Topic 1 Cells

Question 1

Why does a bacterial cell lack a true nucleus?

Answer 1

Instead of it containing chromosomes, the DNA is arranged in a single strand in the cytoplasm

Question 2

What are plasmids? (In the bacterial cell)

Answer 2

Small rings of DNA

Question 3

Cell membrane

Answer 3

Selectively permeable boundary surrounding the cell which allows some substances to enter and leave while preventing others

Question 4

Cytoplasm

Answer 4

Chemical reactions take place here

Question 5

Nuclear membrane

Answer 5

Surrounds nucleus

Question 6

Nucleus

Answer 6

Control centre. Contains cell’s genetic information arranged in chromosomes

Question 7

Mitochondria

Answer 7

Site of cell respiration. Very abundant in cells which need a lot of energy eg muscle cells

Question 8

Cellulose cell wall

Answer 8

Rigid structure outside the cell membrane that provides support

Question 9

Vacuole

Answer 9

Contain cell sap and when full pushes the cell membrane against the cell wall, providing support

Question 10

Chloroplast

Answer 10

Contains chlorophyll - a green pigment that traps light for photosynthesis

Question 11

Chlorophyll

Answer 11

Absorbs light for photosynthesis

Question 12

How do you prepare an onion cell slide?

Answer 12

1. Use forceps to peel off a layer of onion epidermis
2. This single layer allows light through
3. Place a drop of iodine on top of the onion to stain the structures
4. Use a mounted needle to place cover slip on (so no bubbles)

Question 13

What is the purpose of the iodine and methylene blue on your temporary mounts?

Answer 13

To act as a stain and allow the structures in the cell to be seen

Question 14

Why must the onion tissue used be one cell thick?

Answer 14

To allow enough light to come through the specimen. If there was more than one layer it would be difficult to see the cells

Question 15

Why is it important to only use the fine focus when viewing at high power?

Answer 15

To avoid crashing the lens into the slide and damaging it

Question 16

What happens to the area of the specimen you can see as you increase magnification?

Answer 16

The area you see will decrease as you increase magnification

Question 17

Properties of the low power objective lens

Answer 17

FOV is wider - there are more cells in less detail

Question 18

Properties of the high power objective lens

Answer 18

FOV is smaller - there are fewer cells in more detail

Question 19

How do you calculate total magnification?

Answer 19

Eyepiece magnification (x10) x objective lens magnification

Question 20

What is the total magnification if the objective lens is x20?

Answer 20

10 x 20 =200

Question 21

What is the total magnification if the objective lens was x100?

Answer 21

10 x 100 =1,000

Question 22

How do you calculate magnification, image size or actual size? (IAM)

Answer 22

I = A X M
A = I / M
M = I / A

Question 23

How do you convert micrometers into millimetres?

Answer 23

/1000

Question 24

How do you convert millimetres into micrometers?

Answer 24

X1000

Question 25

Unit of measurement for micrometers

Answer 25

μm

Question 26

How do you use IAM when there is a scale bar?

Answer 26

Treat the scale bar as the ACTUAL SIZE

Question 27

Properties of electron microscopes

Answer 27

Pass beams of electrons through a specimen and have a much greater resolution. They allow us to clearly see inside the parts of the cell eg chloroplasts or mitochondria

Question 28

What is resolution?

Answer 28

The ability to see detail in an image

Question 29

What substances need to enter the cell?

Answer 29

Oxygen, water, dissolved food molecules and mineral ions

Question 30

What substances need to pass out of the cell?

Answer 30

Carbon dioxide and nitrogen wastes

Question 31

What is diffusion?

Answer 31

Random movement of a substance from a region of high concentration to a region of low concentration

Question 32

What is an example of diffusion?

Answer 32

Oxygen moves from a high concentration in the lungs to low concentration in the blood

Question 33

Where does diffusion happen?

Answer 33

Across the cell membrane which is selectively permeable (allows some things through, stops others)

Question 34

What is diffusion rate affected by?

Answer 34

Concentration gradient, temperature and surface area

Question 35

What is concentration gradient?

Answer 35

The difference in the high/low concentrations

Question 36

Why does temperature affect rate of diffusion?

Answer 36

Higher temperature gives particles more kinetic energy

Question 37

Why does surface area affect rate of diffusion?

Answer 37

The larger the area where diffusion can happen the more diffusion rate increases

Question 38

Why are single celled organisms small?

Answer 38

They have a large surface area compared to their volume. Since their needs can be met purely by diffusion it has to be small enough to do this. A larger cell has a smaller surface area compared to its volume’s needs. If there isn’t enough area for the cell to survive purely on diffusion, it will die.

Question 39

What are Unicellular organisms?

Answer 39

Single called organisms

Question 40

What are multicellular organisms?

Answer 40

Made up of lots of cells

Question 41

Does diffusion provide enough for unicellular organisms?

Answer 41

Yes as distances are short - they have a large surface area

Question 42

Does diffusion provide enough for multicellular organisms?

Answer 42

No as the distances are to great - smaller surface area

Question 43

How does a multicellular organism provide for itself?

Answer 43

It develops gas exchange organs (eg lungs) which have a greatly increased surface area. They also need a transport system (eg circulatory/respiratory) to deliver materials to/from exchange surfaces

Question 44

How many cells are used for the processes carried out in unicellular organisms?

Answer 44

They are carried it by one cell

Question 45

How are processes carried out in multicellular organisms?

Answer 45

Their cells differentiate and are specialised. They are then organised into groups eg tissue, organs, organ systems etc

Question 46

Different groups of cells

Answer 46

Cells - tissues - organs - organ systems - organisms

Question 47

Function and main organs of the respiratory system

Answer 47

To move air into the body and to remove carbon dioxide. Main organs are lungs, throat, mouth etc

Question 48

Functions and main organs of the digestive system

Answer 48

Digest/absorb food, remove waste. Main organs include mouth, stomach, small/large intestine

Question 49

What is a stem cell?

Answer 49

Simple, unspecialised cells that. Have the ability to divide into smaller cells of the same type. They can also differentiate into a variety of specialised cells

Question 50

Where can stem cells be harvested in humans?

Answer 50

Embryo’s, umbilical cord or adult bone marrow

Question 51

Difference between embryonic and adult stem cells

Answer 51

Embryonic can change, adult cant

Question 52

What type of cells can bone marrow stem cells only turn into?

Answer 52

Blood cells

Question 53

Where can stem cells be harvested from in plants?

Answer 53

Meristems

Question 54

What are meristems?

Answer 54

Apical growing points

Question 55

Where are meristems found?

Answer 55

End of shoots and roots

Question 56

Are stem cells stuck with their specialisation? How can this benefit science?

Answer 56

No, they can be reversed under certain conditions. This means scientists can produce large numbers of genetically identical plants by cloning

Question 57

Benefits of using stem cells in medicine

Answer 57

Treating leukaemia- chemotherapy/ radiotherapy destroys and stops the production of new blood cells. A matching donor’s stem cels allows new, healthy blood cells to be made in the patient

Question 58

Risks of using stem cells in medicine

Answer 58

Infection - radiotherapy and chemotherapy leaves patient with no white blood cells and therefore no immune system Risk of uncontrollable division leading to tumours/unwanted cell types Transfer of viruses/diseases

Question 59

What is peer review in medicine?

Answer 59

New research is validated or rejected by other experts in the same field to prevent spread of misinformation

Question 60

Ethical issues relating to stem cells

Answer 60

Destruction of potential human life, some religions are opposed to it, ‘playing God’, human rights issues