3.3.4 Mass transport in animals Flashcards
Describe the structure of haemoglobin
Globular, water soluble. Consists of 4 polypeptide chains, each carry a haem group
Describe the role of haemoglobin
Present in RBC
Oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues
Name 3 factors affecting oxygen-haemoglobin binding
- Partial pressure of oxygen
- Partial pressure of carbon dioxide
- Saturation of haemoglobin with oxygen
How does partial pressure of oxygen affect oxygen-haemoglobin binding
As partial pressure of oxygen increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, oxygen is released from haemoglobin
How does a partial pressure of carbon dioxide affect oxygen-haemoglobin binding
As partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases so oxygen is released from haemoglobin. This is known as the Bohr effect
How does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding
It is hard for the first oxygen molecule to bind. Once it does it changes the shape to make it easier for the second and third molecules to bind known as positive cooperativity. It is then slightly harder for the fourth oxygen molecule to bind because there is a low chance of finding a binding site
Explain why oxygen binds to haemoglobin in the lungs
Partial pressure of oxygen is high
Low conc of CO2 in lungs so affinity is high
Positive cooperativity
Explain why oxygen is released from haemoglobin in respiring tissues
Partial pressure of oxygen is low
High conc of CO2 in respiring tissues so affinity decreases
What do oxyhaemoglobin dissociation curves show
Saturation of haemoglobin with oxygen plotted against partial pressure of oxygen. Curves further to the left to show the haemoglobin has a higher affinity for oxygen
How does CO2 affect the position of an oxyhaemoglobin dissociation curve
Curve shifts to the right because haemoglobin’s affinity for oxygen has decreased
Name some common features of a mammalian circulatory system
- Suitable medium for transport, water-based to allow substances to dissolve
- Means of moving the medium and maintaining pressure throughout the body, such as the heart
- Means of controlling flow so it remains unidirectional such as valves
Relate the structure of the chambers to their function
Atria - thin-walled and elastic, so they can stretch when filled with blood
Ventricles - thick muscular walls pump blood under high pressure. The left ventricle is thicker than the right because it has to pump blood all the way around the body
Relate the structure of the vessels to their functions
Arteries have thick walls to handle high pressure without tearing, and are muscular and elastic to control blood flow
Veins have thin walls due to lower pressure therefore requiring valves to prevent the backflow of blood. Have less muscular and elastic tissue as they dont have to control blood flow
Why are 2 pumps needed instead of one
To maintain blood pressure around the whole body
When blood passes through the narrow capillaries of the lungs, the pressure drops sharply and therefore would not be flowing strongly enough to continue around the whole body. Therefore its returned to the heart to increase the pressure
Describe what happens during cardiac diastole
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atrioventricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valves remain closed
Describe what happens during atrial systole
The atria contract, pushing any remaining blood into the ventricles
Describe what happens during ventricular systole
The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves. Blood flows into the arteries
Name the nodes involved in heart contraction and where they are situated
Sinoatrial node (SAN) = wall of right atrium
Atrioventricular node (AVN) = inbetween the 2 atria
What does myogenic mean
The heart’s contraction is initiated from within the muscle itself, rather than by nerve impulses
Explain how the heart contracts
SAN initiates and spreads impulse across the atria so they contract
AVN receives, delays, and then conveys the impulse down the bundle of His
Impulse travels into the Purkinje fibres which branch across the ventricles, so they contract from the bottom up
Why does the impulse need to be delayed
If the impulse spread straight from the atria into the ventricles, there would not be enough time for all the blood to pass through and for the valves to close
How is the structure of capillaries suited to their function
Walls are only one cell thick; short diffusion pathway
Very narrow so can permeate tissues and RBC can lie flat against the wall, effectively delivering oxygen to tissues
Numerous and highly branches, providing a large surface area
What is tissue fluid
A watery substance containing glucose, amino acids, oxygen and other nutrients
It supplies these to the cells, while also removing any waste materials
How is tissue fluid formed
As blood is pumped through increasing small vessels, this created hydrostatic pressure which forces fluid out the capillaries. It bathes the cells then returns to the capillaries when the hydrostatic pressure is low enough
Explain how valves maintain blood flow in one direction (right)
(happens on either side this is for right) Blood enters right atrium from vena cava
Atrium contracts the volume decreases so pressure increases, when pressure in atrium is greater than ventricle then the atrioventricular valve opens
Blood moves into right ventricle
Right ventricle contracts so volume decreases so pressure increases, pressure in ventricle is greater than the atrium so atrioventricular valve closes
Pressure in ventricle is greater than pulmonary artery so semi lunar valve opens
Blood moved into pulmonary artery
Pressure in pulmonary artery greater than ventricle so semi lunar valve closes
