Cell Theory

Question 0

What evidence does not support the cell theory?

Answer 0

Fungal cells: challenges the idea that a cell is a single unit. Fungal hyphae are very large with many nuclei and a continuous cytoplasm - there is no end cell wall or membrane.

Question 1

What 3 things does the cell theory state?

Answer 1

1. Living organisms are composed of cells.
2. Cells are the smallest units of life.
3. Cells come from pre-existing cells.

Question 2

What evidence did Leeuwenhoek find to support the cell theory?

Answer 2

He observed living organisms using a microscope.

Question 3

What functions do all living things carry out?

Answer 3

Metabolism, homeostasis, growth, reproduction, response and nutrition.

Question 4

Nanometer = 1x10^-9
Micrometer = 1x10^-6

Answer 4

Molecules = 1nm
Membranes = 10nm
Virus = 100nm
Bacteria = 1mm
Organelles = 10mm
Cells = 100mm

Question 5

What are multicellular and unicellular organisms?

Answer 5

Multicellular: organisms made up of more than one cell.
Unicellular: organisms made up of only one cell.

Question 6

What term describes cells becoming specialized? How does this happen?

Answer 6

Differentiation. Some genes become switched off so only specialized functions are carried out.

Question 7

What are emergent properties?

Answer 7

When something is more than the sum of the parts.

Example: One brain cell can transmit electricity but 2 & 3 billion nerve cells can be capable of thought, memory and emotion.

Question 8

What are stem cells?

Answer 8

Cells within organisms that retain their ability to divide and differentiate into various cell types.

Question 9

Why are stem cells different from other cells?

Answer 9

Stem cells are different from other cell types in three ways:

1. They are unspecialised cells capable of renewing themselves through cell division.
2. They can be induced to differentiate and become organs or tissue.
3. In bone and gut marrow, they divide to repair and replace worn out or damaged tissues.

Question 10

Where do stem cells come from?

Answer 10

Human embryo: embryonic stem cells

Adult tissues: stomatic stem cells

Question 11

How are stem cells used as therapy for disease?

Answer 11

They may be helpful in transplant therapies.

Examples: bone growth, pancreatic cells to make insulin, heart repair after heart attack, brain repair in some conditions.

Question 12

Outline one therapeutic use of stem cells.

Answer 12

Bone marrow transplants:
Stem cells found in the bone marrow give rise to the red blood cells, white blood cells and platelets in the body. These can be used in bone marrow transplants to treat people. Who have certain types of cancer.

1. Chemotherapy kills cancer cells as well as normal cells in bone marrow.
2. Before treatment, he can undergo a bone marrow harvest in which stem cells are removed from the bone marrow by using a needle, which is inserted into the pelvis.
3. After treatment stem cells are transplanted back into body via vein in either chest or arm.
4. Useful as it allows patients to undergo high chemotherapy treatment, hence bettering their chances of killing the cancer.