Biology Revision 1 Solution

1. In living organisms, enzymes may be used in reactions to convert large molecules into smaller ones. (a) State the term used for all
(i) molecules on which enzymes act, ................................................................... (ii) molecules that are formed in a reaction. ........................................................[2] (b) For a chemical reaction that begins in the stomach, state (i) the original large molecule, .................................................................................... (ii) the stomach enzyme involved, .............................................................................. (iii) the smaller molecules formed. ...................................................................... [3]

(c) Fig. shows diagrammatically how an enzyme-controlled reaction may occur.

(i) Identify region A on Fig. ............................................................................ [1] (ii) State the hypothesis illustrated in Fig.

(a) (i) substrate/s; (ii) product/s; [2]
(b) (i) protein (ii) protease/pepsin/proteolytic
(iii) (poly)peptides/peptones/proteoses (A amino acids); [3]
d) (i) active site/place where substrate fits AW (R lock / key); [1](ii) lock and key (A words in a description); [1]

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2. Fig. shows some food just before it enters the stomach and the same food as it leaves the stomach four hours later.

(a) On Fig., label structures K and L. [2]
(b) The food consisted solely of meat and potatoes. By placing ticks ( ✓ ) in the appropriate boxes in Table, show how the major components of the food compare at positions M and N.

Fig. shows the same food at O, and 24 hours later, at P.

(c) (i) Explain what has happened to the protein between O and P.

(ii) Name the region of the alimentary canal which will contain fibre in the highest proportion and give reasons for your answer. region of alimentary canal
reasons _____________

a) K oesophagus ; L duodenum / small intestine ; [2]
(b) starch – almost the same ; protein – less ; fibre – almost the same ; [3]
(c) (i) digested / changed / broken down / ref. enzyme action ; to amino acids / (poly)peptides ;
absorption (available only with ref. amino acids) ; [max 2]
(ii) colon / rectum / large intestine ; no suitable enzyme / not digested ; ref. cellulose / lignin ;
therefore no absorption / egested as faeces

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3. During heart transplant procedures, it is possible to keep the heart beating while it is being transported many miles from the donor to the patient. Fig. shows diagrammatically how the heart is kept beating during transportation.

(a) Identify structures L and M on Fig.

(b) Suggest two chemicals which must be added to the blood in the reservoir, and explain your suggestions. chemical 1 ... explanation ...................................................................................................................... chemical 2 .................. explanation___________

(c) Using your knowledge of the structure of the heart, explain why blood entering the aorta from the reservoir flows into the heart muscle and not into the left ventricle.
a) (L) right + atrium / auricle ; (M) pulmonary vein ; [2]
(b) (chemicals) glucose ; oxygen ; [2]
(explanation max 2 – each mark available once only either under glucose or oxygen)
for energy (R production) ; during respiration ;
heart muscle / cells / tissue ; (max 2) [4]
(c) valve (if named, must be aortic / semi-lunar) ;
closes (available with wrongly-named valve) ; sending blood through coronary blood vessel / artery(ies) (R vein) ; [3]

(a) Structure L is the right atrium or auricle, and structure M is the pulmonary vein.
(b) Chemical 1 that must be added to the blood in the reservoir is glucose. This is because glucose is the main source of energy for the heart muscle during respiration. Chemical 2 that must be added is oxygen, as oxygen is necessary for the heart muscle to produce energy through aerobic respiration.
(c) Blood entering the aorta from the reservoir flows into the heart muscle and not into the left ventricle because of the presence of the aortic valve. The aortic valve closes, preventing blood from flowing back into the left ventricle, and instead sends the blood through the coronary blood vessels or arteries, supplying the heart muscle with oxygen and nutrients.

Explanation

(a) Structure L is the right atrium or auricle, and structure M is the pulmonary vein.
(b) Chemical 1 that must be added to the blood in the reservoir is glucose. This is because glucose is the main source of energy for the heart muscle during respiration. Chemical 2 that must be added is oxygen, as oxygen is necessary for the heart muscle to produce energy through aerobic respiration.
(c) Blood entering the aorta from the reservoir flows into the heart muscle and not into the left ventricle because of the presence of the aortic valve. The aortic valve closes, preventing blood from flowing back into the left ventricle, and instead sends the blood through the coronary blood vessels or arteries, supplying the heart muscle with oxygen and nutrients.

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4. Fig. shows a section through the heart.

(a) (i) Identify blood vessels M, N and O in Fig.

