2.6 Cell Division, Cell Diversity and Cell Differentiation ✓

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

phase of cell cycle where cell isnt dividing and is subdivided into growth and synthesis phases

type of nuclear division that produces daughter cells genetically identical to each other and parent cell

-G1/S
-G2/M

restriction point

-prevent uncontolled division which would lead to tumors
-to detect and repair damage to DNA
- ensure cycle cannot be reversed
-ensure DNA only duplicated once each cell cycle

-cell growth stops
-nuclear division consisting of stages (prohphase, metaphase etc)
-cytokinesis

-cells undergo apoptosis, differentiation or senescence
-some cells remain here for long time/ indefinitely

-cells grow and inc in size
-transcription of genes to make RNA
-organelles duplicate
-biosynthesis

programmed cell death

p53 (tumour suppressor) gene

-DNA replicates
-cell committed to completing cell cycle
-when all chromosomes duplicated each consists of pair of identical chromatids

exposed DNA base pairs more susceptible to mutagenic agents so reduces chances of spontaneous mutations

Cells grow

gap

synthesis

growth phase

-triggers condensation of chromatin
-ensures cell is ready for mitosis

-triggered at restriction point

ensures cell ready to enter S phase and begin DNA synthesis

1) housekeeping genes (active in all cells)
2) genes normally inactive in specific cells

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

replicates of chromosomes

-asexual reproduction
-growth
-tissue repair

growth factors secreted by platelets, macrophages and damaged cells of blood vessel walls stimulate proliferation of endothelial and smooth muscle cells to repair damaged blood vessels

1) prophase
2) metaphase
3) anaphase
4) telophase

-chromosomes that replicated in S phase consist of 2 identical sister chromatids that shorten and thicken as DNA supercoils
-nuclear envelope breaks down
-centriole in centrosome in animal cells divides and 2 new daughter centrioles move to opposite poles of cell
-cytoskeleton protein (tubulin) threads form spindle between centrioles, in plants tubulin threads form from cytoplasm

-pairs of chromatids attach to spindle threads at equator region
-they attach by centromeres

-centromere of each pair of chromatids splits
-motor proteins walk along tubulin threads and pull each sister chromatid to opposite poles
-centromere goes first so chromatids (now chromosomes) in v shape

-separated chromosomes reach poles
-new nuclear envelope forms around each set
-cell now contains 2 genetically identical nucleus

plasma membrane folds inwards and ‘nips in’ cytoplasm

end plate forms where equator spindle was and new plasma membrane and cellulose cell wall form on either side

cell having only 1 set of chromosomes (represented by ‘n’) so half the normal amount

matching chromosomes containing same genes at same places (loci) and may contain different alleles pf some genes

type of nuclear division resulting in formation of cells containing half number of chromosomes of parent cell

cells with full set of 46 chromosomes

zygote

diploid

gonads (ovaries and testes)

DNA replicated during S phase

prophase 1, metaphase 1, anaphase 1, telophase 1, (maybe short interphase), prophase 2, metaphase 2, anaphase 2, telophase 2

in plane at right angles to meiosis 1

-chromatin condenses and chromosomes supercoil
-nuclear envelope breaks down
-spindle threads of tubulin protein form from centriole in animal cells
-chromosomes come together in homologous pairs (each member of pair containing 2 chromatids)
-non-sister chromatids wrap around each other and shuffle alleles (crossing over)

-pairs of homologous chromosomes attach along equator by spindle
-each attaches to spindle thread by centromere
-homologous pairs arranged randomly ech member facing opposite poles

-homologous chromosomes pulled apart by motor proteins dragging them along tubulin threads
-centromeres dont divide and each chromosome consists of 2 chromatids
-crossed over areas separate (allele shuffling)

-2 nuclear envelopes form around sets of chromosomes
-cytokinesis
-short interphase where chromosomes uncoil
(new nucleus has half original chromosones but each chromosome has 2 chromatids)

no go straight from anaphase 1 to prophase 2

-nuclear envelopes break down if there
-chromosomes coil and condense
-spindles form

2

no

-chromosomes attach by centromere to equator of spindle
-chromatids of each chromosome randomly arranged

-centromeres divide
-chromatids of each chromosome pulled apart by motor proteins that drag them along tubulin thread to opposite poles

