Topic 8 - Exchange and Transport in Animals Flashcards
What waste product would a cell get rid of, whilst taking in substances it needs for life processes from the environment?
Cells need oxygen for aerobic respiration, which produces carbon dioxide as a waste product. These two gases move between cells and the environment by diffusion.
What waste product would water get rid of, whilst taking in substances it needs for life processes from the environment?
Water is taken up by cells by osmosis. In animals, dissolved food molecules (the products of digestion, e.g. glucose, amino acids) and mineral ions diffuse along with it.
What is urea?
A waste product produced by animals from the breakdown of proteins
What is urea removed from and by?
It diffuses into the blood plasma for removal from the body by the kidneys
What does a small surface area to volume ratio mean?
The organism is larger
What does a big surface area to volume ratio mean?
The organism is smaller
How do you calculate the volume?
volume = length * width * height
How do you calculate the surface area of an object?
Find the area of all the sides, using the equation, area = length * width. Then add all the areas together.
How should a surface area to volume ratio be written?
The volume should always be 1.
Why are exchange surfaces needed in single-celled organisms?
In single-celled organisms, gases and dissolved substances can diffuse directly into (or out of) the cell across the cell membrane. It’s because they have a large surface area compared to their volume, so enough substances can be exchanged across the membrane to supply the volume of the cell.
Why are exchange surfaces needed in multicellular organisms?
Multicellular organisms (such as animals) have a smaller surface area compared to their volume. This makes it difficult to exchange enough substances to supply their entire volume across their outside surface alone. This means they need some sort of exchange surface for efficient diffusion and a transport system to move substances between the exchange surface and the rest of the body.
What factors affect the rate of diffusion?
- Temperature
- Surface area
- Concentration difference (gradient)
- Distance to move
How does temperature affect the rate of diffusion?
If the temperature increases, the rate of diffusion increases, but if temperature decreases the rate of diffusion decreases
How does surface area affect the rate of diffusion?
The more surface there is available for molecules to move across, the faster they can get from one side to the other.
How does the concentration difference (gradient) affect the rate of diffusion?
Substances diffuse faster if there is a big difference in concentration between the area they are diffusing from and the area they are diffusing to. If there are lots more particles on one side, there are more there to move across.
How does the distance to move affect the rate of diffusion?
Substances diffuse more quickly when they haven’t as far to move. The thinner the exchange surface (e.g. a cell membrane) the shorter the distance substances have to diffuse across it and so the faster the rate of diffusion. The posh way of saying this is that the substances have a ‘short diffusion pathway’.
What is Fick’s law?
rate of diffusion ∝ (surface area * concentration difference) ÷ thickness of membrane
What does Fick’s law mean?
The rate of diffusion increases in proportion to (at the same rate as) the surface area or concentration difference and inverse proportion to the thickness of the membrane
How can the rate of diffusion double (using Fick’s law)?
- if the surface area or concentration doubles
or - if the thickness of the membrane halves
What is the rate of diffusion measured in?
a.u.
What does a.u. stand for?
arbitrary units
In humans (and other mammals), where are gases exchanged by diffusion?
alveoli
What is the function of the lungs?
To transfer oxygen to the blood and remove waste carbon dioxide from it.
Label a gas exchange in the alveolus diagram
https://www.purposegames.com/game/the-alveoli-and-gas-exchange
Label a lungs diagram
https://www.purposegames.com/game/respiratory-system-labeling-interactive-game
What are the alveoli surrounded by?
blood vessels known as capillaries
Where has the blood arriving to the alveoli come from?
It has come from the rest of the body, so it contains lots of carbon dioxide and not much oxygen. This maximises the concentration gradient for the diffusion of both gases.
How is the concentration gradient maximised for oxygen and carbon dioxide, once the blood has come from the body?
- There is a higher concentration of oxygen in the air than in the blood, so oxygen diffuses out of the air in the alveoli and into the blood in the capillaries.
- Carbon dioxide diffuses in the opposite direction, from a high concentration in the blood to a low concentration in the alveoli, to be breathed out.
What are the adaptations of the alveoli?
- Large surface area to enable more diffusion of oxygen to the blood and more carbon dioxide out of the blood
- One cell thick so the diffusion distance is small
- Lots of blood capillaries to ensure a good blood supply to maintain concentration gradients of oxygen and carbon dioxide
- Moist surfaces for gases to dissolve in, to form a solution to pass through the cell membrane
What does the circulatory system include?
- Blood
- Blood vessels
- Heart
What is the function of the circulatory system?
- To get food and oxygen to every cell in the body
- Carries waste products like carbon dioxide and urea, to where they can be removed from the body
What is a tissue?
A group of similar cells that work together to perform a specific function
What is blood?
a tissue
What is the function of blood?
To transport substances around the body
What is blood made up of?
- Red blood cells
- White blood cells
- Platelets
- All the above are suspended with plasma
What is another name for red blood cells?
Erythrocytes
What is the function of a red blood cell?
To transport oxygen around the body
Why do red blood cells have a biconcave shape?
To give them a large surface area for absorbing oxygen