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Across what structure does the exchange of substances occur in cells?
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Across what structure does the exchange of substances occur in cells?
The exchange of substances in cells occurs across the cell membrane.
Name three transport processes used by living organisms for the exchange of substances.
Three transport processes used for exchange of substances are:
Diffusion
Osmosis
Active transport
True or False?
Unicellular organisms have a small surface area to volume ratio.
False.
Unicellular organisms have a large surface area to volume ratio.
Why don't unicellular organisms need specialised exchange surfaces for the exchange of substances?
Unicellular organisms do not need specialised exchange surfaces because they have a very large surface area to volume ratio. This allows diffusion at the cell surface to meet the organism's needs.
Give an example of a substance, or type of substance, that a unicellular organism would exchange with its environment.
A substance, or type of substance, that a unicellular organism would exchange with its environment could be:
Nutrients, e.g. glucose
Oxygen
Waste products, e.g. carbon dioxide
True or False?
Unicellular organisms have a short diffusion distance from their cell membrane to the centre of the cell.
True.
The distance from the cell membrane to the centre of a unicellular organism is relatively short. This means that not only do they not need specialised exchange surfaces, they also do not need a specialised transport system.
Define the term multicellular organism.
Multicellular organisms are organisms with bodies made up of more than one cell.
Give an example of a transport system.
Examples of transport systems include:
The circulatory system in humans
The vascular system, i.e. xylem and phloem, in plants
True or False?
Unicellular organisms do not need transport systems because their diffusion distances are so short.
True.
Unicellular organisms are made up of only one cell, so the distance from the cell surface to the centre of the cell is relatively short. This short diffusion distance means that a transport system is not needed.
Why do multicellular organisms need transport systems?
Multicellular organisms need transport systems because they contain many layers of cells which increases the diffusion distances involved in the movement of substances. Diffusion alone would take too long to reach all of the cells.
True or False?
Diffusion alone can meet the transport needs of multicellular organisms.
False.
Diffusion alone is too slow to meet the needs of multicellular organisms, which generally have high metabolic requirements
Define the term phloem.
The phloem are vessels, or tubes, that transport sucrose and amino acids in plants.
True or False?
Transport in the phloem only occurs in one direction.
False.
Movement in the phloem can occur in any direction depending on where substances are being produced or stored.
From where, and to where, does phloem transport occur?
The phloem transports materials from the parts of plants where they are produced or stored, to the parts of plants where they are needed, e.g.
From the photosynthesising leaves to the rest of the plant
From a storage organ to newly developing leaves
True or False?
The phloem is part of the vascular tissue of plants.
True.
Phloem and xylem together make up the vascular tissue in plants. This vascular tissue is the plant transport system.
True or False?
Phloem vessels transport sugars in the form of glucose.
False.
Sugars are transported in the form of sucrose within the phloem.
Define the term xylem.
Xylem are vessels, or tubes, that transport water and mineral ions in plants.
True or False?
Xylem vessels transport sugars within plants.
False.
Xylem vessels transport water and mineral ions. Sugars are transported in the phloem.
In which direction does xylem transport occur?
Xylem transport always occurs from the roots, upwards to the rest of the plant.
True or False?
Xylem vessels transport mineral ions from the roots to the leaves of plants.
True.
Minerals are transported from the soil, into the roots and upwards in the xylem.
Why are xylem vessels essential to plant survival?
Xylem vessels are essential to plant survival because they transport water which is needed for photosynthesis, as well as mineral ions which are needed to build molecules, e.g. chlorophyll and amino acids
How are root hair cells adapted to aid the absorption of water and mineral ions?
Root hair cells are adapted for absorption as follows:
They have a large surface area
They contain mitochondria which release energy for active transport
True or False?
Minerals move into root hair cells by osmosis.
False.
Mineral ions move into root hair cells by active transport. Only water can move by osmosis.
Why do root hair cells need energy from respiration?
Root hair cells need energy to fuel the active transport of mineral ions from the soil against a concentration gradient.
What causes water to move into root hair cells?
Water moves into root hair cells by osmosis due to the water concentration gradient between the soil and the cell cytoplasm. Minerals, and other dissolved substances, in the cytoplasm of root hair cells lower the water concentration, so water moves into the cells by osmosis.
