1.
State what is meant by a eukaryotic cell.
[1 mark]
- a cell with a nucleus / membrane-bound organelles
JD SCIENCE
B1 Cell-level systems
Indicative marking points. Award marks for equivalent scientific or mathematical wording. Do not issue this sheet with the student worksheet.
2.
State what is meant by a prokaryotic cell.
[1 mark]
- a cell with no nucleus, DNA free in the cytoplasm
3.
State what is meant by the nucleus.
[1 mark]
- organelle that contains DNA / controls the cell
4.
State what is meant by the cell membrane.
[1 mark]
- partially permeable barrier around the cell
5.
State what is meant by a chloroplast.
[1 mark]
- organelle where photosynthesis occurs
6.
State what is meant by diffusion.
[1 mark]
- net movement of particles from high to low concentration
7.
State what is meant by osmosis.
[1 mark]
- net movement of water from dilute to concentrated solution through a partially permeable membrane
8.
State what is meant by active transport.
[1 mark]
- movement against a concentration gradient using energy
9.
State what is meant by mitosis.
[1 mark]
- cell division producing two genetically identical diploid cells
10.
State what is meant by a stem cell.
[1 mark]
- an undifferentiated cell that can divide and specialise
11.
Grace is asked about a eukaryotic cell in a OCR Biology paper.
(a) [2 marks]
- has nucleus, mitochondria, cytoplasm, cell membrane
(b) [3 marks]
- why muscle cells contain many mitochondria
12.
Grace is asked about a prokaryotic cell in a OCR Biology paper.
(a) [2 marks]
- has cell wall, chromosomal DNA, plasmids, flagella
(b) [3 marks]
- why bacteria can transfer plasmids
13.
Grace is asked about the nucleus in a OCR Biology paper.
(a) [2 marks]
- surrounded by a nuclear membrane, contains chromosomes
(b) [3 marks]
- why a red blood cell has no nucleus when mature
14.
Grace is asked about the cell membrane in a OCR Biology paper.
(a) [2 marks]
- controls what enters and leaves
(b) [3 marks]
- why osmosis needs a partially permeable membrane
15.
Grace is asked about a chloroplast in a OCR Biology paper.
(a) [2 marks]
- contains chlorophyll and membranes
(b) [3 marks]
- why root hair cells have no chloroplasts
16.
Grace is asked about diffusion in a OCR Biology paper.
(a) [2 marks]
- passive, no energy from respiration
(b) [3 marks]
- why gas exchange uses diffusion
17.
A cell image is 10 mm across. The actual cell is 0.02 mm. Calculate the magnification.
[3 marks]
- magnification = image size ÷ actual size
- Final answer: 500
18.
Magnification is ×500. The image is 20 mm. Calculate the actual size in µm.
[3 marks]
- actual = image ÷ mag; 1 mm = 1000 µm
- Final answer: 40.00 µm
19.
A cube cell of side 4 mm has what surface area to volume ratio?
[3 marks]
- SA = 6a², V = a³
- Final answer: 1.5 : 1
20.
A microscope uses a ×10 eyepiece and a ×60 objective. What is the total magnification?
[3 marks]
- multiply the two lenses
- Final answer: ×600
21.
Grace counts 24 cells in a 0.004 mm³ haemocytometer square. Estimate the number of cells in 1 mm³.
[3 marks]
- scale up
- Final answer: 6000
22.
A cell divides by mitosis every 2 hours. Starting from 1 cell, how many cells after 8 hours?
[3 marks]
- 4 divisions, 2⁴
- Final answer: 16
23.
Grace carries out the microscopy required practical to view onion epidermis. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: not always applicable / stain used
- Dependent: clarity of organelles seen
(b) [2 marks]
- same light intensity / same stain time
- so the test is fair / only one variable is changed
(c) [2 marks]
- cells overlapping
- count only single-layer cells
24.
Grace carries out the osmosis required practical with potato cylinders. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: concentration of sugar solution
- Dependent: change in mass / length
(b) [2 marks]
- same temperature, same start length, blot dry
- so the test is fair / only one variable is changed
(c) [2 marks]
- surface water left on the potato changes mass
25.
Grace carries out an investigation of diffusion in agar cubes with indicator. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: cube size / concentration
- Dependent: time for colour to disappear
(b) [2 marks]
- same temperature
- so the test is fair / only one variable is changed
(c) [2 marks]
- cubes not identical size
26.
Grace carries out preparing a cheek-cell slide. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: n/a
- Dependent: quality of the image
(b) [2 marks]
- thin layer of cells
- so the test is fair / only one variable is changed
(c) [2 marks]
- too many cells / air bubbles
27.
Compare diffusion with active transport.
[4 marks]
- diffusion is down the gradient / passive
- active transport is against the gradient / needs ATP
28.
Compare animal cells with plant cells.
[4 marks]
- both have nucleus, cytoplasm, membrane, mitochondria
- only plant cells have cell wall, chloroplasts, permanent vacuole
29.
Compare mitosis with meiosis.
[4 marks]
- mitosis: two identical diploid cells
- meiosis: four haploid genetically different cells
30.
Compare embryonic stem cells with adult stem cells.
[4 marks]
- embryonic can become most cell types
- adult are more limited / fewer ethical issues
31.
Apply your knowledge of osmosis to this situation: water leaves the cells
[3 marks]
- water leaves the cells
32.
Apply your knowledge of active transport to this situation: soil concentration is lower than inside the cell
[3 marks]
- soil concentration is lower than inside the cell