1 - Cell Biology

Question 1

What are two features of light microscopes?

Answer 1

• They are cheap to make
• They allow you to see the outlines of cells.

Question 2

What are electron microscopes used for?

Answer 2

To visualise finer details including organelles (sub-cellular structures).

Question 3

Why do electron microscopes show more detail than light microscopes?

Answer 3

Because they have greater resolving power and higher resolution.

Question 4

What is the formula for magnification?

Answer 4

Magnification = Image size ÷ Object (cell) size.

Question 5

How long are cells usually?

Answer 5

A few micrometers (µm) long.

Question 6

What is 1 micrometer (µm) in meters?

Answer 6

1 µm = 1 × 10⁻⁶ m

Question 7

How do you convert micrometers (µm) to millimeters (mm)?

Answer 7

Divide by 1000.

Question 8

What type of cells are animal and plant cells?

Answer 8

Eukaryotic cells.

Question 9

What type of cells are bacteria?

Answer 9

Prokaryotic cells.

Question 10

What does the cell membrane do in eukaryotic cells?

Answer 10

It is semi-permeable and controls what enters and leaves the cell.

Question 11

What is the function of the nucleus in eukaryotic cells?

Answer 11

It contains DNA.

Question 12

What is the role of mitochondria in eukaryotic cells?

Answer 12

They are the site of respiration.

Question 13

What is the function of the cytoplasm?

Answer 13

It holds the cell’s components and is where many cell reactions occur.

Question 14

What do ribosomes do in eukaryotic cells?

Answer 14

They are the site of protein synthesis.

Question 15

What three structures are found in plant cells but not in animal cells?

Answer 15

Chloroplasts, a permanent vacuole, and a cell wall.

Question 16

What do chloroplasts do?

Answer 16

They contain chlorophyll and are the site of photosynthesis.

Question 17

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

Answer 17

It stores sap.

Question 18

What is the plant cell wall made of, and what is its function?

Answer 18

It is made of cellulose and provides structure and support.

Question 19

Where is the DNA found in prokaryotic (bacterial) cells?

Answer 19

In the cytoplasm.

Question 20

How do bacteria reproduce?

Answer 20

Binary fission.

Question 21

How often can bacteria divide in binary fission?

Answer 21

Every 20 minutes.

Question 22

How many bacteria will there be after 1 hour, if there are 2 to begin with?

Answer 22

16

Question 23

How many bacteria will there be after 2 hours, if there are 2 to begin with?

Answer 23

128

Question 24

What is the first step in making cultures using aseptic technique?

Answer 24

Lift the lid of the petri dish towards a flame to sterilise the air.

Question 25

What is done after sterilising the air when making cultures?

Answer 25

Put a drop of culture on agar and spread it evenly.

Question 26

What is added to the culture if needed?

Answer 26

Drops or discs of antibiotics.

Question 27

Why are only a few bits of tape used on the petri dish?

Answer 27

To allow aerobic respiration.

Question 28

At what temperature should cultures be incubated?

Answer 28

25°C.

Question 29

How do you measure the size of bacterial cultures or clear zones?

Answer 29

Use the formula πr².

Question 30

How many pairs of chromosomes do human diploid cells have?

Answer 30

23 pairs.

Question 31

What are gametes and how many chromosomes do they have?

Answer 31

Gametes are egg and sperm cells; they have 23 chromosomes (haploid).

Question 32

What is mitosis used for in the body?

Answer 32

For growth and repair.

Question 33

What happens first in mitosis?

Answer 33

The genetic material is duplicated.

Question 34

What happens after the genetic material is duplicated in mitosis?

Answer 34

The nuclear membrane dissolves.

Question 35

What happens after the nuclear membrane dissolves during mitosis?

Answer 35

The two sets of chromosomes line up along the center of the cell.

Question 36

What happens after the chromosomes line up in mitosis?

Answer 36

Both sets of chromosomes are pulled to opposite ends of the cell.

Question 37

What forms after chromosomes are pulled to opposite ends in mitosis?

Answer 37

New nuclei are formed (the nucleus divides).

Question 38

What is the result of mitosis?

Answer 38

Two genetically identical diploid cells are produced.

Question 39

What happens to other organelles during mitosis?

Answer 39

They are also duplicated.

Question 40

What are stem cells?

Answer 40

Cells that can specialise to perform specific functions.

Question 41

Where are stem cells found in animals and plants?

Answer 41

In animal embryos and plant meristems.

Question 42

Where are stem cells found in adults, and what can they become?

Answer 42

In bone marrow; they can only specialise into blood cells.

Question 43

Why might embryo clones be made?

Answer 43

To harvest stem cells for treating conditions without rejection by the patient's body.

Question 44

What are two other uses of cloning?

Answer 44

To preserve species and produce crops with desired traits.

Question 45

What is diffusion?

Answer 45

The movement of particles from a high to low concentration, down the concentration gradient.

Question 46

Does diffusion require energy?

Answer 46

No, it is passive.

Question 47

What three factors increase the rate of diffusion?

Answer 47

Greater concentration difference, larger surface area, and higher temperature.

Question 48

What is osmosis?

Answer 48

The diffusion of water across a semi-permeable membrane to balance concentrations.

Question 49

Why must only water move across the membrane in osmosis?

Answer 49

Because larger molecules can't pass through the membrane.