Unit 1

Question 1

What are the 3 tenets in the Cell Theory

Answer 1

• all living organisms are made up of cells (one or more)
• cells are the smallest units of life
• all cells arise from pre-existing cells

Question 2

What are the 7 functions of life?

Answer 2

M - metabolism (the sum of all chemical reactions in a cell)
R - reproduction (the creation of an offspring – sexually or asexually)

S - sensitivity (response to external and internal stimuli)
H - homeostasis (the maintenance of certain conditions in a cell)
E - excretion (the expulsion of waste)
N - nutrition (the exchange of materials and gases with environment)
G - growth (the change in the organism’s shape or size)

Question 3

What three cell types challenge the three tenets of cell theory?

Answer 3

Striated muscle cells, aseptate hyphae and Acetabularium (large algal cell)

Question 4

What are the different type of stem cells?

Answer 4

1. Totipotent
2. Pluripotent
3. Multipotent
4. Unipotent

Question 5

What are the types of membrane bound proteins?

Answer 5

Peripheral, channel, integral and glycoproteins.

Question 6

What falsified the Davson-Danielli model?

Answer 6

Freeze fracturing, fluorescent antibody tagging and analysis and positioning of membrane proteins (polarity)

Question 7

What were the reasons behind the Davson-Danielli model?

Answer 7

• chemical tests finding both proteins and phospholipids present
• the amount of phospholipids present in a red blood cell
• the membrane can act as a barrier, so the protein walls could be the reason as to why that is

Question 8

What are the functions of membrane-bound proteins?

Answer 8

Transport
Receptors
Anchoring
Cellular identification
Intercellular connection
Enzymatic action

Question 9

What is a phospholipid

Answer 9

A phosphate head (polar) and two fatty acid tails (non-polar). Which, in turn, makes them amphipathic.

Question 10

How do phospholipids act in cold conditions and how does cholesterol affect that?

Answer 10

In cold conditions phospholipids have less kinetic movement so there is smaller distance between them, so they are less fluid. However cholesterol, lengthens the distance between phospholipids as they are in between them.

Question 11

How do phospholipids act in warmer conditions and how does cholesterol affect that?

Answer 11

Hot temperatures cause the phospholipids to have greater kinetic movement, so the distance is greater, making the cell more fluid. Cholesterol acts as a ‘binder’ between phospholipids as they naturally stick to cholesterol, which decreases the distance between phospholipids, making it less fluid.

Question 12

What happens to cells in a hypertonic solution?

Answer 12

The cells will become shrivelled (plasmolysed)

Question 13

What happens to cells in a hypotonic solution?

Answer 13

They become turgid and can lyse.

Question 14

Why are the expression of genes beneficial to multicellular organisms?

Answer 14

1) Although each cell contains the organisms whole genome
2) The function of different cells require different proteins, so expressing only some genes allows for 3) differentiated cells with specialised functions.

Question 15

Why is there controversy surrounding the use of embryonic stem cells?

Answer 15

The harvesting of embryonic stem cells in a therapeutic usage destroys the fertilised embryo (1), which can pose ethical question (the right to life) (1) as it has the potential to become a developed human (1)

Question 16

Describe how to prepare a slide for viewing plant cells in a light microscope

Answer 16

1. place a one cell thick sample of the plant cells on the glass slide
2. put a drop of stain on the sample
3. place cover slip over the top (abstain from trapping bubbles underneath)
4. remove excess stain using a towel

Question 17

Describe how to view a sample in a light microscope

Answer 17

1. place the glass slide containing the sample on the stage
2. use the lowest power lens
3. focus on the cell using coarse-focus knob
4. then use the finer-focus knob to view specific elements
5. use a higher power objective lens

Question 18

What is the function of a plant vacuole?

Answer 18

To increase the surface area to volume ratio (1) which increases the rate of exchange (1)

Question 19

Describe 2 therapeutic uses of stem cells (5)

Answer 19

Treatment of Stargardts macular dystrophy (1):
Embryonic stem cells are harvested from a fertilised embryo, stem cells are planted into the eye. Vision is then repaired (1)
Leukaemia (1):
Cancerous cells are killed using chemotherapy, then are replaced with adult stem cells (1).

Question 20

State the pros and cons of therapeutic stem cell treatment

Answer 20

Pros:
Cures the patient with condition (1)
Cons:
Ethics surrounding the destruction of fertilised embryo’s (possibility of it becoming human life) (1)
Painful to extract adult stem cells from the femur (1)
Possibility for totipotent stem cells to form cancerous tumours (1)

Question 21

Paramecium is a heterotrophic unicellular organism, name another unicellular organism which is an autotroph

Answer 21

Chlorella

Question 22

Compare and contrast the functions of life in a paramecium and in another unicellular autotroph

Answer 22

Paramecium and Chlorella Similarities:
Metabolism: both undergo chemical reactions in the cytoplasm
Homeostasis: they both maintain internal environments (i.e. water concentration with contractile vacuoles)

Paramecium and Chlorella Differences:
Reproduction: paramecium reproduces sexually and asexually. Chlorella reproduces asexually.
Sensitivity: paramecium and chlorella move utilising a beating cillia, but paramecium is reactive to touch and chlorella is sensitive to light.
Excretion: paramecium excretes carbon dioxide whereas chlorella excretes oxygen.
Nutrition: paramecium rely on the ingestion and digestion of other organisms, whereas chlorella produces it’s own food utilising photosynthesis.
Growth: paramecium grows utilising organic matter which is ingested, whereas chlorella grows utilising it’s own food synthesised internally using photosynthesis

Question 23

Which piece of apparatus allowed scientists to be able to determine the ultrastructure of cells?

Answer 23

Electron microscope

Question 24

Why is compartmentalisation beneficial? (2)

Answer 24

1. it allows for optimal conditions for metabolic conditions to be maintained
2. organelles can be transported around the cell
3. harmful substances can be trapped inside a membrane (i.e. digestive enzymes)
4. Enzymes and substrates can have a higher concentration in the area which it’s needed in