Diffusion

Question 1

Diffusion:

Answer 1

• The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient until equilibrium Is reached
• It Is a passive form of transport

Question 2

What direction does diffusion occur in?

Answer 2

Diffusion occurs in all directions and travels from an area of high concentration to an area of low concentration

Question 3

How may substances move into and out of cells?

Answer 3

Via diffusion

Question 4

What are factors which increase the rate of diffusion?

Answer 4

• The difference in concentrations (steeper concentration gradient)
• The temperature - the higher the temperature the more kinetic E for the particles ar the faster they can diffuse
• The surface area of the membrane for particles to diffuse
• Short diffusion pathway - thin membrane for particles to diffuse into

Question 5

What does every living organism need to do?

Answer 5

Exchange materials with its surroundings

Question 6

What does the amount of material which needs to be exchanged depend on?

Answer 6

Its volume

Question 7

Where can the process of exchange only take place?

Answer 7

Across its surface

Question 8

What are some substances that are transported into cells by diffusion?

Answer 8

Take in substances like glucose and oxygen (gas exchange) for respiration in gas exchange

Question 9

What are some substances that are transported out of cells by diffusion?

Answer 9

• CO2 from gas exchange
• The waste product urea from cells into the blood plasma for excretion in the kidney
• Waste products need to be removed

Question 10

Why do organisms stop growing after a certain stage?

Answer 10

Organisms stop growing after they reach a certain stage because if their volume increased more required substances may not be able to reach cells in the inside and their surface area wouldn’t be big enough for their volume

Question 11

Why can’t cells grow enormous?

Answer 11

Cells can’t grow enormous because there wouldn’t be enough accessible substances

Question 12

What is the effectiveness of an exchange surface (allows better diffusion) is increased by?

Answer 12

• Having a large surface area - increases site of exchange
• A membrane that is thin - provides a short diffusion pathway
• (in animals) having an efficient blood supply
• (in animals for gaseous exchange) being ventilated
• A method of transporting substances to and from the exchange site (e.g. a good blooc supply) - maintains a steep concentration gradient

Question 13

Gas exchange in humans:

Answer 13

At each cell in your body, oxygen is exchanged for a waste gas called carbon dioxide. Your bloodstream then carries this waste gas back to the lungs where it is removed from the bloodstream and then exhaled. Your lungs and respiratory system automatically perform this vital process, called gas exchange.

Question 14

Function of villus in the small intestine:

Answer 14

Each villus moves nutrients from the intestine to a network of capillaries and fine lymphatic vessels. These lymphatic vessels are called lacteals. The lacteals transports excess fluid, fatty acids, and glycerol away from the small intestine into the blood.

Question 15

Adaptations for exchanging materials of villus in small intestine:

Answer 15

A large surface area. Microvilli on the surface of the villus further increase the surface available for absorption.

A short diffusion distance. The wall of a villus is only one cell thick.

Question 16

Function of plant roots:

Answer 16

The roots of a plant take up water and nutrients from the soil. They also anchor the plant to the ground and keep it steady. The stem carries water and nutrients to different parts of the plant. It also provides support and keeps the plant standing upright.

Question 17

What substances are exchanged in plant roots?

Answer 17

Plant leaves are adapted for photosynthesis and gas exchange. Roots absorb water and mineral ions through root hair cells and are transported up the plant by the xylem.

Question 18

Adaptations for exchanging materials of plant roots:

Answer 18

Roots have specialised cells called root hair cells. These have long thin projections that stick out into the soil.

Question 19

Function of plant leaves:

Answer 19

Leaves are the main (but not only) organ responsible for turning sunlight into food.

Question 20

Adaptations for exchanging materials in plant leaves:

Answer 20

They are thin which gives a short diffusion distance.
They are flat which provides a large surface area to volume ratio.
They have many stomata which allow movement of gases in and out of the air spaces by diffusion.

Question 21

Function of gills in fish:

Answer 21

Fish gills are organs that allow fish to breathe underwater. Most fish exchange gases like oxygen and carbon dioxide using gills that are protected under gill covers (operculum) on both sides of the pharynx (throat). Gills are tissues that are like short threads, protein structures called filaments.

Question 22

Adaptations for exchanging materials in gills in fish:

Answer 22

the large surface area of the gills.
the large surface area of the blood capillaries in each gill filament.
the short distance required for diffusion – the outer layer of the gill filaments and the capillary walls are just one cell thick.

Question 23

Function of lungs:

Answer 23

The lungs and respiratory system allow us to breathe. They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (called expiration, or exhalation).

Question 24

How have lungs ensured maximum gas exchange?

Answer 24

Large surface area - many alveoli are present in the lungs with a shape that further increases surface area. Thin walls - alveolar walls are one cell thick providing gases with a short diffusion distance. Moist walls - gases dissolve in the moisture helping them to pass across the gas exchange surface.

Question 25

Adaptations for exchanging materials in lungs:

Answer 25

The walls of the alveoli are one cell thick to create a short diffusion distance for gas exchange.

There are millions of alveoli to increase the surface area of the lungs for gas exchange.

Question 26

How does the circulatory system contribute to the diffusion of gases?

Answer 26

The systemic circulation is under high pressure - it has to deliver blood to the extremities of the body. The pulmonary circulation is under lower pressure, because: blood is delivered to the lungs only, which are very close to the heart.