topic 1 - cell biology

Question 1

what is the function of a nucleus

Answer 1

contains DNA and controls the activities of the cell

Question 2

what is the function of the cell membrane

Answer 2

controls what enters and leaves the cell

Question 3

what is the function of the cytoplasm

Answer 3

where cell activities and reactions happen

Question 4

what is the function of the mitochondria

Answer 4

provides energy from aerobic respiration

Question 5

what is the function of ribosomes

Answer 5

make proteins- site of protein synthesis

Question 6

what is the function of chloroplasts

Answer 6

where photosynthesis occurs - only found in plant cells

Question 7

what is the function of the vacuole

Answer 7

used to store water and other chemicals as sell sap - only found in plant cells

Question 8

what is the function of a cell wall

Answer 8

strengthens and supports the cell (made of cellulose in plants and peptidoglycan in bacteria cells)

Question 9

what is a DNA loop

Answer 9

a loop on DNA not in a nucleus

Question 10

what is the function of plasmids

Answer 10

a small circle of DNA, may contain genes associated with antibiotic resistance

Question 11

how are sperm cells specialised

Answer 11

• streamlined head and long tail to aid swimming
• many mitochondria which supplies energy allowing the cell to move
• the acrosome (top of the head) has digestive enzymes which break down the outer layers of membrane of the egg cell

Question 12

how are nerve cells specialised

Answer 12

long to cover more distance, branched connections at their ends to connect to other nerve cells and form a network throughout the body

Question 13

how are muscle cells specialised

Answer 13

long so they have space to contract, contain lots of mitochondria to generate the energy needed for contraction

Question 14

how are root hair cells specialised

Answer 14

large surface area meaning more water can move in, mitochondria to provide energy from respiration for active transport

Question 15

what is differentiation

Answer 15

the process by which a cell changes to become specialised for its job

Question 15

what are stem cells

Answer 15

undifferentiated cells that can differentiate into different types of cells

Question 16

what are the two types of stem cells

Answer 16

embryonic and adult

Question 17

what are embryonic stem cells

Answer 17

found in early human embryos, they have the potential to turn into any kind of cell

Question 18

what are adult stem cells

Answer 18

only found in certain places, like bone marrow. they cant turn into any cell type at all, only certain ones such as blood cells

Question 19

why are embryonic stem cells useful in medicine

Answer 19

they could be used to replace faulty cells in sick people, you could make insulin- producing cells for people with diabetes or nerve cells for people paralysed by spinal injuries etc

Question 20

what is therapeutic cloning

Answer 20

a type of cloning where an embryo could be made to have the same genetic information as the patient. this means that the stem cells produced from it would also contain the same genes so wouldn’t be rejected by the patients body if used to replace faulty cells

Question 21

why are some people against stem cell research

Answer 21

they feel that human embryos shouldn’t be used for experiments since each one is a potential human life

Question 22

why can stem cells produce identical plants and what is it used for

Answer 22

1. stem cells found in meristems
2. through the plants entire life, cells in the meristem tissues can differentiate into any type of plant cell
3. these stem cells can be used to produce clones of whole plants quickly and cheaply
4. they can be used to grow more plants of rare species
5. they can also be used to grow crops of identical plants that have features desired by farmers (e.g disease resistance)

Question 23

how many copies of each chromosome do body cells normally have

Answer 23

2 - one from the organisms “mother” and one from its “father”

Question 24

what is mitosis

Answer 24

the stage of the cell cycle when the cell divides

Question 25

what are the two main stages of the cell cycle

Answer 25

1. growth and DNA replication
2. mitosis

Question 26

describe the growth and DNA replication stage of the cell cycle

Answer 26

the cell grows and increases the amount of subcellular structures such as mitochondria and ribosomes. it then duplicates its DNA - the DNA forms x shaped chromosome (each “arm” is an exact duplicate of the other)

Question 27

describe mitosis

Answer 27

the chromosomes line up at the centre of the cell and cell fibres pull them apart, the two arms of each chromosome go to opposite ends of the cell. membranes form around each of the sets of chromosomes - these will become the new nuclei. lastly the cytoplasm and membrane divide

Question 28

what are chromosomes

Answer 28

coiled up lengths of DNA molecules that carry a large number of genes

Question 29

how to prokaryotic cells replicate

Answer 29

by binary fission

Question 30

describe binary fission

Answer 30

1. the circular DNA and plasmids replicate
2. the cell gets bigger and the circular DNA strands move to opposite ‘poles’ (ends) of the cell
3. the cytoplasm begins to divide and new cell walls begin to form
4. the cytoplasm divides - two daughter cells are produced - each have one copy of circular DNA, but can have a variable number of copies of the plasmids

Question 31

how can you calculate the number of bacteria in a population

Answer 31

total time that the bacteria are producing cells / mean division time (average amount of time it takes for one bacterial cell to divide into two)