Cell physiology Flashcards
Animal cells – 3 compartments
1) cell membrane
2) cytoplasm
3) nucleus
protoplasm = cytoplasm + nucleus
functions of plasma membrane
1) barrier b/w cell & environment
(cells, ISF/plasma)
2) SELECTIVELY PERMEABLE MEMBRANE
3) I.e. UNIQUE internal cell environment
cell membrane structure
75% phospholipids
phospholipids are…
amphipathic
both polar and non-polar components
nonpolar fatty acid tails
polar phosphate head
cell membrane structure (bilayer)
high amounts of phospholipids in aqueous solution
= phospholipid bilayer
= phosphate heads towards water, FA tails away from water (towards each other)
majority of phospholipid bilayer is (hydrophilic? hydrophobic?)
hydrophobic (tails)
consequence of majority hydrophobic bilayer
only hydrophobic (non-polar) molecules can pass through
hydrophilic (polar) molecules need carrier/channel mediation
exception to what can/can’t typically pass through lipid bilayer
Size is important variable
some small polar molecules can pass through – even though polar
some large nonpolar molecules may need transport (?) – even though nonpolar
permeable to…
Non-polar, hydrophobic, uncharged, (small?) – E.G. STEROIDS, O2, CO2
impermeable to…
polar, hydrophilic, charged – E.G. IONS, LARGE PROTEINS
example of exception
H2O – permeable to some degree – even though POLAR, HYDROPHILIC
what happens if lose selective permeability?
cell would no longer be able to maintain homeostasis – would be destroyed
lipid bilayer is composed of which lipids?
75% phospholipids
20% cholesterol
5% glycolipids
cholesterol in the lipid bilayer
carries a (polar) OH group (HYDROXIL GROUP)
attaches to phosphate group (polar head)
function of cholesterol in lipid bilayer
structure @ high temp
fluidity @ low temp
1) maintains structure @ high temperatures
(by keeping phospholipids locked together)
2) maintains fluidity of membrane @ low temperatures
(Non-polar portion prevents phospholipids (tails?) interacting)
GLYCOLIPIDS in the lipid bilayer
sugar attached to lipid
FOUND ON EXTRACELLULAR SIDE
which side are glycolipids?
extracellular side
function of GLYCOLIPIDS in cell membrane
SIGNAL TRANSDUCTION (convert signal type)
CELL TO CELL ADHESION
what is GLYCOCALYX composed of?
“sugary coat”
composed of carbohydrate portion of glycolipids (& glycoproteins)
function of GLYCOCALYX
1) cell recognition/signalling
2) protection
3) regulates cell behaviour
Cell membrane PROTEIN categories
1) Integral proteins
2) Peripheral proteins
integral proteins
crosses bilayer (“embedded”)
contains both polar/nonpolar parts (AMPHIPATHIC?)
complex/large
peripheral proteins
on surface of membrane (external or internal side)
attach to polar head of phospholipid
or attach to integral proteins
less complex/large
membrane proteins functional types
1) Transporters
2) Ion Channels
3) Receptors
4) Enzymes
5) Linkers
6) Markers
1) Transporters
INTEGRAL
transports POLAR molecules
E.g.
GLUCOSE transporter
AMINO ACID transporter
2) Ion Channels
INTEGRAL
transports IONS
can be…
ONE WAY
TWO WAY
SINGLE ION
MULTI ION
3) Receptors
INTEGRAL
“lock & key”
Takes specific LIGAND
E.G
INSULIN & IT’S RECEPTOR
“ligare” – to bind
HORMONE IS LIGAND, BUT LIGAND NOT ALWAYS HORMONE
Hormone = type of ligand
4) Enzymes
INTEGRAL OR PERIPHERAL
Active side faces inside or outside cell
Acts on SUBSTRATE
1) Breaks down SUBSTRATE –> products
2) CATALYZES REACTIONS (accelerate/cause)
E.G.
