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Biology A level > 2.1.6 cell division and cellular organisation > Flashcards

2.1.6 cell division and cellular organisation Flashcards

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1
Q

what is the cell cycle

A

the process that all body cells in multicellular organisms use to grow and divide

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2
Q

how many chromosomes do humans have in each cell

A

46 chromosomes, 23 pairs

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3
Q

what is interphase

A

the stage of cell growth before division
the cell carries out normal functions but also prepares to divide. the cells DNA is unravelled and replicated. organelles are replicated and ATP content is increased.
split into G1, S and G2

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4
Q

what is M phase

A

the period of cell division

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5
Q

what is the G1 (gap phase 1) stage

A

cell grows and new organelles and proteins are made

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6
Q

what does the G1 checkpoint check for

A

checks that all the chemicals needed for replication are present and any damage to the DNA

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7
Q

what is the G2 stage

A

cell keeps growing and proteins are needed for cell division are made

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8
Q

what does the G2 checkpoint check for

A

checks whether the replicated DNA has no damage

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9
Q

what is the S stage (synthesis)

A

cell replicates its DNA ready to divide my mitosis

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10
Q

what is the structure of a chromosome in mitosis

A

2 sister chromatids joined in the centre by a centromere. there is 2 because it has been replicated

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11
Q

what is mitosis

A

needed for the growth of multicellular organisms and a method of asexual reproduction. it produces two identical daughter cells

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12
Q

what happens in prophase (mitosis)

A

the chromosomes condense. centrioles move to opposite ends of the cell forming a network of protein fibres called a spindle. the nuclear envelope breaks down

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13
Q

what happens in metaphase (mitosis)

A

the chromosomes (each with two chromatids) line up along the equator and are attached to the spindle fibres by the centromere.

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14
Q

what happens in the metaphase checkpoint

A

cell checks that all chromosomes are attached to the spindle

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15
Q

what happens in anaphase (mitosis)

A

the centromeres divide separating the sister chromatids. the spindles contract pulling the chromatids to opposite ends of the cell

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16
Q

what happens in telophase (mitosis)

A

the chromatids reach the opposite ends of the cells. they uncoil and become less condensed again. they are chromosomes again.
the nuclear envelope forms around them so there is two nuclei.

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17
Q

what is cytokinesis

A

the cytoplasm and cell membrane divides to form two separate cells

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18
Q

what is sexual reproduction

A

two gametes join together at fertilisation to for a zygote which develops into a new organism

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19
Q

what is an advantage of sexual reproduction

A

it produces genetically different offspring

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20
Q

what is a gamete

A

have half the number of chromosomes than a normal cell

21
Q

what is meiosis

A

meiosis is the formation of gametes in sexual reproduction

22
Q

what is a homologous pair

A

a pair of chromosomes, one from the father one from the mother. the chromosomes that make up each pair are the same size and have the same genes although they may be different versions of these genes

23
Q

what happens in meiosis I

A

it is the reduction division it halves the number of chromosomes. two haploid daughter cells are formed.

24
Q

what happens in prophase I

A

chromosomes condense. the chromosomes arrange themselves into homologous pairs and crossing over occurs. nuclear envelope breaks down and centrioles move to opposite ends of the cell to form the spindle.

25
Q

what happens in metaphase I

A

the homologous pairs line up across the equator of the cell and attach to the spindle fibres by their centromeres.

26
Q

what happens in anaphase I

A

the spindles contract separating the homologous pairs, one chromosome goes to each end of the cell

27
Q

what happens in telophase I

A

nuclear envelope reforms forming 2 nuclei. two haploid daughter cells are produced.

28
Q

what happens in meiosis II

A

4 haploid daughter cells are made from 2 haploid daughter cells

29
Q

what is the difference between anaphase 1 and anaphase II

A

in anaphase II the sister chromatids are separated and in anaphase I the homologous pairs are separated

30
Q

what is crossing over

A

homologous pairs of chromosomes come together to pair up. the chromatids twist around each other and parts of the chromatids swap over. they contain the same genes but have a different combination of alleles.

31
Q

when does crossing over occur

A

prophase I

32
Q

what is independent assortment

A

when homologous pairs line up in metaphase I and are pulled apart in anaphase II it is completely random which pair ends up in each daughter cell.
so the gametes are all different combinations of maternal and paternal chromosomes
this leads to genetic variation

33
Q

what are stem cells

A

unspecialised cells that can develop into different specialised cells

34
Q

what is the difference between adult and embryonic stem cells

A

adult stem cells can only differentiate into a limited range of cells, embryonic can differentiate into all specialised cells

35
Q

what can stem cells in the bone marrow differentiate into

A

they can differentiate into blood cells to replace worn out ones. this includes erythrocytes and neutrophils

36
Q

what can stem cells in vascular cambium meristem differentiate into

A

they can differentiate into xylem vessels and phloem sieve tubes

37
Q

how may we use stem cells in the treatment of Alzheimer’s

A

we could use stem cells to regrow healthy nerve cells after they die in people with Alzheimer’s

38
Q

how may we use stem cells in the treatment of Parkinson’s

A

transplanted stem cells could regenerate dopamine producing cells that are lost in patients with Parkinson’s

39
Q

how are erythrocytes specialised for their function

A

erythrocytes carry oxygen in the blood. they have a biconcave shape which provides a large surface area for gas exchange. they have no nucleus so there is more room for haemoglobin.

40
Q

how are neutrophils specialised for their function

A

neutrophils defend the body against disease. they are flexible due to their multilobed nucleus which allows them to engulf pathogens. they also have many lysosomes to break down the engulfed pathogens.

41
Q

how are epithelial cells specialised for their function

A

epithelial cells cover the surface of organs. the cells are connected by interlinking cell membranes.
ciliated epithelium has cilia which beat to move particles away
squamous epithelium is very thin to allow efficient diffusion

42
Q

how are sperm cells specialised for their function

A

have flagellum so they can swim to the egg to fertilise it. they have lots of mitochondria to provide the energy to move. the acrosome contains digestive enzymes to penetrate the eggs surface

43
Q

how are palisade cells specialised for their function

A

palisade mesophyll cells do most of the photosynthesis. they contain many chloroplasts so thy can absorb sunlight. the walls are thin so CO2 can diffuse in easily

44
Q

how are root hair cells specialised for their function

A

root hair cells absorb water and mineral ions from the soil.
they have a large surface area and thin permeable cell wall for efficient diffusion.
they also have lots of mitochondria to provide energy for active transport

45
Q

how are guard cells specialised for their function

A

they surround a stoma which is a pore in the leaf used for gas exchange. in light they take up water and become turgid. this bends them outwards opening the stomata which allows gas to diffuse in for photosynthesis.

46
Q

what is a tissue

A

a group of similar cells working together to preform a specific function

47
Q

what is an organ

A

a group of tissues working together to preform a specific function

48
Q

what is an organ system

A

a group of organs working together to preform a specific function

Biology A level (13 decks)

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