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ocr a level biology > cell division > Flashcards

cell division Flashcards

1
Q

what are the 3 stages in the interphase?

A

GAP PHASE 1

SYNTHESIS

GAP PHASE 2

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2
Q

what is the M phase?

A

Mitosis and cytokinesis

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3
Q

what is the gap phase 1

A

when the cell grows and new organelles and proteins are made

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4
Q

what is gap phase 2

A

cell keeps growing and proteins needed for division are made

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5
Q

what is synthesis

A

cell replicates its dna ready to divide by mitosis

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6
Q

in which stage does the g1 checkpoint occur

A

in the gap phase 1

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7
Q

in which stage does the g2 checkpoint occur

A

gap phase 2

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8
Q

what happens in the g1 checkpoint?

A

cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering the s phase

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9
Q

what happens in the g2 checkpoint?

A

cell checks whether all the DNA has been replicated without any damage

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10
Q

what occurs in the interphase?

A

the cells DNA is unravelled and replicated. the organelles are also replicated, ATP content is increased

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11
Q

what occurs in the prophase?

A

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

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12
Q

what occurs in the metaphase?

A

chromosomes line up along the middle of the cell and become attached to the spindle by their centromere

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13
Q

what occurs in the anaphase?

A

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

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14
Q

what occurs in the telophase?

A

The chromatids reach the opposite poles on the spindle, uncoil and become long and thin, they are now chromosomes. a nuclear envelope forms around each group of chromosomes

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15
Q

what occurs in cytokinesis?

A

a cleavage furrow forms to divide the cell membrane, cytoplasm divides

usually begins in anaphase and ends in telophase

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16
Q

what is the outcome of mitosis

A

2 genetically identical daughter cells are formed

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17
Q

define meiosis

A

production of gametes for sexual reproduction, all cells formed are genetically different to each other

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18
Q

how chromosomes do humans have?

A

46 chromosomes

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19
Q

what are homologous pairs of chromosomes?

A

have the same size and the same genes although they can have different version of those genes (alleles)

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20
Q

what happens in meiosis 1, prophase 1?

A

chromosomes condense
chromosomes arrange themselves in homologous pairs
centrioles move to opposite ends of cell
spindle fibres form
nuclear envelope breaks down

21
Q

what happens in meiosis 1, metaphase 1?

A

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

22
Q

what happens in meiosis 1, anaphase 1?

A

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

23
Q

what happens in meiosis 1, telophase 1?

A

nuclear envelope forms, around each group of chromosomes, cytokinesis occurs and 2 haploid daughter cells are produced.

24
Q

what happens in meiosis 2, anaphase 2?

A

pairs of sister chromatids are separated, each new daughter cell inherits one chromatid from each chromosome.

4 genetically identical haploid daughter cells are produced. these are the gametes

25
Q

what are 2 events in meiosis that lead to genetic variation?

A

crossing over of chromatids

independent assortment of chromosomes

26
Q

in which stage of meiosis does crossing over of chromatids occur?

A

meiosis 1, prophase 1

27
Q

in which stage of meiosis does independent assortment of chromosomes occur?

A

metaphase 1 and prophase 1

28
Q

what are stem cells?

A

unspecialised cells

29
Q

where in humans are stem cells found?

A

early embryos and bone marrow

30
Q

why is it better to have stem cells from early embryos rather than the bone marrow?

A

as they can develop into any type of cell whereas in adults it can only develop into a limited range of cells

31
Q

what do cells in the bone marrow differentiate into?

A

bloods cells, erythrocytes RBC and neutrophils WBC

32
Q

what do cells in meristems differentiate into?

A

xylem and phloem

33
Q
A
34
Q

how might stem cells be used to treat Parkinson’s disease?

A

the disease causes a loss of a type of nerve cell in the brain, these cells release a chemical called dopamine which is needed to control movement, transplanted stem cells may help to regenerate the dopamine producing cells

35
Q

how does neutrophils structure help them perform their function?

A

they have flexible shape which allows them to engulf foreign particles

they have many lysosomes in their cytoplasm which contain digestive enzymes to break down engulfed particles

36
Q

how does erythrocytes structure help them perform their function?

A

have a biconcave disc shape which gives a large surface area for gas exchange

no nucleus so more room for haemoglobin

37
Q

how does epithelial cells structure help them perform their function?

A

ciliated epithelia (AIRWAY) have cilia that beat to move particles away

squamous epithelia (LUNGS) are very thin to allow efficient diffusion of gases.

38
Q

how does sperm cells structure help them perform their function?

A

have a flagellum, so they can swim to the egg

lots of mitochondria to provide energy to swim

the acrosome contains digestive enzymes to enable sperm to penetrate the surface of the egg.

39
Q

how does palisade mesophyll cells structure help them perform their function?

A

many chloroplasts for photosynthesis, absorb a lot of sunlight

thin walls so co2 can diffuse into the cell

40
Q

how does root hair cells structure help them perform their function?

A

large surface area for absorption of mineral ions and water from soil

thin permeable cell wall for entry of water and ions

cytoplasm contains extra mitochondria to provide energy needed for active transport

41
Q

how does guard cells structure help them perform their function?

A

thin outer walls and thickened inner walls force them to bend outwards opening the stomata allowing the leaf to exchange gases for photosynthesis

42
Q

what is a tissue?

A

a group of cells that are specialised to work together to carry out a particular function, a tissue can contain more than one type of cell

43
Q

name 2 examples of animal tissues

A

muscle tissue and cartilage

44
Q

name 2 types of plant tissues

A

xylem tissue and phloem tissue

45
Q

what is an organ?

A

is a group of different tissues that work together to perform a particular function

46
Q

what is a example of an organ?

A

the lungs have squamous epithelial tissues, ciliated epithelia tissue and vascular and elastic connective tissue.

47
Q

what is an organ system?

A

organs that work together to make up an organ system, each system has a particular function

48
Q

what are 2 examples of an organ system?

A

the respiratory system

the circulatory system

ocr a level biology (17 decks)

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