Define the term transpiration.
Transpiration is the loss of water vapour from the leaves of plants by evaporation.
What is the role of the spongy mesophyll cells in transpiration?
The spongy mesophyll cells are involved in transpiration as follows:
water vapour evaporates from the surface of spongy mesophyll cells and enters the leaf air spaces
water vapour diffuses from the leaf air spaces out of the leaf
True or False?
Transpiration stops when guard cells close the stomata.
True.
Guard cells can cause the stomata to close, preventing water vapour from exiting the leaf and stopping transpiration.
True or False?
Transpiration results in the upward movement of sucrose and amino acids.
False.
Transpiration involves the loss of water from the xylem of plants, so does not affect sucrose and amino acids, which are transported in the phloem.
By what process does water vapour exit the leaf air spaces?
Water vapour exits the leaf air spaces by the process of diffusion.
Which four factors can affect the rate of transpiration in plants?
Four factors that affect the rate of transpiration are:
Humidity
Wind speed / air movement
Temperature
Light intensity
What happens to transpiration rate as light intensity increases?
As light intensity increases, the transpiration rate increases.
True or False?
Transpiration rate increases at high light intensity because the stomata close.
False.
Transpiration rate increases with light intensity because the stomata open at high light intensities to enable gas exchange for photosynthesis.
What happens to transpiration rate as temperature decreases?
As temperature decreases the transpiration rate decreases.
True or False?
Transpiration rate increases at higher temperatures due to the increased kinetic energy of molecules.
True.
At higher temperatures water molecules have more kinetic energy and are more likely to diffuse out via the stomata.
True or False?
Transpiration rate increases as wind speed increases.
True.
As wind speed increases the transpiration rate increases.
Why does transpiration occur faster on a windy day?
Transpiration is faster on a windy day because wind blows water vapour away from the surface of leaves, maintaining a water vapour concentration gradient between the inside and the outside of leaves.
How will putting a plant inside a plastic bag affect its rate of transpiration?
Putting a plant inside a plastic bag will decrease its rate of transpiration. This is because the bag will trap water vapour and raise humidity levels, decreasing the water vapour concentration gradient between the leaf and the surrounding air.
True or False?
Increasing humidity levels will increase the rate of transpiration.
False.
Increasing humidity levels will decrease the rate of transpiration. This is because humid conditions decrease the water vapour concentration gradient between the inside and the outside of the leaf.
Define the term water vapour concentration gradient in the context of transpiration.
The water vapour concentration gradient is the difference in water vapour concentration between the inside and the outside of a leaf.
Name the piece of equipment used to measure transpiration rate in a plant shoot.
The piece of equipment used to measure transpiration rate in a plant shoot is known as a potometer.
Describe how a bubble potometer works to measure transpiration rate.
A bubble potometer works to measure transpiration rate as follows:
A bubble is introduced into a tube containing a cut plant stem
As the plant transpires water is pulled up the stem, causing the bubble to move
The distance the bubble moves in a given time indicates the transpiration rate
How can a potometer be set up to ensure that the system is airtight?
An airtight potometer system can be ensured by:
A potometer can be set up underwater to prevent entry of air bubbles
Petroleum jelly can be used to seal any joins
What is the C of CORMMS when investigating the effect of air movement on transpiration rate? (CORMMS)
The C of CORMMS stands for change. When investigating the effect of air movement on transpiration rate the variable that is changed is the speed of the air movement, e.g. no air movement, low air movement, high air movement.
This is part of the CORMMS criteria for planning an investigation.
The effect of which environmental factor on transpiration rate can be investigated by altering the position of a lamp in relation to a bubble potometer?
Altering the position of a lamp in relation to a potometer allows the effect of light intensity on transpiration rate to be investigated.
How could you investigate the effect of air movement on transpiration rate using a potometer?
The effect of air movement on transpiration rate can be investigated by setting up a fan or hairdryer blowing air over the plant shoot.
True or False?
The effect of humidity on transpiration rate can be measured by tying a plastic bag around the leafy shoot.
True.
The effect of humidity on rate of transpiration can be assessed by enclosing the plant shoot in a plastic bag. Any water vapour lost by transpiration will be trapped, raising the humidity inside the bag.