LACTASE protruding from EPITHELIAL cells of small intestine
–> breaks down lactose
5) Linker
Integral or peripheral
attach/link other proteins
attach/link other cells
STRUCTURAL STABILITY of membrane
E.G.
Blood clots via fibrinogen and platelets
holds filaments inside/outside membrane
6) Markers
cell identity
MAJOR HISTOCOMPATIBILITY PROTEINS
MHC proteins
–> ON OUTSIDE OF IMMUNE CELLS (e.g. macrophage)
Display peptide fragment from PATHOGENS to T-cells for recognition
miscellaneous fact about drugs and membrane proteins
membrane proteins are target of over 60% of all drugs
Fluid mosaic model
fluid movement of phospholipids
= membrane fluidity
cell types examples
nerve cell
sperm cell
egg cell
skin
muscle
bone
immune
fat
epithelial
etc.
two types of transport
1) Passive transport
2) Active transport
passive transport does not require
energy, ATP
uses potential energy
passive transport, where does energy come from?
electric gradient
concentration gradient
solutes move down gradient
potential energy (gradient) becomes kinetic
how is membrane gradient created
selective permeability
resting membrane potential
neurons and muscle fibres
facilitates Action Potentials (nerve impulse)
2 Types of Passive transport
1) Diffusion (solutes)
2) Osmosis (water)
Variables affecting Rate of Diffusion
1) Temperature
2) Surface area
3) Ratio of gradient
4) Size of particles
5) Thickness of membrane
(distance)
2 types of Diffusion
1) Simple Diffusion
(directly through membrane)
2) Facilitated Diffusion
(transmembrane (integral) protein)
why facilitate diffusion?
larger, polar, hydrophilic/charged molecules
e.g.
Ions
hormones
drugs
Facilitated diffusion via..
A) (Ion) Channel protein or
B) Carrier (transporter) protein
(ion) channel…
DOES NOT CHANGE SHAPE
OPENS OR CLOSES
E.g.
Calcium ion
Potassium ion
carrier (tranporter)…
CHANGES SHAPE
E.g.
glucose
fructose
vitamins
gated channel protein
gate determines when ions can/can’t flow in
types of gated Channel proteins
(a type of facilitated diffusion, a type of passive transport)
LIGAND gate
(ligand, e.g. hormone)
VOLTAGE gate
(voltage change)
MECHANICAL gate
(pressure)
Leak channels (in contrast to gated channels)
leak channels always open
OSMOSIS (passive transport)
water from high concentration to low
When membrane impermeable to solutes
Via membrane directly
or
Via AQUAPORINS (channel proteins for water)
(“water pores”)
OSMOTIC PRESSURE
minimum pressure that needs to be applied to SOLVENT to prevent it from passing into a solution VIA OSMOSIS
measure of concentration of solution (?)
I.e. pressure is directly proportional to concentration of solute
Pressure is against SOLUTE-heavy (?) side
(Pressure required to return to starting conditions)
ONCOTIC pressure
colloid osmotic pressure
pressure in BLOOD PLASMA
via proteins (E.g. ALBUMIN)
ALBUMIN controls blood osmotic pressure
–> prevents fluid leaking out of Blood Vessels
PULL WATER BACK INTO VENOUS CIRCULATION
BCOP
Blood Colloid Osmotic Pressure
HYDROSTATIC PRESSURE
Pressure exerted by fluid on surroundings
EQUILIBRIUM–> HYDROSTATIC PRESSURE = OSMOTIC PRESSURE
in U-tube e.g. –> EQUILIBRIUM = UNEVEN WATER LEVELS
TONICITY & osmosis
CONCENTRATION of solutes in solution
measures ability to change volume by changing water content
HYPOTONIC solution
ISOTONIC solution
HYPERTONIC solution
“hypertonic” EXTERNAL solution relative to INTERNAL cell environment
hypertonic solution
= cell shrinks
“CRENATION”
hypotonic solution
= cell bulges (if beyond tolerated force, cell will rupture)
“LYSIS”
Active transport
Sodium Potassium Pump
Sodium Potassium Pump – which cell not found in
RBC
Sodium Potassium Pump – function
maintains resting membrane potential (RMP)
REMOVES 3 NA+ (ions)
BRINGS 2 K+ (ions)
Requires ATP
Sodium Potassium Pump establishes…
CONCENTRATION GRADIENT
ELECTRICAL GRADIENT
(i.e. RMP)
Concentration gradient via Na+K+ pump
more Na+ outside cell
more K+ inside cell
Electrical gradient via Na+K+ pump
more positive outside cell
more negative inside cell
RMP
every cell negative inside (negative RMP)
why negative RMP inside cell?
