BIOLOGY T2 Flashcards
Describe the structure of ATP.
ATP (or Adenosine triphosphate) is made up of a nucleotide consisting of three phosphate groups, one ribose sugar, and one adenine ring (nitrogenous base).
What are the different uses of energy in the human body?
Uses of energy:
- muscle contraction
- protein synthesis
- cell division
- active transport
- growth
- the passage of nerve impulses
- maintenance of a constant body temperature
Define aerobic respiration.
Chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.
What is the word equation for aerobic respiration?
Glucose + Oxygen > Carbon Dioxide + Water + Energy
What is the balanced chemical equation for aerobic respiration?
C6H12O6 + 6O2 > 6CO2 + 6H2O
Define anaerobic respiration.
Chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.
What is the difference between aerobic respiration and anaerobic respiration?
Anaerobic breaks down nutrient molecules to release energy without using oxygen. This means that it releases much less energy per glucose molecule compared to aerobic respiration.
What is the word equation for anaerobic respiration in yeast?
Glucose > Ethanol + Carbon Dioxide
What is the balanced chemical equation for anaerobic respiration in yeast?
C6H12O6 > 2C2H5OH + 2CO2
What is the word equation for anaerobic respiration in humans?
Glucose > Lactic Acid + Energy
What is the balanced chemical equation for anaerobic respiration in humans?
C6H12O6 > 2C3H6O3
When and why does anaerobic respiration occur?
Anaerobic respiration occurs during strenuous exercise when not enough oxygen can reach your muscle cells and so normal aerobic respiration is replaced by anaerobic respiration because this does not require oxygen to release energy.
What is the problem with anaerobic respiration?
Lactic acid is produced as a waste product during anaerobic respiration. It builds up in the muscles which causes pain and tiredness and can lead to cramp. Lactic acid is then removed when aerobic respiration recommences.
How is lactic acid removed?
The lactic acid is transported to the liver through the blood where it is either oxidised into carbon dioxide and water or is converted into glucose and then glycogen.
What is oxygen debt?
During strenuous exercise, lactic acid builds up due to anaerobic respiration and so after the exercise has stopped, a high level of oxygen consumption is needed to oxidise the excess lactic acid. This is known as oxygen debt and is why a person continues to breathe quickly and deeply for a time after exercise.
What is the xylem and its function?
The xylem transports water and mineral salts from the roots up to other parts of the plant through a process known as transpiration stream.
What is the phloem and its function?
The phloem transports sucrose and amino acids from the leaves and other parts of the plant, through the process of translocation.
Relate the structure of the xylem to its function.
Mature xylem consists of elongated dead cells, arranged end to end to form continuous vessels (tubes).
Mature xylem vessels:
- Contain no cytoplasm
- Are impermeable to water
- Have tough walls containing a woody material called lignin.
Relate the structure of the phloem to its function.
Phloem consists of living cells arranged end to end. Unlike xylem, phloem vessels contain cytoplasm, and this goes through the holes in the sieve plates from one cell to the next.
Where are the xylem and phloem located in the root?
Xylem is at the center of the plant root or vein whereas phloem are at the outside. Both the xylem and phloem are combined together in the vascular bundle.
Describe the process of transpiration.
Transpiration is the loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by the diffusion of water vapour through the stomata. This creates a water shortage in the leaf (lower water potential than the rest of the plant) which draws up more water from the rest of the plant, which in turn draws more water up from the roots.
Transpiration has two benefits:
- It transports minerals from the soil
- It cools the plant
Describe the process of translocation.
Translocation is the movement of sucrose and amino acids in the phloem, from regions of production (the ‘source’) to regions of storage or to regions where they are used in respiration or growth (the ‘sink’). Food is made in the leaves by photosynthesis. The soluble products are sugars, amino acids and fatty acids. Phloem may contain up to 25% dissolved solids. These are carried to all parts of the plant in solution in the phloem.
Describe the factors which affect transpiration.
The rate of transpiration is affected by 4 things:
1. Amount of light
2. Temperature
3. Amount of air movement (wind)
4. Humidity of the surrounding air
So the rate of transpiration is greatest on hot, dry, windy sunny days i.e. weather that dries clothes fast.
This constant stream of water has the advantage of transporting vital minerals from the soil into the roots and all around the plant (nitrates, magnesium etc.)
What is diffusion?
The net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient.
The steeper the concentration gradient, the faster diffusion occurs.
What is osmosis?
The movement of water molecules through a partially permeable membrane, from a solution of high water potential, to a solution of lower water potential.
What is the function of a partially permeable membrane?
It allows some substances to pass through but not others.
It has unequal concentration of ions on both sides of the membrane.
What is water potential?
Water potential is the measure of the tendency of water to move from one place to another.
Dilute solution = high water potential
Concentrated solution = low water potential
Same concentration = equal water potential.
Hypotonic - higher water potential
Hypertonic - lower water potential
(both in comparison to eachother).
Isotonic - equal potential.
Describe how water is taken up into the plant through the soil.
Water is absorbed by the root hairs which are long and thin. They have a large surface area through which water and minerals can enter.
Water passes into the root hairs by osmosis as the cell sap has lower water potential than the surrounding soil. The water eventually reaches the xylem and is carried up the xylem to the leaves.
What is the circulatory system and its function?
It is made up of a pump (heart) and blood vessels with valves so blood only flows one way.
It transports nutrients, oxygen, and waste products.
Different organisms have different types of circulatory system (single and double circulation).
