It is important for substances to be transported into organisms because they are essential for various biological processes. Nutrients, such as carbohydrates, proteins, and fats, provide energy for cellular activities and growth. Oxygen is necessary for cellular respiration, which generates energy. Water is crucial for maintaining hydration and facilitating chemical reactions. Additionally, hormones, enzymes, and other signalling molecules regulate physiological functions. Without the transport of these substances, organisms would not be able to survive or function properly.

Exchange surfaces and transport systems

Specialised surfaces allow efficient transport of substances form one area to the next.

- In the lungs

oxygen is transferred to the blood and carbon dioxide is transferred to the lungs. This takes place across air sacs called alveoli and they are covered in capillaries

- In the small intestine

Cells have projections called villi. Digested food is absorbed over the membrane of the villi and diffused into the blood stream

Surface area : Volume

The size of the surface are compared to it’s volume.

Surface area- Length x width The larger the number, the less likely the organism is to need exchange

Volume- Length x width x height surfaces because rate of diffusion is sufficient

Multicellular organisms- the surface area to volume ratio is small so they cannot depend on diffusion. Instead, they have a number of adaptations to allow molecules to diffuse.

Adaptation of alveoli

• Alveoli are small and arranged in clusters so it creates a large surface area for diffusion to take place

• Capillaries contribute a large blood supply it maintains the concentration gradient

• The walls are thin so it has a short diffusion pathway

Blood structure and function

Plasma

• Carries the components in the blood such as glucose, amino acids, platelets, white blood cells and urea

Red blood cells

• Carry oxygen from lungs to the cells in the body

• have a biconcave shape for large surface area

• have no nucleus so it can carry more oxygen

• Contain a red pigment called haemoglobin which binds with oxygen to form oxyhaemoglobin

White blood cells

• Part of the immune system that defences the body against pathogens

• Lymphocytes- produce antibodies to fight against pathogens

• Phagocytes- engulf pathogen in the process called phagocytosis

Platelets

• Help blood to clot once a wound has been formed

• small fragments of bone marrow

• no nucleus

Structure and function of blood vessels

Arteries- carry blood AWAY from the heart

• the lumen has layers of muscle to make it strong

• elastic fibres allow the arteries to stretch

• helps the vessels to withstand high pressure created by the pumping of the heart

Veins- carry blood TOWARDS the heart

• the lumen is wide to allow low pressure blood to flow through

• they have values to blood does not flow the wrong way

Capillaries- allow blood to flow close to sells and allow diffusion

• one cell thick creates short pathway for diffusion

Heart and circulatory system structure and function

The heart pumps blood around the body in a double circulatory system. This means that there are two circuits

• Deoxygenated blood - flows into the right atrium and goes into the right ventricle and pumps blood into the lungs to undergo gas exchange

• Oxygenated blood- flows into the left atrium and then the left ventricle and pumps oxygenated blood around the body

Structure of the heart

- Muscular walls to provide a strong heartbeat

- Walls on the left ventricle are thicker because blood has to pumped all around the body rather than just to the lung

- there are four chambers that separate the oxygenated blood from the deoxygenated blood

- there are valves to ensure that the blood does not flow backwards

- coronary arteries to cover the heart and make sure that it has it’s own blood supply

Process of pumping blood

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

2) The atria contracts and the blood in forced into the ventricles

3)The ventricles contract and pushes blood into the left ventricle and to the the aorta to be taken around the body

4) When this happens, the valves close so that blood does not flow backwards

The natural resting heart rate is around 70 bpm and is controlled by a group of cells found in the right atrium named pacemakers. They provide a stimulation through small electrical impulses which pass as a wave across the heart muscle and causes it to contract. Without this, the heart will not pump fast enough and deliver the amount of oxygen that is required to the whole body.

An artificial pacemaker can be made if the individual has an irregular heartbeat. It is an electrical device that produces a signal to cause the heart to beat at a normal speed.

Respiration

• Cellular respiration- exothermic reaction which occurs continuously in living cells to release energy for metabolic processes including aerobic and anaerobic respiration

Core Practical

Investigate the rate of respiration in living organisms

We will use a respirometers to measure the effect of temperature on the oxygen consumption of small organisms.

1. pick small organism to measure the rate of respiration

2. place 5cm cubed of soda lime into a test tube

3. place a gauze on top

4. add a three-way tap, capillary tube and syringe into the test tube

5. insert coloured liquid in the capillary tube

6. turn the three way tap and allow oxygen to fill the tube for five minutes

7. record how far the coloured liquid has moved against a scale

Calculating heart rate, stroke volume and cardias output

Heart rate- number of times the heart beats per minute

Stroke volume- the volume of blood pushed into the aorta in each beat(measured in LITRES)

Cardiac output- volume of blood pushed into the aorta each minute.

Calculation of cardiac output- Cardiac output= stroke volume x heart rate