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Biology > Module 2.6 - Cell Division, Cell Diversity And Cell Differentiation > Flashcards

Module 2.6 - Cell Division, Cell Diversity And Cell Differentiation Flashcards

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1
Q

(MA) Describe the organisation of cells in a multicellular organism.

A
  • Cells differentiate
  • Groups of similar specialised cells working together to perform a common function form tissues
  • Groups of tissues working together form organs
  • Groups of organs working together form organ systems
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2
Q

(MA) What happens during the interphase of the cell cycle?

A
  • Made up of G1, S + G2 phases
  • G1: cell grows, respires, proteins made + organelles replicated
  • S: DNA replication occurs, chromosomes become sister chromatids joined by centromere
  • G2: DNA replication checked for mistakes, organelles replicated
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3
Q

(MA) What happens during the cytokinesis phase of the cell cycle?

A
  • Cytoplasm cleaves down furrow to split cytoplasm

- Produces 2 new genetically identical daughter cells (also genetically identical to parent cell)

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4
Q

(MA) Describe the stages of mitosis.

A

-Prophase:
> Sister chromatids supercoil to shorten + thicken
> Sister chromatids now consist of sister chromatids joined by a centromere
> Now visible under a light microscope
> Nuclear envelope breaks down
> Centriole divides in 2 + each daughter centrioles goes to a pole of the cell
> Spindle fibres (microtubules) begin to form
-Metaphase:
> Sister chromatids line up along equator
> Spindle fibres attach to centromeres
-Anaphase:
> Centromere splits
> Chromatids separate
> Spindle fibres shorten
> Pull identical chromatids so they move to opposite poles with the centromere leading
-Telophase:
> Chromosomes uncoil
> Nuclear envelope reforms
> Spindle fibres break down

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5
Q

(MA) Compare mitosis and meiosis.

A

-Mitosis produces 2 genetically identical diploid daughter cells used for growth + repair (+ asexual reproduction). Occurs in all body cells. 1 division
-Meiosis: produces 4 genetically different haploid daughter cells. Used for producing gametes. Only occurs in ovaries + testes. 2 divisions
(-Both start from a single parent cell)

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6
Q

(MA) Describe the cell division and budding in yeast cells.

A
  • Nuclei divided by mitosis
  • Bulge in surface of cell
  • Nucleus moves to bulge
  • Bulge nips / pinches off
  • Leaves an uneven distribution of cytoplasm in the 2 cells
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7
Q

(MA) Describe the structure and function of erythrocytes as specialised cells.

A
  • No nucleus or many other organelles e.g. Golgi, mitochondria + ER, max space for Hb to increase O2 carrying capacity
  • No nucleus + organelles make more flexible to fit through capillaries
  • Filled w Hb that can bind w O2 to form oxyHb to transport it round to aerobically respiring cells
  • Biconcave disc shape to provide larger SA:vol ratio for O2 exchange for more efficient O2 uptake into RBCs
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8
Q

(MA) Describe the structure and function of root hair cells as specialised cells.

A
  • Hair like projection into soil for large SA for osmosis + mineral uptake (active transport) into roots
  • Thin walk for short diffusion path
  • Many mitochondria to provide energy for active transport of minerals
  • Many carrier proteins for active transport of minerals
  • Many channel proteins for uptake of water via osmosis
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9
Q

(MA) Describe the structure and function of neutrophils (phagocytes) as specialised cells.

A
  • Contain lots of lysosomes containing lysine enzymes to digest pathogens
  • Multi-lobed nucleus to fit between gals in endothelial cells of capillaries to leave blood
  • Contain many mitochondria to move lysosomes + phagosomes through cell along microtubules
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10
Q

(MA) Describe the structure and function of sperm as a specialised cell.

A
  • Haploid nucleus so when it fertilises an egg, the zygote diploid
  • Many mitochondria to provide energy for movement of flagellum
  • Shape: long + thing - ease of movement
  • Enzyme contained in acrosome so when sperm meets egg it can penetrate it to fertilise it
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11
Q

What are the two main checkpoints during the cell cycle?

A
  • G1/S checkpoint (restriction point)

- G2/M checkpoint

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12
Q

What is the purpose of checkpoints during the cell cycle?

