Cell membranes & transport

Question 1

What is the fluid mosaic model

Answer 1

Arrangement of molecules on the membrane, phospholipids have a double layer and because they are constantly moving the bilayer is “fluid” , proteins are scattered through the bilayer like tiles in a “mosaic” which includes channel and carrier proteins

Question 2

Name all the components in a membrane

Answer 2

Phospholipid channel proteins carrier proteins , glycoproteins (carbohydrates with a protein attached) glycolipids ( carbohydrates with a lipid), cholesterol

Question 3

What so the function of cholesterol in the membrane

Answer 3

Gives the membrane stability , causes the phospholipids to bind closely together which then restricts movement making the membrane less fluid and more rigid

Question 4

What are factors that affect the rate or diffusion and facilitated diffusion

Answer 4

Diffusion: concentration gradient, thickness of exchange surface, surface area
Facilitated Diffusion: concentration gradient and number of carrier and channel proteins

Question 5

Define isotonic, hypotonic, and hypertonic

Answer 5

Isotonic: 2 solutions have the same water potential
Hypotonic: solutions with higher water potential compared to inside the cell - net movement of water out the cell
Hypotonic: solutions with lower water potential than the cell - net movement of water into the cell

Question 6

what are factors affecting the rate of osmosis

Answer 6

1-water potential gradient - higher the water potential gradient the faster the rate of osmosis is
2-thickness of surface exchange- thinner it is the faster osmosis is
3-surface area of the exchange surface- larger the faster

Question 7

describe the role of carrier proteins for active transport

Answer 7

molecule attaches to the protein
protein changes shape
moves the molecule across the membrane releasing it on the other side
low to high concentration gradient
requires ATP

Question 8

what is a type of carrier protein

Answer 8

co-transporters

Question 9

describe the role of co-transporters

Answer 9

bind 2 molecules together at a time and uses the conc. gradient of one molecule to move the other molecule against its own conc. gradient

Question 10

describe the co-transport and absorption of glucose

Answer 10

1- sodium ions are actively transported out the epithelial cells in the ileum and into the blood by a sodium-potassium pump
2- which causes the sodium ions to diffuse from the lumen(middle) of the ileum into the epithelial cell down the conc. gradient by sodium-glucose co-transporter proteins
3-co-transporter carries glucose into the cell with sodium , the conc. of glucose in the cell increases
4- glucose diffuses out the cell into the blood down its conc. gradient through a protein channel by facilitated diffusion

Question 11

what factors affect the rate of active transport

Answer 11

1-speed of individual carrier proteins
2-number of carrier proteins present
3- rate of respiration of the cell and the amount of ATP available

Question 12

Describe transports of carbohydrates in plants (6)

Answer 12

1. sucrose is activity transported into the phloem
2. by transfer cells
3. this lowers water potential and water enters the xylem by osmosis
4. this produces a high hydrostatic pressure gradient
5. mass flow to respiring cells
   6.removed form phloem by active transport

Question 13

Factors of the rate of transpiration (5)

Answer 13

1.temperature
2.light intensity
3.increased kinetic energy-causes more water loss
4.stomata open allowing gas exchange
5.stomata’s close reducing transpiration