Topic 1 - Cell Biology

Question 1

State the cell theory

Answer 1

1. Cells are the basic unit of structure in all living things (smallest unit of life)
2. All living organisms are composed of cells.
3. New cells are formed from pre-existing cells.
4. All cells contain hereditary information (DNA) which is passed on from cell to cell during cell division

Question 2

What are the exceptions to the cell theory?

Answer 2

1. Striated muscle cells
2. Giant algae
3. Fungal cells (Aseptate hyphae)

Question 3

How do the exceptions challenge the cell theory?

Answer 3

1. Striated Muscles cell
   
   1. cells always function as autonomous, independent units
2. Giant Algae
   
   1. larger organisms are always made of many microscopic cells
3. Aseptate Fungal Hyphae
   
   1. living structures are composed of discrete cells

Question 4

Formula for magnification

Answer 4

Magnification = size of the image/actual size of the specimen

Question 5

What are the functions of life?

Answer 5

Metabolism: The web of all enzyme-catalyzed reactions in a cell or organism

Response: Living things can respond to and interact with the environment

Homeostasis: The maintenance and regulation of internet cell conditions

Growth: Living things can grow or change size/shape

Reproduction: Living things produce offspring, either sexually or asexually

Excretion: The removal of metabolic waste

Nutrition: Feeding by either the synthesis of organic molecules or the absorption of organic matter

Question 6

Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.

Answer 6

Question 7

How does SA : VOL ratio act as a limiting factor on cell size

Answer 7

Increase in cell size = increase in chemical reactions = ↑ substances need to be taken in = ↑ substances need to be removed

1. The surface area affects the rate at which particles can enter and exit the cell
2. The volume affects the rate at which materials are made or used within the cell

Question 8

Why do cells reproduce?

Answer 8

For growth in multicellular organisms

For reproduction in single-cell organisms

To replace dead/damaged cells

Question 9

What are emergent properties?

Answer 9

Emergent properties arise when the interaction from the interaction of component parts

Emergent properties are properties of a group that are not possible when any of the individual elements of that group act alone

Question 10

Define stem cells

Answer 10

an undifferentiated cell of a multicellular organism which is capable of giving rise to indefinitely more cells of the same type, and from which certain other kinds of cell arise by differentiation.

Question 11

How does a stem cell differ from other body cells?

Answer 11

1. Stem cells can continually divide (self-sustaining)
2. Stem cells are undifferentiated (unspecialized) and can differentiate in different ways to produce different cell types
3. Is able to produce large quantities of identical cells

Question 12

How are specialised cells developed?

Answer 12

certain genes are expressed while others are not = able to differentiate and form specialized tissues

Gene expression results in proteins made that determine the function of the cell

Question 13

What does ‘committed’ mean in cells?

Answer 13

Once a cell has differentiated they cannot change type, hence the cell is said to be “committed” and are no longer stem cells

Question 14

Why are stem cells necessary in embryonic development?

Answer 14

1. After the formation of a zygote, there is a large increase in the number of cells = relies on the ability of stem cells to continually divide
2. Early embryonic stem cells are capable of becoming any type of specialized cell (pluripotent stem cells)
3. Cells of the embryo start to commit to different pathways of cell differentiation and become limited in the types of specialized cells they can form
4. Fully specialized cells are no longer flexible to form other types of specialized cells
5. Some stem cells remain in fully developed organisms. In humans, these include blood and skin cell stem cells

Question 15

State and define the type of stem cells

Answer 15

Embryonic stem cells: Cells from the embryo that are undifferentiated can become any type of cell = found in the inner cell mass of blastocysts

Adult stem cells: Cells found in certain adult tissues that can become a limited number of types of cell. Adult tissues include the bone marrow or liver

Question 16

Define Stargardt’s Disease

Answer 16

A genetic disease that can cause blindness in children

Question 17

What does the Stargardt’s Disease affect?

Answer 17

affects a membrane protein in the retina causing photoreceptor cells in the retina to become degenerative

Question 18

How can Stargardt’s Disease be treated ?

Answer 18

The treatment involves injecting embryonic stem cells that can develop into retina cells into the back of the eyeball

The cells attach to the retina and begin to grow, improving an individual’s vision

Question 19

Define leukaemia

Answer 19

a malignant progressive disease in which the bone marrow produce increased numbers of white blood cells = suppress the production of normal blood cells, leading to anaemia

Question 20

How is leukaemia treated

Answer 20

Bone Marrow Transplant

1. Using hematopoietic stem (HS) cells (blood stem cells) derived from bone marrow tissue.
2. These cells will divide continually to form new red and white blood cells.
3. Stem cells are removed from the bone marrow of the patient or from a donor person.
4. The patient undergoes chemotherapy and radiation therapy to kill the cancer cells in the bone marrow. However, normal dividing cells in the blood will also be killed.
5. After chemotherapy and radiation therapy the HS cells will be transplanted directly into the bloodstream through a tube called a central venous catheter.
6. The stem cells find their way into the bone marrow, where they will begin reproducing and making healthy new blood cells.

Question 21

State the ethics of stem cells

Answer 21

Health and quality of life of patients suffering from otherwise incurable conditions may be greatly improved

Early-stage embryos lack a nervous system so do not feel pain or suffer in other ways during stem cell procedures

If embryos are produced deliberately, no individual that would otherwise have had the chance of living is denied the chance of a life

Larger numbers of embryos by IVF are never implanted and do not get the chance of a life

Question 22

Draw a comparison between prokaryotic cells and eukaryotic cells

Answer 22

Question 23

Answer 23

Question 24

Benefits of compartmentalisation Ideal conditions or particular processes can be maintained within the compartments such as pH

3) Organelles with their content can be moved around the cell
4) Damaging substances such as digestive enzymes (lysosome) can be contained within their organelle

Answer 24

1. Enzymes that serve a specific function or catalyze a specific reaction can be concentrated within the compartment instead of being spread throughout the cytoplasm
2. Ideal conditions or particular processes can be maintained within the compartments such as pH
3. Organelles with their content can be moved around the cell
4. Damaging substances such as digestive enzymes (lysosome) can be contained within their organelle