(ii) Name the type of tissue which forms the major part of the heart and name the blood vessel which supplies this tissue with oxygen unless it is blocked by heart disease. type of tissue .................................... blood vessel ...................................... [2]

(b) The four statements below describe some of the events that occur during the flow of blood through the heart. Arrange the correct sequence of these events, starting immediately after deoxygenated blood has entered the heart and ending as the blood is sent to the lungs. A The right atrium contracts. B The semilunar valves open. C The right ventricle contracts. D The tricuspid valve closes. [3]

In part (a)(i), M is identified as the inferior vena cava, which is a large vein that carries deoxygenated blood from the lower body to the right atrium of the heart. N is identified as the systemic aorta, which is the largest artery in the body and carries oxygenated blood from the left ventricle of the heart to the rest of the body. O is identified as the pulmonary vein, which carries oxygenated blood from the lungs to the left atrium of the heart. In part (a)(ii), the type of tissue that forms the major part of the heart is muscle, and the blood vessel that supplies this tissue with oxygen is the coronary artery. In part (b), the correct sequence of events during the flow of blood through the heart after deoxygenated blood has entered is A (The right atrium contracts), D (The tricuspid valve closes), B (The semilunar valves open), and C (The right ventricle contracts).

Explanation

In part (a)(i), M is identified as the inferior vena cava, which is a large vein that carries deoxygenated blood from the lower body to the right atrium of the heart. N is identified as the systemic aorta, which is the largest artery in the body and carries oxygenated blood from the left ventricle of the heart to the rest of the body. O is identified as the pulmonary vein, which carries oxygenated blood from the lungs to the left atrium of the heart. In part (a)(ii), the type of tissue that forms the major part of the heart is muscle, and the blood vessel that supplies this tissue with oxygen is the coronary artery. In part (b), the correct sequence of events during the flow of blood through the heart after deoxygenated blood has entered is A (The right atrium contracts), D (The tricuspid valve closes), B (The semilunar valves open), and C (The right ventricle contracts).

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5. Fig. shows a section through a small surface wound to the skin.

a) Name structure O and the type of blood vessel P shown in Fig.

b) State two features that are characteristic of the type of blood vessel P.

c) Explain what is happening to the bacteria in Fig.
(i) at M:
(ii) at N:

(d) Explain how the wound is being sealed in the region under the scab.
(a) (O) WBC/phagocyte, (P) capillary ; [2]
(b) walls + very thin/one cell thick ;
microscopic/narrow/small bore/allow RBCs only in single file ;
walls leaky/permeable /allow substances to pass through ;
slow blood flow
(c) (i) M - WBC/lymphocyte + antibodies ; clumping (of bacteria) ; [2]
(ii) N - engulfing/ingesting/phagocytosis
(d) action of platelets, fibrinogen to fibrin ; trapping of RBCs, prevention of further bacterial entry, blood clot

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6. Fig. is a flow-diagram showing the pathways taken by oxygen and carbohydrate from their absorption into a mammal’s blood to their use in the liver.

(a) By filling in the spaces, complete Fig. to state • the structures involved • the blood vessels used • what happens in the liver cells. [8]

(b) State a waste product formed from proteins in the liver.

(c) Suggest (i) a chemical element present in the waste product you mention in (b) that is also present in a fat.

(ii) a chemical element present in the waste product that is not normally found in a fat. (a) alveoli/capillaries/air sacs ; (micro) villi ;
1 pulmonary vein ;
2 aorta (in any order)
3 hepatic artery ;
respiration/oxidation of glucose ; 1/2 respiration
1/2. conversion from/to glycogen ; max. 8 (b) urea/uric acid (Ignore nitrogenous waste); 1
(c) (i) H(hdrogen/C(arbon/O(xygen)
(ii) N(itrogen)

The flow diagram in Fig. shows the pathways taken by oxygen and carbohydrate from their absorption into a mammal's blood to their use in the liver. The structures involved in this process are the alveoli/capillaries/air sacs, microvilli, pulmonary vein, aorta, and hepatic artery. Oxygen and carbohydrate are absorbed into the blood through the alveoli/capillaries/air sacs and microvilli. The oxygen-rich blood is then carried to the liver through the pulmonary vein, while the carbohydrate is transported through the aorta. In the liver, the oxygen is used for respiration/oxidation of glucose, and the carbohydrate is converted to glycogen. A waste product formed from proteins in the liver is urea/uric acid. Urea/uric acid contains the chemical element nitrogen, which is also present in fats. However, urea/uric acid also contains the chemical element hydrogen/carbon/oxygen, which is not normally found in fats.

Explanation

The flow diagram in Fig. shows the pathways taken by oxygen and carbohydrate from their absorption into a mammal's blood to their use in the liver. The structures involved in this process are the alveoli/capillaries/air sacs, microvilli, pulmonary vein, aorta, and hepatic artery. Oxygen and carbohydrate are absorbed into the blood through the alveoli/capillaries/air sacs and microvilli. The oxygen-rich blood is then carried to the liver through the pulmonary vein, while the carbohydrate is transported through the aorta. In the liver, the oxygen is used for respiration/oxidation of glucose, and the carbohydrate is converted to glycogen. A waste product formed from proteins in the liver is urea/uric acid. Urea/uric acid contains the chemical element nitrogen, which is also present in fats. However, urea/uric acid also contains the chemical element hydrogen/carbon/oxygen, which is not normally found in fats.

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