Give three environmental variables that should be kept the same when investigating the effect of temperature on transpiration rate. (CORMMS)
Environmental variables that should be kept the same when investigating the effect of temperature on transpiration rate include:
Air movement
Light intensity
Humidity
This is part of the CORMMS criteria for planning an investigation.
How can the distance moved by the bubble and the recorded time be used to calculate a rate of transpiration?
Transpiration rate can be calculated as follows:
Transpiration rate = distance moved by bubble ÷ time
Give an example of the O of CORMMS when investigating the effect of humidity on the rate of transpiration. (CORMMS)
The O of CORMMS stands for organism. When investigating the effect of humidity on the rate of transpiration this could be:
Same species of plant
Same age of plant shoot
Same number of leaves present on plant shoot
This is part of the CORMMS criteria for planning an investigation.
What is the main component of blood by volume?
Plasma, which constitutes over half of the blood volume.
What are the main components of blood?
The main components of blood are:
Red blood cells
White blood cells
Platelets
Plasma
What is the primary function of red blood cells?
The primary function of red blood cells is to transport oxygen (via haemoglobin).
What is the primary function of white blood cells?
White blood cells are primarily involved in the immune response and defence against pathogens.
What is the primary function of platelets?
Platelets play a crucial role in blood clotting and wound healing.
Which component of blood is responsible for maintaining blood pressure?
Plasma helps maintain blood pressure (and transports nutrients, hormones, and waste products).
Which component of blood is responsible for its clotting ability?
Platelets are primarily responsible for blood clotting.
What is the role of plasma in the transport of substances?
Plasma transports various substances such as carbon dioxide, digested food, mineral ions, urea, hormones, and heat energy.
How is carbon dioxide transported in the blood?
Carbon dioxide is dissolved in plasma as hydrogen carbonate ions and transported from respiring cells to the lungs.
What substances are absorbed from the small intestine and transported in plasma?
Digested foods e.g. glucose and amino acids are absorbed from the small intestine and transported in plasma to cells around the body.
What is the function of plasma in the transport of urea?
Plasma transports urea, a waste substance produced in the breakdown of proteins by the liver, to the kidneys.
How are hormones transported in the body?
Hormones, chemical messengers released by endocrine organs, are transported in plasma and delivered to target tissues/organs.
How is heat energy distributed in the body?
Heat energy released during respiration is transferred by plasma to cooler parts of the body or to the skin for dissipation.
What is the main function of red blood cells?
Red blood cells transport oxygen to respiring cells.
What is the role of haemoglobin in red blood cells?
Haemoglobin, a protein in red blood cells, binds to oxygen.
Why do red blood cells lack a nucleus?
Red blood cells lack a nucleus to create more space for haemoglobin, allowing for more efficient oxygen transport.
How is the shape of red blood cells described?
The shape of red blood cells is described as a "biconcave disc," providing a large surface area to volume ratio for efficient oxygen diffusion.
What is the advantage of the biconcave shape of red blood cells?
The biconcave shape provides a large surface area to volume ratio, maximising the diffusion of oxygen in and out of the cell.
What is the main function of white blood cells?
White blood cells are part of the body's immune system and defend against pathogenic microorganisms.
What are the two main types of white blood cells?
The two main types of white blood cells are phagocytes and lymphocytes.
What is the role of phagocytes in the immune system?
Phagocytes engulf and digest pathogens through phagocytosis.
Be careful not to use the work "eat" in place of engulf.
What is the main function of lymphocytes?
Lymphocytes produce antibodies, which are proteins that bind to specific antigens on pathogens, and antitoxins to neutralise toxins released by pathogens.
What is the role of antibodies in the immune response?
Antibodies attach to antigens on pathogens, binding the pathogens together, preventing them from moving, and signalling phagocytes to destroy them.
What is the role of antitoxins produced by lymphocytes?
Antitoxins neutralise toxins released by pathogens, preventing them from causing harm to the body.
True or False?
The body's response to infection involves antigens recognising antibodies.
False.
The body's response to infection involves antibodies recognising antigens.
Define immunity.
Immunity is having sufficient levels of antibodies to protect the body from a particular disease, preventing the individual from suffering from the disease or its symptoms.
What is the difference between antigen, antibody, and antitoxin?
