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Foundations > Cell division > Flashcards

Cell division Flashcards

1
Q

The Eukaryotic Cell cycle

A

-Cells reproduce by duplicating their contents and splitting into two new daughter cells

-Nuclear/ cytoplasmic division = m-phase (mitosis/cytokinesis) between each m-phase= interphase

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2
Q

What is interphase/ importance

A

preparation for cell division in a sequence with checkpoints

important as: Prevents uncontrolled cell division, Detects and repairs damage to DNA, makes sure only one set of DNA is replicated, Cell cycle only progresses in one direction and does no go backwards

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3
Q

How are tumours supressed and made?

A

Hayflick Constant = Average number of Cell divisions if uncontrolled then tumours occur/ greater proportion become tumour as uncontrolled

Proto- oncogenes regulate cell division by coding for proteins that regulate growth if mutate = oncogenes- cells fail to undergo apoptosis and instead keep on dividing – TUMOUR

P53 Gene (Tumour suppressor Gene) -Triggers two main checkpoints

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4
Q

Prokaryotic Cell Cycle

A

-Binary Fission
-Cell grows to limit in size and splits in two – before divides DNA rep
-DNA pulled to opp poles and cell wall forms separating bacterial cell
-Mitochondria and Chloroplasts also rep by Binary Fission

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5
Q

Interphase sequence

A

GO
G1
S
G2
M - Mitosis

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6
Q

M-Phase

A

-Checkpoint chemical triggers condensation of Chromatin
-½ through, metaphase ensures cell ready to undertake mitosis

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7
Q

Events within the cell M-Phase

A

-Cell growth stops
-PMAT
-Cytokinesis

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8
Q

G0 Phase

A

-Resting phase triggered early in G1 at restriction point by checkpoint chemical
-Some cells i.e epithelial cells lining the gut don’t have

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9
Q

Events within the cell G0 Phase

A

-Cells may undergo apoptosis/differentiation/senescence
-Some cells i.e neurones stay in phase indefinitely or for long periods of time

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10
Q

G1 Phase – Growth

A
  • Checkpoint ensures cell ready to go into S phase and begin DNA synthesis
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11
Q

Events within the cell G1 Phase – Growth

A

-Cells grow and increase in size
-Transcription
-Organelle duplicates
-Biosynthesis (i.e protein synthesis) including making enzymes for DNA rep in S phase
-P53 (tumour suppressor) gene helps control phase

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12
Q

S Phase – Synthesis

A

-Chromosomes are unwound, DNA is diffuse = all DNA replicated
-House keeping genes (active in all cells) rep first
-Inactive rep last

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13
Q

Events within the cell S Phase – Synthesis:

A

-Once entered committed to cell cycle
-DNA rep
-Chromosomes = chromatids
-Rapid and as DNA base pairs more susceptible to mutations- reduces the chance

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14
Q

G2 Phase:

A

Special chemicals ensure cell is ready for mitosis by stimulating proteins involved in making chromosomes condense and in formation of spindle

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15
Q

Events within the cell G2 Phase:

A

-Cells Grow

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16
Q

Mitosis significance

A

-Asexual reproduction
-Growth
-Tissue Repair

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17
Q

Mitosis significance Asexual reproduction

A

-Single celled Protoctists: Amoeba and Paramecium divide by mitosis to produce two identical individuals.
-Fungi reproduce asexually
-Female Sharks when in captivity – Parthenogenesis ( Humans can’t do this as we have too many genes that need to be rep from both the sperm ( accounts for 58% of DNA) and egg ( has mitochondria DNA) so need both – also genetic variety)

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18
Q

Mitosis significance Growth

A

All multicellular organisms grow by producing cells that are genetically identical and to parent cell in which they arose

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19
Q

Mitosis significance Tissue Repair

A

Wounds heal when growth factors secreted by White Blood Cells and damaged cells of Blood vessel walls stimulate the proliferation of endothelial and smooth muscled cells to repair damage to blood vessels

