Topic 8 - Exchange and transport in animals Flashcards
Which substances may need to be transported into and out of organisms and why?
Oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea.
This is to prevent them from accumulating. We need to intake oxygen and get rid of waste products
What is the equation for surface area to volume ratio and what does it mean?
Volume = length x width x height
Surface area = length x width
Write the ratio in the smallest whole numbers.
If the ratio is large the organism is less likely to require specialised exchange surfaces and a transport system because the rate of diffusion is sufficient in supplying and removing the necessary gases.
Describe villi
In the small intestine, cells have protections called villi. Digested food is absorbed over the membrane of these cells, into the bloodstream
Why is having a large surface area a beneficial adaptation?
The greater the surface area, the more particles can move through, resulting in a faster rate of diffusion.
e.g. Villi or leaves flattened shape and air spaces inside allows more carbon dioxide to enter the cells
Why is having an efficient blood supply/being ventilated (in animals) a beneficial adaptation?
It creates a steep concentration gradient, so diffusion occurs faster
Why is having a thin membrane a beneficial adaptation?
It provides a short diffusion pathway, allowing the process to occur faster e.g. villi
Explain how alveoli are adapted for gas exchange
Alveoli are small ‘air sacs’ in the lungs. They are surrounded by blood vessels with thin walls, allowing gas exchange between the lungs and blood.
-They are very small and arranged in clusters, creating a large surface area for diffusion to take place over
-The capillaries provide a large blood supply, maintaining the concentration gradient
-The walls of the alveoli are very thin, meaning there is a short diffusion pathway
They gas exchange by diffusion between air in the lungs and blood in the capillaries.
How does surface area affect the rate of diffusion?
The larger the surface area, the higher the number of particles that will be able to move in a given time (more space for particles to move through) so the rate of diffusion is faster
How does concentration gradient affect the rate of diffusion?
Diffusion is faster if there is a big difference in the concentration between the area the substance travels from and the area that it is moving to
How does diffusion distance affect the rate of diffusion?
If the diffusion distance is small, diffusion happens faster because the particles do not have as far to travel
What is Fick’s law?
rate of diffusion ∝ surface area*concentration difference/thickness of membrane
Explain how the structure of red blood cells (erythrocytes) is related to its function
Its function is to carry oxygen molecules from the lungs to all the cells in the body
-They have no nucleus so they can contain more haemoglobin (a red pigment which can combine with oxygen)
-They have a biconcave disc shape to maximise their surface area for oxygen absorption
-They are thin so there is only a short distance for the oxygen to diffuse to reach the centre of the cell
Explain how the structure of white blood cells (phagocytes and lymphocytes) is related to its function
They are a part of the immune system, which defends against pathogens.
-70% of white blood cells are phagocytes which engulf and destroy unwanted microorganism that enter the blood by the process of phagocytosis
-25% are lymphocytes which produce soluble proteins called antibodies when a foreign body such as a microorganism enters the body.
Explain how the structure of plasma is related to its function
The liquid that carries components in the blood including red blood cells, white blood cells, platelets, glucose, amino acids, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins
Explain how the structure of platelets is related to its function
Platelets are cell fragments produced by giant cells int he bone marrow which help stop bleeding.
-They have proteins on their surface that enable them t stick to breaks in a blood vessel and clump together
-They secrete proteins that result in a series of chemical reactions that make blood clot, which plugs a wound
-The clot dries and hardens to form a scab, this allows new skin to grow underneath while preventing microorganisms from entering
-They have no nucleus
