Ocr As Biology 11 January 2012

Front 1

1a)i) The mammalian lungs contain many air sacs.

Name the air sacs and state why there are many air sacs in the lungs (2)

Back 1

Alveoli;

To provide large surface area;

(accept large surface area to volume ratio)

Front 2

1a)ii) Name the type of epithelium in the walls of the air sacs (1)

Back 2

Squamous/pavement;

Front 3

1a)iii) The air sacs contain many elastic fibres.

Explain the role of these elastic fibres during ventilation (2)

Back 3

to prevent bursting;

recoil;

to return air sac to original size/shape;

to help expel air;

(2 max)

Ignore stretch/contract

Front 4

1b)i) For efficient gaseous exchange to occur, a steep diffusion gradient must be maintained between the air in the air sacs and the blood. A steep diffusion gradient can be maintained by ventilating the lungs. This refreshes the air in the air sacs.

Explain how refreshing the air in the air sacs helps to maintain a steep diffusion gradient.(2)

Back 4

1 increases partial pressure/concentration, of oxygen; (accept high concentration of oxygen)

2 so concentration of oxygen (in the air sac) is higher thanthat in the blood;

3 decreases, partial pressure/concentration, of carbon dioxide (in air sac);

4 so concentration of CO2 (in the air sac) is lower than that in the blood ;

Front 5

1b)ii) Describe and explain one other way in which a steep diffusion gradient is maintained in the lungs. (2)

Back 5

EITHERD1 (continuous) blood flow (in the capillaries);

E1 to, bring in (more) carbon dioxide / take away (more)oxygen;

OR

D2 oxygen combines with haemoglobin;

E2 to keep concentration in, blood/plasma, low;

Front 6

2a) Complete the following paragraph about cells by using the most appropriate term(s).

Cells that are not specialised but still have the ability to divide are called ... cells. Such cells can be found in the ... of the long bones of mammals. These can ... into other types of cell, such as erythrocytes that carry oxygen in the blood. In plants, ... tissue also contains cells that are not specialised. (4)

Back 6

stem / undifferentiated;

(bone) marrow;

differentiate;

meristem(atic) / cambium;

Front 7

2b)i) Suggest one function of the flagellum in the collar cell (1)

Back 7

idea of: create flow of water / move water ;

Front 8

2b)ii) Suggest one possible role for the collar of mucus in the cell (1)

Back 8

strain/filter (the water) OR trap particles;

to catch food (particles);

1 max

Front 9

2c) In more advanced organisms, cells are organised into tissues consisting of one or more types of specialised cells.

Describe how cells are organised into tissues, using xylem and phloem as examples. (4)

Back 9

Xylem:

consists of vessels; one cell specialisation described;

transpiration stream ORmovement of, water/minerals;

Phloem:

sieve tube element(s) and companion cell(s); one cell specialisation described; translocation ORtransports sucrose/assimilates/products of photosynthesis/amino acids; AVP ;

4 max

Front 10

3a) fill in the table

Back 10

Front 11

3b)i) In a closed circulatory system,. blood is kept inside blood vessels.

Suggest two advantages of keeping the blood inside vessels

Back 11

maintain / high(er), (blood) pressure;

increase rate of, flow / delivery;

flow can be, diverted / directed / any other alternate wording ;

Front 12

3b)ii) Describe and explain how the wall of an artery is adapted both to withstand and maintain high hydrostatic pressure.

In your answer you should use appropriate technical terms, spelt correctly. (5)

Back 12

Front 13

4a) Explain the difference between magnification and resolution. (2)

Back 13

magnification isthe number of times larger the image is compared to the object ;

resolution isability to, distinguish / differentiate between, two separate pointsORthe, level / degree, of detail that can be seen ;

Front 14

4b) State the resolution that can be achieved by each of the following types of microscope.

Light Microscope

Transmission Electron Microscope (2)

Back 14

light 50 - 200 nm ;

TEM 0.05 - 1.0 nm ;

units required

Front 15

4c)i) A student stated that Fig.4.1 was taking using a scanning electron microscope. What evidence supports the student's statement? (1)

Back 15

3 dimensional / 3D, (image);

can see the surface (detail);

1 max

Front 16

4c)ii) On Fig.4.1. the nuclear pore complex, labelled A, is 3mm wide.

Calculate the actual diameter of the pore, in nanometres (2)

Back 16

120nm

Front 17

4c)iii) State the function of the nuclear pores (1)

Back 17

allow communication between nucleus and cytoplasm

or

allow, molecules / named substances (RNA/mRNA/ribosomes/DNA), to, enter / leave (the nucleus);

Front 18

4d) State two features of a eukaryotic cell, other than nuclear pores, that would not be visible using medium power of a light microscope (2)

Back 18

(named) membranes/phospholipid bilayer;ribosomes;

Golgi;

endoplasmic reticulum/ER/RER/SER;

cytoskeleton/microtubules /microfilaments/spindle fibres;

centrioles;

vesicles/lysosomes;

mitochondria;

2 max

Front 19

5a)i) Describe the trend shown in the mean rate of transpiration as light intensity increases from 20 to 50 a.u. (2)

Back 19

increases / rises / goes up ;use of figures to illustrate ;

Front 20

5a)ii) Suggest why the rate of transpiration did not change between light intensities 10 a.u. and 20 a.u. (1)

Back 20

stomata are (nearly) closed;

idea that light intensity not high enough ;

1 max

Front 21

5b)i) Explain why transpiration is unavoidable during the day. (3)

Back 21

1 stomata are open; 2 allow gaseous exchange/entry of CO2/exit of O2; 3 for photosynthesis; 4 water vapour leaves (the leaf);

5 down a water potential gradient;

6 high(er) temperatures (during the day);

7 causes greater evaporation/some water vapour loss through leaf surface all the time;

3 max

Front 22

5b)ii) Describe the xerophytic features of this leaf and explain how each feature reduces loss of water vapour. QWC (5)

Back 22

Front 23

6a) State three roles of membranes inside cells (3)

Back 23

Front 24

6b)i) Cells contain a large number of membrane-bound vesicles. Many of these vesicles transport substances between organelles.

Outline how the vesicles are moved from one organelle to another. (2)

Back 24

cytoskeleton/microtubule/microfilament;

provide, pathways/tracks, (for movement);

(vesicle) moves along, microfilaments/microtubule;

microtubules, extended/broken down;

uses, ATP/(metabolic) energy;

AVP ;

2 max

Front 25

6b)ii) The Proteins embedded in the membranes of vesicles have different functions. COPI and COPII proteins are known as 'address proteins'. Vesicles that transport materials from the Golgi to the RER are coated in COPI proteins. Vesicles that transport materials to the Golgi from the RER are coated in COPII proteins. Suggest how these proteins ensure that a vesicle is transported to the correct target organelle. (2)

Back 25

receptor found only on, correct/target, (named) organelle;

idea that: address protein provides a way of, labelling/identifying/recognising, the vesicle;

protein/COPI/COPII, has a specific shape;

(shape of) receptor and (address) protein are complementary;

2 max

Front 26

6c) Cells in the pancreas secrete proteins such as the enzymes pancreatic amylase and protease. Describe how these extracellular enzymes are secreted from the cells. (2)

Back 26

exocytosis;

vesicle fuses/merges;

(with), cell surface/plasma, membrane;discharging/ releasing, enzyme/contents (to exterior)

2 max