A
  • Prevent uncontrolled decision that’d lead to tumours (cancers)
  • Detect + repair damage to DNA (e.g. damage by UV light)
  • Ensures cycle can’t be reversed
  • Ensures DNA can only be replicated once during each cell cycle
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13
Q

What occurs during the G1 phase of interphase?

A
  • G1 checkpoint ensures cell ready to enter S phase + begin DNA synthesis
  • Cells grow + increase in size
  • Transcription of genes to make RNA
  • Organelles duplicate
  • Biosynthesis e.g. protein synthesis incl making enzymes needed for DNA replication in S phase
  • p53 (tumour suppressor) gene helps control this phase
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14
Q

What occurs during the S phase of interphase?

A
  • As chromosomes unwound + DNA diffuse, every molecule of DNA replicated. Specific sequence to gene replication: housekeeping genes (active in all cells) duplicated first. Genes normally inactive in specific cells replicated last
  • Once cell enters this phase, committed to completing cell cycle
  • DNA replicates
  • When all chromosomes duplicated, each one consists of a pair of identical sister chromatids
  • Phase is rapid, as exposed DNA base pairs are more susceptible to mutagenic agents. Reduces chances of spontaneous mutations
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15
Q

What occurs during the G2 phase of interphase?

A
  • Special chemicals ensure cell ready for mitosis by stimulating proteins involved in making chromosomes condense + formation of spindle
  • Cell grows
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16
Q

What is mitosis used for?

A
  • Asexual reproduction
  • Growth
  • Tissue repair
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17
Q

Describe the events in the prophase phase of mitosis.

A
  • Replicated chromosomes (from S of interphase) + consist of identical sister chromatids, now shorten + thicken as DNA supercoils
  • Nuclear envelope breaks down
  • Centriole in animal cells (in centrosome) divides + 2 new daughter centrioles move to opposite poles of cell
  • Cytoskeleton protein (tubulin) threads form spindle between centrioles. Spindle: 3D structure. In plants, tubulin threads formed from the cytoplasm
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18
Q

Describe the events in the metaphase phase of mitosis.

A
  • Pair of chromatids attach to spindle threads at equator region
  • Attach by their centromeres
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19
Q

Describe the events in the anaphase phase of mitosis.

A
  • Centromere of each pair of chromatids splits
  • Motor proteins, walking along tubulin threads, pull each sister chromatid of a pair, in opposite directions towards opposite poles
  • As centromere leads, chromatids (now called chromosomes) assume a V shape
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20
Q

Describe the events in the telophase phase of mitosis.

A
  • Separated chromosomes reach poles
  • Nuclear envelope forms around each set of chromosomes
  • Cell now contains 2 nuclei each genetically identical to each other + parent cell from which they arose
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21
Q

What is the purpose of meiosis?

A

-Increases genetic variation (due to fertilisation)

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22
Q

What are homologous chromosomes?

A
  • Matching chromosomes, containing same genes at same places. May contain different alleles for some genes
  • Matching pairs one maternal + one paternal chromosome
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23
Q

Describe the events in prophase 1 of meiosis.

A
  • Chromatin condenses + each chromosome supercoils. Can now take up stains + be seen w a light microscope
  • Nuclear envelope breaks down + spindle threads of tubulin protein form from centriole in animal cells
  • Chromosomes come together in their homologous pairs
  • Each member of the pair consists of 2 chromatids
  • Crossing over occurs when non-sister chromatids wrap around each other + may swap sections so alleles are shuffled
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24
Q

Describe the events in metaphase 1 of meiosis.

A
  • Pairs of homologous chromosomes, still in crossed over state, attach along equator of spindle
  • Each attaches to a spindle thread by its centromere
  • Homologous pairs are arranged randomly, with members of each pair facing opposite poles of cell. Arrangement = independent assortment
  • The way they line up in metaphase determines how they’ll segregate independently when pulled apart during anaphase
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25
Q

Describe the events in anaphase 1 of meiosis.

A
  • Members of each pair of homologous chromosomes are pulled apart by motor proteins that drag them along tubulin threads of spindle
  • Centromeres don’t divide + each chromosome consists of 2 chromatids
  • Crossed over areas separate from each other, resulting in swapped areas of chromosomes + allele shuffling
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26
Q

Describe the events in telophase 1 of meiosis.

