14.1. Homeostasis in mammals
A subsection of Biology, 9700, through 14. Homeostasis
Listing 10 of 95 questions
is a light micrograph of a small part of the pancreas. Name structures A and B. A B With reference to , explain why the pancreas is an endocrine gland. Insulin and glucagon are involved in the control of blood glucose concentration. When blood glucose concentration rises, secretion of insulin increases. Outline two ways in which insulin affects the activity of cells in the liver. 1. 2. Some forms of diabetes are caused by an inability to secrete insulin and can be controlled by regular injections of insulin. Most of this insulin is now produced using genetically modified Escherichia coli. Explain the advantages of using this type of insulin, rather than insulin obtained from animal sources.
9700_s08_qp_4
THEORY
2008
Paper 4, Variant 0
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Adipose tissue is specialised connective tissue that functions as the major storage site for fat in the form of triglycerides. The human body contains two types of adipose tissue: white adipose tissue (WAT) and brown adipose tissue (BAT). • WAT is more common and is found under the skin and around some internal organs. • BAT is found in infants around the back and shoulders. • BAT is also found in adults but in relatively smaller quantities. • BAT cells contains more mitochondria than WAT cells. • BAT is involved in the maintenance of a constant blood temperature when the external environment is cold. Blood temperature in humans is maintained by a process called homeostasis. With reference to blood temperature, outline the main principles of homeostasis. Suggest why infants have relatively more BAT than adults. Mitochondria in BAT cells function differently from those in other cells during periods of cold environmental conditions. shows part of a mitochondrion in a BAT cell. cytosol outer membrane intermembrane space uncoupling protein 1 heat energy ATP ADP+Pi electron transport chain H+ H+ H+ H+ H+ H+ H NAD reduced NAD e– process 3 process 2 matrix process 1 B A Name structures A and B. A B Draw an arrow on to indicate the direction of the proton gradient that exists between the matrix and the intermembrane space. State the two processes, shown in , that will be more active during periods of cold external environmental conditions. State the by-product that is obtained as a result of processes 1 and 2. Suggest the main respiratory substrate for BAT cells.
9700_s14_qp_42
THEORY
2014
Paper 4, Variant 2
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Some people have a condition called diabetes. In type 1 diabetes the pancreas does not produce enough insulin. shows the blood glucose concentrations of a type 1 diabetic person and a non-diabetic person, at regular intervals after drinking a glucose drink. time / h blood glucose concentration / mg 100 cm–3 glucose drink taken non-diabetic person diabetic person Describe the results shown in . Name the location of the receptors in a non-diabetic person that detect a change in blood glucose concentration. Name the homeostatic mechanism by which blood glucose concentration is maintained. The urine of a non-diabetic person does not contain glucose. A person with type 1 diabetes will excrete glucose in urine. A reading of the concentration of glucose in the urine can be estimated using a dipstick. outlines how a dipstick works. glucose in urine enzyme A gluconic acid + hydrogen peroxide hydrogen peroxide + colourless chromogen enzyme B water + coloured chromogen The higher the concentration of glucose in the urine, the darker the colour on the dipstick. Name enzymes A and B. A B An electronic biosensor can be used to measure the glucose concentration in a drop of blood. Suggest one advantage of using a biosensor and one advantage of using a dipstick to measure glucose concentration. biosensor dipstick Describe the role played by insulin in the control of blood glucose concentration.
9700_s19_qp_41
THEORY
2019
Paper 4, Variant 1
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In mammals, some cell signalling molecules are steroid hormones. These hormones are transported in the bloodstream to reach capillary networks. At a capillary network, hormones pass out of the blood into tissue fluid. is a diagram of a capillary network. tissue fluid body cells blood from artery blood to vein X Describe the differences between the blood arriving at the arterial end of the capillary network and the tissue fluid surrounding the body cells. Not all the tissue fluid passes back into the blood capillaries to enter the bloodstream. Some of the tissue fluid drains into blind‑ended vessels, such as vessel X shown in . Name the fluid that is formed in vessel X. Hormone S is a steroid hormone involved in cell signalling. shows the sequence of events that occurs when hormone S enters a target cell. R B G C hormone-receptor complex cell surface membrane not to scale hormone S cell surface membrane receptors cytoplasmic receptors nuclear receptor messenger RNA molecule polypeptide KEY: nuclear envelope DNA Explain why hormone S, shown in , does not need to pass through a transport protein to enter the cytoplasm of the target cell. The target cell can respond to other cell signalling molecules in addition to hormone S. The cell has receptors in the cell surface membrane, in the cytoplasm and in the nucleus. Explain why hormone S binds only with receptor R in the cytoplasm and not with the other receptors shown in . The hormone‑receptor complex shown in enters the nucleus and binds to DNA. This switches on a gene coding for a polypeptide that is synthesised in the cytoplasm. Name the structure through which the hormone‑receptor complex enters the nucleus. Name the processes occurring at B and C. B C Name structure G. Cell signalling by hormone S results in the production of a functioning globular protein molecule composed of three identical polypeptide chains. After the synthesis of these polypeptides, changes need to occur to form the functioning globular protein molecule. Outline the changes that need to occur to form the functioning globular protein molecule.
9700_s21_qp_22
THEORY
2021
Paper 2, Variant 2
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The bottlenose dolphin, Tursiops truncatus, is an aquatic mammal. It has adaptations to conserve heat when swimming in cold water. shows a bottlenose dolphin. flipper The arteries in the bottlenose dolphin that carry blood to the flippers are surrounded by veins bringing blood back to the rest of the body. Outline how this arrangement of blood vessels is an adaptation to conserve body heat. When a dolphin has exercised for a long time, it may need to lose excess heat. Unlike humans, dolphins do not produce sweat. Suggest how a dolphin may lose excess heat. The control of blood glucose concentration in dolphins is the same as in most mammals. A study was carried out to investigate the concentration of insulin in the blood of dolphins that were provided with a diet of fish, supplemented with glucose. • One group of dolphins ate fish with 3 g of glucose for every kg of fish. • Another group ate fish with 11 g of glucose for every kg of fish. The concentration of insulin in the blood was measured 60 minutes before being fed, at the time of being fed and at regular intervals afterwards. Measurements were also taken for a third group of dolphins, at the same time intervals, that were not fed any fish . The results of the study are shown in . –60 time / min food given mean concentration of insulin in blood / pmol cm–3 fasting 3 g / kg 11 g / kg Key: Describe the trends shown in . The mean concentration of insulin in the blood changes over time for the dolphins that were fed fish with 11 g of glucose per kg of fish. Calculate the rate of change in the mean concentration of insulin in this group of dolphins from the time of being fed until the concentration reaches its maximum. Show your working. pmol cm–3 min–1 Blood glucose concentration is regulated by negative feedback. Explain what is meant by negative feedback.
9700_s21_qp_43
THEORY
2021
Paper 4, Variant 3
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Questions Discovered
95