain across a membrane to convert energy harvested in NADH into bonds in ATP. OUTER Intermembrane (periplasmic) space H+ H+ H+ H+ H+ H+ e- INNER e- e- ADP + P ATP NADH NAD + H+ O2 2 O-- 2 H2O FADH FAD + H+ 2H+ 2H+ SAME THING: Electrons transferred, H+ ions pulled across membrane, and flood back across creating ATP. But O2 is the final electron acceptor, making WATER!! MORE electrons transferred, stronger ‘pull’ exerted by oxygen, more ATP made.

31. P 2 ADP + 2 2 ATP i Glycolysis Glucose LE 9-17a 2 Pyruvate 2 NAD+ 2 NADH CO2 2 + 2 H+ 2 Acetaldehyde 2 Ethanol Alcohol fermentation

32. P 2 ADP + 2 2 ATP i Glycolysis Glucose LE 9-17b 2 NAD+ 2 NADH + 2 H+ 2 Pyruvate Lactate 2 Lactate Lactic acid fermentation