MOVEMENT OF SUBSTANCE

Question 1

the cell/plasma membrane is _____ _______
and is made up of _______ ________

Answer 1

selectively permeable
phospholipid bilayer

Question 2

3 ways substances cross the plasma membrane(enter or leaving the cell)

Answer 2

diffusion, osmosis and active transport
DOAT

Question 3

diffusion definition

Answer 3

the net movement of particles (molecules or ions) from a region of their higher concentration to a region of their lower concentration, down a concentration gradient.

Question 4

diffusion is a _____ process; it is ______

Answer 4

passive
non-energy requiring

Question 5

4 factors the rate of diffusion depends on

Answer 5

The concentration gradient
The distance over which diffusion takes place
The area over which diffusion takes place
The size and nature of the diffusing molecule

Question 6

how does The concentration gradient affect rate of diffusion

Answer 6

The greater the difference in concentration between two regions of a substance, the higher the rate of diffusion is. In other words, the steeper the concentration gradient for a substance, the greater the rate of diffusion is.

Question 7

how does The distance over which diffusion takes place affect the rate of diffusion

Answer 7

The shorter the distance between two regions of different concentrations, the greater the rate of diffusion is.

Question 8

how does The area over which diffusion takes place affect the rate of diffusion

Answer 8

The larger the surface area, the higher the rate of diffusion is. Diffusion surfaces frequently have structures for increasing their surface area and hence the rate at which they exchange materials. These structures include microvilli on cells lining the small intestine.

Question 9

how does The size and nature of the diffusing molecule affect the rate of diffusion

Answer 9

Small molecules diffuse at a higher rate than larger ones. Fat-soluble molecules diffuse more rapidly through cell membranes than water-soluble molecules.

Question 10

Simple diffusion definition

Answer 10

Simple diffusion involves the movement of small, uncharged and lipid-soluble substances(such as oxygen across the phospholipid bilayer (cell membrane) down their concentration gradient unaided.)
–> simple diffusion is the normal one
the net movement of particles (molecules or ions) from a region of their higher concentration to a region of their lower concentration, down a concentration gradient.

Question 11

y cant charged particles fit thru the plasma membrane

Answer 11

Charged particles are repelled by the hydrophobic fatty acid tails in the phospholipid bilayer. In the plasma membrane, transport proteins such as channel and carrier proteins assist charged particles to diffuse in or out of the cell.

Question 12

hydrophobic meaning

Answer 12

repels water

Question 12

hydrophilic meaning

Answer 12

water-loving

Question 13

what is facilitated diffusion

Answer 13

Facilitated diffusion is applied to the use of certain membrane proteins to assist charged particles
(such as sodium ions), and hydrophilic molecules such as glucose, to pass through the membrane.

Question 13

channel protein description

Answer 13

like a sort of tunnel protein that brings substances into the cell through the cell/plasma membrane

Channel protein forms a water-filled pore in the membrane. The lining of the channel is hydrophilic so that water-soluble substances can pass through it easily.

Question 13

what is aquaporin

Answer 13

Aquaporin is a special type of channel protein found in the cell membrane that specifically allows water molecules to pass through.

Question 14

carrier protein

Answer 14

like a short of pacman protein that eats from the outside substances and shits them inside the cell through the cell membrane

Carrier protein contains binding sites for the diffusing substance. The carrier protein alternates between two conformations, moving a solute across the membrane as the shape of the carrier protein molecule changes.

Question 15

osmosis definition

Answer 15

Osmosis is defined as the net movement of water molecules from a region of less negative water potential to a region of more negative water potential, down a water potential gradient through a selectively permeable membrane.

Question 16

water potential definition

Answer 16

Water potential of a solution is a measure of whether it is likely to gain or lose water molecules from another solution

Question 17

A dilute solution contains more water molecules per unit volume than a concentrated solution so it has a ____ _______ water potential than a concentrated solution which has ____ ________ water potential.

Answer 17

less negative(higher)
more negative(lower)

Question 18

what has the highest water potential

Answer 18

pure water

Question 19

how are water potential gradients created

Answer 19

When two solutions of different water potential are separated by a selectively permeable membrane,

Question 20

osmosis definition

Answer 20

Osmosis is defined as the net movement of water molecules from a region of less negative water potential to a region of more negative water potential, down a water potential gradient through a selectively permeable membrane.

Question 21

importance of a water potential gradient in the uptake of water by plants

Answer 21

The soil solution consists of water molecules and dissolved mineral salts that are not bound tightly to soil particles. The soil solution has a less negative water potential than that of the root hair cell.
Hence, Water molecules move into the root hair cell by osmosis down a water potential gradient through the selectively permeable cell membrane (plasma membrane of the root hair cell). Water molecules pass from one cell to another by osmosis down a water potential gradient in the root cortex until they reach the xylem vessel.

