Bio Jan 2011 unit 1

Question 1

Suggest two ways that cell division in plants differs from cell division in animals. (2)

Answer 1

(cell), plate / wall, forms (between new cells) ;
idea of :
cytokinesis starts from middle of cell ;
(only) occurs in meristem ;
no centrioles ;

Question 2

As part of an allergic response, certain cells in the lungs release histamine. Histamine is a cell signalling molecule that stimulates smooth muscle in the wall of structure A to contract.

Suggest how histamine stimulates smooth muscle contraction. (2)

Answer 2

1 (histamine), binds / attaches, to, receptor
/ glycoprotein ;
idea of :
2 in / on, plasma / cell surface, membrane
(of muscle cell) ;
3 complementary (shape) ;
4 triggers response / causes effect, inside
cells ;

Question 3

Another action of histamine is to make capillary walls more permeable.

Suggest two effects this increased permeability may have on the surrounding tissues. (2)

Answer 3

1 more tissue fluid formed / increase in
 volume of tissue fluid ;
2 increase pressure in tissue ;
3 swelling / inflammation / oedema;
4 (more) white blood cells pass into tissues ;
5 larger molecules / (named) proteins ,
 pass into tissue fluid 

It says ignore refernces to:
IGNORE refs to the capillaries becoming more leaky
IGNORE more water passes out
DO NOT CREDIT cells swell
ACCEPT (more) white blood cells leave the capillary
IGNORE ref to more, glucose / nutrients / gases, leave blood capillary
IGNORE ref to increased rate of diffusion

Question 4

Large, active organisms need a circulatory system because they have a small
………………………………………………………………………………………………………………….. .
Haemoglobin is a pigment found in red blood cells. These cells are also known as
……………………………………….. . Haemoglobin has a high ………………………………….. for oxygen. In the
lungs, the haemoglobin associates with oxygen to form ……………………………………………………. .
In respiring tissues, the oxygen is released by dissociation. In very active tissues, the amount of
oxygen released can be increased by the presence of more …………………………………………………. .
This is called the ……………….. effect

Answer 4

surface area to volume ratio ;
erythrocytes ;
affinity ;
oxyhaemoglobin ;
carbon dioxide / CO2 / hydrogen ions / H+ ;
Bohr / bohr (shift) ;

other notes
ACCEPT SA / VOL or SA:Vol
ACCEPT minor spelling errors if phonetically correct e.g. erythocyte
DO NOT CREDIT erthocytes, erephosite, erthrocyte
IGNORE red blood cells
ACCEPT attraction
ACCEPT HbO / HbO8
DO NOT CREDIT HbO2 etc
ACCEPT carbonic acid
DO NOT CREDIT CO2
DO NOT CREDIT hydrogen, H, H2
ACCEPT phonetic spellings e.g. borr, bore, borh

Question 5

Define the term transpiration. (2)

Answer 5

evaporation / loss of water vapour ;
from, aerial parts of plant / leaf / leaves ;
via stomata ;

Other points
movement of water vapour out of leaf = 2 marks
DO NOT CREDIT loss of water alone
CREDIT loss through cuticle / epidermis

Question 6

Describe and explain how transpiration contributes to the mechanism of water transport up the stem (6)

Answer 6

In the leaf:
idea of :
1 water loss (from leaf) is replaced ;
2 via, apoplast / symplast / vacuolar, pathways ;
3 down water potential gradient / AW ;
4 (lost water replaced) by water from the xylem ;
In the xylem:
5 (loss of water) causes, low / negative, (hydrostatic)
pressure (at top / in leaf)
OR
creates pressure gradient ;
idea of :
6 water moves, from higher pressure to lower pressure /
down pressure gradient ;
7 under tension / pulled up / drawn up ;
8 by mass flow ;
9 cohesion / attraction, between water molecules ;
idea of :
10 column / stream / chain, of water (molecules) ;

Question 7

Suggest why a bunch of flowers may survive longer if the ends of the stems are removed immediately before the flowers are placed in water. (2)

Answer 7

Ref to :
bubbles / air (present / being removed) ;
(blockage) in xylem ;
restore (continuous) column of water (in xylem) ;

guidence
air in the xylem = 2 marks

Question 8

Microtubules and microfilaments are part of the cytoskeleton.

Suggest two roles of the cytoskeleton in the type of cell shown in Fig. 5.1. (2)

Answer 8

1 provides, strength / stability / support (cell) ;
2 determines shape / changes shape / moves membrane
(for endo / exocytosis) ;
3 movement of, organelles / named organelle /
RNA / protein / chromosomes / chromatids ;
4 attachment to / hold, organelles / named organelle, in place;
5 make up, centrioles / spindle fibres ;

Guidence

1. IGNORE structure
2. IGNORE movement of (whole) cell
3. e.g. vesicles, cilia, mitochondria, ribosome

Question 9

The cells of a multicellular organism are usually specialised to perform a particular function.

Name the process in which a cell becomes specialised. (1)

Answer 9

differentiation

DO NPT CREDIT
specilisation

Question 10

Neutrophils are phagocytic blood cells that can engulf and digest foreign cells found in
the blood.

Describe how the ultrastructure of a neutrophil is specialised to enable it to perform this function.

Answer 10

1. (many) lysosomes / vesicles containing enzymes ;
   2 (many) microfilaments / microtubules
   OR
   ref to, extensive / well developed, cytoskeleton ;
   3 (many) ribosomes / (a lot of) rough endoplasmic
   reticulum / (a lot of ) RER ;
   4 (many) mitochondria ;
   5 (lots of) Golgi ;
   6 (many) receptor (sites) on, cell surface / plasma ,
   membrane ;

Question 11

Describe the routes that water molecules take through the cell surface membrane. (2)

Answer 11

1. fit between (phospho)lipids / through (phospho)lipid (bi)layer ;
2. via, protein channels / protein pores / aquaporins ;

Guidance
DO NOT CREDIT fit through phospholipids (molecules)
DO NOT CREDIT carrier proteins – if this is used do not
award mp 2
IGNORE transport proteins

Question 12

A student carried out an investigation to determine the effects of different sucrose
concentrations on cells from pieces of onion epidermis.
• Strips of epidermis were taken from an onion.
• Separate pieces of epidermis were placed into water and a range of sucrose
solutions.
• The pieces of epidermis were left for 30 minutes before being removed.
• The pieces of epidermis were then viewed at high power under the microscope.
The student counted 100 cells from each piece of the epidermis. The student noted how many cells had become plasmolysed.

Suggest how the student could modify the procedure to make the results more reliable and accurate

Answer 12

reliable
R1 observe more pieces of onion (epidermis from each
solution) ;
R2 count more cells (in each piece of epidermis) ;
R3 calculate a mean ;
R4 identify / ignore anomalous results ;
max 3
accurate
idea of:
A1 use, more / intermediate, concentrations within existing
range / smaller gap between concentrations /
closer (concentration) values ;
A2 narrower range around 50% plasmolysis /
0.4 - 0.7 mol dm-3 / -1120 to -2180 kPa ;
A3 take photographs and mark cells as counting ;