Cell Transport

Question 1

amphipathic

Answer 1

hydrophobic and hydrophilic sections

Question 2

peripheral proteins

Answer 2

protein that temporarily attaches to membrane

Question 3

how does cholesterol contribute to cell membrane

Answer 3

controls fluidity

Question 4

transmembrane proteins

Answer 4

umbrella term
- protein that goes THROUGH the membrane allowing molecules to pass thru

Question 5

diffusion

Answer 5

small molecules moving along their conc grad without expending energy

Question 6

what factors affect rate of diffusion

Answer 6

1. conc grad: low conc grad = less collisions = slower diffusion
2. distance (thickness)
3. SA:V ratio (area involved)
4. barriers (polarity - likes dissolves likes, size - larger= harder to diffuse, state of transporters)

Question 7

what properties would maximize diffusion across a cell

Answer 7

high S/A, low Volume
- more surface area = more collisions = more diffusion
- sphere shape is good

Question 8

conc gradient

Answer 8

difference in conc

Question 9

osmosis

Answer 9

movement of water
- water ALWAYS moves along its own conc grad
- water is solvent

Question 10

how does water cross the cell membrane as a polar molecule

Answer 10

aquaporins

Question 11

aquaporins: what are they and how do they work

Answer 11

specific to water
- non polar aa outside and middle and polar top and bottom to pull water in
- thru the interactions with a.a inside tube water is pushed/pulled thru
- 6 alpha-helixes in circle shapei

Question 12

isotonic

Answer 12

equal amounts of solute and solvent
- no net movement

Question 13

hypertonic

Answer 13

more solute OUTSIDE cell
- net movement OUT

Question 14

hypotonic

Answer 14

more solute INSIDE cell
- net movement IN

Question 15

how do really large molecules cross the cell membrane

Answer 15

facilitated diffusion
- diffusion thru transport proteins

Question 16

general characteristics of active transport

Answer 16

• requires energy
• pumping sols AGAINST conc grad
• always involves carrier proteins
• proteins change conformation with ATP

Question 17

what are the diff types of membrane transporters

Answer 17

1. uniport
2. symport
3. antiport

Question 18

what type of substances need to move across the membrane against their conc grad

Answer 18

ions, glucose, gastric acid
- critical for a cell to maintain certain concentrations for homeostasis

Question 19

explain how the Na/K pump works

Answer 19

1. pump is facing the intercellular side, 3 Na and ATP come in and bind to the pump
2. PO4 from ATP attaches and changes shape (phosphorylated pump), making pump turn around and face the extracellular side
3. 2 K ions bind while the 3 Na leave, PO4 detaches changing pump shape AGAIN
4. the 2 K ions leave the pump and enter the intercellular membrane

Question 20

coupled transport

Answer 20

active and passive transport combined
- use active transport to create conc grad the equals out thru diffusion

Question 21

cotransport

Answer 21

piggybacking
- molecule piggy backs off another and gets free ride inside
- ex: glucose - H

Question 22

endocytosis

Answer 22

bringing molecules in bulk

Question 23

exocytosis

Answer 23

removing molecules by fusing it out membrane thru vesicles

Question 24

phagcytosis

Answer 24

cell eating
- bringing in large solids

Question 25

pinocytosis

Answer 25

cell drinking
- bringing in small amounts of fluid

Question 26

what is the difference between channel proteins and carrier proteins

Answer 26

CHANNEL: continuous passage, passive transport (substances move along conc grad)
- can be pores (always open) or gated (opens and closes based on stimulus)

CARRIERS: not continuous, has at least 2 gates that dont open simultaneously (unlike gated channels)
- slower than channels

Question 27

ionophores

Answer 27

transport ions

Question 28

glycolipds/glycoproteins

Answer 28

Carbohydrate chains attached to lipids (glycolipids) or proteins (glycoproteins) often are involved in cell recognition and signalling processes