Describe single circulation in fish.
It is a very simple circulatory system. The blood only goes through the heart once each loop and it is a low pressure system which makes it inefficient.
Describe double circulation in mammals.
The blood passes through the heart twice for each loop. It has higher pressure than a single circulatory system and this higher pressure means higher blood flow rate to the body tissues. It also prevents the mixing of oxygenated and deoxygenated blood.
Explain the advantages of a double circulatory system.
There is higher pressure in the double circulatory system and so there is a higher blood flow rate which makes it much more efficient than the low pressure single circulatory system.
Describe coronary heart disease.
Over time a fatty substance called atheroma is deposited on the inside of the arteries.
The surface of the atheroma can become rough which causes fibrinogen in the plasma to stick to it and build up.
This can build up to form a thrombus (blood clot) which may get large enough to block the artery and restrict blood flow,
If the blood clot forms in the coronary artery it will starve the heart muscles of oxygenated blood leading to a severe heart attack.
Describe the structure and function of the arteries.
Arteries carry oxygenated blood (except the pulmonary artery).
They have thicker, muscular walls with elastic fibres and fibrous tissue to carry blood at high pressure.
They have a narrow lumen (centre) but the elastic capabilities allow it to expand when blood is pumped through it.
They divide into smaller vessels called arterioles.
Describe the structure and function of the veins.
Veins carry deoxygenated blood (except the pulmonary vein), this blood is also higher in CO2.
They have thin walls with little or no elastic tissue and predominantly fibrous tissue to carry blood at low/constant pressure.
They have large/wide lumen to reduce resistance to blood flow.
Valves are present to prevent the backflow of blood.
They connect to smaller vessels called venules.
Describe the structure and function of the capillaries.
They are the smallest blood vessels.
They are permeable with one cell thick walls to allow diffusion of materials between the capillary and surrounding tissue.
The lumen is one red blood cell wide so the cells pass through slowly to optimise diffusion to and from them.
The blood is still under pressure.
Plasma is able to pass through the walls but not blood cells (partially permeable).
No cell in the body is far from a capillary.
Describe the structure of blood vessels.
The blood vessels are made up of layers:
- Tunica externa: The external layer of fibrous connective tissue (collagen) that anchors the blood vessel to nearby structures.
- Tunica media: The middle layer of blood vessels composed of smooth muscle and elastic tissue.
- Tunica intima/Endothelium: The internal layer that lines the blood vessel. Consists of primarily epithelial cells.
Describe the movement of blood through the heart.
Blood moves into the right atrium from the vena cava and then into the right ventricle through the tricuspid valve.
Blood moves out of the right ventricle and into the pulmonary artery through the pulmonary valve.
Blood returns from the lungs through the pulmonary vein and enters the left atrium. It then moves through the bicuspid (mitral) valve into the left ventricle.
The blood is then pumped out of the left ventricle through the aortic valve and then moves out to the head and body through the aorta.
What are the two types of valve in the heart?
Atrioventricular valves:
Tricuspid valve - between right atrium and ventricle.
Bicuspid valve (or mitral valve) - between left atrium and ventricle.
Semi-lunar valves:
Pulmonary valve - between the right ventricle and the pulmonary artery.
Aortic valve - between the left ventricle and the aorta.
What are the different types of blood?
- Red blood cells.
- White blood cells.
- Platelets.
- Plasma.
Describe the structure and function of red blood cells.
Red blood cells:
- Are disk shaped (biconcave).
- Have no nucleus.
- Are made in the bone marrow.
- Transport oxygen around the body. Haemoglobin combines with oxygen to form oxyhaemoglobin.
What are the different types of white blood cells?
There are several different kinds, all play a different role in the immune system.
The most common are phagocytes and lymphocytes.
Lymphocytes produce antibodies.
Phagocytes engulf and destroy pathogens through phagocytosis.
Describe the structure and function of platelets.
Platelets:
- Assist in clotting the blood and stopping bleeding at the site of a wound.
- Are produced in the bone marrow.
Describe the structure and function of plasma.
Plasma is the liquid part of the blood.
It contains many dissolved substances such as ions, amino acids, lipids, glucose, hormones etc.
Carbon dioxide, urea and other waste products are also dissolved into the blood plasma.
What are the apoplastic and symplastic pathways?
The apoplast and symplast are two separate pathways in plants which transport water and ions.
The apoplastic pathway is where water and minerals flow through the cell walls of the plant cells.
The symplastic pathway is where water moves through the plasmodesmata through the network of cytoplasm between each cell.
What is the casparian strip?
The casparian strip is a band of corky, waterproof tissue that is found on the walls of the endodermis in root cells. The strip prevents water from entering the pericycle except through the cytoplasm, just blocking the apoplastic pathway in the cell wall and forcing it into the cytoplasm. This is important in maintaining root pressure.
What are arterioles and shunt vessels?
Arterioles are small arteries that have branched off from larger arteries.
They can vasoconstrict and vasodilate to control the distribution of blood around the body.
Shunt vessels are the vessels that blood is diverted through if arterioles are to vasoconstrict.
Describe the process of blood clotting.
Clotting is a mechanism to prevent loss of blood and entry of pathogens.
The process begins whenever damage to the endothelium of blood vessels occurs.
Platelets are activated and trigger a number of activation factors to stimulate the conversion of fibrinogen to fibrin.
Fibrinogen is a soluble protein, but fibrin is not. Fibrin forms a mesh around a wound which gathers more platelets and blood cells, causing a clot.