A
  • Most animal cells: 2 nuclear envelopes form around each set of chromosomes + cell divides by cytokinesis. There’s then short interphase when chromosomes uncoil
  • Each new nucleus contains half no. of chromosomes, but each chromosome consist of 2 chromatids
  • Most plant cells: cell goes straight from anaphase 1 to prophase 2
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27
Q

Describe the events in prophase 2 in meiosis.

A
  • If nuclear envelopes have reformed, they break down again
  • Chromosomes coil + condense, each one consisting of 2 chromatids
  • Chromatids of each chromosome no longer identical, due to prophase 1’s crossing over
  • Spindles form
28
Q

Describe the events in metaphase 2 in meiosis.

A
  • Chromosomes attach by their centromere to equator of spindle
  • Chromatids of each chromosome are randomly arranged
  • Way they’re arranged determines how the chromatids separate during anaphase
29
Q

Describe the events during anaphase 2 in meiosis.

A
  • Centromeres divide
  • Chromatids of each chromosome pulled apart by motor proteins that drag them along tubulin threads of spindle, towards opposite poles
  • Chromosomes therefore randomly segregated
30
Q

Describe the events during telophase 2 in meiosis.

A
  • Nuclear envelopes form around each of the 4 haploid nuclei
  • Animals: the 2 cells now divide to give 4 haploid cells
  • Plants: tetrad of 4 haploid cells is formed
31
Q

How does meiosis produce genetic variation?

A
  • Crossing over (prophase 1)
  • Independent assortment of chromosomes (anaphase 1) leads to random distribution of maternal + paternal chromosomes in each pair
  • Independent assortment of chromatids (anaphase 2) leads to further random distribution of genetic material
  • Haploid gametes are produced, which can undergo random fusion w gametes derived from another organism of the same species
32
Q

Give some examples of what may change when an undifferentiated cell (e.g. embryonic stem cells).

A
  • Proportions of different organelles
  • Shape of cell
  • Some of the cell’s contents
33
Q

How are erythrocytes specialised to their function?

A
  • V small (7.5μm diameter) so large SA:vol ratio so O2 can diffuse across membranes + easily all regions inside cell. Biconcave shape also increases SA:vol ratio
  • Flexible: well developed cytoskeleton allows erythrocytes to change shape so can twist + turn as they travel through narrow capillaries
  • Most organelles lost at differentiation so no nucleus, mitochondria or ER + little cytoplasm. More space for many Hb molecules. Hb synthesised within immature RBCs, when still have nucleus, ribosomes + ER
34
Q

How are neutrophils specialised to their function?

A
  • Twice size of erythrocytes + each neutrophil contains a multilobed nucleus
  • Attracted to + travel towards infection site by chemotaxis
  • Function: ingest bacteria + some fungi by phagocytosis
35
Q

How are spermatozoa specialised to their function?

A
  • Many mitochondria for aerobic respiration providing ATP for undulipodium to move + propel cell towards ovum
  • Long + thin so can move easily
  • Once sperm reaches ovum, enzymes are released from acrosome (specialised lysosome). Enzymes digest outer protective covering of ovum allowing sperm head to enter ovum
  • Head of sperm contains haploid gamete nucleus + very little cytoplasm
36
Q

How are epithelial cells specialised to their function?

A

(-Lining tissue)

  • Squamous epithelial cells: flattened in shape
  • Many cells of epithelium have cilia
37
Q

What are palisade cells specialised for and how are they specialised to carry out this function?

A
  • Photosynthesis
  • Long + cylindrical so pack together quite closely but w a little space between them for air to circulate, CO2 in these air spaces diffuses into cells
  • Large vacuole so chloroplasts are near periphery of cell reducing diffusion distance for CO2
  • Contain many chloroplasts
  • Contain cytoskeleton threads + motor proteins to move chloroplasts nearer to upper surface of leaf when light intensity low + further down when high
38
Q

How are guard cells adapted to their function?

