SB8 - Exchange and Transport in Animals Flashcards
What substances need to be transported into and out of the body?
- urea (poison produced by breaking down amino acids) - removed by kidneys
- carbon dioxide ( produced in aerobic respiration) - breathed out
- glucose and oxygen need to be moved into your body for aerobic respiration. Dissolved food molecules and mineral ions are needed to produce new substances in the body.
What are the properties of diffusion surfaces that make them well adapted?
- they are thin so that particles so not have to diffuse very far
- they have a large surface area, so that there is more room for particles to diffuse (increases rate of diffusion)
Why do multicellular organisms need transport systems?
It would take too long for materials to diffuse through the cells on the outside of a tissue to reach cells on the inside.
What is the surface area to volume ratio?
Surface area divided by volume
Surface area / volume
What is the relationship between the size of a cell and the surface area to volume ratio?
The larger a cell is, the smaller the surface are to volume ratio. If the ratio is too small, a cell cannot get raw materials fast enough. So, there is a limit to the size of cells.
Describe how gases are exchanged in the alveoli in the lungs?
- blood enters from the body with a higher concentration of carbon dioxide and a lower concentration of oxygen,
- the blood moves around the alveolus, with the net movement of carbon dioxide being into the alveolus and the net movement of oxygen being into the blood (this is because the alveolus has a higher concentration of oxygen and a lower concentration of carbon dioxide than the blood)
- blood goes to the rest of the body with a lower concentration of carbon dioxide and a higher concentration of oxygen.
How are the alveoli adapted to fast gas exchange?
- the alveoli have a large surface area to increase the rate of diffusion
- both the alveoli and the capillaries are one cell thick, increasing the rate of diffusion.
What is the relationship between concentration gradient and rate of diffusion?
The bigger the difference in concentrations, the steeper the concentration gradient and the faster the rate of diffusion.
The rate of diffusion is directly proportional to the concentration gradient
What is the relationship between surface area and rate of diffusion?
If the surface area of a membrane is increased, there is more space through which the particle can pass (so more particles pass in a given amount of time). This means that the rate of diffusion is faster.
Rate of diffusion is directly proportional to surface area
What is the relationship between thickness of membrane and rate of diffusion?
The further particles have to diffuse, the slower the rate of diffusion. Increasing thickness decreases rate of diffusion.
Rate of diffusion is inversely proportional to thickness of membrane
What is Fick’s law?
Fick’s law shows the relationship between the variables that affect diffusion.
Rate of diffusion is directly proportional to concentration gradient x surface area / thickness of membrane
How are arteries adapted to high blood pressure?
With each beat, the heart squirts blood into the arteries under high pressure. Artery walls are thick to withstand this pressure, but it makes them stretch. A wave of stretching then passes along the artery walls. You feel this as your pulse. After stretching, muscle and elastic fibres in the artery walls cause the arteries to contract again. The stretching and contracting of arteries makes blood flow more smoothly.
How are veins adapted?
Blood flows under low pressure in veins, so only thin walls are needed. As you move, muscles help push the blood along the veins. Veins have valves to prevent back flow (blood flowing in the wrong direction).
What does plasma do?
Plasma is a straw-coloured liquid in the blood which carries dissolved substances such as glucose carbon dioxide and urea. It also suspends all blood cells so they can move around the body. Plasma is mainly made of water so it can carry dissolved substances easily.
What do platelets do?
Platelets are tiny fragments of cells which have no nuclei. They produce substances needed to clot the blood at the site of an injury, when the skin is cut. This prevents bleeding and also forms scabs to stop pathogens from entering.
