Module 2 Section 5 - Transport Across Cell Membranes

Question 1

Define diffusion

Answer 1

Diffusion is the random net movement of particles from an area of higher concentration to an area of lower concentration, down the concentration gradient

Question 2

Which way will molecules diffuse

Answer 2

Both ways, but net movement will be to area of lower concentration

Question 3

When will diffusion stop

Answer 3

Diffusion continues until particles are evenly distributed throughout the liquid or gas

Question 4

What is the concentration gradient

Answer 4

The path from an area of higher concentration to an area of lower concentration

Question 5

How do particles diffuse

Answer 5

Down the concentration gradient

Question 6

What type of process is diffusion

Answer 6

Passive process

Question 7

What is a passive process

Answer 7

A process that requires no energy needed for it to happen

Question 8

What type of molecules diffuse through cell membranes

Answer 8

Small, Polar molecules

Question 9

Give example of small polar molecules

Answer 9

Oxygen, Carbon Dioxide

Question 10

How do small polar molecules diffuse through cell membranes

Answer 10

Small polar molecules are able to diffuse easily through spaces between phospholipids

Question 11

What is the diffusion of water molecules called

Answer 11

Osmosis

Question 12

Is water small enough to diffuse

Answer 12

Yes, even though water is polar it can diffuse through plasma membranes

Question 13

What affects the rate of diffusion

Answer 13

Steepness of Concentration gradient
Thickness of exchange surface
Surface area
Temperature

Question 14

How does concentration gradient affect rate of diffusion

Answer 14

The steeper the concentration gradient the faster the rate of diffusion

Question 15

How does the thickness of exchange surface affect rate of diffusion

Answer 15

The thinner the exchange surface, the faster the rate of diffusion

Question 16

How does the surface area affect the rate of diffusion

Answer 16

The larger the surface area the faster the rate of diffusion

Question 17

How does temperature affect the rate of diffusion

Answer 17

The warmer it is, the faster rate of diffusion because the particles have more kinetic energy

Question 18

What does facilitated diffusion use to diffuse molecules

Answer 18

Carrier and channel proteins

Question 19

What type of molecules use facilitated diffusion

Answer 19

Ions and polar molecules

Question 20

Why can’t ions and polar molecules use simple diffusion

Answer 20

Because they can’t directly pass through the phospholipid bilayer of the cell membrane

Question 21

How do ions and polar molecules diffuse

Answer 21

Through channel or carrier proteins

Question 22

How do particles in facilitated diffusion move

Answer 22

Down the concentration gradient

Question 23

What type of process is facilitated diffusion

Answer 23

Passive process

Question 24

What do carrier proteins move

Answer 24

Large molecules into or out of the cell (down concentration gradient)

Question 25

Describe the three steps a carrier proteins makes to diffuse substances

Answer 25

-Large molecule attaches to a carrier protein -protein changes shape -this releases the molecule on the opposite side of the membrane

Question 26

What do channel proteins move

Answer 26

Charged particles

Question 27

What do channel proteins form for charged particles to diffuse

Answer 27

They form pores

Question 28

Different carrier proteins facilitate….

Answer 28

The diffusion of different molecules

Question 29

Different channel proteins facilitate…

Answer 29

The diffusion of different charged particles

Question 30

What is active transport

Answer 30

The movement of molecules or ions across a cell membrane from a region of lower concentration to higher concentration - against the concentration gradient

Question 31

What type of process is active transport

Answer 31

Active process - it needs energy for the process to be completed

Question 32

How do particles move in active transport

Answer 32

Against the concentration gradient

Question 33

What does active transport involve

Answer 33

Carrier proteins

Question 34

Active transport is very similar to facilitated diffusion but there is only one difference what is it

Answer 34

The only difference is that energy is used to move the solute against its concentration gradient

Question 35

How do cells take in substances

Answer 35

Endocytosis

Question 36

Why are substances taken into a cell by endocytosis

Answer 36

Because they are too large to be taken into a cell by carrier proteins

Question 37

What happens when a substance undergoes endocytosis

Answer 37

-The cell surrounds the substance with a section of its plasma membrane -The membrane pinches off to form a vesicles inside the cell containing the ingested substance

Question 38

What type of process is endocytosis

Answer 38

Active process

Question 39

How do cells secrete substances

Answer 39

Exocytosis

Question 40

Substances produce by the cell are released by

Answer 40

Exocytosis

Question 41

What are steps of Exocytosis

Answer 41

-Vesicle containing these substances pinch off the sacs of the Golgi apparatus and move towards plasma membrane -the vesicles fuse with the plasma membrane and release their contents outside the cell

Question 42

Something different happens to some substances in Exocytosis

Answer 42

Some substances e.g. membrane proteins, aren’t released outside the cell - instead they are are inserted straight into the plasma membrane

Question 43

What type of process is Exocytosis

Answer 43

Active process

Question 44

What is osmosis

Answer 44

The diffusion of water molecules across a partially permeable membrane down a water potential gradient.

Question 45

What is meant by down the water potential gradient

Answer 45

The water molecules move from an area of higher water potential to an area of lower water potential

Question 46

What is water potential

Answer 46

The potential of water molecules to diffuse out or into a solution

Question 47

What has the highest water potential

Answer 47

Pure water

Question 48

Cell are affected by…

Answer 48

The water potential of the surrounding solution

Question 49

What happens to an animal cell in a hypotonic solution

Answer 49

Net movement of water molecules is into the cell. **Cell bursts**

Question 50

What happens to an animal cell in an **isotonic** solution

Answer 50

Water molecules pass into and out of the cell in equal amounts. **the cell stays the same**

Question 51

What happens to an animal cell in a hypertonic solution

Answer 51

Net movement of water molecules is out of the cell. **the cell shrinks**

Question 52

What happens to a plant cell in a hypotonic solution

Answer 52

Net movement of water is into cell. Vacuole swell. The vacuole and cytoplasm push against the cell wall. **The cell becomes turgid (swollen)**

Question 53

What happens to plant cell in an isotonic solution

Answer 53

Water molecules move into and out of the cell in equal amounts. **the cell stays the same**

Question 54

What happens to a plant cell in a hypertonic solution

Answer 54

Net movement of water is out of the cell. The cell becomes **flaccid (limp)**. The cytoplasm and the membrane pull away from the cell wall, **the cell is plasmolysed**