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20
Q

Prophase events

A

-Chromosomes from S-phase shorten and thicken as DNA super coils
-Nuclear envelope breaks down
-Centriole in animals (found in centrosome) divides and two new daughter centrioles move to opp poles
-Cytoskeleton thread (tubulin) form spindle between centrioles. Spindle – 3d are like lines of longitude on globe
-Plant cell tubulin formed from cytoplasm

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21
Q

Metaphase events

A

-The pairs of Chromatids attach to spindle threads at equator region
-They attach by centromeres

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22
Q

Anaphase events

A

-Centromere of each chromosome splits
-Non – Kinetochore microtubules push poles apart
-Kinetochore microtubules push chromosomes towards poles
-Motor proteins walk along threads pulling each chromatid of a pair in opp directions

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23
Q

Telophase events

A

-Separated chromosome reach poles and start to decondense
-New nuclear envelope forms around each new set of chromosomes and nucleolus reappears
-Cell contains 2 new nuclei genetically similar

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24
Q

Cytokinesis

A

Once Mitosis is complete cell splits in two so each new cell contains a nucleus

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25
Q

Cytokinesis animal vs plant

A

-Animal cell – plasma membrane folds inwards and ‘nips in’ cytoplasm
-Plant Cell – end plate forms where equator of spindle was, cell wall and plasma membrane forms on either side of this end plate

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26
Q

What part of the plant cannot undergo mitosis

A

Plant Palisade Mesophyll cells can’t undergo Mitosis as they are differentiated, have a large vacuole. Have rigid cell walls

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27
Q

Meiosis

A

type of nuclear division which results in formation of cells containing half the number of chromosomes as opposed to parent Cell.

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28
Q

Meiosis significance

A

-Increases Genetic Variation as combines Genetic info of two unrelated individuals by Fertilisation

-Genetic Variation: Increases a species chance of survival in change of environment, as some have will be better adapted

-For Sexual Reproduction must have haploid gametes, so when two gamete nucleui fuse during Fertilisation, a diploid zygote is produced and normal chromosome number is maintained during the generations

-You only need half the amount of 46 chromosomes in egg/ sperm as when fertilised that’s when get other half

-Zygote divides by mitosis and forms by meiosis by primary spermatocyte (sperm) or primary oocyte (egg)

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29
Q

Haploid

A

One set of Chromosomes – half the normal amount of a Diploid

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30
Q

Meiosis (detailed description)

A

means ‘reduction’ and occurs in diploid germ cells to produce haploid gametes. Diploid germ Cells undergoing meiosis are in specialised organs called gonads – ovaries and testes – these cells have been in interphase before entering meiosis

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31
Q

Homologous Chromosomes

A

-In body 46 Chromosomes, half from female half from male = can form matching pairs = the same genes at the same places on chromosomes
-Although have the same genes may have differing alleles(variants) for gene

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32
Q

When does meiosis occur

A

Before meiosis, in S phase, each chromosome duplicated and replicated – two sister chromatids. In meiosis chromosomes line up in homologues pairs

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33
Q

Stages of Meiosis

A

-2 divisions, 4 stages
-PMAT 1 then may have short interphase then PMAT 2 then maybe cytokinesis

34
Q

Prophase 1events

A

-Chromosome condenses; DNA supercoils
-Nuclear envelope breaks down, spindle threads form
-Chromosomes come together in homologous pairs – each member – two chromatids
-Crossing over may occur when two non-sister chromatids wrap around each other and may swap sections, so alleles are shuffled
-Point of breakage= chiasmata

35
Q

Metaphase 1events

A

-Homologous chromosomes attach along equator
-Each attaches to spindle thread by centromere
-Independent assortment: Each of the pairs are placed randomly
-Way they are placed determines how wills segregate independently in Anaphase

36
Q

Anaphase 1events

A

-Pairs pulled apart by motor proteins that drag them to opp poles
-Centromere does not divide, each chromosome = two chromatids
-Crossed over areas separate resulting in swapped areas and allele shuffling

37
Q

Telophase 1 events

A

-Animal – two nuclear envelopes and cell divides by cytokinesis. Then short interphase where chromosomes uncoil
-Each nucleus half the number of chromosomes but each chromosome – two chromatids
-Plant cells skip this stage

