B1 - Cell biology

Question 1

What are the 5 main structures found in an animal cell?

Answer 1

Cell membrane - controls passage of substances in and out of the cell

Nucleus - contains all the DNA and controls the activities of the cell

Cytoplasm - liquid gel in which all the organelles are suspended

Mitochondria - respiration takes place here releasing energy for the cell

Ribosomes - protein synthesis takes place here

Question 2

What structures do plant cells contain?

Answer 2

All the components of animal cells

Cell wall made of cellulose that strengthens the cell

Chloroplasts are found in the green parts of a plant, and they contain chlorophyll which absorbs light for the plant to photosynthesise

Permanent vacuole which contains the cytoplasm, and helps keep the cell rigid

Question 3

What are examples of eukaryotic cells?

Answer 3

Animal and plant cells

They contain a cell membrane, cytoplasm and genetic material is contained within a nucleus

Question 4

What is a prokaryotic cell?

Answer 4

Bacteria are examples. Prokaryotic cells are 1 to 2 orders of magnitude smaller than eukaryotic cells, and their genetic information is not enclosed in a nucleus, but found free in the cytoplasm

They also contain extra small rings of DNA called plasmids that can code for specific features such as antibiotic resistance.

Question 5

What is a specialised cell, and how is it formed?

Answer 5

A specialised cell is adapted to perform a particular function, and it is formed by differentiation of cells at an early stage of development.

Question 6

How is a sperm cell adapted to its function?

Answer 6

Long tail helps move the sperm towards the egg

Lots of mitochondria which provides energy for the tail to move

Large nucleus to pass on the genetic information.

Question 7

How are root hair cells specialised?

Answer 7

Increase the surface area for absorption of water

Contain lots of mitochondria to transfer the energy needed for active transport

Contain a large permanent vacuole that speeds up the movement of water

Question 8

How are xylem cells specialised?

Answer 8

Cell walls made of lignin which makes them impermeable and very strong

Hollow tube for the water to move up them easily

Question 9

How are phloem cells specialised>

Answer 9

Sieve plates between the cells allow water carrying dissolved food to move freely up and down the tubes.

Lots of mitochondria to transfer the energy needed to move the dissolved food up and down the tube.

Question 10

Define diffusion.

Answer 10

The passive movement of a substance from a area of high concentration of that substance to an area of low concentration of that substance.

Question 11

What affects the rate of diffusion>

Answer 11

A higher temperature speeds up diffusion

A higher concentration gradient (difference in concentration) speeds up diffusion, whereas a lower concentration gradient slows down the rate of diffusion.

A larger surface area increases the rate of diffusion.

Question 12

What is the net movement?

Answer 12

Net movement = (Particles moving in) - (particles moving out)

Question 13

What is an example of diffusion in the body?

Answer 13

Gas exchange in the lungs

Movement of oxygen from lungs into the red blood cells.

Question 14

Define osmosis

Answer 14

The movement of water particles from a high water concentration (i.e. a dilute concentration) to a low water concentration (i.e. a concentrated solution) through a partially permeable membrane.

Question 15

What solution in regards to a cell when it has a the same concentration as the cell?

Answer 15

Isotonic

Question 16

What is a solution when it has a lower concentration than a cell?

Answer 16

HypOtonic

O - lOwer

Question 17

What is a solution when is has a higher concentration than a cell?

Answer 17

HypERtonic

ER - highER

Question 18

What is active transport?

Answer 18

Active transport is the movement of substances from a dilute solution to a concentrated solution against a concentration gradient. It uses energy released from food during respiration.

Question 19

What structure in a cell is usually in abundance whenever active transport is required?

Answer 19

mitochondria

Question 20

What is an example of when active transport is used in plants?

Answer 20

Mineral ions are found in dilute solutions in the soil, which is more dilute than the solution in the plant root hair cells.

Question 21

What is an example of when active transport is used in the body?

Answer 21

Glucose is moved into the bloodstream from the guts when it is against a concentration gradient.

Question 22

How is having a larger surface area to volume ratio an important adaptation in organisms?

Answer 22

A short distance for diffusion while having a large enough surface to diffuse through.

Question 23

How does having an efficient blood supply improve exchange of materials?

Answer 23

Moves the diffusing substances away from the exchange surface so more substances can diffuse, maintaining a steep concentration gradient.

Question 24

What is a gene?

Answer 24

A small packet of information that controls characteristics of the body.

Question 25

What is a chromosome?

Answer 25

A group of genes that carries genetic information about cells, tissues and organs.

Question 26

What is DNA

Answer 26

The unique molecule that makes up the chromosome.

Question 27

What is the name given the the process of cell division?

Answer 27

Mitosis - producing two identical cells

Question 28

Why is cell division by mitosis essential?

Answer 28

For regular, healthy growth

Repairing of replacement of cells, as 300 million cells die per minute.

Question 29

What is the first stage of mitosis?

Answer 29

DNA replicates to form two copies of each chromosome and the cells grow bigger

Question 30

What is the second stage of mitosis?

Answer 30

The chromosomes are pulled to different sides of the cell

Question 31

What is the third cell of mitosis?

Answer 31

The cell membrane and cytoplasm divide into two identical cells.

Question 32

What is the name given to the cell that produced the new cells?

Answer 32

Parent cell

Question 33

What is the name given to the cells that were created?

Answer 33

Daughter cells

Question 34

What specific type of cells are able to differentiate?

Answer 34

Stem cells can differentiate into specialised cells e.g. nerve cells and muscle cells

Question 35

What are the undifferentiated cells in a plant called?

Answer 35

Meristems

Question 36

What is the name of the process of producing identical offspring?

Answer 36

Cloning

Question 37

What is the name of the single new cell formed when an egg and sperm fuse?

Answer 37

Zygote

Question 38

What could embryonic stem cells be used for?

Answer 38

Growing new cells

Growing new organs, perhaps for transplants

Treating diseases

Question 39

What could plant stem cells be used for?

Answer 39

Preserving rare plant species

Producing plants for selling

Producing crops with special features such as disease resistance

Question 40

What are some of the main arguments against stem cell development?

Answer 40

They come from aborted or spare embryos, which had a potential to be a human, so this could be a violation of human rights.

They have only been in development for around 20 years, so the signals that control differentiation are not yet fully understood.

As embryonic stem cells divide and grow rapidly, there is a concern that stem cell treatment could cause cancer in patients.

The stem cells could be infected with viruses, posing the risk of contamination, or they could be rejected by the immune system.

A lot of money is being spent on stem cell research, and people argue that it could be used elsewhere more usefully.

Question 41

Where can adult stem cells be predominantly found?

Answer 41

In bone marrow