1.1 Introduction to cells

Question 1

What are the prinicples of the cell theory?

Answer 1

1. All living things are composed of cells
2. The cell is the smallest unit of life
3. Cells only arise from pre-existing cells

Question 2

What common tratits do all cells share?

Answer 2

1. Every living cell is surrounded by a membrane
2. Cells contain genetic material which stores all the instructions needed for the cell’s activities
3. Many of these activities are chemical reactions, catalysed by ensymes produced in the cell
4. Cells have their own energy release system that powers all the cell’s activities.

Question 3

Examples of atypical cells

Answer 3

• Striated muscle
• Giant algae
• Aseptate fungal hyphae

Question 4

Why is striated muscle an atypical example?

Answer 4

• Muscle cells have more than one nucleus per cell
• Muscle cells (fibres) can be very long, up to 300mm
• They are surrounded by a single plasma membrane but are multi nucleated

Question 5

Why is giant algae an atypical example?

Answer 5

• Very large, ranges from 0.5 to 10 cm, but still only have 1 nucleus
• Complex structure

Question 6

Why is aseptate fungal hyphae an atypical example?

Answer 6

• Long threads with many nuclei
• Cytoplasm is continuous along the hyphae with no end cell wall or membrane

Question 7

What are the seven functions of life?

Answer 7

• Metabolism
• Response
• Homeostasis
• Growth
• Reproduction
• Excretion
• Nutrition

Question 8

What is metabolism?

Answer 8

All chemical reactions occuring within the body

Question 9

What is growth?

Answer 9

An irreversible increase in size

Question 10

What is response?

Answer 10

The ability to react to changes in the environment

Question 11

What is homeostasis?

Answer 11

Keeping conditions inside the body within tolerable rate

Question 12

What is reproduction?

Answer 12

Producing offspring either sexually or asexually

Question 13

What is excretion?

Answer 13

Getting rid of waste products from metabolism

Question 14

What is nutrition?

Answer 14

Obtaining food, providing energy and the materials needed for growth

Question 15

Examples of unicellular organisms?

Answer 15

• Viruses
• Paramecium

Question 16

What is cell differentiation?

Answer 16

Cell differentiation happens because different gene sequences are expressed in different cells

Question 17

What is gene expression?

Answer 17

Gene expression is when a gene in a cell is being used. This means that a cell expresses certain genes, but not others, to perform a certain function

Question 18

What is important for cell size?

Answer 18

The surface area to volume ratio

Question 19

Why is the surface area to volume ratio important?

Answer 19

If the ratio is too small substances will be absorbed at a slower rate than they are needed, and waste will accumulate since it will not be disposed of quickly enough. It may also cause the cell to overheat

Question 20

What are stem cells?

Answer 20

Cells that are unspecialised, meaning they haven’t differentiated

Question 21

What are the 2 key features of stem cells?

Answer 21

• Self renewal
• Potency

Question 22

What is self renewal?

Answer 22

The cells can contnuosly divide and replicate

Question 23

What is potency?

Answer 23

The cells have the ability to differentiate in different ways

Question 24

What are the 3 ways in which stem cells can be obtained?

Answer 24

• Embryonic stem cells
• Cord blood stem cells
• Adult stem cells

Question 25

What are the pros and cons of embryonic stem cells?

Answer 25

Pros:
* Almost unlimited growth potential
* Can differentiate into any type of cell
* Less chance of genetic damage

Cons:
* More risk of becoming tumour cells
* Likely to be genetically different from adult patient
* Removal of cells from the embryo kills it, unless only one or two are removed

Question 26

What are the pros and cons of cord blood stem cells?

Answer 26

Pros:
* Easily obtained and stored
* Commercial collection and storage available
* Fully compatible with the adult that grows from the baby
* The umbilical cord is discarded whether or not stem cells are collected

Cons:
* Limited capacity to differentiate, only blood cells
* Limited quantity

Question 27

What are the pros and cons of adult stem cells?

Answer 27

Pros:
* Less chance of malignant tumours
* Fully compatible with the adult’s tissue
* Removal of stem cells does not kill the adult

Cons:
* Difficult to obtain
* Less growth potential than embryonic stem cells
* Limited capacity to differentiate

Question 28

What 2 diseases (chosen to know) have a therapeutic use of stem cells?

Answer 28

• Stargardt’s disease
• Parkinson’s disease

Question 29

What is Stargardt’s disease?

Answer 29

A genetic disease, that develops between ages 6-12. It causes the cells of the retina to die, so vision will progressively worsen until the patient turns blind.

Question 30

How can stemcells be used for Stargardt’s disease?

Answer 30

Researchers can grom stem cells into retina cells. This was first tested on mice cells, which were injected to mice with similair eye diseases. When the results were good, human trials were allowed. The human cells are also injected into the eye where they attach to the retina. The human trials have also shown good results, but it is still in the trial stage and not used as treatment yet.

Question 31

What is Parkinson’s disease?

Answer 31

A degenerative disorder of the central nervous system caused by the death of dopamine-secreting cells in the brain. Patients have tremors, rigidity, and slowness of movement.

Question 32

How can stem cells be used for Parkinson’s disease?

Answer 32

By replacing the dead nerve cells with living, dopamine-producing ones.

Question 33

How is magnification calculated?

Answer 33

• Measure picture in mm (milimeter)
• Multiply by 1000 to turn into µm (micrometers)
• Divide by actual size (given by scale bar)

Magnification = Image size/Actual size
Actual size = Image size/Magnification