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Biology > Cell Division,cell Diversity And Cellular Organisation 2.16 > Flashcards

Cell Division,cell Diversity And Cellular Organisation 2.16 Flashcards

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1
Q

State two processes that occur in a cell during INTERPHASE to prepare for a meiotic division

(2marks)

A
  • DNA replication
    -synthesis of organelles

(Other marking points: respiration, synthesis of proteins)

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2
Q

What is interphase?

A

Phase of cell cycle where the cell is not dividing - it is subdivided into growth and synthesis phases
Consists of G1phase , S phase and G2 phase

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3
Q

What events happen within the cell during G1?

A

-Cell growth and increase in size
-Transcription of genes to make RNA occurs
-Organelles duplicate
-Biosynthesis e.g. protein synthesis
-the p53 (tumour suppressor ) gene helps control this phase

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4
Q

What events within the cell happen during S phase?

A

-every molecule of DNA is replicated
-when all chromosomes have been duplicated each one consists of a pair of identical sister chromatids

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5
Q

What happens within the cell during G2 phase?

A

-cells grow
-chemicals ensure the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in the formation of the spindle

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6
Q

What is cytokinesis?

A

Cytoplasmic division following nuclear division, resulting in 2 new daughter cells

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7
Q

What are the cell cycle checkpoints?

A

MAIN CHECKPOINTS
- G1/S checkpoint also called restriction point
-G2/M checkpoint

OTHER CHECKPOINTS
-one halfway through mitosis
-one in early G1

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8
Q

List the purpose of checkpoints during the cell cycle

A

-to prevent uncontrolled cell division that would lead to tumours (cancer)
-to detect and repair damage to DNA
-they also ensure that the cell cycle cannot be reversed and that DNA is only replicated once during each cell cycle

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9
Q

What happens during the G0 phase?

A

-cells may undergo apoptosis (programmed cell death ), differentiation or senescence (ageing)
-some types of cells (e.g neurones) remain in this phase for a very long time or indefinitely

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10
Q

When does G0 phase happen?

A

-it is a resting phase triggered during early G1 at the restriction point by a checkpoint chemical
-some cells e.g. epithelial cells lining the gut do not have this phase

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11
Q

What is the importance of mitosis ?

A

-growth
-tissue repair
-asexual reproduction

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12
Q

What is the importance of meiosis ?

A

-the production of haploid cells
-genetic variation (by independent assortment and crossing over)

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13
Q

What is the function of erythrocytes ?

A

-red blood cells
-comes from bone marrow
-carry oxygen from the lungs to respiring cells

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14
Q

How are erythrocytes adapted to their function ?

A

-red blood cells are very small around 7.5 μm in diameter , so they have a large SA/V ratio -so oxygen can diffuse across their membranes and easily reach all regions inside the cell
-biconcave shape increases SA/V ratio
-flexible- due to a well developed cytoskeleton , they can travel through narrow capillaries
-most of their organelles are lost at differentiation they have no nucleus , mitochondria , endoplasmic reticulum and very little cytoplasm- provides more space for haemoglobin

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15
Q

When is haemoglobin synthesised in erythrocytes?

A

-it is synthesised in immature erythrocytes , whilst they still have their nucleus ,ribosomes and rough endoplasmic reticulum

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16
Q

What is the function of neutrophils?

A

-a type of white blood cells
-ingest invading pathogens
-attracted to and travel towards infection sites by chemotaxis
-have many lysosomes
-comes from bone marrow

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17
Q

How are spermatozoa adapted ?

A

-sperm cells have many mitochondria carry out respiration. The ATP provides energy for the undulipodium (tail ) to move and propel the cell to the ovum
-small but long and thin so they can move easily
-once it reaches ovum enzymes are released from the acrosome to digest the outer protective covering of the ovum, allowing the sperm head to enter the ovum
-the head on the sperm contain the haploid male gamete nucleus and very little cytoplasm

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18
Q

What are epithelial cells?

A

-lining tissue
-squamous epithelial cells are flattened in shape
-many of the cells in epithelium have cilia

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19
Q

What is the function of a palisade cell?

A

Photosynthesis

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20
Q

Adaptions of palisade cell

A

-long and cylindrical-so they pack together quite closely but with little space between them for air to circulate. Carbon dioxide in these air spaces diffuse into the cells
-they have a large vacuole so the chloroplasts are positioned nearer to the periphery of the celll, this reduces diffusion distance for carbon dioxide
-contain many chloroplasts
-contain cytoskeleton threads and motor proteins to move the chloroplasts -nearer to the upper surface of the leaf when the sunlight intensity is low but further down when it is high

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21
Q

Can guard cells carry out photosynthesis?

A

They contain chloroplasts however they cannot carry out photosynthesis as they do not have the enzymes needed for the second stage of the process

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22
Q

How do guard cells work?

