Topic 3 Organisms Exchange Substances With Their Environment Flashcards
(18 cards)
Why is SA:mass better than SA:V
Easier to find and more accurate due to irregular shapes
What is metabolic rate and how is it measured
Metabolic rate is the amount of energy used up by an organism within a given period of time
Measured by O2 uptake as it is used in aerobic respiration to produce ATP for energy release
Explain the relationship between SA:V and metabolic rate in an organism
As SA:V increases, metabolic rate increases
Because rate of heat loss per unit body mass increases
So higher rates of respiration required to replace the heat loss
To maintain a constant body temperature
Suggest why lung diseases reduce the rate of gas exchange
Thickened lung tissues
So increases diffusion distances for oxygen
Alveolar wall breakdown
So reduces SA for diffusion
Reduced lung elasticity
So lungs recoil and expand less, reducing concentration gradients of O2/CO2
Suggest why lung diseases reduces ventilation
Reduced lung elasticity, lungs expand and recoil less
So reduced volume of air in each breath - tidal volume
So maximum volume of air breathed out in one breath - forced vital capacity
Narrow airways so reduced airflow in and out of lungs
So less maximum volume of air breathed out in one second - forced expiratory volume
Reduced rate of gas exchange so increased ventilation rate to compensate reduced oxygen in blood
Suggest the importance of ventilation
Brings air with high concentration of oxygen and removes air with low concentration of oxygen
To maintain a concentration gradient of O2
Suggest why expiration is normally passive at rest
Internal intercostal muscles don’t normally contract
Expiration aided by elastic recoil in alveoli
Suggest why membrane-bound digestion enzymes are important
Membrane bound enzymes are located on the cell membranes of epithelial cells lining ileum
By hydrolysing molecules near at the site of absorption, it maintains concentration gradient for absorption
Pathway for the absorption of products of digestion
Lumen of ileum, epithelial cells lining ileum, blood
Describe evidence of cooperative nature of oxygen binding
At low PO2, as concentration of O2 increases, there is a small increase in the % saturation of haemoglobin with oxygen when it binds to the first oxygen
At high PO2, as concentration of O2 increases, there is a greater increase in the % saturation of haemoglobin with oxygen showing it has got easier for oxygen to bind with haemoglobin
Describe the evidence of the Bohr shift
At a given PO2, the % saturation of haemoglobin with oxygen is lower
Explain why different types of haemoglobin have different oxygen transport properties
Each haemoglobin are made of polypeptides with slightly different amino acid sequences
So different tertiary/ quaternary structures of haemoglobin
So they have different affinities for O2
Suggest the importance of a double circulatory system
To prevent mixing of oxygenated blood and deoxygenated blood
So blood carried to respiring tissues to the body is fully saturated with oxygen needed for aerobic respiration to produce ATP
Blood can be pumped to the body at a high pressure
So substances can be taken to the body more efficiently
Suggest why is the wall of the left side of heart thicker than the right side
Thicker muscle to contract with greater force
To generate higher pressure in order to pump oxygenated blood around the whole of the body to respiring cells and tissues
Explain the pressure and volume changes and associated valve movements during the cardiac cycle that maintain a unidirectional flow of blood
Atrial systole occurs where the atria contracts.
So their volume decreases and pressure increases
The AV valves forced open as the pressure in the atria exceeds the pressure in the ventricles
Semi-lunar valves remain shut as the pressure in the armies exceed the pressure in the ventricles
So blood is pushed into the ventricles.
Then ventricular systole occurs where the ventricles contract.
So their volume decreases and pressure increases.
The semi lunar valve forced open as pressure in ventricles exceed pressure in arteries but the AV valves close shut as pressure in ventricles exceed pressure in atria.
So blood pushed out of heart through arteries
Then there is diastole where both the atria and ventricles relax
So their volume increases and pressure decreases.
The semi lunar valve shuts closed as pressure in the arteries exceeds pressure in ventricles.
The AV valve opens when pressure in atria exceeds pressure in ventricles
So blood fills atria via veins and flows passively to ventricles
Heart rate calculation from cardiac cycle data
Heart rate = 60 (seconds)/ length of one cardiac cycle (seconds)
Equation for cardiac output
Cardiac output (Volume of blood pumped out of heart per minute) = stroke volume (volume of blood pumped out in one heart beat) x heart rate (number of beats per min)
Explain how the structure of arteries relates to its function
Thick muscle tissue -> can contract and control high pressures
Thick elastic tissue -> can stretch as ventricles contract and recoil as ventricles relax, to reduce pressure surge
Thick wall -> to withstand high pressures and prevent bursting
Smooth endothelium -> reduces friction
Folded endothelium -> can stretch
Narrow lumen -> increases high pressures