38
Q

Prophase 2 events

A

-If nuclear envelope formed – now break down
-Chromosome’s coil and condense
-Chromatids no longer identical due to crossing over
-Spindles form

39
Q

Metaphase 2 events

A

-Chromosomes attach at centromere at equator
-Chromatids randomly arranged
-Arrangement determines how chromatids separate in anaphase

40
Q

Anaphase 2 events

A

-Centromeres divide
-Chromatids pulled apart and dragged to opp poles
-Chromatids randomly segregated

41
Q

Telophase 2 events

A

-Nuclear envelope forms around 4 new haploid nuclei
-Animals – cell divides to give 4 haploid cells
-Plant – tetrad of four haploid cells forms

42
Q

How is Genetic Variation achieved in meiosis

A

-Crossing over in Prophase 1 shuffles alleles
-Independent assortment in Metaphase 1 leads random distribution of maternal/paternal chromosomes
-Independent assortment Anaphase 2 = full random distribution of genetic material
-Haploid gametes produced can undergo random fusion of another organism of the same species

43
Q

The need for Cell differentiation and Specialisation:

A

-Single celled organisms have a large SA: V – oxygen can easily diffuse into their membrane and waste products easily out
-Multicellular organisms have a small SA: V – most cells are not inContact with external environment = need specialised cells to carry out functions

44
Q

Differentiation

A

Stem cells become specialised into different types of cells

45
Q

Differentiation process from zygote

A

-Zygote forms by fertilisation- not specialised as all its genes in genome can be expressed – can divide by mitosis = A stem cell

-After several miotic divisions an embryonic cell forms containing many undifferentiated embryonic stem cells

-Embryonic cells differentiate ( become different) as genes are turned on and off and other genes may be expressed more so that:
Proportions of different organelles differ from those of other cells
Shape of cell changes
Some of cells content changes

46
Q

specialised animal Cells:

A

-Erythrocytes and Neutrophils (Both have differing functions, but both derived from stem cells in bone marrow)
-Spermatozoa
-Epithelial Cells – lines alveoli and capillaries and intestines

47
Q

How are erythrocytes adapted

A

carry O2 from lungs to respiring cells
-Small and biconcave so have small SA: V – easy diffusion
-Flexible – twist and turn through capillaries
-No nucleus; mitochondria; ER and little cytoplasm = more space for haemoglobin molecules

48
Q

How are neutrophils adapted

A

(50% of white blood cells in body) – ingest invading pathogens

-2x size of erythrocytes and contains multilobed nucleus
-Attracted to and travel towards infection sites by chemotaxis
-Function to ingest bacteria and some fungi by phagocytosis

49
Q

How are Spermatozoa adapted

A

-Lots of mitochondria for aerobic respiration. ATP provides energy for undulipodia to move and propel towards ovum
-Small/long/thin – move easily
-Once reaches ovum enzymes released from acrosome (specialised lysosome.) Enzymes digest protective covering of ovum allowing sperm head to enter
-Head contains haploid male gamete nucleus and little cytoplasm

50
Q

How are Epithelial Cells adapted

A

-Squamous epithelial cells flattened in shape –Many have cilia

51
Q

Specialised plant cells

A

-Palisade cells -within leaves and adapted for photosynthesis
-Guard cells -within lower epidermis of leaf that contain chloroplast. Can’t carry out photosynthesis as don’t have enzymes for second half
-Root hair cells – epidermal cells on outer-layer of young plant roots

52
Q

How are Palisade cells adapted

A

-Long/cylindrical – packed closely but with little space for air to circulate for CO2 to diffuse into cells
-Large vacuole so chloroplast near periphery of cell, reducing diffusion distance for CO2
-Contain many chloroplasts for photosynthesis
-Contain cytoskeleton threads and motor proteins to move chloroplasts – near upper half when sun low and near bottom when high