1) Na+K+ pump
2) more K+ (diffusion) channels (more permeable to K+ within cell
3) many negatively charged organic molecules inside cell (e.g. Proteins)
examples of RMP of various cells
neurons = -70mV
skeletal muscles = -90mV
smooth muscles = -60mV
photoreceptor cells = -40mV
RBC = -10mV
2 types of Active transport
Primary Active transport
(via ATP)
Secondary Active transport
(via kinetic energy released by concentration gradient (passive movement) of other solutes)
example of primary active transport
Na+K+ pump
2 types of Secondary Active transport
Symporters (move 2 substances in same direction)
Antiporters (2 substances in opposite direction)
Vesicular transport
Active (requires ATP)
1) ENDOCYTOSIS
2) EXOCYTOSIS
exocytosis
1) secretion of hormones
E.g.
insulin
oxytocin
2) excretion of wastes
E.g.
Urea (kidneys)
endocytosis
1) phagocytosis
2) pinocytosis
3) receptor-mediated endocytosis
1) phagocytosis
eat large particles
E.g.
cells, bacteria, virus
E.g.
WBC, PSEUDOPODS
monocyte
macrophage
neutrophil
dendritic cells
osteoclasts
eosinophil
2) pinocytosis
bulk-phase endocytosis
intake of fluid+solutes inside
function of pinocytosis
Controls cell volume
transports molecules
proves nutrients to cell via digestion of molecules (Via DIGESTIVE ENZYMES INSIDE VESICLE/lysosome)
receptor mediated endocytosis
selective endocytosis
targets specific LIGANDS (ions/molecules) –
Via receptor proteins?
receptor proteins recycled
goes to endosome
digested/destroyed in lysosome
TRANSCYTOSIS
combo of exocytosis and endocytosis
e.g.
antibodies cross placenta
(endocytosis to cell of placenta
exocytosis to other side toward fetus)
note terms:
phagosome
pinosome
lysosome
endosome
exosome
cytoplasm consists of
cytosol (fluid)
organelles
cytosol % of cell volume
55%
cytosol % that is water
70-90%
list of organelles
Cytoskeleton
Centrosome
Cilia & flagella
Ribosomes
Endoplasmic reticulum
Golgi complex
Vesicles
Mitochondria
Nucleus
Nucleolus
vacuole vs vesicle
Vacuoles are somewhat larger than vesicles, and the membrane of a vacuole does not fuse with the membranes of other cellular components
cytoskeleton 3 types
Microfilaments
Intermediate filaments
Microtubules
microfilament, intermediate filament, microtubule
orientation (?)
microfilaments close to membrane (?)
intermediate filaments in b/w (?)
microtubules closest to centre (?)
Microfilaments (protein?)
smallest of 3
ACTIN protein
usually near cell membrane
microfilaments functions
1) movement and support
2) Cytokinesis (cell division)
3) muscle contraction
4) connect cytoskeleton to integral proteins
5) form microvilli
intermediate filaments (protein?)
medium size
protein KERATIN
intermediate filaments function
1) internal stability
2) organelles in specific position
3) bind adjacent cells (cell junctions)
microtubules
largest
protein TUBULIN
long/hollow
made in CENTROSOME
microtubules functions
1) Cell’s shape
2) movement of organelles (e.g. vesicles)
3) movement of chromosomes during cell division
4) Cilia and the Flagellum
(9 + 2 arrangement of microtubules)
centriole vs centrosome
A centriole is a barrel-shaped organelle which lives normally within the centrosome.
