Transport across cell membranes

Question 1

What is the structure of a cell surface membrane and what are the components

Answer 1

Phospholipid bilayer

Phospholipids
Glycoproteins - aid cell attachment
Glycolipids - aid cell attachment
Channel proteins
Carrier proteins
Cholesterol - to provide stability

Question 2

What does Fluid mosaic model mean

Answer 2

Molecules can flow freely

lots of different types of molecule

Question 3

Simple diffusion across a cell membrane

Answer 3

Movement of small, non polar, lipid soluble particles through the bilayer

Question 4

Facilitated diffusion across a cell membrane

Answer 4

movement of larger, polar, water soluble molecules through channel or carrier proteins

Question 5

How do carrier proteins allow larger molecules into a cell

Answer 5

the molecule enters and attaches to the carrier protein, causing the tertiary structure of the protein to change and thus allows the molecule to enter the cell on the other side

Question 6

What is active transport

Answer 6

Movement of molecules against the concentration gradient using carrier proteins, requiring ATP hydrolysis for energy

Question 7

What is co transport

Answer 7

The movement of two molecules together through a membrane, one molecule moving down the conc gradient, while the other moves up

occurs via a carrier protein

Question 8

Co-transport in the ileum

Answer 8

Sodium ions and glucose are co transported from the lumen to the epithelium

then sodium ions are actively transported into the blood via an Na - K pump, to maintain a concentration gradient between the lumen and the epithelium

Glucose is then transported from the epithelium into the blood by facilitated diffusion through channel proteins

Question 9

What is osmosis

Answer 9

the movement of water molecules across a selectively permeable membrane from a region of HIGH water potential to LOW water potential

Question 10

What does isotonic mean

Answer 10

That the water potential is in equilibrium on each side of a selectively permeable membrane

Question 11

Adaptations of cell membranes and how they are useful

Answer 11

Increased surface area - more area for diffusion to occur across a membrane so a faster rate of diffusion

increased number of carrier/channel proteins - more areas that can move larger, polar molecules across a membrane