Topic 1- Cell Biology

Compare the structure of a red blood cell to a plant cell.

(6 marks)

Differences:

• red blood cell has no nucleus, plant cell has a nucleus

• red blood cell has no cell wall, plant cell has a cell wall

• red blood cell is a biconcave disc

• plant cells do not contain haemoglobin

• red blood cells do not contain chlorophyll or

similarities:

• both have cytoplasm

• both have cell membrane

• both have pigments.

When placed into a beaker of water, explain why a red blood cell bursts and a plant cell doesn’t.

(2 marks)

• water enters cell via osmosis

• plant cell has a cell wall which prevents that

Name of this specialised cell:

• Root hair cell

Name of this specialised cell:

• Nerve cell

Explain why root hair cells contain mitochondria.

(4 marks)

• aerobic respiration occurs in mitochondria

• mitochondria releases energy

• energy used for active transport

• to transport ions from low to high conc

Compare the structure and function of xylem tissue and phloem tissue.

(6 marks)

Structure:

• xylem is made of dead cells, whilst phloem is made of living cells

• phloem cells have pores in their end walls, whilst xylem cells don’t

• xylem is hollow, whilst phloem contains cytoplasm

• both are: .tubular .made of cells

Function:

• xylem transports water/mineral ions whilst phloem transports dissolved sugars

• xylem= transpiration, phloem= translocation

• xylem transports unidirectionally, phloem transports directionally

• both transport substances through plant

Describe what happens during each stage of the cell cycle.

(4 marks)

1. dna duplicate and subcellular structures increase in number

2. dna condense into chromosomes in middle of cell and one set is pulled to either side of cell

3. cell membrane and cytoplasm divide, creatin 2 new daughter cells

Explain how a transplant of bone marrow cells can help to treat medical conditions.

(2 marks)

• the cells can differentiate into many types of cells

• so they can cure diseases caused by damaged cells, by replacing them

Define the term double circulatory system.

(1 mark)

• blood is pumped into lungs by right side of heart

• blood is pumped to body by left side of heart

Explain why an axolotl may die in water with a low concentration of oxygen.

(4 mark)

• conc gradient of oxygen is less steep

• (therefore) less oxygen diffuses into blood

• less aerobic respiration occurs so less energy is available

• so less metabolism

What is a stem cell?

(2 marks)

• an undifferentiated cell

• that can differentiate into many other cells

Suggest how a stent in the trachea helps to keep the patient alive.

(2 marks)

• stent opens up the trachea

• allowing air to flow through.

Evaluate the use of stem cells from a patient’s own bone marrow instead of stem cells from an embryo.

(6 marks)

Embryo Advantage:

• can create many embryos in a lab

• painless technique

• can treat many diseases, whereas bone marrow can treat a limited number

  Disadvantages-

  . harm to embryo

  . ethical issues

  . may not work

Bone Marrow Advantages:

• no ethical issues

• can treat some diseases

• procedure is relatively safe

• reliable

  Disadvantages:

  . risk of infection

  . can only treat a few diseases

Both Advantages:

• can treat the disease

  Disadvantages:

  . risk of transfer or viral infection

  . stem cells become cancerous

Explain how the human lungs are adapted for efficient exchange of gases by diffusion.

(6 marks)

• many alveoli

  . for large surface area

  . for higher diffusion rate

• capillaries are thin

  . which provides a short diffusion pathway for oxygen and co2

  . this allows for quicker diffusion

• lungs are ventilated

  . to bring fresh oxygen and remove co2

  . helps maintain a good conc gradient

• good blood supply

  . removes oxygenated blood quickly

  . maintains conc gradient.

Give two reasons why a kidney transplant is a better method for treating kidney disease than dialysis.

(2 marks)

• less chance of infection/blood clots

• no restrictions on diet

• cheaper