Centrosomes are structures found inside of cells. They are made from two centrioles. Centrioles are microtubule rings. The main purpose of a centrosome is to organize microtubules and provide structure for the cell, as well as work to pull chromatids apart during cell division.
centrosome
Microtubule organize
mitosis & meiosis (cell division)
2 centrosomes in each cell
near the nucleus
centrosome consists of
Centrioles
= a pair of cylindrical structures composed of 9 clusters of 3 microtubules
pericentriolar material
Pericentriolar material
contains TUBULIN protein to help build microtubules
Surrounds the centrioles and forms the starting point for mitotic spindles during mitosis
cilia
cilium singular
1) cell mobility (egg cells down the fallopian tubes)
2) sweep foreign particles along an epithelial lining (respiratory tract)
MADE OF MICROTUBULES
flagella
flagellum singular
propels cell forward
only in sperm cells
ribosomes made of
made of…
ribosomal proteins
rRNA
50% protein 50% rRNA in eukaryotes
ribosome functions
protein synthesis (TRANSLATION)
free-floating vs attached to ROUGH ER
free floating vs rough ER ribosomes function
floating =
produce proteins for use in cytosol
rough ER ribosomes =
proteins for…
A) organelles
B) cell membrane
C) exocytosis
ribosome composition
2 subunits of rRNA
(Large unit and small unit)
made in nucleus
assembled in cytosol
tiny granules under a microscope
ribosomes also found in…
mitochondria
for ENZYME synthesis
(one of SIX membrane protein types)
Endoplasmic reticulum
network of flattened sacs
extend from nuclear membrane
smooth ER (no ribosomes)
rough ER
smooth ER function
lipid production
phospholipids, cholesterol
smooth ER in liver cells…
detoxify drugs
breaks down glycogen to glucose
smooth ER in muscle cells…
called SARCOPLASMIC RETICULUM
stores/releases CA2+
rough ER
protein synthesis
e.g.
integral membrane proteins
hormones
structural proteins
rough ER continuous with…
nuclear membrane
proteins of rough ER exported via
“secretory pathways”
golgi complex
AKA
golgi apparatus
golgi body
Receive/modify/transport proteins from the rough ER
more complex/numerous Golgi body = larger secretory role.
golgi complex sacs
has 3 small sacs (cisternae):
Entry/cis face
= CONVEX
= facing rough ER
= receives protein via transport vesicles
intermedias (medial) cisternae
= protein becomes glycoproteins or lipoproteins (via ENZYME)
Exit/trans face
= concave side
= releases product
vesicles
formed by a lipid bilayer
separating contents from the cytoplasm or ECF
vesicles examples
Lysosome
Peroxisome
Secretory Vesicles
lysosome
digest substances (via enzymes)
Acidic pH for optimal enzyme function –> pH <7
A) Autophagy :
Removal of unnecessary or dysfunctional organelles
B) Autolysis:
self-digestion (destruction of entire cell)
autophagy
autolysis
peroxisome
breakdown of some organic molecules (very long FAs)
Contains many digestive proteins
peroxisomes neutralize H2O2 (hydrogrenperoxide – byproduct of metabolism)
Secretory vesicles
to the plasma membrane for exocytosis
e.g. proteins, hormones
mitochondria
ATP via aerobic metabolism (requires O2)
via glucose, protein, lipids —> ATP
note gluconeogenesis
mitochondria more numerous in…
muscle and nerve cells (active)
mitochondria not present in…
RBC
mitochondria structure
Structure:
outer and inner membrane
CRISTAE (folds) of inner membrane
between cristae is MATRIX
= most reactions take place
= Analogous with cytoplasm of the cell
Contain ribosomes
own set of DNA
ability to self-replicate proteins
mitochondria DNA
DNA is different from the main set of chromosomes in the nucleus
Only one “mitochondrial chromosome”
many per mitochondria
Much small than DNA in nucleus (?)
