Lipids And Membranes

Question 1

What are lipids

Answer 1

Non polar organic compounds
Not soluble in water, soluble in non polar solvents
Used in membrane formation, energy storage, precursors of signalling molecules

Question 2

What does a fatty acid contain

Answer 2

Carboxylic acid which is polar and hydrophilic
Unbranched hydrocarbon chain which is non polar and hydrophobic

Question 3

How does c=c bond affect melting point

Answer 3

As the number of C=C bonds increase, the melting point of the lipid decreases

Question 4

Why does a c=c affect melting point

Answer 4

Alkene= geometric isomerism (cis/trans)
Chains are bulky and bend
More C=C means more bending
Affects the ability of hydrocarbon chains to pack together
Low mp

Question 5

What are polyunsaturated fatty acids

Answer 5

Precursors for biosynthesis of important signal molecules

Question 6

What are triacylglycerols

Answer 6

Energy storage in fat cells and released by hydrolysis for energy productions
One molecule of fatty acid to form 3 ester links

Question 7

What are phospholipids

Answer 7

Used in biological membranes= phospholipid bilateral
Amphipathic= both hydrophilic and hydrophobic
Phosphate group

Question 8

What is cholesterol

Answer 8

Used for structural=c part of cell membranes to increase membrane fluidity
Used as a biosynthesis precursor for bit D, bile acids and steroid hormones

Question 9

What do membranes do

Answer 9

Provide structure and control localisation of nutrients
Control the internal conditions of each compartment
Control which molecules can come in and out (nutrients+ waste)
Cellular communication

Question 10

What type of self assembled structures can form lipids

Answer 10

Miscelles
Phospholipid bilayer
Liposomes= hollow aq centre which can be used for drug delivery

Question 11

Characteristics of lipid bilayer

Answer 11

Fluid= gives bilayers flexibility
Impermeable to anything charged/polar= allows cell to retain things it needs to function/ stops leakage of essential nutrients
Transport proteins= allows access for a specific molecule

Question 12

What are integral proteins

Answer 12

Embedded in the bilayer and only removed by disruption of the membrane by detergents
Transmembrane proteins

Question 13

What are peripheral proteins

Answer 13

Loosely attached to one face of the membrane
Removed by mild changed of ph or ionic strength

Question 14

What are transmembrane proteins

Answer 14

Allow entry/exit of polar molecules which cannot cross the bilayer
Big proteins allowing polar compounds to lass without coming in contact with fatty acid tails

Question 15

Passive diffusion

Answer 15

Transfer of solutes or ions down conc gradient
No energy expenditure
Can be facilitated by a specific carrier proteins

Question 16

Ligand gating

Answer 16

Ion channel opens in response to the binding of a particular molecule

Question 17

Voltage gating

Answer 17

Where the channel opens in response to a change in membrane potential

Question 18

Types of carrier proteins

Answer 18

Uniporters transport only one type of solute
Co-transporters transfer 2 different solutes

Question 19

Types of co transporter

Answer 19

Symporters= carries 2 solutes across the membrane in the same direction
Anti-otters= transport one solute in one direction and a different solute in the opposite direction (countertransport)

Question 20

Glucose transport

Answer 20

1) epithelial cell/blood surface, the Na+/K+ ATPase anti potter uses ATP to drive the active transport of K+ into the epithelium and Ns+ out of it, decreasing the concentration of Na+
2) Na+ moves down its concentration gradient from the gut lumen into the cell via the Na+ glucose symporter, providing the free energy to bring glucose into the cell from the gut lumen against its concentration gradient. This creates Hugh glucose concentration inside the epithelial cell
3) glucose flows down its conc gradient into the blood via a glucose uniporter

Question 21

Ion pump

Answer 21

1) Ca2+ bonds closed channel on cytoplasmic side
2) atp binds nucleotide binding site
3) atp hydrolysis, releasing energy
4) energy dependent conformational changes releases ca2+ into er
5) phosphate hydrolysis
6) channel reverts to closed state

Question 22

Pinocytosis

Answer 22

Uptake of fluid in vesicles

Question 23

Phagocytosis

Answer 23

Uptake or large particles forming a vacuole

Question 24

Receptor mediated endocytosis

Answer 24

Some molecules are selectively taken up in vesicles when bound by a specific receptor proteins on the cell surface