CIE A Level Biology (Transport in mammals)

Why can small animals use diffusion but larger animals need transport systems to exchange substances with their environment

small aminals that have a large surface area to volume ratio can rely on diffusion alone to exchange oxygen, carbon dioxide and nutrients with their environment. Larger animals have a smaller surface area to volume ratio, so diffusion alone isn't sufficient for exchange of materials between cells further from the surface of the organism with the environment.

What are circulatory systems

they are systems which carry fluids containing materials needed by the organism as well as waste materials that need to be removed

What is an closed circulatory system

it's a circulatory system in which blood is pumped around the body and is contained within blood vessels, it is present in all vertebrates and many invertebrates.

What is an open circulatory system

it's a circulatory system in which blood is not contained within blood vessels and is pumped directly into body cavities, it is present in arthropods and molluscs.

What are arteries

they are blood vessels that carry blood away from the heart. They have a narrow lumen, endothelium, elastic tissue, smooth muscle tissue and collagen.

What are elastic arteries

they are arteries that are located closer to the heart and so carry blood at a higher pressure, they contain more elastic fibres and less smooth muscle tissue. They aren't able to carry vasoconstriction and vasodilation. They have a thick tunica Media as they carry blood at a high pressure.

What are muscular arteries

they are arteries that branch off into arterioles and also have more smooth muscle tissue and posses less elastic fibres. They are able to carry out vasoconstriction and vasodilation. They have a thin tunica Media as they carry blood at a lower pressure.

Relate the structure of arteries to its function

they have elastic tissue to stretch and recoil and maintenance the blood pressure
they have smooth muscle tissue to vary blood flow
they have a narrow lumen to withstand high blood pressure
they have collagen for strength and structure
they have thick walls to withstand high blood pressure

What are veins

they have a wide lumen and thin walls,they are blood vessels that take blood away from the heart, they contain elastic tissue, smooth muscle tissue and on their outer surface they have lots of collagen

Describe the pulmonary circulatory system

it contains the pulmonary artery(on the right side of the heart) and the pulmonary vein(which is on the left side of the heart)the pulmonary artery carries deoxygenated blood from the heart to the lungs. The pulmonary vein carries oxygenated blood from the lungs back to the heart.

Describe the systemic circulatory system

It contains the Aorta (on the left side of the heart) and the Vena cava (on the right side of the heart). The aorta carries oxygenated blood from the heart to the rest of the body, the Vena cava carries deoxygenated blood from the rest of the body to the heart.

What are capillaries

they are blood vessels that thin walls, no elastic, smooth muscle tissue or collagen. They are one cell thick, and are used in diffusion

What is a distinctive structure of red blood cells (erythrocytes)

they have no nucleus to make more room for oxygen to bind to haem groups of haemoglobin

What is a distinctive feature of monocytes

they have a kidney or bean-shaped nucleus

What is a distinctive feature of neutrophils

they have a multi-lobed nucleus

what is a distinctive feature of lymphocytes

they have a very large nucleus

how is tissue fluid removed

it drains into the lymphatic system where it's referred to as lymph. The lymph returns to the blood via the subclavian veins.

Compare and contrast the similarities and differences in the composition of tissue fluid and blood plasma

Blood plasma and tissue fluid are mainly composed of water. This is because water is a small enough molecule to pass through the gaps in the capillary walls and into the tissue fluid. Blood plasma and tissue fluid differ because proteins such as albumin, are too large to fit between the gaps in the capillary wall and so they remain in the blood.

steps of tissue fluid formation

When blood passes through the arterial end of the capillary, hydrostatic pressure is great enough to push molecules out of the capillary.
Proteins remain in the blood; the increased protein content creates a water potential between the capillary and the tissue fluid. However, overall movement of water is out from the capillaries into the tissue fluid
At the venous end of the capillary, less fluid is pushed out of the capillary as pressure within the capillary is reduced
The water potential gradient between the capillary and the tissue fluid remains the same as at the arterial end, so water begins to flow back into the capillary from the tissue fluid
Overall, more fluid leaves the capillary than returns, leaving tissue fluid behind to bathe cells.If blood pressure is high (hypertension) then the pressure at the arterial end is even greater.This pushes more fluid out of the capillary and fluid begins to accumulate around the tissues. This is called oedema

equation to show binding of oxgyen to haemoglobin

4O2 + Hb (Haemoglobin) -------------> HbO8 (oxyhaemoglobin)

