Ocr As Biology 14 May 2012

Front 1

1a)i) Yeast reproduces asexually by a process called budding. During this process, cell division occurs.

Name the type of cell division that occurs in asexual reproduction (1)

Back 1

mitosis

Front 2

1a)ii) Before the division of the nucleus of a cell, the genetic material must replicate. Explain why this is essential. (2)

Back 2

idea that:cells, genetically identical / have same DNA;

so both (daughter) cells receive a full, copy/complement ;

allow 'daughter cells have all the identical genetic material' for 2 marks

Front 3

1b) Unlike yeast, the nuclei of most eukaryotic organisms contain homologous pairs of chromosomes. Explain what is meant by a homologous pair of chromosomes. (3)

Back 3

1 one maternal and one paternal / AW;

2 carry same genes;

3 carry, same / different, alleles;

4 (usually) same / similar, length;

5 centromere in same position;

6 same banding pattern;

7 pair up in meiosis / form bivalent;

3 max

Front 4

1c)i) State what is meant by the term tissue (2)

Back 4

a, group / collection, of cells;

(cells) specialised / AW;

to perform a function(s) / working together;

2 max

Front 5

1c)ii)

Back 5

Front 6

2a)i) Name the structures labelled C, D and E (3)

Back 6

C (secretory / Golgi) vesicle;

D plasma membrane or cell surface membrane;

E ribosome;

Front 7

2a)ii) suggest one type of extracellular protein secreted at B (1)

Back 7

enzyme/(peptide) hormone/glycoprotein;

ACCEPT named example e.g. insulin, mucus, cytokine,antibodies, collagen

IGNORE haemoglobin, histamine, steroid hormones e.g.testosterone

Front 8

2a)iii) Suggest one stage during the secretion of a protein that requires energy. (1)

Back 8

transport vesicles to, plasma/cell surface, membrane;

fusing vesicle to membrane/exocytosis ;

1 max

Front 9

2a)iv) Outline the role of the Golgi apparatus (2)

Back 9

1 receives proteins from the, (R)ER/ribosomes;2 modify/process, proteins or make glycoproteins/ add named molecule(s)/described;

3 (re)package/AW, into vesicles;4 make lysosomes;5 replenishes, plasma/cell surface, membrane;6 lipid synthesis;

2 max

modifies and packages proteins into vesicles = 2 marks

Front 10

2b)i) Identify two features, visible in Fig.2.1, which would not be present in a prokaryotic cell. (2)

Back 10

nucleus or nuclear, envelope/pore/ membrane;mitochondrion/mitochondria;

(rough / smooth) endoplasmic reticulum/ER OR ribosomes attached to membrane;

Golgi (body / apparatus);

(secretory) vesicle(s);

2 max

Front 11

2b)ii) Name one feature that would be present in the cytoplasm of a prokaryotic cell that is not found in a eukaryotic cell. (1)

Back 11

(free / circular / naked) DNA / genetic material / nucleoid;

plasmid;

18nm/70S/smaller, ribosomes;

1 max

Front 12

3a)

Back 12

double circulatory system, closed circulatory system. Bottom right.

Front 13

3b)i) The pressure fluctuates as the blood flows along the aorta, as shown in Fig.3.1.

Explain what causes this fluctuation (2)

Back 13

systole / contraction, increases pressure;diastole / relaxation/ blood flowing onwards, decreases pressure;(contraction of) ventricle, muscle / wall;left (ventricle);

2 max

‘contraction of left ventricle’ = 1 mark‘contraction of muscle in left ventricle’ = 2 marks‘ventricular systole increases pressure’ = 2 marks

Front 14

3b)ii) State the term used to describe the number of fluctuations per minute (1)

Back 14

pulse / heart, rate ;

Front 15

3c) Using the information in Fig.3.1 describe the pressure changes in the blood as it flows through the circulatory system from the aorta to the veins. (3)

Back 15

marks for pressure change:pressure drops, as distance from heart increases;greatest/rapid/significant, pressure drop while blood is in the arteries;pressure, constant / does not drop, in veins; marks for amplitude of fluctuations:fluctuation / AW, decreases from aorta to arteries;no fluctuation in, capillaries / veins;

use of comparative figures with unit; 3 max

Front 16

3d)i) using the information in Fig3.1, explain what causes the overall change in pressure as blood flows from the aorta to the arteries and from the arteries to the capillaries (2)

Back 16

blood flows into larger number of vessels;

(total) cross-sectional area of the arteries is greater than the aorta;

(total) cross-sectional area of the capillaries is greater than the, aorta / arteries;

ignore ref to lumen size

2 max

Front 17

3d)ii) Explain why it is important that the presure changes as blood flows from the aorta to the capillaries (2)

Back 17

capillary (wall) is, thin / only one cell thick;

(high pressure would) burst / damage, capillary (wall);

reduce chance of, tissue fluid build up/oedema;

2 max

Front 18

4a)i) A student wanted to observe some red blood cells under the microscope. The student placed a small sample of blood onto a microscope slide and added a drop of distilled water. When viewed at high power, the student observed that the red blood cells had burst.

In a similar procedure using plant epidermis, the student observed that the plant cells did not burst. Explain these observations QWC (5)

Back 18

Front 19

4a)ii) Suggest how the student could modify the procedure to observe red blood cells without them bursting (1)

Back 19

use a, salt / sugar, solution OR add solute to water;

use a solution with the, same / similar / lower, water potential as blood cells ;

1 max

Front 20

4b) Oxygen enters red blood cells as they pass through the capillaries in the lungs. Name the mechanism by which oxygen enters the red blood cells. (1)

Back 20

diffusion

do not credit facilitated diffusion

Front 21

4c) The cells in the epidermis of a plant root are specialised to absorb minerals from the surrounding soil. State the process by which root epidermal cells absorb minerals from the soil and describe how these cells are specialised to achieve absorption. (3)

Back 21

1 active, transport / uptake;

plus any two from:

2 cells have, extensions/hairs;

3 thin cell wall;

4 large/increased, surface area;

5 many/more, mitochondria;

6 (many) carrier proteins in cell (surface) membrane ;

3 max

Front 22

5a)i) Name the measurement represented by the line X (1)

Back 22

Tidal volume

Front 23

5a)ii) What is happening to the elastic fibres in the walls of the alveoli at point A (1)

Back 23

being stretched/stretching;

ACCEPT lengthening

Front 24

5b) Explain what causes the change in the volume of air between points B and C QWC (4)

Back 24

Front 25

5c) Using Fig5.1, calculate the breathing rate of this student in breaths per minute (2)

Back 25

12

Front 26

5d) about 1dm^3 of air cannot be expelled from the lungs. This is known as the residual volume. Suggest why it is not possible to expel all the air from the lungs (2)

Back 26

idea that:thorax / rib cage / lungs, cannot be completely , compressed / flattened;

trachea / bronchi, held open by cartilage;

bronchioles / alveoli, held open by elastic fibres;AVP;

2 max

Front 27

6a)i) Name the sugar most commonly transported through the stem of a plant and the tissue that transports this sugar. (1)

Back 27

sucrose

and

phloem

Front 28

6a)ii) Sugar molecules are actively loaded into the transport tissue. Describe how active loading takes place. (3)

Back 28

Front 29

6b) Suggest brief explanations for these results. (3)

Back 29