Exam 3

What is the main difference between membrane lipids and storage lipids?

Membrane lipids are polar and storage lipids are neutral

How does chain length and saturation affect the melting point of fatty acids?

Longer chains increase melting point, and saturated fats have higher melting points than unsaturated fats.

What are the main types of lipids, and what is an example of each?

Phospholipids (e.g., phosphatidylcholine), sphingolipids (e.g., sphingomyelin), glycolipids, waxes, and sterols (e.g., cholesterol).

What is a distinguishing feature of sphingolipids compared to phospholipids?

Sphingolipids have a sphingosine backbone, while phospholipids have a glycerol backbone.

What are the four main types of membrane phospholipids, and why are they important?

Phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), and sphingomyelin (SM); they contribute to membrane structure and function.

Describe the three types of membrane proteins.

Integral (span the bilayer), peripheral (loosely attached to membrane surfaces), and anchored (covalently attached to lipids or carbohydrates on the membrane).

How do anchored proteins differ from integral and peripheral proteins?

Anchored proteins are attached to the membrane via covalently bound lipids or carbohydrates, while integral proteins span the bilayer and peripheral proteins attach loosely to the surface.

What are the primary structures that lipids form in water?

Monolayers, micelles, bilayers, and vesicles.

What role does cholesterol play in membrane fluidity?

Cholesterol modulates membrane fluidity by making membranes less permeable and stabilizing them at varying temperatures.

What is the fluid mosaic model?

A model describing the membrane as a flexible layer with proteins embedded within or associated with the lipid bilayer.

What is membrane asymmetry?

The distribution of lipids and proteins differs between the inner and outer leaflets of the bilayer, which affects membrane function.

What functions do flippase, floppase, and scramblase serve in a cell membrane?

They help move lipids between membrane leaflets: flippase and floppase move specific lipids in one direction, while scramblase moves lipids bidirectionally.

What types of molecules can pass freely through a lipid bilayer, and which require transporters?

Small, nonpolar molecules can pass freely, while ions and polar molecules typically require transporters.

Describe the purpose of a FRAP experiment.

FRAP (Fluorescence Recovery After Photobleaching) measures lipid mobility within the bilayer by tracking the recovery of fluorescence.

What is the Kennedy-Rothman experiment, and what does it study?

It studies vesicle fusion with membranes, helping to understand lipid and protein dynamics in membranes.

What are lipid rafts, and what is their function?

Lipid rafts are microdomains rich in cholesterol and sphingolipids that organize signaling proteins and membrane trafficking.

How are membrane transporters classified?

Transporters are classified as symport (same direction), antiport (opposite directions), and uniport (single substance transport).

How do you calculate Km and kcat for a transporter?

By using the Michaelis-Menten equation, which models the rate of substrate transport.

What are the five nucleobases in nucleic acids?

Adenine (A), Thymine (T), Guanine (G), Cytosine (C), and Uracil (U).

What components make up a nucleotide?

A phosphate group, a sugar (ribose or deoxyribose), and a nitrogenous base.

What is the difference between a nucleotide, nucleoside, and nucleobase?

A nucleotide includes the phosphate, sugar, and base; a nucleoside is only the sugar and base; and a nucleobase is just the base.

What are the base-pairing rules in DNA?

Adenine pairs with Thymine (A-T), and Guanine pairs with Cytosine (G-C).

What is the structure of double-stranded DNA?

It is an antiparallel double helix with base-stacking interactions between paired bases.

What role does DNA polymerase play in replication?

DNA polymerase synthesizes DNA in the 5' to 3' direction, requiring a primer and Mg²⁺ ions.

What are the key steps and reagents for PCR?

Denaturation, annealing, and extension, with DNA template, primers, nucleotides, and DNA polymerase.

What is Sanger sequencing used for?

It determines DNA sequence using dideoxynucleotides to terminate replication at specific bases.

How does DNA electrophoresis work?

It separates DNA fragments by size as they move through a gel in an electric field.

How do you identify a redox reaction?

Look for changes in oxidation states, where one species is oxidized (loses electrons) and another is reduced (gains electrons).

What distinguishes high-energy from low-energy phosphoryl and carbonyl groups?

High-energy groups release more free energy upon hydrolysis compared to low-energy groups.

What makes ATP a reactive molecule?

ATP contains high-energy phosphoanhydride bonds that release energy when hydrolyzed.

Why is coupling reactions important in bioenergetics?

Coupling allows non-spontaneous reactions to occur by pairing them with spontaneous reactions, making the overall process favorable.

How do you calculate ΔG for a reaction?

Use the equation ΔG = ΔG°' + RT lnQ, or by summing ΔG values for coupled reactions.

How do you find ΔG from Keq?

ΔG°' = -RT lnKeq, which relates standard free energy to the equilibrium constant.