Human Transport Flashcards
Why do simple, unicellular organisms rely on diffusion for movement of substances in and out of the cells?
Because they have a large surface area: volume ratio
What is the need for a transport system in multicellular organisms?
They have a small surface area: volume ratio which means diffusion is too slow as some of the organisms are too big. The cells in our body need glucose and oxygen and they need to get rid of waste products. They need a transport system to get these substances around the body fast enough.
What is the transport system called in multicellular organisms?
Circulatory System
What does the human transport system consist of?
Blood
Heart
Blood Vessels
What is the blood?
The blood is a tissue as it contains a variety of cell types suspended in plasma.
The blood consists of plasma, red blood cells, white blood cells and platelets.
What does plasma look like and what is their function?
Straw coloured liquid
Carries all the different cells along
Acts like a solvent
Which substances does the human transport carry around the body? (6)
- Carbon dioxide - dissolves in the plasma and travels to the lungs to be breathed out.
- Urea - the plasma carries the urea from the lungs to the kidneys to be made into urine.
- Small soluble products of digestion (glucose for example) - the plasma carries this from the small intestine to every cell in the body.
- Hormones - the plasma carries this to their target organ. E.g hormone (ADH) to kidney.
- Heat energy - carried around to help maintain body temperature.
- It also carries red blood cells, white blood cells and platelets.
What makes the blood look red?
The red blood cells as they contain haemoglobin
What is the function of the red blood cell?
To transport oxygen from the lungs to all the cells in the body
How are the red blood cells adapted to do its function? (4)
- No nucleus so that there is more room for carrying oxygen because they can hold more haemoglobin. This means that they can’t divide to make new cells. The liver gets rid of the old ones and the bone marrow creates new ones.
- They contain haemoglobin which combines with oxygen to form oxyhaemoglobin. This is how they transport oxygen around the body. The oxyhaemoglobin releases the oxygen when it reaches the cell.
- They have a biconcave disc which gives the cell a large surface to volume area for absorbing oxygen by diffusion.
- They are really small and flexible so that they can squeeze through the smallest capillaries.
People who live at high altitudes have a higher red blood cell count than people who live at sea level. Why do some athletes choose to train at high altitudes before a major competition?
They acquire more red blood cells which allows their blood to carry more oxygen. This means more aerobic respiration is there which means more energy, less fatigue and therefore a better performance.
What is the function of white blood cells?
They are a part of the immune system. They help the body fight infections and other diseases.
What are the two mains groups of the white blood cells?
Phagocytes and lymphocytes
How can the body tell if the infections are foreign and if they should attack them?
The body has particular shaped antigens whilst foreign cells have different shaped antigens and so can tell if they are foreign and then can attack them
What are antigens?
A protein on the surface of a substance that triggers a immune response.
Function of a phagocyte and the name of the process
They engulf pathogens by flowing around them until they are completely enclosed and digest and kill them. This is called phagocytosis.
Function of a lymphocyte
They produce antibodies that specifically match the pathogen. They attach to the surface of the antigens of the pathogen and they either attract phagocytes to engulf the pathogen or cause the pathogen to break open.
They also produce memory cells.
They also produce antitoxins which neutralise the harmful toxins produced by microorganisms.
Why do lymphocytes produce memory cells?
Memory cells remain in the blood long after the pathogen has been destroyed. If they meet the pathogen again, they make lots of antibodies quickly which kills the pathogen before you can become ill. You are now immune to the pathogen.
How do vaccines work?
· Vaccine injects a weakened or dead version of the pathogen so that it doesn’t cause illness but still has antigens on its surface
· Lymphocytes respond to the antigens on the pathogen in the vaccine and produce antibodies specific to that pathogen
· These antibodies destroy the pathogen
· Lymphocytes also produce memory cells which remain in the blood - if the same pathogen enters the body in future memory cells instantly recognise it and stimulate lymphocytes to produce more antibodies and faster
· The pathogen is destroyed before any symptoms develop = immunity
Why is it possible to catch a cold/influenza etc more than once in a lifetime?
The pathogens that cause the infections can mutate, changing the shape of their surface molecules frequently so memory cells do not recognise them when the pathogen infects you the next time.
Do lymphocytes have a nucleus?
A large nucleus
What are platelets?
Small fragments of larger cells
No nucleus
Why are platelets important?
They are important in blood clotting
· They respond to damaged blood vessels by releasing an enzyme which causes the formation of a fibrous protein called fibrin. Fibrin traps other platelets and red blood cells to form a clot. This clot prevents you from bleeding to death and forms a scab, which protects the new skin and prevents bacteria getting into the body
In mammals, why is the circulatory system called a double circulatory system?
Because blood flows through the heart twice for every single time it flows through the body tissues.
Why is double circulation necessary?
Because blood pressure in the circulation through the tissues can be kept higher than through the lungs. The high pressure needed to get blood all the way to the limbs and back would burst the tiny capillaries in the lungs which are much closer to the heart.
What does the double circulatory system ensure that?
That the oxygenated blood is kept separate from deoxygenated blood allowing fast delivery of fully oxygenated blood to cells that need it for respiration.