Circular DNA (same as bacteria)
Maternal inheritance only
mitochondria theory of origin
mitochondria are of bacterial origin
nucleus
“Brain” of cell
responsible for…
genetics
protein synthesis
(analogous to the CPU of a computer)
The nucleus is where we find the DNA, our genetic material
found in nucleus
the DNA, our genetic material
how many nuclei?
Most cells have 1 nucleus (UNINUCLEATE)
some have more (i.e. muscle cells) = (MULTINUCLEATE)
some have NONE (i.e. mature red blood cells)
nucleus structure
NUCLEAR ENVELOPE
= double membrane
= separates from cytoplasm
= like plasma membrane
NUCLEAR PORES
= substances in/out
= Proteins/hormones in
= RNA out
Nucleolus
largest structure in the nucleus
spherical body
made of clusters of RNA & protein
Function is to make rRNA (ribosomes)
DNA
double stranded helix
backbone of alternating pentose sugars and phosphate group
complementary nitrogenous base pairs form hydrogen bonds
stretch out DNA in a cell
DNA in body
would be 6 feet long
would be 108 billion KM
(150,000 round trips to moon)
genes
segments of DNA
encode for traits
codes for proteins that change structure/function/appearace
how many genes in human genome
20,000 genes
less than 1/2 function is known
genes examples
124 genes for hair colour
16 genes for eye colour
4 genes for freckles
Allele
variation of DNA sequence at a GENOMIC location
E.g.
Allele for red hair
Allele for blonde hair
Allele for brown hair
Genotype
sequence of base pairs in gene
“what genes say you should look like”
Phenotype
observable traits form genotype
“what you look like”
Histones
protein balls
DNA double helix coils around “
Nucleosome
combination of histone and DNA double helix
Linker DNA
section of DNA that links NUCLEOSOMES together
Chromatin
DNA/RNA/proteins prior to cell division
scattered throughout nucleus before cell division
granular mass when cell not dividing
chromatin clusters –> forms chromosomes before cell division
groups of NUCLEOSOMES = chromatin (???)
groups of CHROMATIN
=chromatin fibre (???)
chromatin fibre
composed of chromatin
section of many NUCLEOSOMES & Linker DNA
chromatin condensation
forms chromosome
chromosomes
arrangement of chromatin fibres during cell division
humans have…
46 chromosomes
23 from each parent
pairs of chromosomes =
HOMOLOGOUS CHROMOSOMES
AUTOSOMAL CHROMOSOMES
1-22
chromosome 23
SEX CHROMOSOME
SEX CHROMOSOME…
determines gender
female = xx
male = xy
CHROMATIDS
1/2 of chromosome
1 pair chromatid = chromosome
centromere
centre portion of chromosome
holds two CHROMATIDS together
(or 2 sister chromatids)
TELOMERES
non-coding
terminal portion of chromosomes
protects end of chromosome
prevents genetic material loss when cell divides
become short eventually –> Cell can’t divide –> cell dies
short telomere
increased disease/aging
GENOME
total genetic info of organism
carried in nucleus of cells
human genome project
2003
mapped out most of genome of human
20,000 genes
took 13 years
2022 –> genome almost entirely mapped
number of genes correlation to intelligence
does NOT correlate with intelligence
PROTEIN SYNTHESIS
new proteins from genome
ONLY IN CELLS W/ NUCLEUS
No nucleus = no DNA = no protein synthesis
E.g. RBC no nucleus
PROTEIN SYNTHESIS begins in NUCLEUS, end in CYTOPLASM
protein synthesis 2 steps
1) Transcription
DNA –> mRNA
2) Translation
mRNA –> protein
Transcription (Protein Synthesis)
transcribing DNA into RNA
all 3 types of RNA
occurs in NUCLEUS
Transcription (RNA POLYMERASE)
RNA POLYMERASE
@ PROMOTER REGION
UNZIPS small section of DNA
(two strands separated)
TEMPLATE STRAND
CODING STRAND
template strand is transcribed
coding strand is not
complementary nucleotide bases are matched
on template strand, new nucleotides can only be added to which end?
