B2 - Cell Structure and Transport

Question 1

B2.1 - Aiming for 4 - How many chromosomes are found in the nucleus of human body cells?

Answer 1

46

Question 2

B2.1 - Aiming for 4 - How many chromosomes are found in the nucleus of gametes?

Answer 2

23

Question 3

B2.1 - Aiming for 4- What is the meaning of the keywords, mitosis, chromosomes, gene, gametes.

Answer 3

1. Mitosis - process of nuclear division in body cells.
2. chromosomes - coiled structures made up of DNA.
3. gene - short sections of DNA that code for proteins.
4. Gametes - A gamete is a sex cell. In humans, gametes are sperm and eggs

Question 4

B2.1 - Aiming for 6 - Explain why chromosomes are normally found in pairs.

Answer 4

One chromosome is inherited from the mother and one is inherited from the father. The chromosomes in each pair carry the same gene in the same location.

Question 5

B2.1 - Aiming for 6 - Describe situations where mitosis is occuring.

Answer 5

Whenever more cells are needed. happens throughout the entire lifespan of a living organism (human, animal or plant) but most rapidly during periods of growth.

Question 6

B2.1 - Aiming for 6 - Describe the process of mitosis using the keywords.

Answer 6

Chromosomes contain genes of male and female parent. Those chromosomes multiply from 2 genes to 4 genes and then divide.

Question 7

B2.1 - Aiming for 8 - Explain why genetic material must be doubled during mitosis.

Answer 7

the cells separate the duplicated chromosomes into the two daughter cells. In this way the correct inheritance of genetic information from one generation of cells to the next is assured.

Question 8

B2.1 - Aiming for 8 - Explain in detail what happens at each stage of the cell cycle.

Answer 8

1st: cells grow and increase in mass, replicate DNA and synthesise more organelles. Ribosomes, Mitochondria and sub-cellular structures are produced.
2nd: Each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides.
3rd: Cytoplasm and cell membrane divide - two identical daughter cells are produced.

Question 9

B2.1 - Aiming for 8 - Write a detailed explanation on why mitosis is an important process in living things and how characteristics are inherited.

Answer 9

Chromosomes carry genetic information in DNA. Mitosis ensures that when a cell divides, each new cell produced has the same genetic information.

Question 10

B2.2 - Aiming for 4 - Define the terms growth and differentiation

Answer 10

Differentiation - The process where a cell becomes specialised to its function.
Growth - an increase in size and mass of a particular organism over a period of time.

Question 11

B2.2 - Aiming for 4 - State why plant clones are genetically identical to each other.

Answer 11

Plants are cloned to produce identical plants quickly and economically. Clones are genetically identical to the original plant providing the meristem cells

Question 12

B2.2 - Aiming for 6 - Describe the importance of cell differentiation in multicellular organisms

Answer 12

Differentiated cells are important in a multicellular organism because they are able to perform a specialised function in the body. Multicellular organisms must retain some unspecialised cells that can replenish cells when needed.

Question 13

B2.2 - Aiming for 6 - Explain how tissue culture creates a clone of a plant

Answer 13

Scientists take a plant they want to clone, divide the plant into tiny pieces. The plant hormones stimulate the plants to grow and develop into fully-grown clones.

Question 14

B2.2 - Aiming for 8 - Compare and contrast differentiation in plants and animals

Answer 14

In animals the cells differentiate early on and lose the ability to specialise
Only stem cells can specialise
In plant cells – mitosis takes place in the meristems which are found in the shoots and root tops
Plants can differentiate all the way throughout their life
Plants can also CLONE themselves (make identical copies) using asexual reproduction

Question 15

B2.2 - Aiming for 8 - Explain why it is easier to clone a plant compared to an animal

Answer 15

A plant cell can become any cell the plant needs to survive similar to a stem cell. Cloning animals is a much more complicated process and often comes with birth defects

Question 16

B2.3 - Aiming for 4 - What is a stem cell?

