Transport And Membranes

Question 1

Cell membrane features

Answer 1

Partially permeable
Phospholipid bilayer
Intrinsic and extrinsic proteins and cholesterol for stability and glycolipids for recognition site

Question 2

What can diffuse through cell membrane and what can’t

Answer 2

Lipid soluble molecules water and other small substances can

Water soluble ones and other large molecules can’t

Question 3

What’s fluid mosaic model

Answer 3

phospholipids can move within the structure relative to one another and it contains shapes and sizes different

Question 4

What’s diffusion

Answer 4

The net movement of particles from an area of high concentration to an area of low concentration across a partially permeable membrane. Passive process down a conc gradient

Question 5

What factors affect diffusion rate

Answer 5

Surface area
Diffusion pathway
Temperature - particles more energy move faster
Concentration gradient

Question 6

What’s facilitated diffusion

Answer 6

When molecule is too large to diffuse across the membrane so can go via protein carriers down the concentration gradient. passive but involves proteins specific to substance crossing

Question 7

What’s osmosis

Answer 7

Net movement of water particles from an area of high water potential to an area of low water potential across a partially permeable membrane. passive no carrier protein

Question 8

What’s a limiting factor in facilitated diffusion

Answer 8

Number of carrier proteins. They may become saturated with molecules

Question 9

Active transport

Answer 9

The net movement of molecules/ions from an area of low concentration to an area of high concentration against the gradient using energy and carrier proteins. Requires ATP

Question 10

How substances move across membrane via carrier proteins using active transport

Answer 10

Ion binds to carrier protein on receptor sites
On the inside of the membrane ATP binds to the protein and binds to protein (hydrolysed to ADO and Pi)
Causes protein to change shape and open to other side
Ion is released
Pi is released from protein so changed back to original shape

Question 11

Active transport in glucose absorption

Answer 11

Co transport
Sodium ions actively transported from ileum epithelium cell to blood by na k pump
maintains/ forms conc gradient for sodium to enter cells from gut and with it glucose
glucose enters by facilitated diffusion/co transport with sodium ions