Equation showing the formation of carbonic acid

carbonic anyhydrase
CO2 + 2H2O <------------> H2CO3(carbonic acid) <-----------> HCO3- (Hydrogencarbonate ion) + H+
Red blood cells contain the catalyst(enzyme) carbonic anyhydrase

Explain the role of diffusion in transport of carbon dioxide from respiring cells

Carbon dioxide diffusers down a concentration gradient from respiring cells into the plasma. Some carbon dioxide also diffuses into red blood cells to combine with haemoglobin, forming carbaminohaemoglobin. Once carried to the lungs, carbon dioxide then diffuses out of the plasma and red blood cells and into the alveoli to be exhaled.

What is the chloride shift?

It describes the movement of chloride ions into red blood cells.

What is the oxygen dissociation curve

It's a graph that shows the relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin.

What is the Bohr shift?

It shows the changes in the oxygen dissociation curve as a result of carbon dioxide levels.

What happens when there's an increase in carbon dioxide levels

Where there's a lot of carbon dioxide such as at respiring tissue, haemoglobin gives up its oxygen to nearby tissues.

When are the valves open?

The valves are open when the pressure behind them is greater than the pressure in front of them.

When are the valves closed?

The valves are closed when pressure of blood in front of them is greater than the pressure behind them.

What is systole?

It is the contraction of the heart.

What is diastole?

The relaxation of the heart

What happens during systole

The atrioventricular valves are closed and the semilunar valves are open

What happens during diastole

The atrioventricular valves are open and the semilunar valves are closed.

steps of the cardiac cycle

1.The sinoatrial node (SAN) initiates a wave of depolarisation that causes the atria to contract.
2.The Annulus fibrosus is a region of non-conducting tissue which prevents the depolarisation spreading straight to the ventricles.Instead, the depolarisation is carried to the atrioventricular node (AVN)This is a region of conducting tissue between atria and ventricles
3.After a slight delay, the AVN is stimulated and passes the stimulation along the bundle of His.This delay means that the ventricles contract after the atria
4.The bundle of His is a collection of conducting tissue in the septum (middle) of the heart. The bundle of His divides into two conducting fibres, called Purkyne tissue, and carries the wave of excitation along them.
5.The Purkyne fibres spread around the ventricles and initiate the depolarization of the ventricles from the apex (bottom) of the heart.
6.This makes the ventricles contract and blood is forced out of the pulmonary artery and aorta

Which pressure is greater at the arterial end of the capillary

Hydrostatic pressure> oncontic pressure

Which pressure is greater st the venous end of the capillary

Oncontic pressure>hydrostatic pressure

Why is a higher concentration of red blood cells important for human populations living at high altitudes?

At high altitudes, the partial pressure of oxygen is low, so the oxygen saturation in red bloods will decrease. To carry an equal volume of oxygen in the blood, a higher concentration of red blood cells is required.

Why are the ventricles thicker and more muscular than the atria

The muscular walls of the atria are thinner than those of the ventricles
When the atria contract, the thin muscular walls do not generate much pressure, but enough to force blood down into the ventricles, through the atrioventricular valves
In contrast, the walls of the ventricles are thicker and more muscular
Following contraction of the atria, the ventricles contract and squeeze blood inwards, increasing its pressure and pushing it out of the heart through right and left semilunar valves

Why are the left ventricles thicker and more muscular than the right ventricles

The muscle of the left ventricle is significantly thicker than the right ventricle.This is because the blood leaving the right ventricle travels less distance than blood leaving the left ventricle.The blood pumped out from the right ventricle travels to the lungs, whereas blood leaving the left ventricle has to travel to the rest of the body to deliver oxygen for respiration.To reach the rest of the body, the blood leaving the left ventricle must be under high pressure.This is generated by the contraction of the muscular walls of the left ventricle.The right ventricle generates less pressure from the contraction of its thinner walls, as blood only has to reach the lungs

