B1.1.2 Bacterial Cells

Question 1

What is a unicellular organism

Answer 1

One of which consist of just one cell

Question 2

Every single cell of bacteria can carry out the seven life processes. What are they?

Answer 2

Movement
Reproduction
Sensitivity
Growth
Respiration
Excretion
Nutrition

Question 3

Size of most bacteria

Answer 3

1um

Question 4

What are prokaryotes

Answer 4

Single celled organisms without a nucleus

Question 5

Examples of prokaryotes

Answer 5

Escherichia coli- cause food poisoning
Streptococcus- cause sore threats
Streptomyces- found in the soil. The antibiotic streptomycin comes from these bacteria, kills many disease causing bacteria

Question 6

Which sub cellular structures do prokaryotic cells contain

Answer 6

Cytoplasm
Cell wall
Cell membrane
Genetic material

Question 7

Function of cell wall

Answer 7

Made of peptidoglycan - holding the cell together and protects it

Question 8

Genetic material

Answer 8

Floats freely in cytoplasm
One long strand of dna called the bacterial chromosome which is circular

Question 9

What are the extra subcellular structures of bacterial cells

Answer 9

Flagella
Pili
Slime capsule
Plasmid

Question 10

Function of flagella

Answer 10

Tail like structures that allow the cell to move through liquids

Question 11

Function of pili

Answer 11

Tiny hairlike structures
Enable the cell to attach to structures
Transfer genetic material between bacteria

Question 12

Function of slime capsule

Answer 12

Layer outside cell wall
Protects bacterium from drying out and from poisonous substances
Helps bacteria stick to smooth surfaces

Question 13

Function of Plasmid

Answer 13

Circular piece of dna used to store extra genes
The genes aren’t normally needed for bacterium’s day to day survival but may help in times of stress
Eg. This is where antibiotic resistance genes are normally found

Question 14

Some species of Salmonella bacteria cause food poisoning. On average, these cells have a width of 2 um. Assuming the bacteria fit side by side, calculate:

a) the number of bacteria that would fit into a gap of 1 mm (3 marks)

b) the size, in mm, of a colony of 20000 Salmonella bacteria lined up end to end (2 marks)

Answer 14

a) Convert the width of one bacterium from micrometers to millimeters:
1mm=1000um
2 um = 0.002 mm

1mm/0.002 mm = 500 bacteria

b) 0.002mm*20000 = 40mm

Question 15

Why do leaf cells have chloroplasts and root cells don’t

Answer 15

Chloroplasts are only found in green areas of the plant such as stem and leaves.
These are higher up the plant as they take in the energy provided by the sun for photosynthesis.
As roots are underground, they don’t have access to sunlight and therefore don’t require chloroplasts.

Question 16

Suggest why it is important for muscle cells to contain many mitochondria: (1)

Answer 16

In order to provide enough energy for the muscle cells to enable movement.

Question 17

Algae are eukaryotic organisms. They live in water and make their own food using photosynthesis. State and
explain which subcellular features you would expect to find in an algal cell.
(6 marks)

Answer 17

Cell membrane - to allow selected substances into or out of the cell
Cell wall - to provide structure
Chloroplasts - to allow the algal cell to produce its own food via photosynthesis
Cytoplasm - where the cell reactions take place
Mitochondria - to release energy for the algal cells
Nucleus - to control the activities of the algal cells
Vacuole - to keep the cells rigid
[each worth 1 mark]

Question 18

Two similarities between a plant and a bacterial cell

Answer 18

Both have a cell wall, cytoplasm and cell membrane

Question 19

What are the differences between plant and bacterial cells?

Answer 19

Plant cells have chloroplasts, permanent vacuole and nucleus unlike bacterial cells