B2.2 - Exchange & Transport Flashcards
Why is a large surface area to volume ration important in very small organisms(tapeworm)
Nutrients can diffuse directly into organism quickly enough to sustain life, as diffusion distances are small
Why can’t most multicellular organisms used simple diffusion to survive?
Bigger organisms have lower surface area:volume ratios
Diffusion over the greater distance can’t occur fast enough to meet cells demands
Exchange surface:
= an area where materials are interchanged
How do lungs maximise the rate of diffusion of oxygen into bloodstream
= contain many alveoli which increase surface area of lungs, ensure efficient gas exchange
How does the small intestine maximise the diffusion rate of digested food molecules into the blood
Walls of small intestine contain finger like villi, increase surface area of intestine wall
Microscopic microvilli on villi increase surface area further
Circulatory system:
What is it made up of?
= Main transport system in animals
Made up of heart & blood vessels
Why is the circulatory system a closed system?
As blood remains within these structures (heart & blood vessels)
What does blood do in the circulatory system?
- transports substances around body to cells that need them (oxygen, glucose for respiration)
- carries away waste products (carbon dioxide)
Why do we have a double circulatory system?
Blood flows through the heart twice during each circuit of the body
Explain the process of the circulatory system:
- heart pumps blood to body organs & tissues
- oxygen & glucose diffuse out of blood into cells
- carbon dioxide diffuses out of cells into blood
- blood travels back to heart, pumps it to the lungs
- in lungs, carbon dioxide diffuses out of blood to be removed from body, oxygen diffuses in
- blood returns to heart & cycle repeats
3 types of blood vessel
- arteries
- veins
- capillaries
Blood vessel:
= tubelike structures that transport blood around body
Lumen:
= hollow cavity in the centre of blood vessels
Arteries function & structure
Carry blood away from heart under high pressure
- thick outer wall
- thick layer of muscle & elastic fibres
- small lumpen
- smooth lining
Vein function & structure
Return blood to heart, have valves
- fairly thin outer wall
- thin layer of muscle & elastic fibres
- large lumen
- smooth lining
Capillary function & structure:
Link arteries & veins in tissues & organs, form network so every cell is close to a capillary
- semipermeable wall, only 1 cell thick
- very small lumen
Why do capillaries have semipermeable, one cell thick walls
So substances can easily move through them
Why do arteries have thick & muscular walls?
Why do arteries have a thick layer of muscles & elastic fibres?
= To withstand the high pressures of blood caused by strong contractions of heart
= Wall expands with force of each contraction then snaps back(recoil) to push blood forward
Why don’t veins need thick, muscular walls?
As blood pressure falls away from heart, pressure in veins is very low
Why do veins contain valves?
Valves keep blood flowing in one direction, as the pressure is low in the veins, the valves are needed to make sure it flows back to the heart
Why is the blood in a double circulatory system under higher pressure than a single one?
For each journey around the body, the blood is pumped twice
High pressure means materials transported quickly around body, essential for larger organisms
What is a heart made of? Why is it different from other cells?
= cardiac muscle
Cardiac muscle cells contract without receiving a nerve impulse from your brain
Four chambers of the heart:
- right atrium (top)
- left atrium (top)
- right ventricle (bottom)
- left ventricle (bottom)
(Opposite left & rights as on picture)
What is blood made up of?
- red blood cells
- white blood cells
- plasma
- platelets
Red blood cells
- small biconcave cells with no nucleus
- contain haemoglobin, carry oxygen
- fit though lumen of capillary 1 cell at a time
White blood cells
- large cells, contain a nucleus
- fight disease by making antibodies/changing shape to engulf microorganisms
Plasma
- liquid that blood cells float in
- 90% water, materials transported by dissolving in plasma
(Amino acid, glucose, CO2, hormones, antibodies)
Platelets
- tiny structures that help blood clot
Factors affecting transpiration
- light intensity
- temperature
- air movement (wind)
- humidity
