Topic 1 - Cell Biology

Question 1

Describe eukaryotic cells

Answer 1

Eukaryotic cells are complex
They include animal and plant cells
They are made up of eukaryotic cells

Question 2

Describe prokaryotic cells

Answer 2

Prokaryotic cells are smaller and simplier (e.g. bacteria)
They are a single-celled organism

Question 3

What is the point of the nucleus?

Answer 3

The nucleus contains the genetic material
The genetic material controls the activities of the cell

Question 4

What is the point of the cytoplasm?

Answer 4

The cytoplasm is where chemical reactions take place
The cytoplasm contains enzymes which controls the chemical reactions

Question 5

What is the point of the cell membrane?

Answer 5

The cell membrane holds the cells together
The cell membrane controls what goes in and out the cell

Question 6

What is the point of the mitochondria?

Answer 6

The mitochondria is where areobic respirations takes place
This respiration transfers energy for cells to work

Question 7

What is the point of the ribosomes?

Answer 7

The ribosomes are where proteins are made

Question 8

What is the point of the rigid cell wall in plant cells?

Answer 8

The rigid cell wall is made up of cellulose
The rigid cell wall supports the cell and strengthens it

Question 9

What is the point of the permanent vacuole in plant cells?

Answer 9

The permanent vacuole contains cell sap
Cell sap is a weak solution of sugar and salts

Question 10

What is the point of the chloroplasts in plant cells?

Answer 10

The chloroplasts is where photosynthesis occurs
Photosynthesis makes food for the plant
The chloroplasts contain a green substance called chlorophyll
Chlorophyll absorbs the light needed for photosynthesis

Question 11

What key subcellular structures do bacterial cells not have?

Answer 11

Bacterial cells don’t have chloroplasts or mitrochondria

Question 12

What do bacterial cells have as there nucleus?

Answer 12

Bacterial cells have a singular circular strand of DNA
This singular circular strand of DNA floats freely in the cytoplasm

Question 13

What does a bacterial cell have that other cells don’t?

Answer 13

Plasmids
Plasmids are small rings of DNA

Question 14

How do light microscopes work?

Answer 14

Light microscopes use light and lenses to form an image and magnify it
With light microscopes you can see individual cells and large subcellular structures (e.g. nuclei)

Question 15

How do electon microscopes work?

Answer 15

Electron microscopes use electrons
Electron microscopes have a higher magnification and resolution
Electron microscopes can see smaller things in more detail (e.g. internal stuctures of mitrochondria and chloroplasts, and tinier things like ribosomes and plasmids)

Question 16

What is the formula for magnification?

Answer 16

Magnification = Image size ÷ real size

Question 17

How do you work out standard form?

Answer 17

Standard form can be worked out by the number of places a decimal point moves to create a number between 1 and 10
This answer is represented by a power of 10

Question 18

How do you prepare your slide during the microscopy practical?

Answer 18

1. Put a drop of water on the middle of the slide
2. Cut an onion into seperate layers, and use tweezers to pull off the epidermal tissue from the bottom of one layer
3. Place the epidermal tissue on the water
4. Put a drop of iodine, which acts as a stain and highlights the objects in a cell by adding colour to them
5. Place the cover slip on top - be careful and avoid air bubbles as that obstructs the view

Question 19

What are the steps in using a light microscope to look at a slide?

Answer 19

1. Clip the slide onto the stage
2. Select the lowest-powered objective lens (the one with the lowest magnification)
3. Use the coarse adjustment knob to move the stage up until it is just below the objective lens
4. Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus
5. Adjust the focus with the fine adjustment knob until you have a clear image
6. To see the image with a greater magnification use a higher-powered objective lens and refocus

Question 20

How do you draw your observations of the microscopy practical?

Answer 20

Use a pencil with a sharp point
Drawing should take up at least half of the space available and it should be drawn with clear, unbroken lines
No colouring or shading in your drawing
If you are drawing cells, make sure the subcellular structures are drawn in proportion
Include a title of what your observing and write down the magnification of the drawing
Label the important features (e.g. nucleus) with straight, uncrossed lines

Question 21

What is the process of differentiation?

Answer 21

Differentiation is when a cell changes to become specialised for its job

Question 22

What happens has the cells change in differentiation?

Answer 22

As the cells change, they develop different subcellular structures and turn into different types of cells which carry out specific functions

Question 23

When does most differentiation occur?

Answer 23

Most differentiation occurs as the organism develops
In most animal cells the ability to differentiate is lost at an early stage, after they have become specialised
Lots of plant cells don’t loose the ability to differentiate

Question 24

What are the cells that differentiate in mature animals mainly used for?

Answer 24

The cells that differentiate in mature animals are mainly used for repairing and replacing cells, such as skin or blood cells

Question 25

What type of cells are undifferentiated?

Answer 25

Stem cells are undifferentiated

Question 26

What are sperm cells specialised for?

Answer 26

Sperm cells are specialised for reproduction

Question 27

How are sperm cells specialised?

Answer 27

The function of the sperm is to get the male DNA to the female DNA
It has a long tail and a streamlined head to help it swim to the egg
It has a lot of mitochondria to provide energy
It has enzymes in the head to digest through the egg cell membrane

Question 28

What are nerve cells specialised for?

Answer 28

Nerve cells are specialised for rapid signalling

Question 29

How are nerve cells specialised?

Answer 29

The function of nerve cells is to carry electrical signals from one part of the body to another
They are long so they can cover more distance
They have branched connections at each end to connect to others and to form a network through the body

Question 30

What are muscle cells specialised for?

Answer 30

Muscle cells are specialised for contraction

Question 31

How are muscle cells specialised?

Answer 31

The function of a muscle cell is to contract quickly
The cell is long so it has space to contract
It contains lots of mitochondria to give it the energy needed for contraction

Question 32

What are root hair cells specialised for?

Answer 32

Root hair cells are specialised for absorbing water and minerals

Question 33

How are root hair cells specialised?

Answer 33

Root hair cells are cells on the surface of plant roots, that grow into long ‘hairs’ that stick out into the soil
This gives the plant a big surface area for absorbing water and mineral ions from the soil

Question 34

What are phloem and xylem cells specialised for?

Answer 34

Phloem and xylem cells are specialised for transporting substances

Question 35

How are phloem and xylem cells specialised?

Answer 35

Phloem and xylem cells form phloem and xylem tubes which transport substances such as food and water around the plants
To form the tubes, the cells are long and joined end to end
Xylem cells are hollow in the centre and phloem cells have very few subcellular structures so stuff can flow through them

Question 36

What is the form of the genetic material that a nucleus contains?

Answer 36

The nucleus contains your genetic material in the form of chromosomes

Question 37

What do chromosomes look like?

Answer 37

Chromosomes are coiled up lengths of DNA molecules

Question 38

What does each chromosome carry?

Answer 38

Each chromosome carries a large number of genes
Different genes control the development of different characteristics (e.g. hair colour)