DAT Cellular Respiration (copy)

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Glucose → ATP

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Cellular Respiration

28 Terms

1

Glucose → ATP

  1. Glycolysis

  2. Pyruvate decarboxylation

  3. TCA (Krebs cycle)

  4. Electron transport chain

<ol><li><p>Glycolysis</p></li><li><p>Pyruvate decarboxylation</p></li><li><p>TCA (Krebs cycle)</p></li><li><p>Electron transport chain</p></li></ol>
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Glycolysis

  • Break down of glucose

  • Anaerobic (no O2)

  • 1 glucose mol. (6 Carbons) → 2 pyruvate mols. (3 Carbons)

    • 2 ATP input → 4 ATP output & 2 NADH = 2 net ATP mols. & 2 NADH

  • Occurs in cytosol (not in organelle)

  • Steps:

    1. Hexokinase: phosphorylates glucose → Glucose-6-phosphate → irreversible rxn

    2. Phosphofructokinase (PFK): phosphorylates Glucose-6-phosphate → Fructose-1,6-bisphosphate → rate limiting step

<ul><li><p>Break down of glucose</p><p></p></li><li><p>Anaerobic (no O2)</p><p></p></li><li><p><mark data-color="yellow">1 glucose mol. (6 Carbons) → 2 pyruvate mols. (3 Carbons)</mark></p><ul><li><p>2 ATP input → 4 ATP output &amp; 2 NADH = <mark data-color="red">2 net ATP mols. &amp; 2 NADH</mark></p><p></p></li></ul></li><li><p>Occurs in cytosol (not in organelle)</p><p></p></li><li><p>Steps:</p><ol><li><p><mark data-color="red"><strong>Hexokinase:</strong></mark> phosphorylates glucose → <u><strong>Glucose-6-phosphate</strong></u> → irreversible rxn</p><p></p></li><li><p><mark data-color="red"><strong>Phosphofructokinase (PFK):</strong></mark> phosphorylates Glucose-6-phosphate → <u><strong>Fructose-1,6-bisphosphate</strong></u> → rate limiting step</p></li></ol></li></ul>
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Most oxidized form of Carbon

  • CO2

  • Waste product of cellular respiration (occurs via oxidation)

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4

Oxidation rxns

  • ADP + Pi → ATP (oxidized)

  • NAD+ + FAD+ → FADH2 + NADH (oxidized)

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Mitochondria

  • Double layered

  • Outer membrane

  • Intermembrane space: H+ build up

  • Matrix:

    • Krebs cycle → produces ATP

    • β-oxidation to break down fatty acids

  • Inner membrane: many folds to ↑ surface area → ↑ electron transport chain output

<ul><li><p>Double layered</p><p></p></li><li><p>Outer membrane</p></li></ul><p></p><ul><li><p><mark data-color="red"><strong>Intermembrane space:</strong></mark> H+ build up</p><p></p></li><li><p><mark data-color="red"><strong>Matrix:</strong></mark></p><ul><li><p><mark data-color="yellow">Krebs cycle</mark> → produces ATP</p></li><li><p>β-oxidation to break down fatty acids</p><p></p></li></ul></li><li><p><mark data-color="red"><strong>Inner membrane</strong></mark>: many folds to ↑ surface area → <mark data-color="yellow">↑ electron transport chain output</mark></p></li></ul>
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Pyruvate decarboxylation

  • Occurs in mitochondrial matrix

  • Aerobic process

  • 2 pyruvate molecules from glycolysis transported into matrix via secondary active transport using protons (doesn’t directly use ATP)

  • 1 Pyruvate + Coenzyme A → Acetyl CoA + 1 NADH + 1 CO2

    • Pyruvate decarboxylate complex (PDC) catalyzes rxn

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How many CO2 and NADH yield from the breakdown of 1 glucose?