3’ (3 prime) end
moves along strand in 3’ to 5’ (5 prime) direction
complementary nucleotide bases (nitrogenous bases)
e.g.
A–> U (T replaced in RNA)
G–> C
T–> A
C–> G
PROMOTER REGION
CODING SEQUENCE
TERMINATOR REGION
regions of gene
RNA polymerase starts at PROMOTER
ends at TERMINATOR region
RNA polymerase then detaches from DNA & pre-mRNA molecule
SPLICING of pre-mRNA molecule (INTRONS and EXONS)
pre-mRNA molecule & snRNPs (Small Nuclear RiboNuclear Proteins)
snRNPs splice pre-mRNA
= moves non-coding segments (introns)
= splices coding segments (exons) together
Alternative Splicing
same pre-mRNA molecule
different mRNA strands
different proteins
snRNPs will splice a pre-mRNA strand differently at different times to produce different mRNA strands which are then translated to different proteins (from the same pre-mRNA molecule)
5’ (5 prime) cap
modified guanine nucleotide
1) “REGULATION of nuclear export”
2) structural stability
3) improve translation
3’ (3 prime) poly-A tail
adenine nucleotides
1) REGULATION of nuclear export
2) structural stability of mRNA
3) facilitate translation
where does mRNA go after?
after splicing & cap/tail –> pre-mRNA becomes mRNA –> EXITS NUCLEUS VIA NUCLEAR PORES
goes to cytoplasm
TRANSLATION OCCURS NEXT
Codon
three nucleotide (nitrogenous) bases
each CODON in mRNA strand
= Codes for specific AMINO ACID
start codon
vs
stop codon
start codon = translation initiates
stop codon = translation stops
Translation
translating mRNA to polypeptide
NUCLEIC ACID –> AMINO ACID
performed by RIBOSOMES
in CYTOPLASM
mRNA & Ribosome
mRNA attaches to SMALL ribosomal subunit (of 2)
ANTICODON of INITIATOR tRNA
binds to…
CODON of mRNA
(complementary bases)
tRNA
takes appropriate AMINO ACID to POLYPEPTIDE
ANTICODON on tRNA binds to CODON of mRNA
anticodon determines AMINO ACID
what happens after tRNA and mRNA connect?
LARGE RIBOSOMAL SUBUNIT attaches to SMALL SUBUNIT & mRNA
Creates functional ribosome
functional ribosomes – 3 binding sites (for tRNA + AA)
A site
P site
E site
A site:
binds tRNA carrying next amino acid (“acceptor” site)
P site:
binds initiator tRNA
= tRNA carrying polypeptide chain
E site:
binds tRNA just before released from ribosome (“Exit” site)
A site after P site
anticodon of another tRNA + AA pairs with mRNA Codon (in A site)
Peptide bond occurs between two AMINO ACIDS of two tRNAs
di-peptide attaches to tRNA on A-site
shifting from A-site to P-site
Ribosome shifts both mRNA (and attached tRNAs) by ONE codon
A-site becomes open again
tRNA that enters E site EXITS
when does translation end?