53
Q

How are guard cells adapted

A

-Light energy used to produce ATP
-ATP – active transport k+ from epidermal cells into Guard cells lowering their WP
-Water now enters from neighbouring epidermal cells by osmosis
-Guard cells swell but at the tips the cell wall becomes more flexible and more rigid where thicker. The tips bulge and stoma enlarges (gap between them)
-As stomata opens air can enter spaces underneath palisade cells
-Gaseous exchange can occur and CO2 will diffuse into palisade cells. As used for photosynthesis a steep conc gradient maintained
-O2 produced during photosynthesis can diffuse out of palisade cells and into air spaces through open stomata

54
Q

How are root hair cells adapted

A

-Hair like projection increases SA for absorption of water and mineral ions (i.e nitrates) from soil in which it projects
-Mineral ions actively transported into root hair cells lowering WP and causing water to follow by osmosis down WP gradient
-Root hair cells have special carrier proteins in plasma membrane to actively transport mineral ions in
-Cells also produce ATP needed for active transport

55
Q

Tissue

A

a group of cells that work together to perform a specific function/functions

56
Q

Animal Tissues

A

-Epithelial/ lining tissue
-Connective tissue – these hold structures together/ provide support i.e blood bone; cartilage
-Muscle tissue – made of cells that are specialised to contract and cause movement
-Nervous Tissue – made of cells specialised to conduct electrical impulses

57
Q

Epithelial tissue

A

Covers and lines free surfaces in the body: Skin, Cavities of digestive/respiratory system (gut and airways), blood vessels, heart chambers, walls of organs

58
Q

Epithelial tissue adaptions

A

-Made up of almost entirely cells
-Cells close and form continuous sheets. Adjacent cells bound by lateral contacts i.e. tight junctions and desmosomes
-No blood vessels within tissue – cells receive nutrients by diffusion from tissue fluid in the underlying connective tissue
-Some have smooth surfaces, some have cilia (propel substance/receive chemical signals) /microvilli (extensions of Plasma membrane to increase SA)
-Have short cell cycles and divide up to two/ three times a day to replace worn/damaged tissue
-Specialised to carry out its functions of: protection, absorption, filtration, excretion, secretion

59
Q

Connective tissue

A

-Widely distributed in the body,
-consists of a non-living extracellular matrix containing proteins (Collagen/elastin) and polysaccharides (hyaluronic acid – traps water) – matrix separates living cells in the tissue and enables it to withstand forces and weight
e.g. Blood, bone, cartilage, tendons, ligaments, skin

60
Q

Cartilage

A

-Immature cells in cartilage called Chondroblasts – divide by mitosis and excrete extracellular matrix
-Once matrix has been synthesised, Chondroblasts mature
-Less active Chondrocytes maintain the matrix

61
Q

3 types of Cartilage

A

Hyaline – forms embryonic skeleton, covers the end of long bones in adults, joins ribs to the sternum, found in the nose in the trachea and larynx (voice box)

Fibrous – occurs in discs in between vertebrae in backbone (spine) and in knee joint

Elastic – makes up outer ear (pinna) and epiglottis (flap that covers over larxynx when you swallow)

62
Q

Muscle Tissue

A

-Well vascularized ( has many blood vessels)
-Cells are called fibres: elongated and contain special organelles called microfilaments, made of proteins actin and myosin – allow muscle tissue to contract

63
Q

Functions of muscle

A

Allow movement, there are three types:

Skeletal muscles – packaged by connective tissue sheets, joined to bones by tendons – when contact cause bones to move

Cardiac muscles – makes up wall of heart and allows heart to beat and pump

Smooth muscles – occur in walls of intestine, blood vessels, uterus and urinary tracts also propels substances along these tracts

64
Q

Plant tissues

A

-Epidermal tissue
-Vascular tissue
-Meristematic tissue

65
Q

Adaptions of Epidermal tissue

A

-Equivalent to epithelial in animals
-Consists of flattened cells, that apart from guard cells, lack chloroplasts
-Form a protective covering over leaves/stems/roots
-Some have walls impregnated with waxy cuticle – reduces water loss of plants in warm places