2 CO2 + 2 NADH

<p>2 CO2 + 2 NADH</p>
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8

TCA (Krebs cycle) / Citric Acid Cycle

  • Occurs in mitochondrial matrix

  • Aerobic process

  • 1 Acetal CoA + oxaloacetate → citrate

    • Citrate further oxidizes until oxaloacetate is formed and the cycle repeats

  • Full cycle yields: 3 NADH + 1 FADH2 + 1 GTP (ATP) + 2 CO2

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Electron transport chain (ETC)

  • Occurs in inner membrane / cristae of mitochondria

  • Aerobic process

  • Removes e- from glucose, pyruvate and Acetyl CoA

  • Oxidative phosphorylation occurs here

  • Carrier proteins (I, II, III, IV) in inner membrane (electron acceptors): receive electrons from electron transporters (NADH, FADH2) → pump protons against [ ] gradient into intermembrane space to supply energy to ATP synthase

    • Highly acidic environment in intermembrane space

    • CoQ (Ubiquinon): can be fully oxidized and reduced during passing of electrons b/w protein complexes

      • Soluble carrier

    • Cyt C (Cytochrome C): bound to Iron atom which transfers electrons b/w Complex III and Complex IV for redox rxns

      • Protein carrier

      • Used for genetic relations

  • Final electron acceptor (after electrons have passed though all proteins): Oxygen → combines w/ H+ to form H2O

  • ATP Synthase: drives protons down the gradient towards matrix (high [ ] → low [ ]) to catalyze ADP + Pi → ATP

    • pH + Electrical Gradient: Proton Motive Force

    • If pH of intermembrane space is higher than normal → less H+ → less cellular respiration occurring

  • NADH creates more ATP (3x) than FADH2 (2x)

    • NADH pumps more protons to carrier proteins than FADH2 because NADH enters the protein complex earlier than FADH2 and it enters Complex I (FADH2 enters Complex II)

  • Total glucose produced = 36 ATP in eukaryotes and 38 in prokaryotes (no mitochondria so don’t need to pump NADH into matrix → saving 2 ATP during glycolysis)

<ul><li><p>Occurs in <mark data-color="yellow"><strong>inner membrane / cristae</strong> of mitochondria</mark></p><p></p></li><li><p>Aerobic process</p><p></p></li><li><p>Removes e- from glucose, pyruvate and Acetyl CoA</p><p></p></li><li><p><mark data-color="red"><strong>Oxidative phosphorylation</strong></mark> occurs here</p></li></ul><p></p><ul><li><p><mark data-color="red"><strong>Carrier proteins (I, II, III, IV)</strong></mark> <strong>in inner membrane (electron acceptors):</strong> receive electrons from electron transporters (NADH, FADH2) → pump protons against [ ] gradient into intermembrane space to <mark data-color="yellow">supply energy to ATP synthase</mark></p><ul><li><p>Highly acidic environment in intermembrane space</p></li><li><p><mark data-color="red">CoQ (Ubiquinon):</mark> can be fully oxidized and reduced during passing of electrons b/w protein complexes</p><ul><li><p><mark data-color="yellow">Soluble carrier</mark></p></li></ul></li><li><p><mark data-color="red">Cyt C (Cytochrome C):</mark> bound to Iron atom which transfers electrons b/w <mark data-color="yellow"><strong>Complex III and Complex IV</strong></mark> for redox rxns</p><ul><li><p><mark data-color="yellow">Protein carrier</mark></p></li><li><p>Used for genetic relations</p><p></p></li></ul></li></ul></li><li><p><mark data-color="yellow">Final electron acceptor</mark> (after electrons have passed though all proteins): <mark data-color="red"><strong>Oxygen</strong></mark> → combines w/ H+ to form H2O</p></li></ul><p></p><ul><li><p><mark data-color="red"><strong>ATP Synthase:</strong></mark> drives protons down the gradient towards matrix (high [ ] → low [ ]) to catalyze ADP + Pi → ATP</p><ul><li><p><mark data-color="yellow">pH + Electrical Gradient: <strong>Proton Motive Force</strong></mark></p></li><li><p>If pH of intermembrane space is higher than normal → less H+ → less cellular respiration occurring</p></li></ul></li></ul><p></p><ul><li><p>NADH creates more ATP (3x) than FADH2 (2x)</p><ul><li><p>NADH pumps more protons to carrier proteins than FADH2 because NADH enters the protein complex earlier than FADH2 and it enters Complex I (FADH2 enters Complex II)</p></li></ul></li></ul><p></p><ul><li><p><mark data-color="yellow">Total glucose produced = 36 ATP in eukaryotes and 38 in prokaryotes (no mitochondria so don’t need to pump NADH into matrix → saving 2 ATP during glycolysis)</mark></p></li></ul>
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10

