Section 8- Exchange And Transport In Animals Flashcards
What do organisms need to do
All organisms must take in substances that they need from the environment and get rid of any waste products
Examples of organisms exchanging materials
- cells need OXYGEN for aerobic respiration, which produces CARBON DIOXIDE as a WASTE PRODUCT. These 2 gases move between cells and the environment by diffusion
- water is taken up by cells by OSMOSIS. In animals, dissolved food molecules and mineral ions diffuse along with it.
- urea (waste product produced by animals from proteins) diffuses from cells to the blood plasma for removal from the body by the kidneys
What is depended on the surface area:volume ratio
How easy it is for an organism to exchange substances with its environment depends on the SA:V
What is the alveoli
- exchange surface found in the lungs of mammals. They’re well adapted for the efficient exchange of oxygen and carbon dioxide
What is exchange in single called organisms
Gases and dissolved substances can diffuse directly into the cell across the cell membrane, it is because they have large surface area compared to their volume, so enough substances can be exchanged across the membrane to supply the volume of the cell
What is exchange in multicellular organisms
They have smaller surface areas compared to their volume. This makes it difficult to exchange enough substances to supply their entire volume across their outside surface alone. So they need some sort of exchange surface for efficient diffusion and mass transport system to move substances between the exchange surface and the rest of the body.
What do exchange surfaces have to allow
They have to allow enough of the necessary substances to pass through, so they are adapted to maximise effectiveness
Gas exchange in mammals in the alveoli
- The job of the lungs is to transfer oxygen to the blood and to remove waste carbon dioxide from it.
- To do this, the lungs contain millions of little air sacs called alveoli where gas exchange takes place.
- Blood arriving at the alveoli has just returned to the lungs from the rest of the body, so it contains a lot of carbon dioxide and not much oxygen. This maximises the concentration gradient for the diffusion of both gases
- Oxygen diffuses out of the air in the alveoli where the concentration of oxygen is higher and into the blood where the concentration of oxygen is low
- Oxygen diffuses in the opposite direction to be breathed out
How is alveoli adapted for efficient gas exchange
- moist lining for dissolving gasses
- a good blood supply to maintain the concentration gradient of oxygen and carbon dioxide
- very thin walls to minimise the distance that gases have to move
- large surface area
What is the role of blood cells
To carry oxygen from the lungs to all the cells i the body
Adaptations of red blood cells
- They have a biconcave disk shape to give a large surface area for absorbing oxygen
- They don’t have a nucleus which allows more room to carry oxygen.
- They contain a red pigment called haemoglobin which contains iron.
What happened to the red blood cells in high altitudes?
The more red blood cells you’ve got the more oxygen you can get your cells at high altitudes. There’s less oxygen in the air so people who live there produce more red blood cells to compensate.
Oxyhaemoglobin
In the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin. In body tissues, the reverse happens, oxyhaemoglobin, split up into haemoglobin and oxygen to release oxygen to the cells.
What is the role of white blood cells?
White blood cells defend against infection
Types of white blood cells
- Phagocytes.
- Lymphocyte.
Phagocytes
Phagocytes are white blood cells that can change shape to engulf microorganisms. This is called phagocytosis.
Lymphocytes
White blood cells that produce antibodies against microorganisms. Some also produce antitoxins to neutralise any toxins produced by the microorganisms.