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BIOLOGY AS > Mod 2 Chap 6: Cell Division, Diversity & Differentiation > Flashcards

Mod 2 Chap 6: Cell Division, Diversity & Differentiation Flashcards

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1
Q

Describe the cell cycle.🌟

A
  • highly ordered sequence of events
  • takes place in a cell, resulting in division of cell + formation of two genetically identical daughter cells
  • has two main phases (in eukaryotes): interphase, and mitotic (division) phase (= mitosis / meiosis)
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2
Q

Generally describe Interphase.🌟

A
  • long periods of growth and normal working separate divisions where a cell is NOT dividing
  • although aka ‘resting phase’, interphase actually = a v active phase, when cell is carrying out all major functions e.g. Producing enzymes / hormones + preparing cell for division
  • has three stages within itself: G1, S + G2
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3
Q

Describe what occurs in the stage of Interphase as a whole.🌟

A
  • DNA replicated + checked for errors in nucleus
  • protein synthesis occurs in cytoplasm
  • mitochondria grow + divide in plant + agal cell cytoplasm
  • normal metabolic processes of cells occur
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4
Q

Describe what occurs in the separate stages within Interphase.🌟

A

G1 (first growth phase): proteins from which organelles are synthesised are produced + organelles replicate, cell increases in size

S (synthesis phase): DNA replicated in nucleus

G2 (second growth phase): cell continues to increase in size, energy stores increase + duplication of DNA is checked for errors

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5
Q

Generally describe the mitotic phase.🌟

A
  • period of cell division

- two stages of cell division: Mitosis (nucleus divides), and Cytokinesis (cytoplasm divides + two cells produced)

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6
Q

Describe the ‘G0’ phase of the cell cycle.

A
  • phase where cell leaves the cycle (temporarily / permanently)

Reasons this happens:

  • differentiation: a cell specialised to carry out a function is no longer able to divide, as carries out this function indefinitely + does not enter cycle again
  • DNA of cell maybe damaged: meaning it’s no longer viable, damaged cells cannot divide and enters period of permanent cell arrest (G0), normal cells only divide limited no of times before becoming senescent
  • age: ageing = no of senescent cells in body increasing, this then linked w/ age relating diseases e.g cancer / arthritis
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7
Q

Describe how the cell cycle is regulated / controlled.🌟

A
  • needed to ensure a cell only divides when it has grown to right size, replicated DNA is correct + when chromosomes are in correct positions during mitosis, so to ensure fidelity of cell division (creation of tow identical daughter cells)
  • control mechanisms of cell cycle = checkpoints
  • checkpoints monitor whether each phase of cycle is accurately completed before cell progresses to next phase
  • occur variously throughput cycle: end of G1 phase, end of G2 phase, + in mitosis
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8
Q

Describe the importance of mitosis.🌟

A
  • mitosis = term for entire process of cell division in eukaryotic cells
  • refers to nuclear division (essential stage in cell division)
  • ensures both daughter cells produced are genetically identical, each new cell has an exact copy of DNA in parent cell + same no of chromosomes
  • necessary for asexual reproduction (production or genetically identical offspring from one parent in multicellular organisms + eukaryotic single celled organisms. But prokaryotic organisms have no nucleus so reproduce asexually by diff process: binary fission.
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9
Q

Describe what happens with the chromosomes PRIOR to mitosis.🌟

A
  • all DNA in nucleus has to be replicated in interphase before mitosis can occur
  • each DNA molecule (chromosome) converted into two identical DNA molecules called chromatids
  • two chromatids then join at region called centromere, so they can be precisely manoeuvred + segregated equally, one each into the two new daughter cells, during mitosis
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10
Q

Name the main stages of mitosis.🌟

A

4 stages:

  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
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11
Q

Describe the Prophase stage of Mitosis.🌟

A
  • chromatin fibres ( = mix of various proteins + DNA + RNA) coil + condense to form chromosomes
  • nucleolus (area of nucleus responsible for RNA synthesis) disappears + nuclear membrane breaks down
  • protein microtubules form spindle-shaped structures linking poles of cell
  • in animal cells + some plant cells; two centrioles migrate to opposite poles of cell
  • spindle fibres attach to specific areas on centromeres + move chromosomes to centre of cell
  • nuclear envelope has disappeared now
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12
Q

Describe the Metaphase stage of Mitosis.🌟

A
  • chromosomes moved by spindle fibres to form a plane in centre of cell, called metaphase plate, then held in position
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13
Q