What is the heart

The heart is a hollow, muscular organ located in the chest cavity.It is protected in the chest cavity by the pericardium, a tough and fibrous sac

Describe the 4 chambers of the heart

The heart is divided into four chambers. The two top chambers are atria and the bottom two chambers are ventricles.The left and right sides of the heart are separated by a wall of muscular tissue, called the septum. The portion of the septum which separates the left and right atria is called the interatrial septum, while the portion of the septum which separates the left and right ventricles is called the interventricular septum.The septum is very important for ensuring blood doesn't mix between the left and right sides of the heart

valves of the heart

Valves in the heart: Open when the pressure of blood behind them is greater than the pressure in front of them. Close when the pressure of blood in front of them is greater than the pressure behind them

Valves are important for keeping blood flowing forward in the right direction and stopping it flowing backwards. They are also important for maintaining the correct pressure in the chambers of the heart. The right atrium and right ventricle are separated by the atrioventricular valve, which is otherwise known as the tricuspid valve. The right ventricle and the pulmonary artery are separated by the pulmonary valve. The left atrium and left ventricle are separated by the mitral valve, which is otherwise known as the bicuspid valve. The left ventricle and aorta are separated by the aortic valve. There are two blood vessels bringing blood to the heart; the vena cava and pulmonary vein. There are two blood vessels taking blood away from the heart; the pulmonary artery and aorta

coronary arteries

The heart is a muscle and so requires its own blood supply for aerobic respiration. The heart receives blood through arteries on its surface, called coronary arteries. It's important that these arteries remain clear of plaques, as this could lead to angina or a heart attack (myocardial infarction)

What to remember when looking at the heart

When looking at the heart, remember the right side of the heart will appear on the page as being on the left. This is because the heart is labelled as if it were in your body and flipped around.

Transport of oxygen in the blood

The majority of oxygen transported around the body is bound to the protein haemoglobin in red blood cells. Each molecule of haemoglobin contains four haem groups, each able to bond with one molecule of oxygen. This means that each molecule of haemoglobin can carry four oxygen molecules (eight oxygen atoms in total). When oxygen binds to haemoglobin, oxyhaemoglobin is formed:
4O2 + Hb (Haemoglobin) → HbO8 (Oxyhaemoglobin)
Oxygen can also dissolve in the water of blood plasma; at normal body temperatures about 0.025 cm3 of oxygen can dissolve in water. 1 dm3 of blood contains 150 g of haemoglobin, which can carry up to 19.5 dm3 oxygen,The binding of the first oxygen molecule results in a conformational change in the structure of the haemoglobin molecule, making it easier for each successive oxygen molecule to bind. The reverse of this process happens when oxygen dissociates in the tissues. The dissociation of the last oxygen molecule is the hardest

Transport of carbon dioxide

Waste carbon dioxide diffuses from tissues and into the blood following aerobic respiration. There are three main ways in which carbon dioxide is transported around the body. A very small percentage of carbon dioxide (~ 10 %) dissolves in blood plasma, forming H2CO3A much larger percentage (~ 70 %) of carbon dioxide dissolves in the cytoplasm of red blood cells. Red blood cells contain the enzyme carbonic anhydrase which catalyses the reaction between carbon dioxide and waterWithout carbonic anhydrase this reaction proceeds very slowly. The plasma contains very little carbon anhydrase hence H2CO3 forms much more slowly in plasma than in the cytoplasm of red blood cells
Carbonic acid dissociates readily into H+ and HCO3- ions :
CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+
The increase in H+ concentration results in a decrease in blood pH, which alters the structure of haemoglobin, encouraging the dissociation of oxyhaemoglobin to release oxygen. This is beneficial - when levels of carbon dioxide are higher, rates of aerobic respiration are greater and therefore the need for oxygen is higher
Hydrogen ions (protons) can combine with haemoglobin, forming haemoglobinic acid.Carbon dioxide can also bind to amino acids and therefore haemoglobin, forming carbaminohaemoglobin - this accounts for ~ 20 % of carbon dioxide transport in the blood

