Biology: Chapter 3

Question 1

Definition of Diffusion

Answer 1

The net movement of particles from a higher concentration region to a lower concentration region (down a concentration gradient), as a result of their random movement.

Question 2

Name of term for the random movement of particles

Answer 2

Brownian motion

Question 2

Energy which is used for particles to diffuse and have random motion

Answer 2

Kinetic energy

Question 3

Definition of Net Movement

Answer 3

Overall/Average movement of particles

Question 4

Definition of Partially-Permeable Membrane

Answer 4

A cell membrane which can restrict the free movement of molecules

Question 4

What is the selection of which cells pass the cell membrane and which do not based on?

Answer 4

Size of particle

Question 4

Functions of Diffusion

Answer 4

• obtain many of their requirement (oxygen/nutrients)
• remove waste products (carbon dioxide & urea)
• carry out gas exchange for respiration

Question 5

3 Examples of Diffusion in Living Organisms

Answer 5

• photosynthesis (movement of CO2 and O2 in and out of leaf)
• nutrient absorption (digestive products–glucose, amino acid, fatty acid and glycerol–in small intestines pass through blood capillary by diffusion)
• gas exchange (movement of O2 from alveoli into the red blood cell)

Question 6

Factors that affect a Rate of Diffusion

Answer 6

Surface area to volume ratio
- The bigger a cell/structure is, the smaller its surface area to volume ratio is
- smaller surface area to volume ratio = lower rate of diffusion
- the bigger the structure, the slower the rate of diffusion

Distance between two areas of diffusion
- smaller distance = faster transport

Temperature
- higher temperature = faster movement of molecules (heat energy&raquo_space; kinetic energy)
- higher temperature = faster rate of diffusion

Concentration gradient
- higher concentration gradient between two sides of membrane = faster rate of diffusion

Question 7

Cells that are adapted for diffusion (that have increased surface area)

Answer 7

• root hair cells in plants (absorb water + mineral ions)
• cell lining the ileum in animals (absorb the products of digestion

Question 8

Definition of Osmosis

Answer 8

The net movement of water by diffusion from a region of high water potential to low water potential through a partially permeable membrane

Question 9

What is the concentration is being referred to in osmosis?

Answer 9

Water potential
- diluted solution = high water potential
- concentrated solution = low water potential

Question 10

Osmosis in animal cells

Answer 10

If an animal cell is placed in pure water:
- inside of the cell is more concentrated that outside of the cell
- water goes in through osmosis
- cell will swell and burst

If an animal cell is placed in a concentrated solution:
- outside of the cell is more concentrated than inside of the cell
- water goes out of the cell by osmosis
- cell will shrink

Question 11

Osmosis in plant cells

Answer 11

If plant cell is placed in pure water:
- water enters the cell by osmosis
- cytoplasm and vacuole will swell
- strong cell wall will prevent it from bursting
- turgor pressure (water pushing outwards) will keep the cell strong and firm (turgid)

If plant cell is placed in concentrated solution:
- water leaves the cell by osmosis
- cytoplasm and vacuole will shrink
- cell wall will stay in position
- cytoplasm and cell wall pull away from cell wall
- cell becomes soft and floppy (flaccid) after losing turgor pressure

Question 12

What is the condition of a cell when its cell membrane tears away from cell wall?

Answer 12

Plasmolysed

Question 13

How is Active Transport is carried out?

Answer 13

Low quantity of molecules
- cells need to take in substances which are only present in small quantities

Carrier protein
- cell membrane pick up molecules from low concentration area
- energy needed to change shape of protein to push molecules through cell membrane

Using ATP
- use energy to move substances across membranes
- energy provided by respiration

Question 14

3 Examples of Active Transport

Answer 14

1. Reabsorption of glucose from glomerular filtrate in blood capillary
2. Root hair cells take in mineral ions
3. Uptake of glucose in small intestines

Question 15

How do ions enter cells by active transport?

Answer 15

1. Nitrate ion enters carrier protein
2. Carrier protein changes shape (requires energy provided by respiration)
3. The change of shape of carrier protein pushes nitrate ion into cell