Topic 8 - Exchange and Transport in Animals✅

Edexcel gcse biology topic 8 i love my life! bio is my fav subject ever! i sit down with a smile on my face when i remember it's time for biology revision!

How is oxygen transported in and out of organisms and why is it needed

• Oxygen is exchanged in the alveoli by diffusion.

• It is needed for aerobic respiration

How is carbon dioxide transported in and out of organisms

• Carbon dioxide is exchanged in the alveoli by diffusion.

• It is a waste product of metabolism

How is water transported in and out of organisms and why is it needed

• Water is exchanged in the nephron by osmosis.

It is needed for cell function

How are dissolved foods transported in and out of organisms and why is it needed

• Dissolved foods are exchanged in the small intestine by diffusion.

• They are needed to make new substances and for respiration

How are mineral ions transported in and out of organisms and why is it needed

• Mineral ions are exchanged by the small intestine by diffusion.

• They are needed to make new substances

How is urea transported in and out of organisms and what is it

• Urea is exchanged in the nephrons by diffusion

• It is a waste product of metabolism

Explain the need for exchange surfaces and a transport system in multicellular organisms

• Multicellular organisms have a smaller surface area compared to their volume

• This makes it difficult to exchange enough substances to supply their entire body

• So, there are exchange surfaces to allow for efficient diffusion

• and a mass transport system to move substance between he exchange the surface and the rest of the body

How are alveoli adapted for gas exchange

• Alveoli are surrounded by blood vessels with thin walls, allowing gas exchange between the lungs and the blood

• They are very small and arranged in clusters, creating a large surface area for diffusion

• The capillaries provide a large blood supply, maintaining the concentration gradient

• The walls of the alveoli are thin, meaning the diffusion distance is small

Factors affecting rate of diffusion

• Concentration gradient

• Diffusion distance

• Surface area

How does concentration gradient affect rate of diffusion

• The greater the difference in concentration, the faster the rate of diffusion

• This is because more particles are moving down the gradient than against it

How does diffusion distance affect rate of diffusion

If the diffusion distance is small, diffusion happens faster because the particles do not have as far to travel

How does surface area affect rate of diffusion

• The greater the surface area, the more space for particles to move through

• Therefore faster rate of diffusion

Formula for rate of diffusion

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What is the structure of the blood

• 45% red blood cells

• 55% plasma

• <1% white blood cells and platelets

How is the structure of red blood cells related to their function

• They have a biconcave disc shape

• Meaning large surface area

• They have no nucleus

• Allowing more room to carry oxygen

• They contain the red pigment haemoglobin

• which binds to oxygen and forms oxyhaemoglobin

How is the structure of phagocyte white blood cells related to their function

• Phagocyte white blood cells change shape to surround and engulf pathogens

What are lymphocyte white blood cells

• Lymphocyte white blood cells produce antibodies which engulf pathogens, and make antitoxins which neutralise toxins made by pathogens

How is the structure of platelets related to their function

• They are small fragments of cells and they have no nucleus

• Platelets help blood clots to form

• These make scabs which block wounds, lower blood loss, and stop pathogens from entering

How is the structure of plasma related to its function

• Plasma carries hormones, proteins, antibodies and antitoxins

• It suspends red and white blood cells and platelets

• Also carries CO₂, glucose, urea

Structure and function of arteries

• Function = Arteries carry blood away from the heart

• Structure = they have layers of muscle in the walls, making them strong

• Elastic fibres mean they can stretch

• Both of these characteristics help arteries withstand the high pressure created by the pumping of the heart

Structure and function of veins

Function:

• They carry blood towards the heart

Structure:

• Lumen is wide, allowing the blood to flow through

• Have valves, ensuring the blood flows in the right direction

Structure and function of capillaries

• They allow the blood to flow close to cells, enabling substances to move in and out of them

• They have one-cell-thick walls, creating a short diffusion distance

• They have permeable walls, so substances can move across them

Explain the double circulatory system

• Deoxygenated blood flows into the right atrium, then the right ventricle, which pumps it to the lungs to undergo gas exchange

• Oxygenated blood flows into the left atrium, then into the left ventricle, which pumps oxygenated blood around the body

What is the structure of the heart

• Muscular walls to provide a strong heartbeat

• The wall of the left ventricle is thicker because blood needs to be pumped all around the body, rather than just to the lung

• There are 4 chambers

• There are valves to make sure blood does not flow backwards

• Coronary arteries cover the heart to provide its own oxygenated blood supply

What is the process of blood travelling around the body

1. Blood flows into the right atrium through the vena cava, and the left atrium through the pulmonary vein

2. The atria contract, forcing the blood into the ventricles

3. The ventricles then contract, pushing the blood in the right ventricle into the pulmonary artery to be taken to the lungs, and blood in the left ventricle to the aorta to be taken around the body

4. As this happens, valves close to make sure the blood does not flow backwards

Describe cellular respiration

• Cellular respiration is an exothermic reaction

• Occurs continuously in living cells

• To release energy for metabolic processes

Difference between aerobic respiration and anaerobic respiration

• Aerobic respiration uses oxygen

• It converts glucose and oxygen to carbon dioxide and water

• Anaerobic respiration does not use oxygen

• In animals, it converts glucose to lactic acid

• In plant and yeast cells, it converts glucose to ethanol and carbon dioxide

When is anaerobic respiration used

As a last resort when there is not enough oxygen

Balanced equation for aerobic respiration

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Core Practical: Investigate the rate of respiration in living organisms METHOD

1. Pick a small organism that you'd like to measure the rate of respiration of e.g. Maggots

2. Place 5cm3 of soda lime in a test tube

3. Place gauze on top and a small amount of the organism being tested on top

4. Attach a three way tap, capillary tube, and syringe to the test tube. Plug the test tube with a stopper

5. Insert a small amount of coloured liquid into the capillary tube

6. Turn the 3 way tap to allow air to enter the test tube for 5 mins. After 5 mins, close the 3 way tap

7. Record how far the liquid moves against a scale

A) Why is soda lime used in this experiment

B) Why must it be handled carefully

A) Soda lime is used to absorb any carbon dioxide produced by the respiring organisms

B) Because it is corrosive

Formula for heart rate, stroke volume and cardiac output

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