Transport

Question 1

Active transport

Answer 1

ATP, against conc gradient, selective process

Involve carrier proteins/pumps

Question 2

How is the cell adapted for active transport

Answer 2

Microvilli, LSA, more carrier proteins, mitochondria for ATP synthesis
Carrier proteins span plasma membrane, bind to molecule or ion to be transported on one side

Question 3

Describe the process of active transport

Answer 3

Molecule/ion binds to receptor sites on protein
On the inside of the cell/organelle, ATP binds to protein, splitting into ADP, phosphate
Protein molecule change shape, opens to opposite side of membrane
Molecule/ion released to other side of membrane
Phosphate released from protein, causes protein to revert to original shape
Phosphate combines with ADP to ATP

Question 4

Simple diffusion

Answer 4

All particles are constantly in motion, KE
Random motion, particles constantly bouncing around
Net movement of molecules or ions from a high to low conc until equilibrium formed
Small, non polar molecules easily diffuse

Question 5

Facilitated diffusion, what doesn’t easily pass through the phospholipid bilayer?

Answer 5

Charged ions, polar molecules do not diffuse easily due to hydrophobic nature of fatty acid tails

Question 6

Describe the process of facilitated diffusion

Answer 6

Relies on KE of diffusing molecules, down conc gradient

Only occurs at specific points on membrane, protein channels, carrier proteins

Question 7

How to increase facilitated diffusion rate

Answer 7

Protein channels and carrier proteins can be added to the phospholipid bilayer

Question 8

How do protein channels work in facilitated diffusion?

Answer 8

Form water filled hydrophilic channels across the membrane
Allow water soluble ions through
Selective channels, gated, open in the presence of a specific ion
Ion binds with the protein causing it to change shape in a way that closes it to one side of the membrane and opens it to the other side

Question 9

How do carrier proteins work in facilitated diffusion

Answer 9

Span plasma membrane
When a specific molecule is present, binds with a protein
Causes a shape change, molecule released to inside of membrane

Question 10

Osmosis

Answer 10

The passage of water from a region of high water potential to an area of lower water potential through a selectively permeable membrane

Question 11

Water potential

Answer 11

Tendency of water molecules in a system to move
Psi, measured in kPa
Pure water=0kPa, highest value
Solutions have -ve value

Question 12

Cells in higher water potential than cell solution in plant cells

Answer 12

Water diffuses in through partially permeable membrane
Contents expand, push out on wall
Wall pushes back on cell contents
Force of wall pushing on cell contents, pressure
Turgid
More water enters, water potential of cell solution rises
Water potential out of cell is equal to water potential in
Equilibrium reached
Fully turgid

Question 13

Cells in lower water potential than cell solution in plants

Answer 13

Water diffuses out of cell through partially permeable membrane
Contents do not push out, flaccid
Plasma membrane eventually pulls away from wall, plasmolysed
External solution fills gap between wall, plasma membrane
Some parts resistant to pulling away from wall
If membrane torn at those points, cells die

Question 14

Cells in higher water potential than cell solution in human cells

Answer 14

Hypotonic solutions
Water diffuses into the cell
No cell wall, lyses

Question 15

Cells in lower water potential than cell solution in human cells

Answer 15

Hypertonic solutions
Water diffuses out
Creates

Question 16

Factors that affect rate of diffusion

Answer 16

SA
Conc difference
Distance
Temp

Question 17

Co transport in the ileum

Answer 17

Sodium potassium pump moves 3 Na+ out of the cell and 2 K+ into the cell, requires ATP, against conc grad
Glucose and Na+ enter together through carrier protein
High conc of glucose in epithelium, fac diff out into blood stream

Question 18

Micelles

Answer 18

Lipid molecules that arrange themselves in sphere in aqueous solution
Formation is response to amphipatic nature of monoglycerides and fatty acids
Have hydrophilic heads, hydrophobic tails, constantly breaking and reforming
When they break near intestinal cell surface, cell absorbs fatty acid and monoglycerides, diff
Carry vitamins, cholesterol from digested food to intenstinal cells

Question 19

Chylomicrons

Answer 19

Lipoprotein made up of triglycerides, phospholipids, cholesterol, protein
Transport dietary lipids from intestine to parts of body

Question 20

Lipids to the lacteal

Answer 20

Fatty acids and monoglycerides leave micelles enter epithelial cell
Fatty acids link to form triglycerides
Fat globules combine with proteins, form chylomicrons in Golgi
Chylomicrons extruded from epithelial cell, enter lacteal (lymph cap)
Lymph in lacteal transport chylomicrons away from intestine