Oxidative phosphorylation

Process of ADP → ATP from NADH and FADH2 via passing of e- through various carrier proteins in the electron transport chain

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11

Electron carriers

NADH and FADH2

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12

What are the products of 1 Glucose molecule that has only undergone the Krebs cycle?

1 glucose → 2 pyruvate → 2 acetyl CoA → 6 NADH + 2 FADH2 + 2 GTP + 4 CO2

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13

Fermentation

  • Occurs when [O2] is too low to carry out aerobic processes in mitochondria

  • NAD+ formation prioritized to form NADH

  • Alcohol fermentation

  • Lactic Acid fermentation

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14

Alcohol fermentation

  • Fungi (yeast), bacteria, plants

  • Reduces pyruvate (from glycolysis) → acetaldehyde + CO2 → ethanol (by product) in a process that oxidizes NADH → NAD+

  • Acetaldehyde is the final e- acceptor from NADH

<ul><li><p>Fungi (yeast), bacteria, plants</p><p></p></li><li><p>Reduces pyruvate (from glycolysis) → <mark data-color="red">acetaldehyde</mark> + CO2  → <mark data-color="red">ethanol</mark> (by product) in a process that oxidizes NADH → NAD+</p><p></p></li><li><p>Acetaldehyde is the final e- acceptor from NADH</p></li></ul>
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Lactic Acid Fermentation

  • Occurs in muscle cells

  • Use glycolysis to produce 2 pyruvate mols.

  • Pyruvate reduced to lactate (by-product) → oxidizes NADH → NAD+

    • Lactate (weak base) → Lactic acid (strong acid)

  • Cori Cycle: lactate from muscle cells transported into blood stream → liver → converted to glucose → blood stream → used to generate ATP through glycolysis

<ul><li><p>Occurs in muscle cells</p></li></ul><p></p><ul><li><p>Use glycolysis to produce 2 pyruvate mols.</p></li></ul><p></p><ul><li><p>Pyruvate reduced to lactate (by-product) → oxidizes NADH → NAD+</p><ul><li><p>Lactate (weak base) → Lactic acid (strong acid)</p><p></p></li></ul></li><li><p><mark data-color="red"><strong>Cori Cycle:</strong></mark> lactate from muscle cells transported into blood stream → liver → converted to glucose → blood stream → used to generate ATP through glycolysis</p></li></ul>
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16

Catabolic rxns

Releases energy by breaking down large molecules into smaller molecules

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Anabolic rxns

Requires energy to build molecules from smaller molecules

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Cellular metabolism

Anabolic & Catabolic rxns

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19

What happens if a cell does not have glucose?

  1. Uses other carbohydrates

  2. Lipids

  3. Proteins (last resort)

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<p>Carbohydrates as a source of energy</p>

Carbohydrates as a source of energy

  • Glycogen (polysacc.): storage for glucose

    • found mainly in muscle and liver cells

  • Glycogenesis: formation of glycogen (glucose → glycogen)

  • Glycogenolysis: break down of glycogen (glycogen→glucose)

  • Glucose-6-phosphate main molecule for rxn

  • Regulated by Insulin and glucagon

  • First broken down in mouth → stomach → duodenum → small intestine

  • Disaccharides hydrolyzed into monosaccharides → converted to glucose or glycolytic intermediates

  • All cells can store glycogen but only skeletal muscle and liver cells can store large amounts

