BIOL 3800 Final

Aerobic Respiration

Glycolysis, Krebs, ETC

Goal of Aerobic Respiration

Make NADH + FADH2 → feed ETC → make ATP

Step 1 Glycolysis

Glucose → Glucose-6-Phosphate

Step 1 Glycolysis Enzyme

Hexokinase

Step 1 Glycolysis Function

Adds Phosphate (USES ATP) + cannot reverse step

Step 2 Glycolysis

Glucose-6-Phosphate → Fructose-6-Phosphate

Step 2 Glycolysis Enzyme

Phosphoglucose Isomerase

Step 2 Glycolysis Function

Rearrange Structure (no ATP used)

Step 3 Glycolysis

Fructose-6-Phosphate → Fructose-1,6-biphosphate

Step 3 Glycolysis Enzyme

PFK-1 (phosphofructokinase-1)

Step 3 Glycolysis Function

Rate Limiting Step (USES ATP)

Step 4 Glycolysis

Fructose-1,6-Biphosphate → DHAP → G3P

Step 4 Glycolysis Enzyme

Aldolase

Step 4 Glycolysis Function

Splitting Step, Converts into G3P and DHAP

Step 5 Glycolysis

DHAP → G3P

Step 5 Glycolysis Enzyme

Triose phosphate isomerase

Step 5 Glycolysis Function

DHAP converts to G3P as DHAP is unusable so converts to create 2 G3Ps

Step 6 Glycolysis

G3P → 1,3-Bisphospoglycerate

Step 6 Glycolysis Enzyme

G3P Dehydrogenase

Step 6 Glycolysis Function

Produces NADH! First energy capturing step

Step 7 Glycolysis

1,3-BPG → 3-Phosphoglycerate

Step 7 Glycolysis Enzyme

Phosphoglycerate kinase

Step 7 Glycolysis Function

Produces ATP, substrate level phosphorylation

Step 8 Glycolysis

3-Phosphoglycerate → 2-Phosphoglycerate

Step 8 Glycolysis Enzyme

Phosphoglycerate mutase

Step 9 Glycolysis

2-Phosphoglycerate → PEP

Step 9 Glycolysis Enzyme

Enolase

Step 10 Glycolysis

PEP → Pyruvate

Step 10 Glycolysis Enzyme

Pyruvate Kinase

Step 10 Glycolysis Function

Produces ATP, Irreversible Step

Glycolysis Summary per 1 Glucose

2 ATP (net), 2 NADH, 2 Pyruvate

Krebs Cycle Step 1 (Citrate Formation)

Oxaloacetate (4C) + Acetyl-CoA (2C) → Citrate (6C)

Krebs Cycle Step 1 Enzyme

Citrate Synthase

Krebs Cycle Step 1 Function

Start of Cycle, Combining molecules to form 6-Carbon Structure, Exergonic

Krebs Cycle Step 2

Citrate → Isocitrate

Krebs Cycle Step 2 Enzyme

Aconitase

Krebs Cycle Step 2 Function

Rearrangement, moves OH Group for oxidation

Krebs Cycle Step 3

Isocitrate → α-ketoglutarate (5C)

Krebs Cycle Step 3 Enzyme

Isocitrate dehydrogenase

Krebs Cycle Step 3 Function

CO2 Released, NAD+ → NADH

Krebs Cycle Step 4

α-Ketoglutarate → Succinyl-CoA (4C)

Krebs Cycle Step 4 Enzyme

α-Ketoglutarate dehydrogenase

Krebs Cycle Step 4 Function

CO2 Released, NADH Produced, CoA Added, Similar to Pyruvate dehydrogenase

Krebs Cycle Step 5

Succinyl CoA → Succinate

Krebs Cycle Step 5 Enzyme

Succinyl-CoA synthetase

Krebs Cycle Step 5 Function

Produces GTP, breaks CoA Bond (high energy) - uses to make ATP

Krebs Cycle Step 6

Succinate → Fumarate

Krebs Cycle Step 6 Enzyme

Succinate dehydrogenase

Krebs Cycle Step 6 Function

Produces FADH2, Not enough energy for NAD+ reduction

Krebs Cycle Step 7

Fumarate → Malate

Krebs Cycle Step 7 Enzyme

Fumarase

Krebs Cycle Step 7 Function

Adding water (hydrogen reaction)

Krebs Cycle Step 8

Malate → Oxaloacetate

Krebs Cycle Step 8 Enzyme

Malate dehydrogenase

Krebs Cycle Step 8 Function

NAD+ → NADH, Regenerates oxaloacetate

Krebs Cycle Output (Per 1 Acetyl-CoA)