A

-light energy is used to produce ATP
-the ATP actively transports potassium ions from surrounding epidermal cells into the guard cells, lowering water potential
-water enters the guard cells from neighbouring epidermal cells by osmosis
-the guard cells swell , but at the tips the cellulose cell wall is more flexible and it is more rigid where it is thicker. The tips bulge and the stoma enlarges
-as these stomata open air can enter the spaces within the layer of cells beneath the palisade cells
-gaseous exchange can occur -carbon dioxide will diffuse into the palisade cells
-oxygen produced during photosynthesis can diffuse out of the palisade cells into the air spaces and out through the open stomata.Water vapour also exits through the stomata

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23
Q

What are root hair cells and some of their adaptions?

A

-epidermal cells on the outer layer of young plant roots
-the hair like projections greatly increases the surface area for absorption of water and mineral ions from the soil
-mineral ions are actively transported into the root hair cells lowering the water potential within them this causes water to follow by osmosis
-root hair cells have special carrier proteins in the plasma membranes in order to actively transport mineral ions in
-cells also produce ATP for active transport

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24
Q

Define a tissue

A

A group of similar cells working together to perform a certain function

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25
Q

What are the four main types of animal tissue?

A

-epithelial
-connective
-muscle
-nervous

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26
Q

List parts of the human body where you would find epithelial tissue

A

Skin
Blood vessels
Heart chambers
Walls of organs

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27
Q

What are some characteristics of epithelial tissue?

A

-it is made up almost entirely of cells
-the cells are very close to each other they form continuous sheets. Adjacent cells are bound together by lateral contacts such as tight junctions and desmosomes
-contain no blood vessels. Cells receive nutrients by diffusion from tissue fluid in the underlying connective tissue
-some have smooth surfaces. But others have projections either cilia or microvilli
-short cell cycles
-specialised to carry out its functions of protection, absorption , filtration , excretion and secretion

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28
Q

What is connective tissue?

A

-they hold structures together and provides support
-consists of a non-living extracellular matrix containing proteins (collagen and elastin) and polysaccharides. The matrix separates the living cells within the tissue and enables it to withstand forces such as weight
-examples in body- blood , bone, cartilage , tendons and ligaments

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29
Q

What is cartilage?

A

A connective tissue

30
Q

What is the difference between chondroblasts and chondrocytes?

A

-chondroblasts are immature cells in cartilage they can still divide by mitosis and secrete the extracellular matrix
-chondrocytes are mature cells in cartilage chondroblasts become these when they have synthesised their matrix

31
Q

What are the three types of cartilage?

A

-hyaline cartilage: forms the embryonic skeleton, found in the nose ,trachea and covers the end of long bones in adults
-fibrous cartilage:occurs in discs between vertebrae in the backbone and in the knee joint
-elastic cartilage: makes up the outer ear (pinna) and the epiglottis

32
Q

Describe muscle tissue

A

-well vascularised(many blood vessels)
-muscle fibres(cells) are elongated and contain special organelles called myofilaments made of the proteins actin and myosin
-myofilaments allow the muscle tissue to contract

33
Q

List three types of muscle tissue

A

-skeletal muscle:packaged by connective tissue sheets, joined to bones by tendons. When these muscles contract they cause bones to move
-cardiac muscle:makes up the walls of the heart and allows the heart to beat and pump blood
-smooth muscle: occurs in the walls of intestine , blood vessels , uterus and urinary tracts. It propels substances along these tracts.

34
Q

Define an organ

A

A collection of tissues working together to perform the same function

35
Q

What are the 4 main stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

36
Q

During mitosis what happens within the cell during Prophase?

A

-chromosomes (that have replicated during S phase of interphase) condense
-the nuclear envelope breaks down
-the centriole in animal cells divides and 2 new daughter centrioles move to opposite poles of the cell
-cytoskeleton protein (tubulin) threads form a spindle between these centrioles. In plants cells tubulin threads are formed from the cytoplasm

37
Q

During mitosis what events happen within the cell during metaphase ?

A

-the pairs of chromatids attach to the spindle fibres at the equator region
-they attach by their centromeres

38
Q

During mitosis what events happen in the cell during anaphase?

A

-the centromere of each pair of chromatids split
-spindle fibres , pull each sister chromatid of a pair , in opposite directions , towards opposite poles

39
Q

During mitosis what happens in the cell during telophase?

A

-the separated chromosomes reach the poles
-a new nuclear envelope forms around each set of chromosomes
-the cell now contains 2 nuclei each genetically identical to each other and to the parent cell from which they arose

40
Q

What happens during cytokinesis?

A

Once mitosis is complete the cell splits in 2 , so that each new cell contains a nucleus

IN ANIMAL CELLS- the plasma membrane folds inwards and ‘nips in’ the cytoplasm

IN PLANT CELLS- an end plate forms where the equator of the spindle was and new plasma membrane and cellulose cell-wall material are laid down on either side along this end plate

41
Q

Define homologous chromosomes

A

-matching chromosomes ,containing the same genes at the same place (loci). They may contain different alleles for some of the genes

42
Q

Define meiosis

A

-type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell

43
Q

Define mitosis

A

-type of nuclear division that maintains the chromosome number, each new daughter cell contains the same genetic information as the parent cell. They are also genetically identical to each other

44
Q

What are the main stages of meiosis ?