Describe the Anaphase stage of Mitosis.🌟

A
  • centromeres holding together chromatid pairs divide
  • chromatids then separated + pulled to opposite poles of cell by shortening spindle fibres
  • ‘V’ shape of chromatids moving towards poles is result of them being dragged by centromeres through the liquid cytosol
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14
Q

Describe the Telophase stage of Mitosis.🌟

A
  • chromatids have now reached poles + now called chromosomes
  • the two new sets of chromosomes assemble at each pole + nuclear envelope reforms around them
  • chromosomes start to uncoil + nucleolus is formed
  • cell division / cytokinesis begins
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15
Q

Generally describe Meiosis.🌟

A
  • gametes are formed by meiosis
  • nucleus (in meiosis) divides to produce 4 daughter cells (gametes)
  • each gamete contains half of chromosome no. of parent cell (it is haploid)
  • Meiosis known as reduction division
  • each nucleus of organism’s cells contains two full sets of genes, so each nucleus gas matching set of chromosomes called homologous chromosomes + so is termed diploid
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16
Q

Describe alleles.

A
  • Diff versions of same gene (aka gene variants)

- the diff alleles of a gene will all have same locus (position on a particular chromosome)

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17
Q

Name and outline the main stages of Meiosis.🌟

A
  • Meiosis involves two divisions: Meiosis 1 and Meiosis 2, each has a single pro, meta, ana and telo phase

Meiosis 1:

  • the reduction division where pairs of homologous chromosomes are separated into 2 cells
  • each intermediate cell only has one full set of genes instead of 2, so cells are haploid

Meiosis 2:

  • second division = similar to mitosis
  • pairs of chromosomes present in each daughter cell are separated, forming 2 more cells
  • so 4 haploid daughter cells produced in total
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18
Q

Describe the Prophase 1 stage of Meiosis 1.🌟

A
  • chromosomes condense, nuclear envelope disintegrates, nucleolus disappears + spindle formation begins (all same as mitosis prophase)
  • also homologous chromosomes pair up, forming bivalents
  • chromosomes moving through liquid cytoplasm as they are brought together results in chromatids entangling = “crossing over”
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19
Q

Describe the Metaphase 1 stage of Meiosis 1.🌟

A
  • same as metaphase in mitosis, except homologous Paris of chromosomes assemble along metaphase plate instead of individual chromosomes
  • orientation of each homologous pair on metaphase plate = random + independent of any other homologous pair
  • maternal / paternal chromosomes can end up facing either pole = called independent assortment, so can result in many diff combinations of alleles facing poles
  • independent assortment of chromosomes in Metaphase 1 results in genetic variation.
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20
Q

Describe the Anaphase 1 stage of Meiosis 1.🌟

A
  • diff from anaphase of mitosis as homologous chromosomes are pulled to opposite poles + chromatids stay joined together
  • sections of DNA on entangled ‘sister’ chromatids now break off + rejoin, which can cause an exchange of DNA
  • points at which chromatids break + rejoin = chiasmata
  • when exchange occurs, recombinant chromatids form, genes exchanged between chromatids
  • genes exchanged may be diff alleles of same gene, so combination” of alleles on recombinant chromatids will be diff from allele combination on either of original chromatids
  • this new combination of alleles makes genetic variation, sister chromatids are no longer identical
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21
Q

Describe the Telophase 1 stage of Meiosis 1.🌟

A
  • essentially same as in mitosis, chromosomes assemble at each pole + nuclear membrane reforms, chromosomes uncoil
  • cell undergoes cytokinesis + divides into 2 cells
  • reduction of chromosome number from diploid to haploid is complete
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22
Q

Describe the Prophase 2 stage of Meiosis 2.🌟

A
  • chromosomes that still consist of two chromatids condense + become visible again
  • nuclear envelope breaks down + spindle formation begins
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23
Q

Describe the Metaphase 2 stage of Meiosis 2.🌟

A
  • differs from metaphase 1, as individual chromosomes assemble on metaphase plate, as in metaphase in mitosis
  • due to crossing over, chromatids no longer identical so there is independent assortment again + more genetic variation produced in metaphase 2
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24
Q

Describe the Anaphase 2 stage of Meiosis 2.🌟

A
  • unlike anaphase 1, 2 results in chromatids of individual chromosomes being pulled to opposite poles after division of centromeres - same as anaphase of mitosis.
25
Q