Answer 16

A stem cell is a cell that is not differentiated

Question 17

B2.3 - Aiming for 4 - What can plant stem cells be used to create?

Answer 17

Plant stem cells can be used to create clones.

Question 18

B2.3 - Aiming for 6 - Describe the differences between embryonic and adult stem cells.

Answer 18

Embryonic stem cells are totipotent and can become any type of cell and found in the embryo whereas adult stem cells are multipotent, but can only become specific cells (blood, bone) and are found in bone marrow.

Question 19

B2.3 - Aiming for 6 - Why are plant clones produced in the agriculture industry?

Answer 19

Plants are cloned to produce identical plants quickly and economically.

Question 20

B2.3 - Aiming for 8 - Explain why embryonic stem cells are more useful for helping medical conditions

Answer 20

Embryonic stem cells are pluripotent, meaning they can divide into more stem cells or can become any type of cell in the body. This can be used to regenerate or repair dead tissue and organs.

Question 21

What is differentiation?

Answer 21

Cells are initially unspecialized, they can become different types of cells and during differentiation, certain genes are switched on or off to become a specialized cell.

Question 22

What are the adult stem cells?

Answer 22

stem cells found in adults that can differentiate and form a limited number of cells

Question 23

What is the cell cycle?

Answer 23

three-stage process of cell division in a body cell that involves mitosis and results in formation of two daughter cells.

Question 24

What is cloning?

Answer 24

production of identical offspring by asexual reproduction

Question 25

What does differentiate mean?

Answer 25

process where cells become specialised for a particular function

Question 26

What are embryonic stem cells?

Answer 26

stem cells from an early embryo that can differentiate to form the specialised cells of the body.

Question 27

what is mitosis?

Answer 27

part of the cell cycle where one set of new chromosomes is pulled to each end of the cell forming two identical nuclei during cell division

Question 28

What are stem cells?

Answer 28

undifferentiated cells with potential to form a wide variety of different cell types.

Question 29

What is therapeutic cloning?

Answer 29

process where an embryo is produced that is genetically identical to the patient so the cells can be used in medical treatment.

Question 30

what is a zygote?

Answer 30

the single new cell formed by the fusion of gametes in sexual reproduction.

Question 31

What are the advantages and disadvantages of using stem cells from embryos instead of adults (6 marks)

Answer 31

``` Embryo: Pros: •can treat a wide range of diseases (pluripotent – can become all of the cells) •Painless procedure •better to use cells rather than waste them. Cons: •harm/death to embryo •long-term effects unknown •embryo cannot give consent. Adult: pros: •reliable technique •no ethical issues or adult can give permission •quick recovery •does not kill donor. Cons: •involves an operation •people may not want to be donors as it is painful •few cell types can be formed or fewer diseases can be treated.(multipotent) ```

Question 32

B2.4 - Aiming for 4 - List some arguments for and against the use of stem cells.

Answer 32

For: Able to turn into different types of cells. Can cure a wide range of diseases. Against: Adult stem cells could be infected with a virus. Huge financial investment into stem cells.

Question 33

B2.4 - Aiming for 6 - Explain the reasons for ethical and religious objections against stem cells.

Answer 33

Religious beliefs mean some cannot accept interference of process of human reproduction. They believe it is wrong as stem cells are living cells, and that it's a violation of human rights.

Question 34

B2.4 - Aiming for 8 - Explain the process of therapeutic cloning organisms.

Answer 34

Therapeutic cloning involves removing the nucleus of an egg cell, replacing it with the material from the nucleus of a "somatic cell" (such as a skin cell), and stimulating this cell to begin dividing.

Question 35

B2.4 - Aiming for 8 - Evaluate the use of stem cells.

Answer 35

Stem cells can divide to produce new cells, which can divide into different cell types. They have the potential to be transplanted into patients to treat medical conditions and diseases. They could be used to replace cells that have been damaged or destroyed, for example: in type 1 diabetes.