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Cell division Flashcards

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Biology 101 flashcards
1
Q

what is the cell cycle?

A

-regulated cell division with intermediate growth periods
1. interphase
2. mitosis or meiosis (nuclear division)
3. cytokinesis (cytoplasmic division)

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2
Q

what happens in interphase?

A

-G1 = cell synthesizes proteins for replication e.g. tubulin spindle fibres and cell size doubles
-S = DNA replicates -> chromosomes consist of 2 sister chromatids joined at a centromere
-G2 = organelles divide

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3
Q

what’s the purpose of mitosis?

A

produces 2 genetically identical daughter cells for:
-growth
-cell replacement/tissue repair
-asexual reproduction

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4
Q

stages of mitosis

A

PMAT

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5
Q

outline what happens in prophase

A

-chromosomes condense, becoming visible
-centrioles move to opposite poles of the cell and mitotic spindle fibres form
-nuclear envelope breaks down - releases chromosomes into cytoplasm

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6
Q

outline what happens in metaphase

A

-sister chromatids line up at equator

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7
Q

outline what happens in anaphase

A

requires energy from ATP hydrolysis
-spindle fibres contract causing centromeres to divide
-sister chromatids separate into 2 distinct chromosomes and are pulled to opposite poles (v-shaped now)
-spindle fibres break down

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8
Q

outline what happens in telophase

A

-chromosomes decondense becoming invisible again
-new nuclear envelope forms around each new set of chromosomes = 2 nuclei, each with 1 copy of each chromosome

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9
Q

what happens during cytokinesis?

A

-CSM cleavage furrow forms
-contractile division of cytoplasm

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10
Q

how is the cell cycle regulated?

A

-there are checkpoints regulated by cell-signalling proteins, to ensure damaged cells don’t progress to the next stage of the cell cycle
-cyclin-dependent kinase (CDK) enzymes phosphorylate proteins that initiate next phase of reactions

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11
Q

describe what happens at each key checkpoint in the cell cycle

A

-between G1 and S, cell checks for DNA damage (via action of p53 (a protein that acts as a tumour suppressor - keeps cells from dividing and growing in an uncontrolled way). After restriction point (once a cell passes this point it is obligated to continue and undergo mitosis), cell enters cycle

-between G2 and M, cell checks the chromosome replication

-at metaphase checkpoint, cell checks that sister chromatids have attached to the spindle correctly

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12
Q

what is meiosis?

A

-type of cell division
-produces 4 genetically different haploid daughter cells
-cells with half the number of chromosomes found in parent cells
-they are called gametes

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13
Q

what happens during meiosis I?

A

-homologous chromosomes pair to form bivalents
-crossing over (exchange of sections of genetic material) occurs at chiasmata
-cell divides into 2 - homologous chromosomes separate randomly - each cell contains either maternal or paternal copy

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14
Q

what are homologous chromosomes?

A

-a pair of chromosomes with same genetic info - 1 maternal, 1 paternal
-some alleles may be the same while others are different

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15
Q

what happens during meiosis II?

A

-independent segregation/assortment of sister chromatids
-each cell divides again, producing 4 haploid cells

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16
Q

how does meiosis introduce genetic variation?

A

-crossing over during meiosis I
-independent assortment (random segregation) of homologous chromosomes and sister chromatids
-results in new combinations of alleles

17
Q

how do cells become specialised?

A

-cells undergo a process called differential gene expression
-where some genes are expressed while some are silenced due to cell differentiation mediated by transcription factors - cells produce proteins that determine their structure and function

18
Q

what is a transcription factor?

A

-a protein that controls the transcription of genes so that only certain parts of the DNA are expressed e.g. in order to allow a cell to specialise

19
Q

how do transcription factors work?

A

-move from cytoplasm into nucleus
-bind to promoter region upstream of target gene
-makes it easier or more difficult for RNA polymerase to bind to gene - this increases or decreases rate of transcription

20
Q

what’s a stem cell?

A

-undifferentiated cells that have to ability to divide indefinitely and turn into other specific cell types

21
Q

name and define 4 types of stem cell

A

totipotent - can develop into ANY cell type, including placenta and embryo
pluripotent - can develop into ANY cell type, excluding placenta and embryo
multipotent - can only develop into a few different types of cell
unipotent - can only differentiate into one type of cell

22
Q

uses of stem cells

A

-repair of damaged tissue e.g. cardiomyocytes after myocardial infarction
-drug testing on artificially grown tissues
-treating neurological diseases like Parkinson’s or Alzheimer’s
-researching developmental biology e.g. formation of organs, embryos

23
Q

describe erythrocytes

A

-RBC
-biconcave shape
-no nucleus
-lots of haemoglobin to carry oxygen

24
Q

describe neutrophils

A

-WBC(leukocyte)
-multi-lobed nucleus
-contains many lysosomes (destroy invading cells)
-they engulf foreign material

25
Q

how do specialised cells in the blood form?

A

-multipotent cells in bone marrow differentiate into:

erythrocytes - which have a short lifespan and can’t undergo mitosis because they don’t have nucleus

leukocytes including neutrophils

26
Q

describe the structure of squamous and ciliated epithelia

A

simple squamous epithelium - single smooth layer of squamous cells (thin and flat with round nucleus) fixed in place by basement membrane

ciliated epithelium - made of ciliated epithelial cells (column-shaped with surface projections called cilia that move in a synchronised pattern)

27
Q

describe the specialised structure of a spermatozoa

A

-acrosome in the head to penetrate egg’s outer layer
-many mitochondria - for aerobic resp. ATP provides energy for the tail (undulipodium/flagellum) and propel itself towards ovum
-haploid nucleus so fertilisation restores diploid chromosome number

28
Q

describe the structure and function of palisade cell

A

-specialised to absorb light energy for photosynthesis therefore contain many chloroplasts
-they occupy large SA for smooth gas exchange
-they have thin cell wall for larger penetration of light into cell
-they are long and cylindrical so can be packed closely together but with small air pockets for carbon dioxide to diffuse in

29
Q

describe structure and function of guard cell

A

-form tiny spores called stomata -> they control gas exchange and water loss (transpiration) - when turgid, stoma open and when flaccid, stoma closes
-needs ATP to actively transport potassium ions from surrounding epidermal cells into guard cells, lowering water potential

30
Q

describe structure and function of root hair cells

A

-hair-like projections to increase SA for absorption of water/carrier proteins needed for active transport of mineral ions like nitrates (ATP needed)

31
Q

what are meristems?

A

-totipotent undifferentiated plant cells that can develop into various types of plant cells like phloem and xylem

32
Q

describe structure of a vascular bundle

A

-cambium (meristematic tissue)
-phloem tissue
-xylem tissue

33
Q

describe structure of phloem tissue

A

-sieve tube elements: form a tube to transport sucrose in the dissolved form of sap
-companion cells: involved in ATP production for active loading of sucrose into sieve tubes
-plasmodesmata: gaps between cell walls where the cytoplasm links, allowing substances to flow in

34
Q

describe structure of xylem tissue

A

-vessel elements: lignified secondary walls for mechanical strength and waterproofing; perforated end walls for rapid water flow
-tracheids: tapered ends for close packing; pits for lateral water movement; no cytoplasm or nucleus

35
Q

what are the 3 types of muscle?

A

smooth - walls of blood vessels and intestines
cardiac - exclusively found in the heart
skeletal - attached to incompressible skeleton by tendons

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