66
Q

Adaptions of vascular tissue

A

Concerned with transport two types: xylem/phloem present in vascular bundles

-Xylem – carry water and minerals from roots to all parts of the plant

-Phloem Sieve Tubes – transfer the products of photosynthesis (mainly sucrose sugar) in solution, from leaves to parts of the plant that don’t photosynthesise i.e. roots, flowers, growing shoots

67
Q

Meristematic tissue

A

-Contains Stem Cells
-From tissue that all other tissues are derived from by cell differentiation
-Found at root and shoot tips/ cambium of vascular bundles – meristems
-Large vacuole and rigid cell walls stop cell from dividing – plants need to grow and produce new cells – new cells arise from meristem by mitosis

68
Q

Cells in Meristems adaptions

A

-Have thin walls containing little cellulose
-Don’t have chloroplasts
-Don’t have large vacuole
-Can divide by mitosis and differentiate into other types of cells

69
Q

How the Xylem derives from Meristems

A

Some cambium cells differentiate into xylem vessels:

-Lignin ( a woody substance) deposited in their cell wall to reinforce/ waterproof them – however kills cells
-End of cells break down so xylem forms continuous columns with wide lumen to carry water and dissolved minerals

70
Q

How the phloem derives from Meristems

A

Other cambium cells differentiate into Phloem sieve tubes/companion cells
-Sieve tubes lose most of their organelles and sieve plates develop in-between
-Companion cells retain organelles and continue metabolic pathways to provide ATP for active loading of sugar into the sieve tubes

71
Q

Plant organs

A

-Leaf - photosynthesis
-Root – support, holds leaves up so exposed to sunlight, Transportation of water minerals, Transportation of products of photosynthesis, storage of products from photosynthesis
-Flower – sexual reproduction (could be considered organ system as has different organs within them i.e., petals, sepals, ovaries, stamens

72
Q

Organ

A

a collection of tissues working together to perform the same function

73
Q

Organs in animals

A

-Circulatory system – heart and blood vessels – transport to and from cells
-Nervous system – brain, spinal cord, nerves – communication control and coordination
-Urinary system – kidney, ureters, bladder – excretion and osmoregulation

74
Q

Stem cells how are they adapted so that they have become important in medical research

A

-Undifferentiated cells capable of becoming any type of organism
-Pluripotent
-Able to express their genes
-Divide by mitosis and provide more cells that can differentiate into specialised cells for growth and tissue repair

75
Q

Sources of stem cells

A

-Embryonic stem cells – present in an early embryo formed when a zygote begins to divide
-Stem Cells in umbilical cord blood
-Adult Stem cells (in infants/children) found on developed tissue i.e. blood, brain, muscle – repair system as renewing undifferentiated cells
-Induced Pluripotent stem cells (IPS) developed in laboratories by reprogramming differentiated cells to switch on certain genes and become undifferentiated

76
Q

Potential uses in research and medicine

A

-Bone marrow transplants
-Drug research
-Developmental Biology

77
Q

Stem cells Bone marrow transplants

A

-Treat diseases in blood (sickle cell amenia) and immune system (SICD)
-Used to restore patients blood system after treatment for specific types of cancer, where cells obtained from treatment are taken, stored, put back after treatment

78
Q

Stem cells Drug research

A

If stem cells can develop into human tissue, drugs can be tested n it rather than on animal tissue

79
Q

Stem cells Developmental Biology

A

Understand how multicellular organisms, grow, develop, and mature

-Study how cell makes particular cell types and what happens when they’re diseased
-If they can extend the capacity embryos have for growth/tissue repair later into life

80
Q

Stem cells Repair/ replacement of tissues

A

Hard to culture Stem cells in lab so research on going. Also need to find out cell signalling molecules needed to direct the differentiated stem cells into other cell types
-Stem Cells used to treat mice with type 1 diabetes by programming IPS cells to become pancreatic Beta Cells – research still underway for humans
-Bone marrow stem cells into liver cells to treat liver disease
-Stem cells for nerve tissue treat Alzheimer’s/ Parkinson’s
-Regenerative Medicine – SC populate bioscafold of organ and then be directed to grow into specific organ for transplanting

Foundations (5 decks)

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