A
  • Light energy used to produce ATP
  • ATP actively transports K+ ions from surrounding epidermal cells into guard cells, lowering water potential
  • Water now enters guard cells from neighbouring epidermal cells by osmosis
  • Guard cells swell but at tips cellulose wall is more flexible + more rigid when thicker. Tips bulge + gaps between them (stoma) enlarge
  • As stomata open, air enters spaces within layer of cells beneath palisade cells
  • Gaseous exchange can occur + CO2 will diffuse into palisade cells. As they use it for photosynthesis a steep conc grad maintained
  • O2 produced during photosynthesis can diffuse out of palisade cells into air spaces + through open stomata (when stomata open, water vapour also exits from them)
39
Q

How are root hair cells adapted to their function?

A
  • Hair like projections greatly increase SA for water absorption + mineral ions (e.g. nitrates) from soil
  • Mineral ions actively transported into RHCs lowering water potential causing water to follow via osmosis down water potential gradient
  • Have special carrier proteins in plasma membranes to actively transport in mineral ions
  • Also produce ATP needed for active transport
40
Q

What are the four types of tissue types?

A
  • Epithelial tissue (lining tissue)
  • Connective tissues (hold structures together + provide support e.g. blood, bone, catilage)
  • Muscle tissue (made of cells specialised to contract + cause movement)
  • Nervous tissue (made of cells specialised to conduct electrical impulses)
41
Q

What are the characteristics of epithelial tissue?

A
  • Made up almost entirely of cells
  • Cells v close to each other + form continuous sheets. Adjacent cells bound together by lateral contacts (e.g. tight junctions + desmosomes)
  • No blood vessels, retrieve nutrients by diffusion from tissue fluid in underlying connective tissue
  • Some have smooth surfaces but some have projections (cilia or microvilli)
  • Have short cycles + divide up to 2 or 3 times a day to replace worn/damaged tissue
  • Specialised to carry out functions of protection, absorption, filtration, excretion + secretion
42
Q

What is the make up connective tissue?

A
  • Non living extra cellular matrix containing proteins (collagen + elastin) + polysaccharides (hyaluronic acid that traps water)
  • Matrix separates living cells within tissue + enables it to withstand forces e.g. weight
43
Q

What are some examples of connective tissue?

A
  • Blood
  • Bone
  • Cartilage
  • Tendons
  • Ligaments
  • Skin also contains connective tissue
44
Q

What are the main types of muscle tissue?

A
  • Skeletal muscle: packaged by connective tissue sheets, joined to bones by tendons. When contract, cause bones to move
  • Cardiac muscle: make up walls of heart + allows heart to beat + pump blood
  • Smooth muscle: occurs in intestine walls, blood vessels, uterus, urinary tracts + propels substances along these tracts
45
Q

Where are meristematic cells found?

A
  • Root + shoot tips

- Cambium of vascular bundles

46
Q

Describe the cells that make up meristematic tissue.

A
  • Thin walks containing v little cellulose
  • No chloroplasts
  • Don’t have a large vacuole
  • Can divide by mitosis + differentiate into other cell types
47
Q

How do cambium cells differentiate into xylem vessels?

A
  • Lignin deposited in cell walls to reinforce + waterproof (kills the cells)
  • Ends break down so xylem forms continuous columns w wide lumens to carry water + dissolved minerals
48
Q

How do cambium cells differentiate into phloem sieve tubes or companion cells?

A
  • Sieve tubes lose most their organelles + sieve plates develop between them
  • Companion cells retain organelles + continue metabolic functions to provide ATP for active loading of sugars into sieve tubes
49
Q

Give some examples of organs in plants and their functions.

A
  • Leaf: photosynthesis
  • Root: anchorage in soil, absorption of mineral ions + water, storage (e.g carrot, parsnip, dahlia, swede roots store carbohydrates)
  • Stem: support, holds leaves up so expose to more sunlight, transportation of water + minerals + products of photosynthesis, storage of products of photosynthesis (potato tubers store starch, rhubarb stems store sugars + polysaccharides)
  • Flower: sexual reproduction
50
Q

What are the tissues and organs involved in the digestive system and what examples of life processes are carried out in this system?

A
  • Oesophagus, stomach, intestines + associated glands, liver + pancreas
  • Nutrition to provide ATP materials for growth + repair
51
Q

What are the tissues and organs involved in the circulatory system and what examples of life processes are carried out in this system?

A
  • Heart + blood vessels

- Transport to + from cells

52
Q

What are the tissues and organs involved in the respiratory system and what examples of life processes are carried out in this system?