Describe the Telophase 2 stage of Meiosis 2.🌟

A
  • chromatids assemble at poles (as in mitosis telophase)
  • chromatids uncoil + form chromatin again
  • nuclear envelope reforms + nucleolus becomes visible
  • cytokinesis results in division of cells forming 4 daughter cells in total, which will be haploid, due to reduction division, + will aslo be genetically diff from each other + from parent cell, due to crossing over + independent assortment
26
Q

Describe the specialised animal cell Erythrocytes, their role and how they are fit for this function.🌟

A

Produced: in bone marrow (soft, highly cellular tissue)

Role: transport O2 around body to respiring cells + carry CO2 from respiring cells to lungs for ventilation

How they are fit for their function:

  • biconcave shape increases SA:V ratio of cell
  • no nucleus / organelles = more space in cell for haemoglobin so each cell can carry more O2
  • flexible so able to squeeze through narrow capillaries
27
Q

Describe the specialised animal tissue Ciliated Epithelium.🌟

A
  • made up of Ciliated epithelial cells that have a hair like structure called cilia on their surface
  • these beat to move particles away from cells to prevent build of particles in areas that would cause infection
  • contains goblet cells that secrete mucus to trap unwanted particles
28
Q

Describe the specialised animal tissue Squamous Epithelium.🌟

A
  • made up of specialised squamous epithelial cells
  • made up of thin, flat cells bound tightly together + is only one cell thick
  • this allows diffusion to occur at faster rate due to short diffusion distance
  • is present when rapid diffusion across a surface is essential
29
Q

Describe the specialised animal cell Neutrophils, their role and how they are fit for this function.🌟

A

Produced: by stem cells in bone marrow

Role:

  • kill microorganisms w/ antimicrobial effectors
  • are first cells to migrate to site of infection
  • keep things under control until immune system kicks in
  • destroy foreign bodies by engulfing them (phagocytosis) and secreting enzymes

How they are fit for their function:

  • multi-lobed nucleus allows easier squeezing through gaps to get to infection site
  • granular cytoplasm has lysosomes containing enzymes to attack pathogens
  • attracted to side of infection by chemical messengers
30
Q

Describe the specialised animal cell Spermatozoa (sperm cells), their role and their structure.🌟

A

Produced: in male sex organs (testes) in the seminiferous tubules

Role:
- are the male gametes responsible for delivering genetic information to female gamete (egg cell), in fertilisation

Structure:

  • tail (flagellum) allows movement
  • have mitochondria in mid piece supplying them w/ energy to swim
  • head contains haploid nucleus = important when gametes fuse, forming a diploid nucleus in zygote
  • acrosome on head has digestive enzymes released to digest protective layers around ovum + allow penetration for sperm, leading to fertilisation
31
Q

Describe the specialised plant cell Root Hair Cells, their roles and their structure.🌟

A

Role: to absorb water + minerals in the soil, to be transported in translocation + transpiration

Structure:

  • large SA due to hair like projections that maximise water uptake + minerals
  • many mitochondria = maximises energy available for active transport to absorb minerals
  • cellulose cell wall = creates shorter diffusion distance
  • vacuoles containing cell sap which decreases water potential, creating a steep gradient so increased rate of osmosis
  • have carrier proteins in cell membrane to aid uptake of ions from soil
32
Q

Describe the specialised plant cell Palisade Cells, their role, location and their structure.🌟

A

Location: within mesophyll below up over epidermis

Role:
- contain chloroplasts to absorb large amounts of light for photosynthesis

Structure:

  • vertically elongated like a rectangular box shape allowing them to be closely packed to form a continuous layer
  • have a thin cell wall, increasing rate of diffusion of CO2
  • have a large vacuole = maintains turgor pressure
  • have many chloroplasts that can move within cytoplasm to absorb more light
33
Q

Describe the specialised plant tissue Xylem Tissue, it’s role and its structure.🌟

A

Role: transport water + mineral ions, + to support rest of plant

Structure:

  • type of vascular tissue
  • composed of vessel elements which are elongated dead cells w/ waterproof material called lignin in their walls = provides structural support
  • vessel has bordered pits = allows water to leave at certain points
34
Q

Describe the specialised plant tissue Phloem Tissue, it’s role and its structure.🌟

A

Role: transports food in form of organic solutes / nutrients (particularly sucrose) around plant, from leaves + stems to everywhere needed

Structure:

  • type of vascular tissue
  • made of cells joined end to end forming a hollow tube structure
  • sieve plates act as pores between end to end cells = allow phloem contents to flow through
  • companion cells linked to sieve tube by plasmodesmata that still contain all organelles, allowing them to control functions of sieve tube elements
  • sieve tubes use companion cells to load sucrose
35
Q

Describe the specialised plant cells Guard Cells, their role and their structure.🌟

A

Role: control the opening and closing if stomata + so control rate of transpiration in plants

  • stomata necessary for CO2 to enter plants for photosynthesis

Structure:

  • contain cellulose hoops = prevent cell from swelling in width when becomes turgid
  • thicker inner wall which is less flexible than thinner outer wall = cause cell to expand outwards into a c-shape, so opening stomata
  • are only cells on lower side of leaf w/ chloroplasts = allows them to detect presence of light + so know when to open + close stomata
36
Q

State the levels of organisation in multicellular organisms.🌟

A 
Specialised cells
⬇️
Tissues
⬇️
Organs
⬇️
Organ systems
⬇️
Whole organism
37
Q

Describe the organisation of cells into tissues.🌟

A
  • a tissue = made up of a collection of differentiated cells w/ a specialised function / function
  • so each tissue adapted for a particular function in an organism
38
Q

Name the four main categories of tissues in animals and their adaptions to function.🌟

A
  • nervous tissue: adapted to support transmission of electrical impulses
  • epithelial tissue: adapted to cover body surfaces (internal + external)
  • muscle tissue: adapted to contract
  • connective tissue: adapted either to hold other tissue together / as a transport medium
39
Q

Describe the epithelial tissue Squamous epithelium, it’s role and its structure.🌟

A

Structure:

  • made of specialised, flattened squamous epithelial cells
  • aka pavement epithelium due to flat appearance
  • sits on a basement membrane
  • v thin due to squat / flat cells that make it up, and also as is only one cell thick

Role:

  • present when rapid diffusion across a surface = essential, as reduces dist of diffusion pathway
  • forms lining of lungs + allows doe rapid diffusion of O2 into blood

Can be simple or stratified.
Simple = one layer of flattened squamous cells on basement membrane
Stratified = multiple layers of flattened squamous cells on basement membrane

40
Q

Describe the epithelial tissue Ciliated Epithelium, it’s role and its structure.🌟

A

Structure:

  • made of Ciliated epithelial cells, which have hair like structure called cilia on one surface that move in a rhythmic manner
  • has goblet cells, releasing mucus to trap any unwanted particles present in air, preventing any bacteria reaching alveoli

Role:

  • movement of cilia shifts material along surface of epithelium, making them specialised cells for their function
  • Ciliated epithelium lines trachea for e.g. Causing mucus to be swept away from lungs
41
Q

Describe the connective tissue Cartilage, it’s role, it’s location and its structure.🌟

A

Location: found in outer ear, nose + at ends of + between bones

Structure:

  • contains fibre ps of protein elastin, to give flexibility, + collagen, to stiffen + strengthen it
  • is firm + flexible
  • composed of Chondrichthyes cells in the extracellular matrix

Role:

  • prevents ends of bones rubbing together + causing damage
  • provides strength + support
  • resistant to tension + compression but not as strong as bone
42
Q

Describe general muscle tissue.🌟

A
  • needs to be able to shorten in length (contract) to move bones, which in turn move diff parts of body
  • diff types of fibres: skeletal muscle fibres (muscles attached to bone, voluntary), smooth muscle (involuntary), + cardiac (only found in heart)
43
Q

Describe the muscle tissue Skeletal muscle, it’s role and its structure.

A

Structure:
- contain myofibrils which contain contractile proteins

Role:
- highly specialised + are multinucleate

Aka muscle fibres (group of fibres = fascicle, group of fascicles = muscle)

44
Q

Describe the muscle tissue Smooth muscle, its role, it’s location and its structure.

A

Location: trachea, bronchi, large bronchioles + other parts of body

Structure:
- contains elastic fibres

Role:
- elastic fibres give elasticity

45
Q

Describe the specialised plant tissue The Epidermis, it’s role and its structure.

A
  • a single layer of closely packed cells covering surface of plants

Structure:

  • usually covered by waxy, waterproof cuticle to reduce loss of water
  • has stomata that open and close - controlled by guard cells

Role:
- stomata in it allow CO2, O2 + water vapour in + out

46
Q

Name the two main categories of tissue in plants and their adaptions to function.

