Biochemistry and Cell Biology: Membranes, Glycoproteins, and Metabolic Pathways

Ricin experiment: What removes surface-bound ricin?

Lactose (competitive binding)

Does dihydroxyacetone have a chiral carbon?

No

Are all (C·H₂O)n monosaccharides reducing sugars?

No

Is sucrose a reducing sugar?

No

Is lactose a reducing sugar?

Yes

Amino acids binding sulfated heparan sulfate domains?

Lysine (K)

Which does NOT distinguish glycoproteins vs proteoglycans?

All statements describe differences

Which protein glycosylation statement is FALSE?

N-linked oligosaccharides attach to Asn and Lys

Fatty acids always contain even # carbons?

False

Glycerophospholipids have nonpolar head and polar tail?

False

PUFAs have lower melting point than saturated fats?

True

Which statement about linoleic acid is FALSE?

Forms a bilayer in water

Identify fatty acid shown (linolenic acid).

16:1(Δ10)

Headgroup shared by sphingomyelin and a glycerophospholipid?

Phosphatidylcholine

Protein dissociating with NaCl is what type?

Peripheral membrane protein

Which membrane protein has hydrophobic surface regions?

Integral membrane protein

Residues needed to span membrane as α-helix?

20

Why don't hydropathy plots detect β-strands?

They may not be exclusively hydrophobic and are too short

Why abundant regular secondary structures in membranes?

Regular structures fully hydrogen-bond the backbone

Which describes CH₃(CH₂)₁₅-PO₃⁻-CH₂CH₂-N⁺(CH₃)₃?

Amphiphilic

Which curve shows facilitated diffusion?

Green curve (plateau)

Can a uniporter be secondary active transport?

No

Can a uniporter be primary active transport?

No

True for both primary and secondary active transport?

Require free energy to move a substance against gradient

Which is NOT a feature of active transport?

Non-specific substrate recognition

PDH prosthetic group

TPP

Activator of PDH

ADP

CAC enzyme in ETC

Succinate dehydrogenase

Reaction releasing CO₂

Isocitrate → α-ketoglutarate

CAC intermediate for gluconeogenesis

Oxaloacetate

Why CAC is amphibolic

Provides both energy and biosynthetic precursors

Enzyme replenishing OAA during fasting

Pyruvate carboxylase

ATP yield from pyruvate oxidation

~12.5 ATP

ATP cost of fatty acid activation

2 ATP equivalents

Molecule transporting fatty acyl-CoA into mitochondria

Carnitine

Step producing FADH₂ in β-oxidation

First oxidation

ATP yield of palmitate oxidation

106 ATP

Products per β-oxidation round

NADH, FADH₂, acetyl-CoA

Rate-limiting step of FA entry

Carnitine acyltransferase I

Inhibitor of β-oxidation

Malonyl-CoA

Hormones that increase lipolysis

Glucagon & epinephrine

Rounds of β-oxidation for C20 FA

9

First step of β-oxidation resembles

Dehydrogenation

Committed step of FA synthesis

Malonyl-CoA formation (ACC)

Carrier in fatty acid synthesis

ACP

Molecule transferring acetyl-CoA to cytosol

Citrate

Allosteric activator of ACC

Citrate

Reductive enzyme in FA synthesis

Fatty acid synthase

Protons pumped per NADH

10

Protons pumped per QH₂

6

Final electron acceptor in ETC

O₂

Complex that does not pump protons

Complex II

Two-electron carrier

Coenzyme Q

Q cycle occurs in

Complex III

Electrons needed to reduce O₂ to H₂O

4

Complex using heme-Cu centers

Complex IV

Cyanide inhibits

Complex IV

Rotenone inhibits

Complex I

Rotating parts of ATP synthase

γ-subunit and c-ring

Number of β-subunits producing ATP

3

Conformation that releases ATP

Open

Force driving ATP synthase rotation

Proton flow

Process uncoupled in thermogenesis

Proton gradient & ATP synthesis

P/O ratio for NADH

2.5

P/O ratio for FADH₂

1.5

Glycerol-3-phosphate shuttle donates to

FAD (Complex II)

Reversible shuttle

Malate-aspartate shuttle

ATP per full rotation of c₈ ring

3

Link between glycolysis & CAC

PDH complex

High NADH/NAD⁺ ratio effect

Inhibits PDH and CAC

Acetyl-CoA activates during fasting

Pyruvate carboxylase

Effect of ETC inhibition on NADH

NADH increases

Pathway requiring NADPH

Fatty acid synthesis