The chloride shift explained

The chloride shift describes the movement of chloride ions into red blood cellsWithin the cytoplasm of red blood cells, an enzyme called carbonic anhydrase catalyses the reaction:
CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+
Negatively-charged hydrogencarbonate ions formed from the dissociation of carbonic acid are transported out of red blood cells via a transport protein in the membrane. To prevent an electrical imbalance, negatively-charged chloride ions are transported into the red blood cells via the same transport protein. If this did not occur, then red blood cells would become positively charged as a result of a buildup of hydrogen ions (formed from the dissociation of carbonic acid)

Explain the role of diffusion in the transport of carbon dioxide from respiring cells

Carbon dioxide diffuses down a concentration gradient from respiring cells into the plasma. Some carbon dioxide also diffuses into red blood cells to combine with haemoglobin, forming carbaminohaemoglobin. Once carried to the lungs, carbon dioxide then diffuses out of the plasma and red blood cells and into the alveoli to be exhaled.

What is the oxygen dissociation curve

The oxygen dissociation curve describes the relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin.
A small change in the partial pressure of oxygen can have a very large impact on the percentage saturation of haemoglobin. This is because haemoglobin has such a high affinity for oxygen. The partial pressure of oxygen in the lungs is high, so haemoglobin picks up oxygen rapidly. In respiring tissues, the partial pressure of oxygen is low, so oxygen is dropped off rapidly. This ensures that oxygen is picked up where there's plenty of it and delivered to where it is needed in respiring tissues

Explain the Bohr shift

Changes in the oxygen dissociation curve as a result of carbon dioxide levels are known as the Bohr shift or Bohr effect. The Bohr effect explains how the ability of haemoglobin to bind to, and release its oxygen changes. When the partial pressure of carbon dioxide is high, in respiring tissues for example, haemoglobin's affinity for oxygen is reduced. This is a helpful change, because it means that haemoglobin gives up its oxygen much more readily. This occurs because CO2 lowers the pH of the blood (by forming carbonic acid), which causes haemoglobin to release its oxygen. Carbon dioxide levels in the lungs are comparatively very low, haemoglobin's affinity for oxygen is increased, which makes it easier for oxygen to bind to haemoglobin
The higher the partial pressure of oxygen, the greater the saturation of haemoglobin with oxygen, and vice versaThe more carbon dioxide there is, the line on the graph shifts to the right (the lower of the two lines)
This shows that more dissociation has occurred, as the percentage saturation of oxygen is lower
This is an important change, as it means that where there is a lot of carbon dioxide, such as at respiring tissues, haemoglobin gives up its oxygen to the nearby tissues

Whats the difference between adult and foetal haemoglobin

foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin.

What is the specific heat capacity

Specific heat capacity is a measure of the energy required to raise the temperature of 1 kg of a substance by 1 oC. Water has a high specific heat capacity of 4200 J / Kg oC - a relatively large amount of energy is required to raise its temperature. This means that water is able to absorb a lot of heat without big temperature fluctuations. This is vital in maintaining temperatures that are optimal for enzyme activity

Why is water vital in transferring heat around the body

Water in blood plasma is also vital in transferring heat around the body, helping to maintain a fairly constant temperature. As blood passes through more active ('warmer') regions of the body, heat energy is absorbed but the temperature remains fairly constant. Water in tissue fluid also plays an important regulatory role in maintaining a constant temperature

Compare and contrast the similarities and differences between tissue fluid and blood plasma.

Blood plasma and tissue fluid are both mainly composed of water. This is because water is a small enough molecule to pass through the gaps in the capillary walls and into the tissue fluid. Blood plasma and tissue fluid differ because blood plasma contains proteins, while tissue fluid does not. This is because proteins, such as albumin, are too large to fit between the gaps in the capillary wall and so they remain in the blood.