A
  • epidermis tissue: adapted to cover plant surfaces

- vascular tissue: adapted for transport of water + nutrients

47
Q

Describe the organisation of tissues into organs.🌟

A
  • organ = collection of tissues adapted to perform a particular function in an organism
    E.g. Mammalian heart = organ adapted for pumping blood around body, made of muscle tissue + connective tissue.
48
Q

Describe the organisation of organs into organ systems.🌟

A 
- large multicellular organisms have coordinated organ systems, each composed of a no. of organs  working together to carry out a major function in body
Animal e.g's:
- digestive system
- cardiovascular system
- gaseous exchange system
49
Q

Describe stem cells and their division.🌟

A
  • all cells begin undifferentiated, originating from mitosis / meiosis = called stem cells
  • stem cells are able to undergo cell division repeatedly, + are source of new cells necessary for growth, development + tissue repair
  • once stem cells become specialised, they lose ability to divide, entering G0 phase of cell cycle
  • stem cell activity = strictly controlled, if do not divide fast enough, tissues are not efficiently replaced, leading to ageing
  • but uncontrolled division leads to formation of masses of cells called tumours, which can lead to development of cancer
50
Q

Describe stem cells’ ability to differentiate into different cell types.🌟

A
  • this ability = its potency

- more no. of cell types it can differentiate into = greater potency

51
Q

Describe what is meant by a Totipotent stem cell.🌟

A
  • stem cells that can differentiate into any type of cell, as well as those destined to eventually produce a whole organism
  • e.gs of totipotents: fertilised egg, zygote
52
Q

Describe what is meant by a Pluripotent stem cell.🌟

A
  • stem cells that can form all tissue types but not whole organisms
  • present in early embryos + are origin of diff types of tissue within an organism
53
Q

Describe what is meant by a Multipotent stem cell.🌟

A
  • stem cells that can only form a range of cells in a certain type of tissue
  • e.gs of multipotents: haematopoetic stem cells in bone marrow as this gives rise to various types of blood cells
54
Q

Describe the production of erythrocytes derived from stem cells in bone marrow.🌟

A
  • erythrocytes = red blood cells
  • all blood cells derived from stem cells in bone marrow
  • their lack of nucleus + organelles means only have a short lifespan (+/- 120 days) so need constant replacing
  • so, stem cell colonies in bone marrow produce roughly 3 billion erythrocytes per kg of body mass per day
55
Q

Describe the production of neutrophils derived from stem cells in bone marrow.🌟

A
  • neutrophils = white blood cells
  • all blood cells derived from stem cells in bone marrow
  • neutrophils only love for roughly 6 hours + colonies of stem cells in bone marrow produce in region of 1.6 billion per kg per hour
  • this amount produced also increases during infection
56
Q

Describe some sources of animal stem cells.

A
  • Embryonic stem cells: present at v early stage of embryo development + are Totipotent. After 7 days, a mass of cells (a blastocyst) forms + cells now pluripotent
  • Tissue (adult) stem cells: present throughout life from birth, found in specific areas e.g. Bone marrow + are Multipotent. Can also be harvested from umbilical chords of newborns
57
Q

Describe some sources of plant stem cells.

A
  • present in Meristemic tissue (Meristems) in plants, this tissue found wherever growth is occurring in plants, e.g. at tips of roots + shoots (= apical meristems)
  • Meristemic tissue also between phloem + xylem tissues (= vascular cambium)
  • pluripotent nature of stem cells in meristems continues throughout life of plant
58
Q

Describe the potential uses of stem cells in research and medicine.🌟

A

Stem cells transplanted into specific areas have potential to treat certain diseases e.g:

  • heart disease
  • type 1 diabetes
  • Parkinson’s disease (treatment of neurological conditions)
  • Alzheimer’s disease (“)
  • birth defects
  • spinal injuries
  • macular degeneration

Stem cells are already used in diverse areas e.g:

  • treatment of burns: can be grown to produce new skin (repair of damaged tissues)
  • drug trials: can have new drugs tested on them before done on animals + humans
  • developmental biology: important in this area (the study of changes tags occur as multicellular organisms grow + develop from a single cell) as they can divide indefinitely and differentiate into most cells of an organism (research)
59
Q

Describe some of the ethics involved with using stem cells in medicine, specifically embryonic stem cells.

A
  • removal of stem cells from embryos usually = destruction of of embryos, but techniques being developed to stop this damage
  • religious + moral objections to use of embryos in this way (e.g. many believe destruction of embryo = murder, does embryo have rights? + who owns this genetic material?)

BIOLOGY AS (12 decks)

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