An antigen is a protein molecule found on the surface of a cell, usually a pathogen
An antibody is a protein produced by lymphocytes that binds to specific antigens on pathogens, causing their destruction
An antitoxin is a protein that neutralises toxins released by pathogens
True or False?
Phagocytes release antibodies as part of their immune response.
False.
Phagocytes carry out phagocytosis and engulf pathogens and other foreign molecules. They do not produce antibodies.
What is the role of vaccines?
Vaccines are used to induce immunity to infectious diseases by introducing harmless versions of pathogens into the body.
How do scientists ensure that vaccines contain harmless pathogens?
Scientists ensure that vaccines contain harmless pathogens by killing the pathogen, making it unable to grow or divide, or using fragments of pathogens rather than whole cells.
What role do lymphocytes have once a vaccination enters the bloodstream?
Lymphocytes recognise the antigens and produce specific antibodies to the antigen in the vaccine.
How does vaccination lead to long-term immunity?
Vaccination triggers a response where memory cells and antibodies remain in the bloodstream. Future infections by the same pathogen result in a faster immune response, preventing disease.
What is the importance of vaccination beyond protecting the vaccinated individual?
Vaccines also reduce the likelihood of infected individuals spreading the pathogen to others within the population, contributing to herd immunity.
Define memory cell.
Memory cells are produced after infection or vaccination and enable future antibody production to the same pathogen/antigen to occur sooner, faster and in greater quantity.
Name three methods of administering vaccines.
Three methods of administering vaccines are:
orally (mouth)
nasally (nose)
injection
What is the role of platelets in the blood?
Platelets are involved in helping the blood clot and forming scabs when the skin is broken or wounded.
True or False?
Soluble fibrin proteins are converted to insoluble fibrinogen proteins during the blood clotting process.
False.
Soluble fibrinogen proteins are converted to insoluble fibrin proteins during the blood clotting process.
What is the effect of insoluble fibrin during blood clotting?
Fibrin forms an insoluble mesh across the wound, trapping red blood cells to form a clot, which eventually dries to become a scab.
Why is blood clotting important?
Blood clotting prevents significant blood loss from wounds and seals them with a scab, preventing entry of microorganisms that could cause infection until new skin grows underneath.
Define the term platelet.
Platelets are fragments of cells that are involved in blood clotting and forming scabs where the skin has been cut or punctured.
What is the function of the heart?
The heart is a double pump that circulates oxygenated blood from the lungs to the rest of the body (systemic circuit) and deoxygenated blood from the body to the lungs (pulmonary circuit).
Describe the pathway of deoxygenated blood through the heart from the body.
Deoxygenated blood from the body:
Enters the right atrium through the vena cava
Flows through the tricuspid valve into the right ventricle
Is pumped through the pulmonary semilunar valve into the pulmonary artery
To the lungs for oxygenation
What is the purpose of the septum in the heart?
The septum separates the left and right sides of the heart, preventing oxygenated and deoxygenated blood from mixing.
Why does the left ventricle have a thicker muscle wall than the right ventricle?
The left ventricle has a thicker muscle wall so that it can pump oxygenated blood at high pressure throughout the body (systemic circuit), while the right ventricle pumps deoxygenated blood at lower pressure to the lungs (pulmonary circuit).
What role do valves play in the heart?
Valves in the heart prevent the backflow of blood, ensuring that blood flows in only one direction through the heart chambers and vessels.
How does blood return from the lungs to the heart?
Oxygenated blood returns from the lungs to the heart via the pulmonary veins.
What supplies the cardiac muscle tissue of the heart with oxygenated blood?
The coronary arteries supply the cardiac muscle tissue of the heart with oxygenated blood, ensuring it receives a constant supply of oxygen and glucose for aerobic respiration to release energy for muscle contraction.
How does the heart prevent damage to the capillaries in the lungs?
The heart maintains low pressure in the pulmonary circuit, preventing damage to the capillaries in the lungs during blood circulation.
True or False?
Deoxygenated blood enters the left side of the heart from the body.
False.
Deoxygenated blood enters the right side of the heart from the body.
True or False?
The right ventricle muscle wall is thinner than the left ventricle muscle wall.
True.
The right ventricle muscle wall is thinner than the left ventricle muscle wall.
