Chapters on Oxidative Phosphorylation, Carbohydrates, and Lipids

Oxidative phosphorylation

Generates ATP, about 28 of 32 total ATP from glucose catabolism

Chemiosmotic theory

ATP is synthesized by proton movement across the mitochondrial membrane

Inner mitochondrial membrane sides

"P" side (intermembrane space, high H+), "N" side (matrix, low H+)

Complex I

Oxidizes NADH

Complex II

Oxidizes FADH2

Complexes I-IV roles

Transfer electrons and pump protons to create a gradient

Protons translocated by Complex I

4 protons

Protons translocated by Complex III

4 protons

Protons translocated by Complex IV

2 protons

Q cycle

Process in Complex III that converts 2e- to two 1e- transfers, reduces cytochrome c

ATP synthase function

Synthesizes ATP using energy from proton flow

F1 subunit states

L (loose), T (tight), O (open)

Protons for 360° rotation

About 10 H+, or ~3.33 per 120° rotation

Electron transport chain inhibitors

Rotenone, Antimycin A, Cyanide, Carbon monoxide

Uncoupling the ETC

Stops ATP synthesis, generates heat

Oxidative phosphorylation regulation

By ADP/ATP ratio and NADH/NAD+ levels

Complex II role

Complex II, also known as succinate dehydrogenase, also transfers electrons to the electron transport chain.

Q cycle location

Complex III

Oligomycin effect

Lowers ATP synthesis by inhibiting Complex V

Most ATP production process

Electron transport system (via proton-motive force)

Carbohydrates elements

Carbon, hydrogen, and oxygen

Carbohydrates general formula

(CH2O)n

Major carbohydrate types

Simple sugars, polysaccharides, glycoconjugates

Oligosaccharides

Simple sugars with 3-20 residues

Cellulose bonds

β-1,4 glycosidic bonds

Starch bonds

α glycosidic bonds

Chitin

Structural polysaccharide in exoskeletons, has β-1,4 bonds

Glycoconjugate

Carbohydrate bound to protein or lipid

Glycosyltransferase

Enzyme that forms glycosidic bonds

Glycosidase function

Breaks glycosidic bonds

Cellulose strength force

Hydrogen bonding

Human sugar storage molecule

Glycogen

Glycobiology

Study of glycans and glycoconjugates

Proteoglycans

Glycoconjugates mostly made of carbohydrate, found in ECM

ABO blood groups components

Glycoproteins and glycolipids

Lipids main functions

Energy storage, membrane structure, signaling

Saturated vs unsaturated fats

Saturated = no C=C, Unsaturated = at least one C=C

Trans fats

Partially hydrogenated unsaturated fats

Saponification

Fat hydrolysis with lye to make soap

triacylglycerols

3 fatty acids esterified to glycerol

three membrane lipid types

Glycerophospholipids, sphingolipids, cholesterol

lipid rafts

Densely packed membrane microdomains with signaling proteins

cholesterol's role in membranes

Regulates fluidity and structure

β-oxidation

Fatty acid breakdown to generate acetyl-CoA, NADH, FADH2

where does β-oxidation occur

In the mitochondrial matrix

carnitine shuttle

Transfers fatty acyl-CoA into mitochondria

four steps of β-oxidation

Dehydrogenation, hydration, oxidation, thiolysis

ketogenesis

Produces acetoacetate and D-β-hydroxybutyrate

where does ketogenesis occur

In the liver during starvation

first step in fatty acid synthesis

Formation of malonyl-CoA from acetyl-CoA

multifunctional enzyme in fatty acid synthesis

Fatty acid synthase

rate-limiting enzyme in cholesterol synthesis

HMG-CoA reductase

statins

Inhibit HMG-CoA reductase

lipoproteins

Lipid transport particles with a phospholipid monolayer

classes of lipoproteins

Chylomicrons, VLDL, LDL, HDL

HDL

Returns cholesterol to the liver

four stages of cholesterol synthesis

Mevalonate, isoprene, squalene, lanosterol/cyclization

abbreviation and symbol for glucose

Glc, blue circle (🔵)

abbreviation and symbol for galactose

Gal, red circle (🔴)

abbreviation and symbol for mannose

Man, green circle ()

abbreviation and symbol for fructose

Fru, purple star ()

abbreviation and symbol for N-acetylglucosamine

GlcNAc, blue square (🔷)

abbreviation and symbol for N-acetylgalactosamine

GalNAc, yellow square (🔶)

abbreviation and symbol for fucose

***, red triangle ()

abbreviation and symbol for xylose

Xyl, yellow star ()

abbreviation and symbol for sialic acid

Neu5Ac, purple diamond (🔺)

amino sugars

Sugars modified with NH₂ instead of OH, e.g., GlcNAc, GalNAc

sugar acids

Oxidized sugars with -COOH, e.g., GlcA, GalA

sulfated sugars

Sugars with sulfate groups, common in glycosaminoglycans, e.g., GlcNS

acylated sugars

Sugars modified with acetyl or fatty acid groups, e.g., Neu5Ac

glycoproteins

Proteins with attached glycans, important for recognition and signaling

proteoglycans

Proteins with long glycosaminoglycan chains, structural components in ECM

glycolipids

Lipids with covalently attached sugars, found in membranes

peptidoglycans

Cross-linked carbohydrate structures in bacterial cell walls targeted by antibiotics