Exchange - Size and Surface Area

Question 1

Organisms need to exchange substances with their environment

Answer 1

1. Cells take in oxygen (for aerobic respiration) + nutrients
2. Cells excrete waste products including co2 + urea
3. Organisms exchange heat with surroundings to keep at a constant temp

Question 2

Surface area to volume ratio

Answer 2

This is how much of the surface is exposed compared to volume.

The higher the SA:V, higher rate of exchange

More of the organisms surface is exposed compared to volume

Question 3

Exchange in single celled organisms

Answer 3

Single celled organisms do not need specialised exhange organs and mass transport systems. Substances move into their cells through the cell surface membranes via diffusion, this happens quickly. This is because there is a small distance for the substances to move across

Question 4

Exchange in multi-cellular organisms

Answer 4

Multi cellular organisms require specialised exchange organs and mass transport systems. Larger animals have low SA:V. The distance between the outside environment and the cells in the organism is large. Diffusion would be too slow.

Question 5

Mass Transport

Answer 5

Carries substances to and from individual cells in multi-cellular organisms

Question 6

General adaptations of gas exchange surfaces

Answer 6

1. Large surface area, increases rate of diffusionj
2. Thin surface layer - usually one layer of epthilial cells. Short diffusion pathway. Increases rate of diffusion by decreasing distance over which it happens
3. High conc gradient across gas exchange surface

Question 7

Gas exchange in single celled organisms

Answer 7

1. Gasses (O2, CO2) directly diffuse through outer surface
2. Because large surface area + thin surface
3. No need for gas exhange system

Question 8

Gas exchange in multi-cellular organisms

Answer 8

1. Fish
2. Insects
3. Plants
4. Humans

Question 9

Fish

Answer 9

Water contains less oxygen than air, therefore, fish haves special adaptations to gas exhange to ensure they get enough oxygen

1. Water enters mouth of fish, then moves through gills
2. Gills are made up of lots of thin plates called gill fillaments, which increase surface area
3. Gill filaments are covered in tiny structures called lamellae which further increase SA
4. Lamella have a thin surface and lots of blood capillaries
5. Blood enters the lamellae in one direction and watere enters in the opposite direction. This is called counter current flow and maintains a high conc gradient of oxygen between water and blood. The conc of O2 in water is always more than blood, so O2 diffuses from water to blood

Question 10

Insects

Answer 10

1. Gas exchange occurs in tracheae
2. Air enters trachea through pores on surface known as spiracles
3. The trachea split into tracheaoles which have thin + permeable walls. They go to each cell
4. Oxygen diffuses down its conc gradient, from air into trachea via spiracles then down tracheaoles to respiring cells
5. CO2 diffuses down its conc gradient, from cells to tracheoles, then from tracheae to air via spiracles
6. Insects use rythmic abdominal movements to move air in and out of spiracles

Question 11

Tidal Volume

Answer 11

Volume of air in each breath

Question 12

Ventilation rate

Answer 12

No. of breaths per min

Question 13

FEV - Forced Expiratory Volume

Answer 13

max vol of air breathed out in 1 second

Question 14

FVC - forced vital capacity

Answer 14

max vol of air forcefully breathed out after taking in deep breath

Question 15

Spirometer

Answer 15

Machine used to measure vol of air breathed in and out. Can be used to work out tidal vol, ventilation rate etc

Question 16

Residual air

Answer 16

Air in lungs which can not be expelled

Question 17

Lung Diseases FAPE

Answer 17

Fibrosis
Asthma
Pulmonary Tuberculosis
Emphysema

Question 18

Pulmomonary Tuberculosis

Answer 18

1. Person infected with tubercuolsis bacteria
2. Immune system cells form a wall around the bacteria in the lungs leading to formation of a hard tuberceles
3. Tissue infected with tubercles dies. This damages gas exhange surface, reducing rate of gas exhange, reducing tidal volume. This means lower vol. of air can be inhaled in each breath, therefore, to ensure enough oxygen enters blood, person breaths faster, so increased ventilation rate
4. Symptoms include persistant cough, coughing up blood and mucus, fatigue, shortness of breath + chest pain

Question 19

Fibrosis

Answer 19

1. Result of scarred tissue in the lungs. Caused by exposure to too much dust or asbestos
2. Scarred tissue is thicker and less elastic than normal lung tissue
3. Less elastic means lungs cannot expand as well as they normally do. Reduces tidal volume. Less air can be inhaled in each breath. So, person breaths faster to ensure that they get enough oxygen in blood, so higher ventilation rate. Also, lower FVC
4. Scarred tissue is thicker meaning that the rate of gas exchange is reduced because rate of diffusion is reduced because thicker exhange surface so longer diffusion pathway
5. Symptoms include: Chest pain, shortness of breath, fatigue, dry cough fatigue

Question 20

Asthma

Answer 20

1. Inflammation and irritation to airways (trachea, bronchi, bronchioles). Caused by allergic reaction to pollen, dust etc
2. During asthma attack, smooth muscle lining in bronchioles contract, leading to production of lots of mucus.
3. This leads to constriction of airways. Less air can be breathed in and out. This reduces tidal volume. Lower vol of air can be inhaled in per breath. So, person breatjs faster to ensure enough oxygen enters blood, therefore, higher ventilation rate. Lower FEV
4. Symptoms include wheezing, tightning of chest, shortness of breath, fatigue
5. Symptoms reduced by taking drugs in inhalers. Relax smooth muscle lining of bronchioles, less mucus production, clearing of airways

Question 21

Emphysema

Answer 21

1. Caused by smoking or long-term exposure to pollution.
2. Foreign particles in air get trapped in alveoli
3. This leads to inflammation which attracts phagocytes
4. Phagocytes release an enzyme which breaks down elastin
5. Elastin is an elastic protein in the alveoli walls which help the alveoli return to normal shape after inhaling air and exhaling air
6. Loss of elastin means alveoli cannot recoil (return to normal shape) so cannot expel air therefore, air is trapped in alveoli
7. Also, when the phagocytes release enzyme which breaks down elastin, this leads to damage of the alveoli walls. Therefore, damage to gas exhange surface, reducing surface area of alveoli / gas exhange surface, reducing rate of gas exhange. Lower tidal volume. Lower vol. of air inhaled in in each breath. Therefore, person starts to breath faster to ensure enough oxygen in blood, so higher ventilation rate
8. Symptoms - shortness of breath, wheezing

Question 22

Why is a common symptom of all lung diseases fatigue, weakness and tiredness?

Answer 22

1. All lung diseases reduce rate of gas exchange
2. Rate of diffusion of oxygen from alveoli to blood is lower
3. Less oxygen absorbed into blood from alveoli
4. Less oxygen recieved by respiring cells
5. Rate of respiration drops
6. Less energy released

Question 23

Risk Factors

Answer 23

Factors which increase the chance of you actually getting the disease. e.g. smoking is a risk factor for cancer