cell biology 2

Question 1

what are the functions of the cell membrane

Answer 1

• selectively permeable
• concentration gradient
• structural scaffold

Question 2

what are the components of the cell membrane

Answer 2

• amphiphilic lipid bilayer - 5mm thick
• membrane proteins - 30% of genome

Question 3

what does amphiphilic mean

Answer 3

molecule which has a hydrophobic and hydrophilic end

Question 4

what ways to lipids move

Answer 4

• lateral diffusion - left to right
• flip-flop - membrane flips
• flexion - tails move
• rotation - spinning

Question 5

what are the properties determining membrane fluidity

Answer 5

• melting temperature - length of fatty acid chain and saturation
• cholesterol - disrupts fatty acid interactions stabilising membrane fluidity
• proteins in the membrane
• cytoskeleton structure

Question 6

what makes a membrane more rigid

Answer 6

• saturated fatty acid
• long chains

Question 7

how do proteins move in the bilayer

Answer 7

• lateral diffusion
• rotate in the bilayer
• no flip flop motion - as proteins are asymmetric
• movement can be restricted by polarised cells

Question 8

what causes HS cytoskeleton cell shape

Answer 8

• hereditary spherocytosis
• molecular defects ankyrin alpha/beta band 3 protein 4.2
• membrane loss

Question 9

what causes HE and HPP cytoskeleton cell shapes

Answer 9

• hereditary elliptocytosis and hereditary pyropoikilocytosis
• alpha/beta spectrin - protein 4.1 glycophorin C defect
• membrane instability

Question 10

what causes SAO cytoskeleton cell shape

Answer 10

• southeast asian ovalocytosis
• band 3 defect
• increase membrane rigidity

Question 11

what happens when there is a loss of membrane integrity

Answer 11

• selective permeability disrupted
• cell death/ malfunction

Question 12

what is passive transport/ facilitated diffusion

Answer 12

• down a concentration gradient
• via transporter or channel

Question 13

what is the difference between charged and uncharged molecules via passive transport

Answer 13

uncharged - concentration gradient drives transport
charged - concentration gradient and electrode potential difference drives transport

Question 14

what are the three times of gated ion channels

Answer 14

• voltage gated
• ligand gated
• mechanical gated

Question 15

how do voltage gated ion channels work

Answer 15

responds to direct changes in the membrane potential

Question 16

how to ligand gated ion channels work

Answer 16

respond to a specific chemical stimulus

Question 17

how do mechanically gated ion channels work

Answer 17

respond to mechanical movement/ vibration

Question 18

how does ATP stimulate insulin release

Answer 18

1) glucokinase responds to glucose in glycolysis
2) ATP produced in the mitochondria
3) ATP-sensitive potassium channels close
4) change across the membrane potential
5) calcium gated open
6) insulin vesicles fuse with membrane
7) insulin released into blood

Question 19

what is active transport

Answer 19

• requires metabolic energy
• can generate a concentration gradient

Question 20

what is primary active transport

Answer 20

• used ATP as energy
• ions transported across the membrane
  eg. sodium potassium pump

Question 21

what is secondary active transport

Answer 21

• concentration gradient of the driving ions used
• ions serve as driving molecules for other molecules to be driven across
  eg. NA+/CA2+

Question 22

what are the three types of primary active transport

Answer 22

• p-type pump - ion transporters
• F and V type pumps - generate ATP
• ABC transporters

Question 23

what are symporters

Answer 23

• cotransporters
• molecules move in the same direction

Question 24

what are antiporters

Answer 24

• exchangers
• molecules move in opposite directions

Question 25

what are ion pumps

Answer 25

• used to stabilise osmolarity
• high cellular concentration of macromolecules, small organic molecules and ions

Question 26

how does glucose transport work

Answer 26

• [NA+] gradient drives glucose transport into the epithelium
• [glucose] gradient drives export to the extrascapular fluid