chapter 3 - the plasma membrane Flashcards

unit 1 aos 1

You may prefer our related Brainscape-certified flashcards:
1
Q

the function of the plasma membrane

A

is selectively permeable, which means that only particular molecules can enter and exit the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

the structure of the plasma membrane

A

is a phospholipid bilayer (arranged in two layers) embedded with proteins, carbohydrates, and cholesterol.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

structure of phospholipid

A

phosphate head
made up of glycerol and a phosphate group.
negatively charged, making it hydrophilic and polar (eg water).

2 fatty acid chains
made up of long chains of carbon and hydrogen.
uncharged, making it hydrophobic and non-polar.

amphipathic molecule
makes plasma membrane stable.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

types of protein

A

integral: permanent part of the membrane
transmembrane: integral proteins that span the entire bilayer
peripheral: temporarily attached to the plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

function of protein

A

transport
communication
catalysis
adhesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

structure of carbohydrates

A

usually in chains that extend outside the cell, rooted in the membrane to lipids (glycolipids) or proteins (glycoproteins).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

function of carbohydrates

A

aids with:
cell-cell communication
signalling
adhesion
recognition of molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

structure of cholesterol

A

lipid steroid that embeds itself between the fatty acid tails of the phospholipid bilayer in animal cells.
is replaced with similar molecules in other kingdoms, but are all functionally similar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

function of cholesterol

A

regulates fluidity of membrane
at higher temperatures, it keeps phospholipids bound together.
at lower temperatures, it stops phospholipids from becoming solid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

the fluid mosaic model

A

the plasma membrane is fluid because phospholipids continually move laterally (side to side) in the membrane.
the mosaic component of the model comes from the proteins and carbohydrates embedded in the model.

explains:
molecules that make up the membrane are not held static in one place.
many different types of molecules are embedded in the plasma membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

diffusion

A

the movement of particles down the concentration gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

passive transport

A

process that doesn’t require energy to move things across the plasma membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

simple diffusion

A

when molecules move from an area of high concentration to an area on low concentration (down concentration gradient)

happens due to kinetic energy stored inside each molecule which causes them to move around and bounce off each other.

leads to even dispersion of the molecules in an area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

which molecules can freely diffuse across the plasma membrane?

A

non-polar and small (like water) molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

facilitated diffusion

A

passive movement of molecules down the concentration gradient through membrane bound proteins (proteins channels).

allows large molecules to move between the intra and extracellular environments.

protein channels and carrier proteins both are specific to the molecules they transport and the selective permeability of the plasma membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

protein channels

A

pores or holes in the membrane that let specific substances in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

carrier proteins

A

binds to the surface that is being transported and undergoes a conformational change to push the substance down the concentration gradient.

18
Q

osmosis

A

the diffusion of water across a selectively permeable membrane from low solute concentration areas to high solute concentration areas.
water can move through the membrane as it is so small even though it is hydrophilic.

19
Q

tonicity

A

differences in solute concentrations between compartments

20
Q

hypertonic

A

solutions have comparatively high solute concentrations, so water moves into the hypertonic solution from adjacent areas with lower solute concentrations.

21
Q

isotonic

A

solutions have equal solute concentrations, so there is no net movement of water.

22
Q

hypotonic

A

solutions have comparatively lower solute concentrations, so water moves from a hypotonic solution into adjacent areas with a higher solute concentration.

23
Q

what happens to cells in a hypotonic solution?

A

animal: lysed (filled with h2o and can burst)
plant: turgid (normal state, swollen with h2o, can occur due to cell wall)

24
Q

what happens to cells in an isotonic solution?

A

animal: normal (h2o flowing in and out)
plant: flaccid (h2o flowing in and out)
no net movement

25
Q

what happens to cells in a hypertonic solution?

A

animal: shrivelled (crenate, water flowing out)
plant: plasmolysed (water flowing out)

26
Q

how does tonicity affect cells?
biological importance?

A

it affects the cell size

high turgor (normal) pressure keeps plants from wilting

saline solution is isotonic to our cells, ensuring they don’t shrivel (hyper) or lyse (hypo)

27
Q

active transport

A

uses protein pumps to move molecules against the concentration gradient
uses energy (ATP)
2 types (protein mediated and bulk)

28
Q

protein mediated transport

A

cells must use energy and protein pumps to move the ions against the concentration and into the cytoplasm.
requires energy (ATP) and membrane proteins.

29
Q

process of active transport

A

binding: target molecules binds to the specific protein pump
conformational change: one P from ATP causes a conformational change in the protein pump
release: target molecule is pushed through the protein and released to the other side of the membrane.

30
Q

bulk transport

A

type of active transport that moves large molecules or groups of molecules (amino acids, proteins, signalling molecules or pathogens) into or out of a cell using vesicles.
two types (endocytosis and exocytosis)

31
Q

exocytosis

A

process that releases contents from a cell
proteins are made by ribosomes located on the surface of the ER, are sorted, packaged, and modified at the end of the Golgi apparatus and then transported in vesicles.
when a vesicle fuses with the plasma membrane, it adds phospholipids to the membrane making the cell slightly bigger.

32
Q

steps of exocytosis

A

vesicular transport: a vesicle containing secretory produce is transported to the membrane.
fusion: membranes of the vesicle and cell fuse.
release: secretory products are released from the vesicle and out of the cell.

33
Q

endocytosis

A

involves transporting molecules or groups of molecules into the cell.
many molecules that the cell requires to survive are too big to enter via protein channels.
takes phospholipids from the plasma membrane, so if large amounts of endocytosis occur the cell can shrink.

34
Q

steps of endocytosis

A

fold: plasma membrane folds inwards to form a cavity that fills with extracellular fluid and the target molecule.

trap: plasma membrane continues to fold back on itself until the two ends of the plasma membrane meet and fuse together.

bud: vesicle (endosome) pinches off the membrane. It can then be transported to the appropriate cellular location.

35
Q

types of endocytosis

A

phagocytosis (cell eating)
-endocytosis of solid materials or food particles

pinocytosis (cell drinking)
-process of engulfing molecules dissolved in extracellular fluid.

36
Q

the concentration of potassium ions, K+, in human blood plasma is approximately 4 mM. in the cytoplasm of red blood cells the concentration of these ions is around 100 mM. explain how this difference in concentration is maintained.

A

this difference in concentration is maintained using active transport.
in active transport, ATP is used by specific protein pumps to transport K+ against its concentration gradient into the red blood cells, increasing the concentration of K+ in the cell. K+ is charged so cannot easily diffuse across the plasma membrane, meaning the cytoplasm remains hypertonic to the blood plasma in terms of K+.

37
Q

example of simple diffusion

A

oxygen/carbon dioxide
uses phospholipids
down concentration gradient

38
Q

example of osmosis

A

water
uses phospholipids
down concentration gradient

39
Q

example of facilitated diffusion

A

glucose
uses protein channels
down concentration gradient

40
Q

example of active transport

A

amino acids
uses protein pumps
up concentration gradient