-nuclear envelope forms around each of 4 haploid nuclei
-animals: 2 cells divide to 4
-plants: tetrad of 4 haploid cells formed

non-sister chromatids wrap around each other and shuffle alleles

Anaphase 1: chromosomes
Anaphase 2: chromatids

process where stem cells specialise into different cell types

phagocytic WBC

unspecialised cell able to express all genes and divide by mitosis

fertilised ovum (egg cell) by spermatozoon

certain genes are switched off and other expressed more

-proportions of different organelles differ
-shape of cell changes
-some contents of cell change

red blood cells

-small and biconcave shape so large SA:V
-flexible due to developed cytoskeleton to travel through narrow capillaries
-most organelles lost at differentiation to provide space for haemoglobin

when erythrocyte immature

-large with multilobed nucleus
-attracted to and travel towards infection sites
-able to ingest bacteria and some fungi by phagocytosis

chemotaxis

cells in lining tissue

-many mitochondria for ATP for undulipodium movement
-long and thin for easy movement
-enzymes released from acrosome that digest outer protective covering of ovum
-head of sperm with gamete nucleus with little cytoplasm

specialised lysosome in sperm

-squamous epithelial cells
-many have cilia

closely packed photosynthetic cells in leaves

cells surrounding stomata in leaf epidermis

-long and cylindrical to pack together with air spaces for CO2
-large vacuole so chloroplast closer to periphery of cell for diffusion of CO2
-contain many chloroplast
-cytoskeleton threads and motor proteins to move chloroplast to move where sunlight intensity ideal

1) light energy used for ATP
2) ATP actively transports K+ from epidermal cells into guard cells lowering water potential
3) water enters guard cells from epidermal cells by osmosis
4) guard cells swell, at tips cell wall more flexible and more rigid where thicker so tips bulge and gap between them enlarges

-hair like projections to increase SA
-special carrier proteins in membrane to actively transport minerals
-ATP production for active transport

group of cells working together to perform specific function

-epithelial
-connective
-muscle
-nervous

-made of of almost only cells
-very close and form continuous sheets, adjacent cells bound by lateral conraxts like tight junctions and desmosomes
-no blood vessels
-smooth surfaces or projections (eg cilia)
-short cell cycles to replace damage

-protection
-absorption
-filtration
-excretion
-secretion

from tissue fluid in connective tissue

non living extracellular matrix containing proteins (collagen and elastin) and polysaccharides which separates living cells in tissues and enables withstanding forces

-blood
-bone
-cartilage
-tendons
-ligaments

immature cells in cartilage

-divide by mitosis
-secrete extracellular matrix

mature chondroblasts/ cartilage cells which maintain matrix

-hyaline
-fibrous
-elastic

-forms embryonic skeleton
-covers ends of long bones
-trachea rings
-nose

-discs between vertebrae in backbone
-knee joint

-outer ear
-epiglottis (flap over voice box when swallow)

-many blood vessels
-fibres: elongated and myofilaments made of proteins (actin and myosin) which allow contraction

-skeletal
-cardiac
-smooth

packaged by connective tissue sheets, joined to bones by tendons which when contract cause bones to move

walls of heart allowing heart beat

occurs in walls of intestine, blood vessls, uterus etc and propels substance along

flattened cells which have walls impregnated by waxy substance (cuticle) and usually lack chloroplast, forming protective covering over leaves stems and roots

transport tissue in plants (xylem and phloem)

-thin walls with little cellulose
-no chloroplast
-no large vacuole
-divide by mitosis and differentiates into other cell types

photosynthesis

-storage
-absorption
-anchorage in soil

-support
-holds up leaves for light
-transportation of nutrients
-storage

sexual reproduction

number of organs working together to carry out overall function

collection of tissues working together to perform same function

-oesophagus
-stomach
-intestines
-associated glands: liver + pancreas

-heart
-blood vessels

-airways
-lungs
-diaphragm
-intercostal

-kidneys
-ureters
-bladder

-skin
-hair
-nails.

-skeleton
-skeletal muscles

-bone marrow
-thymus gland
-skin
-stomach acid
-blood

-brain
-spinal cord
-nerves

glands that make hormones eg thyroid, ovaries, testes, adrenals

-testes
-penis
-ovaries
-uterus
-vagina

-lymph nodes + vessels

-nutrition to provide ATP
-materials for growth and repair

-transport to and from cells

breathing and gaseous exchange excretion

-excretion
-osmoregulation

-waterproofing
-protection
-temp regulation

-support
-protection
-movement

protection against pathogens

-communication
-control
-coordination

-communication
-control
-coordination

reproduction

-transport fluid back to circulatory system
-important in resisting infections

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

early embryos when zygote begins to divide

in developed tissues amongst differentiated cells

labratories by reprogramming differentiated cells to switch on certain genes

-treat blood, liver and immune system diseases
-restore blood system after treatment for some cancers

used to develop into human tissue and test new drugs on it

-study how particular cells function and what goes wring when diseased
-find out if can extend capacity embryos have for growth and tissue repair into later life

cytokine

-research into suring type 1 diabetes
-repair spinal cord injuries or Alzheimers etc
-regenerative medicine (growing organs)
-treat arthritis, strokes, burns, vison etc

stem cell able to make all cells except plancental

stem cells able to make any cell of body

stem cell made in adults (eg bone marrow)