Chapter 7

Question 1

what is the plasma membrane?

Answer 1

the boundary that separates the living cell from its surroundings, allows some substances cross (selective permeability)

Question 2

what are amphipathic molecules and give an example

Answer 2

phospholipids are amphipathic molecules, meaning they contain hydrophobic and hydrophilic regions

Question 3

what does the fluid mosaic model state?

Answer 3

that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it, proteins aren’t randomly distributed

Question 4

what happens to membranes as temperatures cool?

Answer 4

as temperatures cool, membranes switch from a fluid to a solid state, membranes rich in unsaturated fatty acids are more fluid than saturated; they must be fluid to work properly

Question 4

what happens to membranes as temperatures cool?

Answer 4

as temperatures cool, membranes switch from a fluid to a solid state, membranes rich in unsaturated fatty acids are more fluid than saturated; they must be fluid to work properly

Question 5

What is a membrane?

Answer 5

a membrane is a collage of different proteins, often grouped together, embedded in the fluid matrix of the lipid bilayer

Question 6

peripheral proteins?

Answer 6

bound to the surface of the membrane

Question 7

integral proteins?

Answer 7

penetrate the hydrophobic core

Question 8

major functions of membrane proteins

Answer 8

transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to cytoskeleton and ECM

Question 9

Role of Membrane Carbohydrates in Cell-Cell Recognition?

Answer 9

membrane carbohydrates may be covalently bonded to lipids (forming glycolipids) or proteins (forming glycoproteins)

Question 10

are hydrophobic molecules polar or non polar

Answer 10

hydrophobic (hate water) are non polar

Question 11

are hydrophilic molecules polar or non polar

Answer 11

hydrophilic (love water) polar

Question 12

Example of hydrophobic molecules

Answer 12

hydrocarbons

Question 13

Which molecules can pass through the lipid bilayer?

Answer 13

hydrophobic molecules (non-polar) can pass through the lipid bilayer, for example hydrocarbons: Hydrophilic dont cross easily

Question 14

What are transport proteins?

Answer 14

Transport proteins allow passage of hydrophilic (love water) substances across membrane

Question 15

What channel proteins are aquaporins

Answer 15

aquaporins facilitate passage of water

Question 16

what do carrier proteins do

Answer 16

carrier proteins bind to molecules and change shape to shuttle them across the membrane

Question 17

what is passive transport?

Answer 17

passive transport is diffusion of a substance across a membrane with no energy investment

Question 18

what is diffusion?

Answer 18

diffusion is the tendency for molecules to spread out evenly into the available space

Question 19

how do substances diffuse?

Answer 19

substances diffuse down their concentration gradient, the region along which the density of a chemical substance increases or decreases

Question 20

what is osmosis?

Answer 20

osmosis is the diffusion of water across a selectively permeable membrane

Question 21

how does water diffuse across a membrane based on concentration?

Answer 21

water diffuses from lower solute concentration to higher solute concentration until it is equal on both sides

Question 22

what is tonicity?

Answer 22

the ability of a surrounding solution to cause a cell to gain or lose water

Question 23

isotonic solution?

Answer 23

solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

Question 24

hypertonic solution?

Answer 24

solute concentration is greater than that inside the cell; cell loses water

Question 25

hypotonic solution?

Answer 25

solute concentration is less than that inside the cell; cell gains water

Question 26

what is osmoregulation?

Answer 26

osmoregulation, the control of solute concentrations and water balance, is necessary adaptation for life in such environments

Question 27

what happens if a plant cell is placed in isotonic surroundings?

Answer 27

it becomes limp because there is no net movement of water

Question 28

what happens if a plant cell is placed in hypotonic solution?

Answer 28

the plant cell swells up until the cell wall opposes uptake

Question 29

in a hypertonic environment what happens?

Answer 29

plant cells lose water, the membrane pulls away from the cell wall causing plant to wilt which is plasmolysis

Question 30

facilitated diffusion?

Answer 30

in facilitated diffusion, transport proteins speed the passive movement of molecules across the plasma membrane (include channel proteins and carrier proteins)

Question 31

what do ion channels do?

Answer 31

ion channels facilitate the diffusion of ions, some are called gated channels which open or close in response to a stimulus

Question 32

what is active transport?

Answer 32

active transport uses energy to move solutes against their concentration gradient

Question 33

what does active transport require?

Answer 33

active transport requires ATP and is performed by specific proteins embedded in the membranes

Question 34

what is one type of active transport system?

Answer 34

sodium-potassium pump

Question 35

what does active transport allow cells to do?

Answer 35

active transport allows cells to maintain concentration gradients that differ from their surroundings

Question 36

what happens in the sodium potassium pump in terms of cells that go out and come in?

Answer 36

3 sodiums go out of the cell and 2 potassiums come back in

Question 37

steps of sodium potassium pump

Answer 37

sodium bonds to pump, sodium binding is stimulated by atp, protein changes conformation and throws sodium out, potassium binds to protein, phosphate is lost, potassium is released

Question 38

what is membrane potential?

Answer 38

membrane potential is the voltage difference across a membrane

Question 39

what is voltage

Answer 39

voltage is created by differences in the distribution of positive and negative ions across a membrane

Question 40

what is an electrogenic pump?

Answer 40

an electrogenic pump is a transport protein that generates voltage across a membrane

Question 41

what is the main electrogenic pump for animal cells?

Answer 41

sodium potassium pump

Question 42

what is the main electrogenic pump for plant cells?

Answer 42

proton pump

Question 43

how do small molecules and water leave and enter a cell?

Answer 43

through the lipid bilayer or transport proteins

Question 44

how do large molecules, such as polysaccharides and proteins, cross the membrane

Answer 44

they cross in bulk via vesicles which requires energy

Question 45

what is exocytosis?

Answer 45

exocytosis is when transport vesicles migrate to the membrane, fuse with it, and release contents to outside of the cell

Question 46

what is endocytosis

Answer 46

in endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membrane

Question 47

what are the three types of endocytosis?

Answer 47

phagocytosis (cellular eating), pinocytosis (cellular drinking), receptor-mediated endocytosis

Question 48

what happens in phagocytosis?

Answer 48

cell engulfs a particle in a vacuole and vacuole fuses with a lysosome to digest

Question 49

what happens in pinocytosis?

Answer 49

molecules dissolved in droplets are taken up when extracellular fluid is gulped into tiny vesicles

Question 50

what happens in receptor-mediated endocytosis?

Answer 50

binding to ligands to receptors trigger vesicle formation