Topic 8 Exchange and Transport in Animals Flashcards
Do larger organisms have a higher or lower SA:V ratios generally?
Lower
Why don’t single-celled organisms need exchange organs?
Gases and substances can diffuse directly in and out of the cell across cell membrane because they have a large SA:V so enough substances can be exchanged across the membrane to supply the volume of the cell.
Why do multi-cellular organisms need exchange surfaces?
They have a small SA:V so it’s difficult to exchange enough substances to supply the entire volume of the organism.
Exchange surfaces are needed that have efficient diffusion and a transport system to move substances from the exchange surfaces to the rest of the body.
Ways alveoli maximise diffusion
A good blood supply arriving from rest of body to high concentration gradient for diffusion of both CO2 and O2.
Moist lining for dissolving gases.
Very thin walls to minimise distance gases have to move.
Large surface area.
3 factors of rate of diffusion
Distance - quicker diffusion with less travel distance.
Concentration gradient - big difference means more particles to move across from one side.
Surface area - more surface available for molecules to move across.
Rate of diffusion (Fick’s Law)
Rate of diffusion is proportional to surface area and concentration difference and inversely proportional thickness of membrane.
Rate of diffusion will double if difference in concentration or surface doubles or thickness of membrane halves.
When and where is respiration happening
In every living cell of all living organisms all the time.
Uses of respiration
Metabolic processes - making larger molecules from smaller ones (e.g. proteins from amino acids).
Contracting muscles.
Maintaining a steady body temperature.
Equation for aerobic respiration
Glucose + oxygen -> carbon dioxide + water
When does anaerobic respiration happen?
When the body cannot supply enough oxygen to your muscles for aerobic respiration during vigorous exercise even though your heart rate and breathing rate is at maximum. It happens at the same time as aerobic respiration.
How efficient is anaerobic respiration and what does it cause?
It is not as efficient as it transfers much less energy than aerobic respiration.
The glucose is only partially broken down and lactic acid is produced.
The lactic acid build up can become painful and lead to cramp.
Word equation for anaerobic respiration
Glucose -> lactic acid
Word equation for anaerobic respiration in plants
Glucose -> ethanol + carbon dioxide
How to measure rate of respiration in a respirometer
Measure the rate oxygen is used up in a given time.
The oxygen used up decreases the pressure in the tube so the coloured liquid moves toward the test tube containing the organism.
The distance moved is measured and volume of oxygen taken in can be found per minute.
How is the carbon dioxide absorbed from the tube
Using soda lime
Structure and features of red blood cell
Biconcave disc shape to give large surface area for absorbing oxygen.
No nucleus allow more room to carry oxygen.
Contain haemoglobin which contains iron which binds to oxygen in lungs to become oxyhemoglobin and splits at body cells to release oxygen.
Phagocytes
White blood cells that engulf microorganisms (phagocytosis).
Lymphocytes
White blood cells that produce antibodies and antitoxins.
Features and purpose of platelets
Small fragments of cells that have no nucleus.
They help blood clot at wounds.
Plasma features and function
Straw-coloured liquid that carries everything: red and white blood cells and platelets, nutrients such as glucose and amino acids, carbon dioxide, urea, hormones, antibodies and antitoxins.
Arteries
Carry blood away from heart.
Pumps blood at high pressure to go around whole body, strong and elastic walls.
Have thick layer of smooth muscle wall with small lumen.
Have elastic fibres to allow muscle to stretch and spring back.
Capillaries
Narrow to fit between cells to carry blood to every cell in body to exchange substances.
Permeable walls so substances can diffuse through them.
Supply glucose and oxygen and take away CO2.
Have 1 cell thick walls to increase rate of diffusion.
Small lumen to slow blood flow so more substances diffuse.
Veins
Carry blood back to heart.
Blood is at lower pressure so walls don’t need to be as thick.
Bigger lumen to help blood flow at lower pressure.
Have valves to make sure blood flows in right direction.
Right side of the heart
Right atrium receives deoxygenated blood from the vena cava and it is pumped to the right ventricle which pumps it to the lungs.