Which vein is the only vein in the body to carry oxygenated blood?
The pulmonary vein is the only vein to carry oxygenated blood, returning blood to the heart after gas exchange has taken place.
How is heart rate measured?
Heart rate is measured by counting the number of times the heart beats in a minute (bpm).
What factors can influence heart rate?
Heart rate can be influenced by factors such as hormones like adrenaline, exercise intensity, and the body's demand for oxygen and glucose.
What happens to the heart rate during exercise?
During exercise, the heart rate increases to deliver more oxygen and glucose to the muscles, remove waste products, and meet the increased demand for energy release through respiring cells.
Why does the heart rate remain elevated after exercise?
The heart rate remains elevated after exercise because extra oxygen is required in the muscles to break down lactic acid from anaerobic respiration, and this is how the oxygen debt is paid off. The elevated heart rate ensures extra oxygen is transported to the cells.
What is recovery time in relation to heart rate and exercise?
Recovery time is the time taken for the heart rate to return to its resting rate after exercise.
Define the term adrenaline.
Adrenaline is a hormone that increases heart rate.
True or False?
During exercise respiration in the muscle cells decreases.
False.
During exercise respiration in the muscle cells increases.
Which hormone influences heart rate?
The hormone adrenaline influences heart rate by increasing heart rate.
What are the coronary arteries responsible for?
The coronary arteries supply the heart with oxygenated blood, delivering oxygen and glucose while removing waste products such as carbon dioxide.
What does CHD stand for?
CHD stands for coronary heart disease.
What is coronary heart disease (CHD)?
Coronary heart disease (CHD) occurs when fatty deposits (plaque) build up inside the coronary arteries, reducing blood flow and depriving the heart muscle of oxygen.
How does plaque/fatty deposit buildup in the coronary arteries lead to CHD?
Plaque buildup narrows the arteries, reducing blood flow and causing a lack of oxygen to the heart muscle. This can lead to angina (chest pain) or a heart attack.
True or False?
Smoking is not a risk factor for coronary heart disease.
False.
Smoking is a risk factor for coronary heart disease.
How does high blood pressure increase the risk of CHD?
High blood pressure increases the force of the blood against the coronary artery walls and consequently leads to damage of the vessels.
State four risk factors for CHD.
Four risk factors for CHD are:
Smoking
High blood pressure
Obesity
High cholesterol
True or False?
High cholesterol is a risk factor for CHD because it leads to a build-up of fatty deposits in the coronary arteries.
True.
High cholesterol is a risk factor for CHD because it leads to a build-up of fatty deposits in the coronary arteries.
What are the three main types of blood vessel?
The three main types of blood vessel are arteries, veins, and capillaries.
What is the function of arteries?
Arteries carry blood at high pressure away from the heart.
How are the walls of arteries adapted to their function?
Arteries have thick muscular walls containing elastic fibres to withstand high blood pressure and maintain it as the blood recoils. They also have a narrow lumen to help maintain high blood pressure.
What is the function of veins?
Veins carry blood at low pressure towards the heart.
How are the walls of veins adapted to their function?
Veins have thin walls and a large lumen to reduce resistance to blood flow under low pressure. They also contain valves to prevent backflow of blood.
What is the function of valves?
Valves prevent the back-flow of blood in the veins where blood travels under low-pressure.
What are the key features of capillaries?
Capillaries carry blood at low pressure within tissues, have walls that are one cell thick, and allow substances to easily diffuse in and out through their 'leaky' walls.
What is the function of the circulatory system?
The circulatory system consists of a double pump within a closed network of blood vessels connected to the heart, responsible for transporting oxygenated blood to the body cells and returning deoxygenated blood to the heart.
What is the blood vessel carrying blood to the liver?
The blood vessel carrying blood to the liver is the hepatic artery.
True or False?
The renal vein carries oxygenated blood away from the kidneys.
False.
The renal vein carries deoxygenated blood away from the kidneys.
Which blood vessel carries deoxygenated blood to the lungs from the heart?
The blood vessel that carries deoxygenated blood to the lungs from the heart is the pulmonary artery.
True or False?
The pulmonary vein carries oxygenated blood to the lungs from the heart.
False.
The pulmonary vein carries oxygenated blood to the heart from the lungs.