When Ribosome reaches STOP Codon on mRNA
protein detaches from final tRNA
ribosomal subunits separate
which RNA types involved in TRANSLATION?
mRNA, tRNA
also rRNA because ribosomes made of rRNA
what determines orders of AMINO ACIDS (& therefore structure of protein)
CODONS in mRNA (determined by DNA)
free vs attached ribosomes
free produce proteins for cell
attached produce proteins for membrane, or exocytosis
(Enter ER & sent to Golgi body for processing before wrapped by VESICLE)
POLYRIBOSOME (or POLYSOME)
multiple ribosomes TRANSLATING simultaneously
Why?
more proteins quicker
more efficient (less mRNA)
2 types of cell division
1) MITOSIS
exact replica for growth/repair
2) MEIOSIS
creates gametes (sperm, ova)
diploid vs haploid
2 sets of chromosomes = 46
= 2n or diploid
= n is number of distinct chromosomes
1 set of chromosomes = 23
= n or haploid
nearly all cells have 46 chromosomes
= 2 sets of 23
= one from each parent
= diploid
Gametes have 23
= sperm/ova
= haploid
mitosis vs meiosis
mitosis:
= diploid SOMATIC cells replicate
= diploid becomes diploid
meiosis:
= diploid GERM cells replicate
= produce GAMETES
= diploid becomes haploid
cell cycle
cycle for mitosis/meiosis to occur
2 phases of cell cycle
1) INTERPHASE
2) MITOTIC PHASE (meiotic phase for meiosis)
(meiosis goes through cell cycle twice)
mitosis
division of cell produces DAUGHTER CELLS
occurs in SOMATIC CELLS
occurs in GERM CELLS
diploid –> diploid
mitosis and cell cycle
INTERPHASE
duplicate material
MITOSIS
divide contents
CYTOKINESIS
2 daughter cells separate
1) INTERPHASE (mitosis)
1) increase cell size
2) duplicate organelles
3) duplicate DNA
3 PHASES of INTERPHASE (mitosis)
G1 phase (growth 1)
S phase (Synthesis)
G2 phase
G1 PHASE of interphase (mitosis)
cell grow
organelle duplicate
CENTROSOME duplication begins
(centrosome for division)
Note cell is metabolically active
S PHASE of interphase (mitosis)
DNA duplicate (copy for each daughter cell)
1) DNA is unraveled via…
DNA HELICASE
2) complementary strands made via…
DNA POLYMERASE
3) = two identical copies of DNA
I.E.
92 CHROMOSOMES
SISTER CHROMATIDS
I.E.
92 CHROMOSOMES(??? TYPO? SHOULD BE 92 CHROMATIDS INSTEAD?)
identical duplicate chromosomes
G2 PHASE of interphase (mitosis)
growth
proteins/enzymes made
CENTROSOME duplication FINISHES
…
MITOTIC PHASE of mitosis
PMAT (Mitosis) + Cytokinesis = MITOTIC PHASE
Prophase
Metaphase
Anaphase
Telophase
followed by CYTOKINESIS
(early) PROPHASE (PMAT) phase of Mitotic phase (of Cell cycle)
early prophase:
CHROMATIN forms Chromosomes (via chromatin fibres)
Sister chromatids join to form X via Centromere
KINETOCHORE:
protein that stabilizes Centromere
REMINDER:
(histone –> nucleosome –> Linker DNA –> Chromatin –> Chromatin fibre –> Chromosome)
(histone –> nucleosome –> Linker DNA –> Chromatin –> Chromatin fibre –> Chromosome)
KINETOCHORE
KINETOCHORE:
protein that stabilizes Centromere
(late) PROPHASE
nuclear envelope breaks
2 pairs of Centrosomes go to opposite ends
CENTRIOLES of centrosomes connect to CENTROMERES via…
MITOTIC SPINDLES
MITOTIC SPINDLES
CENTRIOLES of centrosomes connect to CENTROMERES via…
2) METAPHASE phase of Mitotic phase (cell cycle)
chromosomes aligned on METAPHASE PLATE (aka equatorial plate)
aligned in single line along middle of cell
3) (early and late) ANAPHASE phase of mitotic phase (cell cycle)
early:
centromeres split apart via MITOTIC SPINDLES pull
towards Centrosomes
sister chromatids pulled apart
late anaphase:
plasma membrane begins to separate
= small CLEAVAGE FURROW
4) TELOPHASE phase of mitotic phase (cell cycle)
Early telophase:
CLEAVAGE FURROW grows larger
–> chromatids at opposite ends (poles)
Late telophase:
separate NUCLEAR ENVELOPES form on each side
Cytokinesis
plasma membrane forms separately around each DAUGHTER CELL
cells move apart
cell cycle / Mitosis complete
Meiosis
division of single cell produce FOUR GAMETES
germ cells to gametes
diploid germ cells to haploid gametes
meiosis differences from mitosis
meiosis cell division TWICE
takes place in gonads (testes males, and ovaries females)
interphase of meiosis
same as interphase for mitosis
spermatogonia (precursor to sperm cell)
ova cells
1) Increase in cell size
2) Duplication of organelles
3) Replication of DNA
PMAT for meiosis (Prophase)
major difference b/w mitosis and meiosis:
HOMOLOGOUS chromosomes join to form TETRAD
tetrad and crossing over of chromosomes
“cross over” to exchange genetic materials
crossing over creates genotypic diversity (GENETIC DIVERSITY)
Prophase (Continued)
same as mitosis:
nuclear envelope break
centrosome move
mitotic spindles
metaphase
only difference is that TETRADS (not single chromosomes) line up
same:
on metaphase plate
anaphase (meiosis)
sister chromatids stay together in meiosis
(mitosis, sister chromatids pulled apart)
telophase + cytokinesis
results in 2 gametes with haploid chromosome (1n = 23)
have 23 chromosomes, but each have sister chromatid (?)
46 chromatids total –> 23 chromosomes
1/2 chromosome from each parent
in mitosis –> 46 chromatids total –> 46 chromosomes (single chromatid)
meiosis 2
two haploid daughter cells enter meiosis 2
meiosis 2 PMAT
same prophase, but no TETRADS –> I.e. same as mitosis (?)
METAPHASE 2 – same as mitosis (?)
ANAPHASE – same as mitosis –> sister chromatids split
TELOPHASE –> same as mitosis
result = 4 gametes (23 chromosomes each, 23 chromatids)
4 gametes similar but not identical
stem cells called germ cells
born with many stem cells (called GERM cells)
they undergo MEIOSIS and form GAMETES
what are the germ cells?
SPERMATOGONIA
OOGONIA
precursors to ova and sperm
spermatogonia and oogonia, diploid or haploid?
diploid
spermatocytes and primary oocytes
spermatogonia and oogonia create PRIMARY SPERMATOCYTES,
and PRIMARY OOCYTES
via…
many rounds of MITOSIS
these primary cells become sperm and ova via MEIOSIS
spermatogonia –> Primary spermatocyte –> secondary spermatocyte –> spermatid –> mature sperm cell
oogonia –> primary oocyte –> secondary oocyte –> mature ovum
how do primary spermatocytes become sperm cells?
males at puberty –> increase in T
primary spermatocytes enter MEIOSIS 1 & 2
results in SPERMATIDS
SPERMIOGENESIS
SPERMATOZOA
spermatid becomes spermatozoa via SPERMIOGENESIS
Oogenesis
In females, mitosis of the oogonium is complete prior to birth
Limited supply of primary oocytes
About 2 million at birth, 400,000 by puberty
The primary oocyte begins meiosis I in fetal development but it is arrested here until puberty
Each month, 6-20 primary oocytes complete meiosis I and enter meiosis II
These cells (usually only one) will finish meiosis II when and only if it is fertilized
terms
While we are on the topic of gametes, let’s add in a few more terms that will pop up over the next few terms
Gamete: sperm or ovum with with 23 chromosomes
Zygote: is the union of 2 gametes (now 46 chromosomes)
Blastocyst: The zygote will divide into 8 celled blastocyst that implants into the uterine wall
