ell Biology

1) Name 2 Eukaryotes and list organelles

present Plant and animal cells (eukaryotic cells) have a cell membrane, cytoplasm and a nucleus.

2) Give an example of a Prokaryotic cell, how

does it differ from an eukaryotic cell. Bacterial cells (prokaryotic cells) are much smaller than Eukaryotic. All have cell membrane surrounded by a cell wall. The genetic material is a DNA loop not in a nucleus. There may be plasmids.

3) What is a plasmid? Small rings of DNA

4) Put 101, 395 into standard form 1.01395 X105

5) A cell measures 0.00234mm put this length into

standard form 2.34 X 10-3

6) List 5 organelles in an animal cell a nucleus, cytoplasm, a cell membrane, mitochondria, ribosomes.

7) What additional organelles does a plant cell have

that an animal cell doesn’t Chloroplasts, a permanent vacuole filled with cell sap, cell wall.

8) What is plant and algal cell walls made of and what

is its function? Cell wall made of cellulose, which strengthens the cell.

9) Put these in order of size from biggest to smallest:

centi, micro, nano, milli centi, milli, micro and nano.

10) What do we use to measure the length of cells? A magnification scale

11) Why is cell differentiation important? Cell differentiation develops specialised cells to carry out certain functions.

12) Why is cell division important? Repair and replacement of cells.

13) When do animal cells differentiate, when do plant

cells differentiate? Animal cells differentiate at an early stage. Plant cells can differentiate throughout life.

14) How are light microscopes different to electron

microscopes? Why are electron microscopes more

useful? An electron microscope has much higher magnification and resolution than a light microscope. Electron microscopes can be used to study cells in much finer detail.

15) What is the magnification triangle, how do you

calculate magnification?

16) What does the nucleus of body cells contain? Pairs of Chromosomes made of DNA molecules

17) What do chromosomes contain? A large number of genes

18) What are the stages of mitosis? The Cell grows and orgnelle number increases, DNA replicates. One set of chromosomes is pulled to each end of the cell and the nucleus divides. The cytoplasm and cell membranes divide to form two identical cells.

19) What is a stem cell?

A stem cell is an undifferentiated cell that can give rise to more of the same type of cell, which differentiate into specialised cells.

20) Where do we get stem cells in plants and animals? Animals: Embryos and adult bone marrow. Plants: meristems.

21) What is each type of stem cell used to produce? Stem cells from human embryos can form most types of human cells. Stem cells from adult bone marrow can form many types of cells including blood cells. Meristem tissue in plants can differentiate into any type of plant cell.

22) What can stem cells be used to treat? Diabetes and paralysis.

23) Describe therapeutic cloning? Stem cells from an embryo with the same genes as the patient are used so they are not rejected by the patient’s body so they may be used for medical treatment.

24) What are the practical and social/ethical risks of

using stem cells? Practical risks: viral transfer. Social and ethical risks: Social or religious objections e.g. life starts at the embryo stage.

25) How can stem cells from plants be used to

benefit humans? Rare species can be cloned to protect from extinction. Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.

26) How do substances may move into and out of

cells across the cell membranes? By diffusion

27) Define diffusion the spreading out of the particles, leading to a net movement from an area of higher concentration to an area of lower concentration.

28) List substances that diffuse into or out of cells? Oxygen and carbon dioxide in gas exchange, and urea

29) What factors affect the rate of diffusion? The difference in concentrations (concentration gradient), the temperature, the surface area of the membrane.

30) Has a single celled organism got a large or small

surface area: volume ratio and why? Large, to transport enough molecules into and out of cells.

31) How do you calculate volume? Length x Width x Height

32) Why do multicellular organisms have an

exchange surface and transport system? They have a small surface area: volume ratio so they have exchange surfaces and transport systems to ensure they get enough substances to meet their needs.

33) How can you increase effectiveness of an

exchange system? All organisms: having a large surface area, a membrane that is thin to provide a short diffusion path. Animals: an efficient blood supply and being ventilated.

34) How does water move across a cell membrane? Osmosis

35) Define Osmosis Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

36) What is the equation for percentage change? A

plant tissue has gone from having a 120g of water to

having 85g, calculate the percentage decease? Percentage change = Difference / Original (X 100). -29%

37) Define active transport and give an example Active transport moves substances against a concentration gradient. This requires energy from respiration. E.g. mineral ions absorbed into plant root hairs.

38) What is the difference between diffusion,

osmosis and active transport. Diffusion and osmosis are passive. Active transport requires energy. Osmosis is diffusion of water.