Question 22

hypertonic vs hypotonic vs isotonic
e.g. solution B is hypotonic with regard to solution A.
aka

Answer 22

hypertonic - more negative - less
hypotonic - less negative - more
isotonic - same
Solution B has a less negative water potential than solution A.

Question 23

when does osmosis end

Answer 23

This movement continues until dynamic equilibrium is reached. At this point there is no net movement of water molecules. Both solutions are of equal concentrations or isotonic to each other.

Question 24

what happens to a plant cell in a solution with a less negative water potential than that of the plant cell
hypertonic solution
(dilute sugar or salt solution or pure distilled water)

Answer 24

1. Water molecules enter the cell by osmosis across the selectively permeable cell membrane.
2. Vacuole increases in size.
3. Cell contents are pushed against the cellulose cell wall.
4. The cellulose cell wall prevents over expansion of the cell by exerting an opposing pressure preventing the entry of more water.
5. The cell becomes turgid.
6. The pressure exerted by the water in the vacuole on the cellulose cell wall is called turgor pressure.
7. The plant cell does not burst because the cellulose cell wall is tough.

Question 25

what happens to a plant cell in a solution with a more negative water potential than that of the plant cell
hypotonic solution
(concentrated sugar or salt solution)

Answer 25

1. Water molecules leave the cell by osmosis across the selectively permeable cell membrane.
2. Vacuole decreases in size.
3. Cytoplasm stops pushing outwards on the cellulose cell wall.
4. The cell loses its turgor and becomes flaccid.
5. As more water is lost, the cytoplasm shrinks further into the centre of the cell but the cellulose cell wall is too stiff to shrink much.
6. When the cell membrane surrounding the cytoplasm has just begun to pull away from the cellulose cell wall, the cell is at incipient plasmolysis.
7. Thus plasmolysis occurs when a plant cell is immersed in a solution of a more negative water potential than the cell.

Question 26

Animal cell is put in distilled water

Answer 26

Water molecules enter cell by osmosis across the selectively permeable cell membrane.
cells swell and burst

Question 27

Animal cell is put in concentrated salt solution

Answer 27

Water molecules leave cell by osmosis across the selectively permeable cell membrane.
cells shrink and shrivel
this process is called crenation

Question 28

active transport definition

Answer 28

the transport of substances against a concentration gradient from a region where they are in lower concentration to a region where they are in higher concentration.

Question 29

y can active transport only occur in living cells

Answer 29

Active transport requires energy; thus it only occurs in living cells because only living cells respire to release energy in the form of ATP molecules.

Question 30

how to tell what cells and tissues carry out active transport the most

Answer 30

Cells and tissues carrying out active transport are characterised by the presence of numerous mitochondria, a high concentration of ATP and a high respiratory rate.

Question 31

bulk transport definition

Answer 31

Bulk transport is defined as the transport of material into or out of a cell by enclosing it within a vacuole or vesicle. A vacuole is a fluid-filled membrane-bound sac, whereas a vesicle is a small vacuole.

Question 32

in bulk transport, how are materials moved around the cells

Answer 32

In bulk transport, materials are released from the cell by exocytosis or taken into the cell by endocytosis. Both are active, energy-requiring processes.

Question 33

how does exocytosis work

Answer 33

Vesicles containing the material are pinched off from the Golgi body and move towards the surface of the cell, fuse with the cell membrane and release the contents outside the cell.

Question 34

2 types of Endocytosis

Answer 34

phagocytosis,
pinocytosis,

Question 35

pinocytosis vs phagocytosis,

Answer 35

In pinocytosis, a liquid is taken into the cell.
In phagocytosis, a solid is taken into the cell,

Question 36

Why are most cells microscopic? Why are all large organisms always multicellular (have bodies made up of many cells and not just one cell)?

Answer 36

By dividing the large cell to many small cells in (c), a high surface area to volume ratio can be restored. This can serve each cell’s need for acquiring nutrients and expelling waste products.

Question 37

simple and facilitated diffusion similarities

Answer 37

1 both are passive processes and hence do not need energy
2 both move down a concentration gradient

Question 38

simple and facilitated diffusion differences

Answer 38

1 facilitated diffusion uses carrier proteins, simple doesnt

2 simple Involves the movement of small, nonpolar molecules, Involves the movement of larger or polar molecules

Question 39

State one observable difference between a channel protein and a carrier protein.

Answer 39

Channel Protein: Forms a pore or channel in the membrane that allows specific molecules or ions to pass through.
Carrier Protein: Binds to the specific molecule or ion it transports, undergoing a conformational change to move the molecule across the membrane

Question 40

what can simple diffuse across the cell membrane

Answer 40

The hydrophobic core of the phospholipid bilayer acts as a barrier to most water-soluble substances, including ions and polar molecules. Only small, nonpolar molecules (like oxygen and carbon dioxide) and some small polar molecules (like water) can pass through the lipid bilayer without assistance.