A
  • Airways + lungs, diaphragm + intercostal muscles

- Breathing + gaseous exchange excretion

53
Q

What are the tissues and organs involved in the urinary system and what examples of life processes are carried out in this system?

A
  • Kidneys, uterus, bladder

- Excretion + osmoregulation

54
Q

What are the tissues and organs involved in the integumentary system and what examples of life processes are carried out in this system?

A
  • Skin, hair, nails

- Waterproofing, protection, temperature regulation

55
Q

What are the tissues and organs involved in the musculo-skeletal system and what examples of life processes are carried out in this system?

A
  • Skeleton + skeletal muscles

- Support, protection + movement

56
Q

What are the tissues and organs involved in the immune system and what examples of life processes are carried out in this system?

A
  • Bone narrow, thymus gland, skin, stomach acid, blood

- Protection against pathogens

57
Q

What are the tissues and organs involved in the nervous system and what examples of life processes are carried out in this system?

A
  • Brain, spinal cord, nerves

- Communication, control + coordination

58
Q

What are the tissues and organs involved in the endocrine system and what examples of life processes are carried out in this system?

A
  • Glands that make hormones e.g thyroid, ovaries, testes, adrenals
  • Communication, control + coordination
59
Q

What are the tissues and organs involved in the reproductive system and what examples of life processes are carried out in this system?

A
  • Testes, penis, ovaries, uterus, vagina

- Reproduction

60
Q

What are the tissues and organs involved in the lymph system and what examples of life processes are carried out in this system?

A
  • Lymph node + vessels

- Transports fluid hack to circulatory system + also important in resisting infections

61
Q

Describe what stem cells are.

A
  • Undifferentiated cells, capable of becoming any type of cell in the organism
  • Pluripotent
  • Able to express all their genes
  • Can divide by mitosis + provide more cells that can then differentiate into specialised cells, for growth + tissue repair
62
Q

What are the sources of stem cells?

A
  • Embryonic stem cells: present in early embryo formed when zygote begins to divide
  • Stem cells in umbilical cord
  • Adult stem cells: found in developed tissues (blood, brain, muscle, bone, adipose tissue + skin). Act like repair system as renew source of undifferentiated cells
  • Induced pluripotent stem cells (iPS cells): developed in labs by reprogramming differentiated cells to switch on certain key genes + become differentiated
63
Q

What are the potential uses of stem cells in research and medicine?

A
  • Bone marrow transplants
  • Drug research
  • Developmental biology
  • Repair of damages tissues or replacement of lost tissues
64
Q

How can stem cells be used in bone marrow transplants?

A
  • Treat diseases of blood (sickle cell anaemia + leukaemia) + immune system (severe combined immunodeficiency SCID)
  • Used to restore patient’s blood system after treatment for specific types of cancer where bone marrow cells can be obtained before treatment, stores + put back inside patient after treatment
65
Q

How are stem cells used in drug research?

A

-If stem cells can be made to develops into particular types of human tissue new drugs tested on these first rather than animal tissue

66
Q

How are stem cells used in developmental biology?

A
  • Can study how these cells make particular cell types (blood, bone, muscle + skin) + learn how each cell type functions + see what goes wrong when they’re diseased
  • Trying to find out if can extend capacity embryons have for growth + tissue repair into later life
67
Q

How are stem cells used to repair damaged tissues or replace lost tissues?

A
  • Used to treat mice w type 1 diabetes by programming iPS cells to become pancreatic beta cells. Research under way to develop such treatment for type 1 diabetes in humans
  • Bone marrow stem cells can be made to develop into liver cells (hepatocytes) + could be used to treat liver disease
  • Directed to become nervous tissue could be used to treat Alzheimer + Parkinson diseases or repair spinal cord injuries
  • May be used to populate bioscaffold of an organ + directed to develop + grow into specific organs for transplanting. Called regenerative medicine. If patient’s cells obtained, reprogrammed to become iPS cells + used to make such an organ there’ll be no need for immunosuppressant drugs
  • May eventually be used to treat conditions (e.g. arthritis, strokes, burns, vision + hearing loss, Duchenne muscular dystrophy + heart disease

Biology (20 decks)

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