3 NADH, 1 FADH2, 1 ATP (GTP), 2 CO2

Krebs Cycle Output (Per 1 Glucose OR 2 Acetyl-CoA)

6 NADH, 2 FADH2, 2 ATP, 4 CO2

ETC Location

Inner Mitochondrial Membrane

ETC Complex I

NADH Dehydrogenase

ETC Complex I Function

NADH Donates Electrons, Becomes NAD+, Pumps H+ into intermembrane

ETC Complex II

Succinate Dehydrogenase

ETC Complex II Function

FADH2 Donates Electrons, becomes FAD, no pumping protons

ETC Coenzyme Q

Ubiquinone

ETC Coenzyme Q Function

Carries electrons from Complexes I and II to Complex III

ETC Complex III Function

Passes Electrons Forward, Pumps H+

ETC Cytochrome C Function

Carries electrons to Complex IV

ETC Complex IV

Cytochrome C Oxidase

ETC Complex IV Function

Electrons + O2 → H2O, O2 is electron acceptor, pumps H+

ETC Complex V or ATP Synthase

Protons go back into matrix using ATP synthase, Oxidative Phosphorylation

ETC Main Point

Creates electrochemical gradient, High H+ outside, Low H+ inside

ATP Yield - NADH

2.5 ATPAT

ATP Yield - FADH2

1.5 ATP

TOTAL AEROBIC RESPIRATION ATP YIELD

30-32 ATP

Total ATP Yield Breakdown

Glycolysis-2 ATP, TCA-2 ATP, and ETC-26-28 ATP

Apical Region

Top side of epithelial cell, faces lumen, Intestine → Microvilli, Lungs → thin for gas exchange

Basolateral Region

Bottom side of epithelial cell, faces neighboring cells, responsible for cell anchoring + communication

Basement Membrane

Specialized ECM, Anchors epithelial cells, provides structural support, 2 Layers (Basal and Reticular lamina)

Basement Membrane Function

Anchors, Selective Barrier, and Scaffolding, Laminin and Collagen

Basal Lamina

Part of Basement Membrane-Touches cell. Made up of Laminin, Collagen, and Proteoglycans

Basal Lamina Function

Cell Attachment, Selective Filtration, and Guides Cell Movement

ECM (Extracellular Matrix)

Network of proteins and carbs that surround the cell, holds tissue together, and allows cells to communicate. Made up of proteins, proteoglycans, and adhesive glycoproteins

ECM (Extracellular Matrix) Functions

Structural support, cell adhesion, cell signaling, and tissue repair

Hemidesmosome

Connects cytoskeleton to basal lamina, Integrins

Desmosomes

Connects cell to cell-uses cadherins, connects to keratin

Adherens Junctions

Connects actin filaments via cadherins to other actin filaments in another cell

Tight Junctions

The continuous barrier between adj. cells, helps maintain polarity, made up of claudins and occludins,

Tight Junctions-Transcelluar

Substance moves through the cell

Tight Junctions-Paracellular

Substances move between cells

Gap Junctions

The tiny tunnels between cells, allow for ions and molecules to pass, made up of connexins

Homophilic Interaction

Same molecule binds to the same molecule (ex. Cadherin ←→ Cadherin) REQUIRE Ca2+

Heterophilic Interaction

Different molecule bind (Ex. Integrin ←→ ECM Protein), determines cell structure

Cadherin

Cell adhesion molecules, mediate cell-to-cell adhesion, bind other cadherins on other cells, help maintain tissue structure. REQUIRES Ca2+

Lectin

Helps bind sugar chains on cell surfaces, helps with cell recognition and signaling, covered in carb patterns, heterophilic interactions

Selectins

Binds carbs, important w/ immune cell movement

Ig-superfamily CAMs

Immune Related, either homo or heterophilic

CAMs (Cell Adhesion Molecules)

Proteins that help with cell-to-cell adhesion and cell-to-ECM adhesion. Functions: Adhesion, cell signaling, cell migration, tissue organization

Collagen

Main structural protein in ECM, triple helix structure (polypeptide chains), Repeating Seq. Gly-X-Y (X-usually proline Y-usually hydroxyproline)

Elastin

Forms elastic fibers, provides elasticity, cross-linked network, stretch and recoil

Proteoglycans

Made up of protein core and GAGs (long sugar chains), NEG CHARGE, attract water, resists compression, looks like bottle brush

Fibronectin

Biological Glue, binds integrins, collagen, and proteoglycans. Connects Cell ←→ ECM and ECM ←→ ECM. Contains RGD-binding site for integrins