<ul><li><p>Glycogen (polysacc.): storage for glucose</p><ul><li><p>found mainly in muscle and liver cells</p><p></p></li></ul></li><li><p><mark data-color="red"><strong>Glycogenesis:</strong></mark> formation of glycogen (glucose → glycogen)</p><p></p></li><li><p><mark data-color="red"><strong>Glycogenolysis</strong></mark>: break down of glycogen (glycogen→glucose)</p><p></p></li><li><p>Glucose-6-phosphate main molecule for rxn</p></li></ul><p></p><ul><li><p>Regulated by Insulin and glucagon</p></li></ul><p></p><ul><li><p>First broken down in mouth → stomach → duodenum → small intestine</p></li></ul><p></p><ul><li><p>Disaccharides hydrolyzed into monosaccharides → converted to glucose or glycolytic intermediates</p></li></ul><p></p><ul><li><p>All cells can store glycogen but <mark data-color="yellow">only skeletal muscle and liver cells</mark> can store large amounts</p></li></ul>
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21

Gluconeogenesis

  • Forming glucose from non-carbs

  • Occurs in liver and kidney

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22

Why is phosphate added to a glucose molecule?

To keep the molecule w/n the cell and prevent it from diffusing out of the cell

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Insulin

  • Endocrine hormone

  • Released by pancreas when glucose ↑

  • Triggers cells to:

    • make glycogen from glucose for storage

    • undergo glycolysis to form ATP → activates Phosphofructokinase (R.D.S)

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Glucagon

  • Released by pancreas when glucose ↓

  • Similar to epinephrine (triggers formation of glucose)

  • Triggers cells to:

    • Glycogenolysis to form glucose

    • Inhibit glycogenesis to inhibit glycogen production

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25

Lipids as a source of energy

  • Long hydrocarbon chains that are highly reduced → have more energy than carbs

  • Triglycerides: 1 glycerol backbone bound to 3 fatty acid chains

  • Lipases in adipose tissue are hormone sensitive (e.g., to glucagon)

  • Lipolysis: break down of lipids into glycerol and the fatty acids by lipase enzymes

    • Glycerol → Glyceraldehyde 3 Phosphate (DAP/G3P/PGAL) → enters glycolysis

    • Fatty acid chains activated by 2 ATPβ-oxidation of saturated FA in mitochondrial matrix (breaks 2 carbons at the β position) → 1 NADH + 1 FADH2 and 1 Acetyl CoA → citrate in Krebs cycle → 120 ATP generated

    • β-oxidation of unsaturated FA → 1 less FADH2 for each double bond

  • Lipids combine w/ soluble proteins → lipoproteins (contain Apoproteins)

    • Classified by density (fat : protein ratio)

    • B/w meals, most lipids in plasma are in the form of lipoproteins

  • Lipoproteins large and less dense when ratio is also large

    • Chylomicrons: first fat transporters to leave enterocyte and enter lacteals (small lymphatic vessels)

    • LDL (low protein density): unhealthy due to high fat content

    • HDL (high protein density): healthy cuz transport fat away from tissues → liver → cholesterol for bile → expelled during digestion

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What carries fatty acids in blood?

Albumin

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Lipid digestion

  • Stored as adipose tissue

  • Only broken down in duodenum:

  1. Bile released from gall bladder to emulsify fats & pancreatic lipase to break down lipids into FA chains and monoacylglycerides

  2. Absorbed into enterocytes of small intestine

  3. Reassembled into triglycerides, and then, along with cholesterol, proteins or phospholipids → packaged into chylomicrons

  4. Chylomicrons move to lymph capillary → circulatory system

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Proteins as a source of energy

  • Excess amino acids used for energy

  • Oxidative deamination: removal of amino group to form metabolic intermediates (Acetyl CoA, pyruvate, Oxaloacetate)

    • Directly removes ammonia from AA

    • Deamination in liver

    • By-product: NH3 (ammonia) → urea → excreted as urine in mammals

      • Uric acid in insects, birds, reptiles

  • Digestion occurs in stomach: pepsin breaks down proteins into polypeptides

  • In the small intestine: trypsin breaks down specific polypeptides into amino acids

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