Topic 2 - Cells and Life

Question 1

mitosis defnition

Answer 1

when a cell reproduces itself to form two genetically identical diploid daughter cells

Question 2

6 stages of cell cycle and mitosis

Answer 2

I PMAT C

Question 3

What happens in interphase?

Answer 3

• cell needs to grow and increase amount of sub - cellular structures such as mitochondria and ribosomes
• it duplicates its DNA and forms X - shaped chromosomes

Question 4

What happens in prophase?

Answer 4

• chromosomes condense getting shorter and fatter
• nuclear membrane breaks down
• centrioles are copied and move to opposite ends of cell

Question 5

What happens in metaphase?

Answer 5

• chromosomes line up at middle of the cell ( equator )

Question 6

What happens in anaphase?

Answer 6

• spindle fibres extending from the centriole contract separates 2 sister chromatids at the centromere
• sister chromatids go towards opposite ends of cell

Question 7

What happens in telophase?

Answer 7

• new nuclear membranes form around each of the sets of chromosomes
• 2 daughter nuclei in parent cytoplasm

Question 8

What happens in cytokinesis?

Answer 8

cytoplasm separates to form two genetically identical daughter cells each with 2 sets of chromosomes

Question 9

What are the three uses of mitosis

Answer 9

• growth
• repair tissue by replacing damaged cells
• reproduce by asexual reproduction to produce genetically identical clones

Question 10

problem with asexual reproduction

Answer 10

• there is no genetic variation in the species so are all susceptible to same diseases
• no evolutionary potential

Question 11

how do cells know when to stop dividing?

Answer 11

• once we have reached adult size or repaired damaged cells a gene in our nucleus tells the cell to stop dividing

Question 12

how do cancers form?

Answer 12

• a mutation may occur in that gene resulting in a cell that divides by mitosis uncontrollably
• makes masses of undifferentiated cells known as tumours
• these tumours can spread and invading normal tissue, causing cancer

Question 13

cell differentiation

Answer 13

when stem cells express the correct genes to make the proteins they need, allowing them to differentiate

Question 14

why are specialised cells important for the human body?

Answer 14

it helps multicellular organisms to work more efficiently because different cell types can carry out different functions

Question 15

cell elongation

Answer 15

where a plant cell expands making the plant grow

Question 16

growth in animals

Answer 16

• all growth in animals is due to cell division
• when they’re young cell division happens at a fast rate
• once animals reach adult size, cell division is mostly only for repair
• cell differentiation lost at an early stage

Question 17

growth in plants

Answer 17

• growth in height mainly due to cell elongation
• cell division just happens in the meristems ( tips of r&s)
• plants grow continuously so continue to differentiate to develop new parts

Question 18

percentile charts

Answer 18

used to assess a child’s growth over time and compare it to children the same age and gender

Question 19

what are stem cells?

Answer 19

stem cells are undifferentiated cells that are not yet specialised for a specific function

Question 20

totipotent embryonic stem cells

Answer 20

can differentiate into every type of specialised cell, so very important for growth + development of human body

Question 21

multi-potent adult stem cells

Answer 21

they are only found in certain places (e.g : bone marrow ) and can only differentiate into certain specialised cells

Question 22

what are adult stem cells used for in the body?

Answer 22

they are used to replace damaged cells

Question 23

adult cells used in medicine

Answer 23

• people with blood diseases can have bone marrow transplants which contain adult stem cells
• these adult stem cells can differentiate to turn into new blood cells replacing faulty ones

Question 24

how could embryonic stem cells be used in medicine

Answer 24

• under certain conditions, could be stimulated to differentiate into any kind of specialised cell
• can be used to replace faulty cells in tissues with no stem cells like spinal cord

Question 25

issues involving using stem cells

Answer 25

- tumour development : stem cells divide very quickly - disease transmission : donor stem cell could be infected with virus - rejection : immune system may recognise cells as foreign and trigger a response to get rid of them.

Question 26

ethical issue involving embryonic stem cell

Answer 26

- human embryos shouldn't be used as each one is a potential human life

Question 27

what are sensory receptors?

Answer 27

- groups of cells that detect stimuli (changes in the environment) and initiate responses to them

Question 28

CNS ( Central Nervous System )

Answer 28

Consists of the brain and spinal cord and co-ordinates and controls the human body

Question 29

what are effectors?

Answer 29

- muscles or glands that respond to nervous impulses and bring about a response to a stimulus

Question 30

transmission of information to and from CNS

Answer 30

stimulus -> receptor -> sensory neurone -> relay neurone(CNS) -> motor neurone -> effector -> response

Question 31

sensory neurones

Answer 31

they carry information as electrical impulses from the sensory receptor to the CNS

Question 32

relay neurones

Answer 32

they carry information as electrical impulses from the sensory neurones to the motor neurones and found in CNS

Question 33

motor neurones

Answer 33

they carry information as electrical impulses from the CNS to the effector

Question 34

dendrons

Answer 34

carry electrical impulses towards cell body

Question 35

axons

Answer 35

carry electrical impulses away from cell body

Question 36

myelin sheath

Answer 36

acts as an electrical insulator around axon, speeding up rate of electrical impulse

Question 37

what are synapses?

Answer 37

a minute gap or junction between neurones through which they communicate with each other

Question 38

how do electrical impulses get transmitted between neurones?

Answer 38

- when an electrical impulse reaches the end of the first neurone - it triggers the release of neurotransmitters ( chemical messengers ) - they diffuse down the concentration gradient and bind to receptor on next neurone - new electrical impulse generated and moves down next neruone

Question 39

why are synapses useful?

Answer 39

- only one end of neurone can make neurotransmitters so it makes sure impulses only travel in 1 direction - slow down the passage of information so it isn't harmful

Question 40

what are reflexes?

Answer 40

- they are exceedingly rapid, automatic responses to certain stimuli. - they protect our bodies from harm by minimising exposure to harmful stimuli

Question 41

how do reflexes do this?

Answer 41

- it minimises the distance impulses have to travel around the body, so minimises number of neurones and synapses that must be crossed - it goes through the unconscious part of brain

Question 42

example of how reflex arc works?

Answer 42

check 23/3/23 in Bio exercise book