3.2.3 Transport across cell membranes

Question 1

what is the phospholipid bilayer structure

Answer 1

• hydrophilic heads and outside bilayer
• hydrophobic fatty acid tails inside bilayer
• form selective permeable barrier
• phospholipids move - fluid

Question 2

what is the cell membrane structure (fluid-mosaic model)

Answer 2

• phospholipid bilayer
• proteins
• glycoproteins
• glycolipid
• cholesterol

Question 3

why are heads on outside of phospholipid bilayer hydrophilic

Answer 3

form intermolecular forces with water

Question 4

why are fatty acid tails on inside of the bilayer hydrophobic

Answer 4

from intermolecular forces with each other

Question 5

why is the phospholipid bilayer selectively permeable

Answer 5

only non-polar molecules can diffuse through fatty acid core

Question 6

what are channel proteins

Answer 6

movement of substances across membranes

Question 7

what are the functions of intrinsic, extrinsic proteins

Answer 7

reception, signalling molecules, membrane stability

Question 8

what is a glycoprotein

Answer 8

• protein with short carbohydrate chain
• used for cell recognition and signalling, cell attachment

Question 9

what is a glycolipid

Answer 9

• phospholipid with a short carbohydrate chain
• used for cell recognition and attachment

Question 10

what is a cholesterol

Answer 10

• reduces membrane fluidity by restricting the movement of other molecules

Question 11

what are the types of movement across membranes

Answer 11

• simple diffusion
• facilitated diffusion
• osmosis
• active transport
• co-transport

Question 12

what is simple diffusion

Answer 12

• passive movement from higher concentration to lower concentration
• across phospholipid bilayer
• nonpolar molecules only

Question 13

what is facilitated diffusion

Answer 13

• passive movement from higher to lower concentration
• requires channel or carrier proteins - specific to substance
• polar molecules and ions

Question 14

what is osmosis

Answer 14

• diffusion of water molecules from higher to lower water potential
• limited across phospholipid bilayer - rapid movement requires channel proteins
• water potential = ability of water molecules to move freely
• pure water = 0kPa. All solutions have neagtive water potentials

Question 15

what is active transport

Answer 15

• movement from lower concentration to higher concentration
• requires specific carrier proteins in membrane
• requires hydrolysis of ATP - phosphorylates carrier protein, causing change shape

Question 16

what is co-transport

Answer 16

• movement for two substances simultaneously through a carrier protein
• one substances moves against concentration gradient
• one substance moves down concentration gradient

Question 17

what are adaptations to increase the rate of transport across membranes

Answer 17

• increased number of channel and carrier proteins
• increased surface area of membrane
• mechanisms to increase concentration gradients
• increased number of mitochondria to supply more ATP for active transport