A

FIRST MEIOTIC DIVISION
-Prophase 1, Metaphase 1, Anaphase 1, Telophase 1

SECOND MEIOTIC DIVISION
-Prophase 2, Metaphase 2, Anaphase 2, Telophase 2

45
Q

During meiosis what happens during Prophase 1?

A

-the chromosomes condense
-the nuclear envelope breaks down , and spindle fibres of tubulin protein form from the centriole in animal cells
-the chromosomes come together in their homologous pairs
-CROSSING OVER occurs where non-sister chromatids wrap around each other and may swap sections so that alleles are shuffled

46
Q

During meiosis what happens during metaphase 1?

A

-the pairs of homologous chromosomes , still in their crossed over state , attach along the equator of the spindle
-each attach to a spindle fibre by its centromere
-Idependent assortment 1 occurs- homologous pairs are arranged randomly with members of each pair facing opposite poles of the cell

47
Q

During meiosis what happens during anaphase 1?

A

-members of each pair of homologous chromosomes are pulled apart by spindle fibres
-the centromeres do not divide and each chromosome consists of 2 chromatids
-the crossed-over areas separate from each other , resulting in swapped areas of chromosome and allele shuffling

48
Q

During meiosis what happens during telophase 1?

A

-2 new nuclear envelopes form around each set of chromosomes and then the cell divides by cytokinesis. Then there is a short interphase when chromosomes uncoil
-cell contains 23 chromosomes and 46 chromatids

-most plant cells go straight from anaphase 1 into prophase 2

49
Q

During meiosis what happens during prophase 2?

A

-if nuclear envelopes had reformed, they now break down
-the chromosomes coil and condense each consisting of 2 chromatids
-chromatids of each chromosome are no longer identical due to crossing over in prophase 1
-spindles form

50
Q

During meiosis what happens during metaphase 2?

A

-the chromosomes attach by their centromere to the equator of the spindle
-the chromatids of each chromosome are randomly arranged (independent assortment 2)
-the way that they are arranged will determine how the chromatids are separated during anaphase

51
Q

During meiosis what happens during anaphase 2?

A

-the centromeres divide
-the chromatids of each chromosome are pulled apart by spindle fibres to opposite poles

52
Q

During meiosis what happens during Telophase 2?

A

-nuclear envelopes form around each of the 4 haploid nuclei
-IN ANIMALS -the 2 cells now divide to give 4 haploid cells
-IN PLANTS- a tetrad of 4 haploid cells is formed

53
Q

What are the 2 types of vascular tissue in a plant ?

A

-xylem
-phloem

54
Q

What is the xylem?

A

-tissue that carries water and mineral ions from the roots to all parts of the plant

55
Q

What is the phloem ?

A

-tissue that carries food and nutrients from the leaves to other parts of the plant

56
Q

How are xylem produced from meristem?

A

-lignin is deposited in the cell walls of cambium cells to reinforce and waterproof them, this also kills them
-the ends of the cells break down so that the xylem forms continuous columns with wide lumens to carry water and dissolved minerals

57
Q

How are phloem sieve tubes produced from meristem ?

A

-sieve tubes lose most of their organelles and sieve plates develop between them
-companion cells retain their organelles and continue metabolic functions to provide ATP for active loading of sugars into the sieve tubes

58
Q

What is the function of a leaf ?

A

Photosynthesis

59
Q

What is the function of a plant root?

A

-anchorage in soil
-absorption of mineral ions and water

60
Q

What is the function of a stem?

A

-support
-transportation of water and minerals
-transportation of products of photosynthesis
-storage of products of photosynthesis

61
Q

What is the function of a flower?

A

-sexual reproduction

62
Q

Define stem cells

A

-an unspecialised cell able to express all of its genes and divide by mitosis, they are a renewing source of undifferentiated cells

63
Q

What are the features of stem cells?

A

-undifferentiated cells
-described as pluripotent
-able to express all their genes
-can divide by mitosis and produce more cells that can differentiate into specialised cells , for growth and tissue repair

64
Q

What are some sources of stem cells?

A

-embryonic stem cells
-stem cells in umbilical-cord blood
-adult stem cells
-induced pluripotent stem cells (iPS cells) developed in laboratories

65
Q

In what stage of meiosis does crossing over occur in?

A

-prophase 1

66
Q

In what stages of meiosis does independent assortment occur in?

A

-metaphase 1 and 2

67
Q

Describe the formation of xylem tissue and phloem tissue
Using the key terms : xylem, lignin, phloem, sieve tube elements

A

Meristem cells in plants are used to generate new plant tissue. When XYLEM tissue is formed LIGNIN impregnates the cell walls, making them impermeable to water. All the cytoplasm is lost.
When PHLOEM tissue is formed the cytoplasm remains, but the SIEVE TUBE ELEMENTS become elongated and lose most of their cytoplasm.

68
Q

What can a microtubule be prevented from functioning by?

A

A respiratory inhibitor

69
Q

What happens if damaged DNA is detected at the G2 checkpoint?

A

-the cell cycle is halted and the cell tries to repair the damage

70
Q

True or false adult stem cells are totipotent?

A

False

Biology (10 decks)

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