1. PLASMA MEMBRANE 2. CYTOPLASM 3. NUCLEUS

Cellular Level of Organization Flashcards by Ira Canania

PARTS OF THE CELL

PLASMA MEMBRANE
CYTOPLASM
NUCLEUS

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part of cell that has flexible outer surface

PLASMA MEMBRANE

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Functions:
○ Selective barrier
■ separates INTERNAL from
EXTERNAL environment
■ regulates flow of material in and
out of the cell
○ Communication

PLASMA MEMBRANE

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part of cell that consists of all the cellular contents between
the plasma membrane and the nucleus.

CYTOPLASM

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Cytoplasm consists of

cytosol and organelles

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intracellular fluid

CYTOSOL

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different organelles:

■ cytoskeleton
■ ribosomes
■ endoplasmic reticulum
■ golgi complex
■ lysosomes
■ peroxisomes
■ mitochondria

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● houses the most of the cell’s DNA
● contains CHROMOSOMES that houses
hereditary units (GENES)

NUCLEUS

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○ The arrangement of resembles a
continually moving sea of fluid
lipids that contains a mosaic of
different proteins

FLUID MOSAIC MODEL

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components of plasma membrane

○ Membrane lipids

○ Proteins

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part of the cell that is ASYMMETRIC

PLASMA MEMBRANE

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FUNCTIONS
● Acts as barrier
● Control flow of substances in and out of
the cell
● Helps identify the cell to other cells
● participates in intracellular signaling

PLASMA MEMBRANE

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Basic structural framework of the

plasma membrane

LIPID BILAYER

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● Three types of lipid molecules

○ Phospholipid (75%)
○ Cholesterol (20%)
○ Glycolipid (5%)

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what is AMPHIPATHIC (has polar
and non-polar parts), hence they are
arranged in a bilayer.

Lipids

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polar part of lipid bilayer is…

hydroPHILIC, faces the extracellular fluid

(ECF) and the cytosol

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non-polar part of lipid bilayer is…`

hydroPHOBIC, faces towards another

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Phospholipid, Polar part

Phosphate containing

head

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Phospholipid, Non-Polar part

Fatty acid tail

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Cholesterol, Polar part

Tiny -OH (hydroxyl) group

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Cholesterol, Non-Polar part

Steroid rings of

hydrocarbon

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Glycolipid, Polar Part

Carbohydrate group

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Glycolipid, Non-Polar Part

Fatty acid tail

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Appears only in the
membrane that faces the
ECF (extra-cellular fluid)

Glycolipid

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protein with carbohydrate attached

Glycoprotein

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lipid with carbohydrate attached

Glycolipid

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Plasma Membrane proteins:

Integral Proteins

- Peripheral Proteins

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Membrane protein that
- Extends INTO or THROUGH the lipid
bilayer
- Mostly TRANSMEMBRANE proteins
(spans the entire bilayer)
- Amphipathic
- Many are glycoproteins

INTEGRAL PROTEINS

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Membrane protein that 
- Is not firmly embedded to the plasma
membrane
- May be attached to:
- Polar heads of lipid proteins
- Integral proteins

PERIPHERAL PROTEINS

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● Formed by the carbohydrate portions of

glycoproteins and glycolipids

GLYCOCALYX

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Functions:
○ MOLECULAR SIGNATURE
○ Enables cells to adhere to one
another
○ Protects cells from enzymatic
degradation
○ Makes red blood cells slippery
○ Protects gastrointestinal and
airway cells from drying out

GLYCOCALYX

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FUNCTIONS OF MEMBRANE PROTEINS

Forms an Ion channel
Acts are carriers
Acts as receptors
Acts as Enzymes
Serves as linkers
Serves as cell-identity markers

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MEMBRANE FLUIDITY depends on..

the NUMBER OF DOUBLE BONDS in the fatty acid tails

○ ↑double bond = ↑ fluidity

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makes the membrane less fluid in normal temperature

Cholesterol

○ ↓ temperature = ↑ fluidity

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Importance of membrane fluidity:

○ Decreases membrane rigidity → improves cell mobility
○ Enables cell processes (cell movement, growth, division, secretion, and cellular
junction formation
○ Allows membrane to self-seal when punctured

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what part of the cell is SELECTIVELY PERMEABLE?

Plasma membrane

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● LIPID BILAYER

○ Permeable to…

nonpolar molecules (oxygen, carbon
dioxide, and steroids

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● LIPID BILAYER

○ Moderately permeable to…

small uncharged molecules

water and urea

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● LIPID BILAYER

○ impermeable to…

ions and large, uncharged polar

molecules (glucose)

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MEMBRANE PERMEABILITY:

○ Acts as channels or carriers

TRANSMEMBRANE PROTEINS

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MEMBRANE PERMEABILITY:

the more hydrophobic or lipid-soluble the substance is

more it readily passes through the plasma membrane

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TYPES OF GRADIENT ACROSS THE PLASMA MEMBRANE:

● CONCENTRATION GRADIENT
● ELECTRICAL GRADIENT
● ELECTROCHEMICAL GRADIENT

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○ Difference in the concentration of a chemical from one place to
another
■ Concentrated in extracellular fluid - O and
Na ions
■ Concentrated inside the cell - CO2 and
K ions

CONCENTRATION GRADIENT

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aka MEMBRANE POTENTIA

ELECTRICAL GRADIENT

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○ The difference of electrical charges in two different regions
■ Due to the difference in distribution of positive and
negatively-charged ions
● Inside the cell - NEGATIVELY CHARGED
● Outside the cell - POSITIVELY CHARGED

ELECTRICAL GRADIENT

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combination of concentration and

chemical gradient

ELECTROCHEMICAL GRADIENT

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○ This contributes to the movement of substances across the

plasma membrane

ELECTROCHEMICAL GRADIENT

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TRANSPORT ACROSS THE

MEMBRANE occur via

ACTIVE / PASSIVE PROCESS

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What type of transport:

requires ATP
movement of substances is UPHILL (lower solute concentration→ higher)

Active transport

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what type of transport in membrane?
- Primary
- Secondary
Vesicle transport
- Endocytosis
- Exocytosis

Active transport

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What type of transport:

does not require ATP
movement of substances is DOWNHILL (higher solute concentration→ lower)

Passive transport

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what type of transport in membrane?
Diffusion
- Simple
- Facilitated
Osmosis

Passive transport

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a passive process in which the random mixing of particles in a solution
occurs because of the particle’s kinetic energy.

DIFFUSION

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what is SOLUTE

the dissolved particles

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what is SOLVENT

liquid that does dissolving

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if solute is present in HIGH concentration in one area of solution, and LOW in another area, where will the solute diffuse?

area of LOWER

CONCENTRATION

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FACTORS THAT INFLUENCE DIFFUSION RATE

steepness of concentration gradient
temperature
mass of diffusing substance
surface area
diffusion distance

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TYPES OF PASSIVE DIFFUSION

simple
facilitated
osmosis

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what type of passive diffusion?
-substances passes freely
through the lipid bilayer without the
help of transport proteins

SIMPLE DIFFUSION

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what type of passive diffusion?

Nonpolar, hydrophobic molecules
Small, uncharged polar molecules

SIMPLE DIFFUSION

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what type of passive diffusion?
-Substances passes with
the help of an integral
membrane protein

FACILITATED

DIFFUSION

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what type of passive diffusion?

channel mediated (ions)
carrier mediated (sugars, vitamins)

FACILITATED

DIFFUSION

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what type of passive diffusion?
-Net movement of a
SOLVENT through a
selectively permeable
membrane
-WATER

OSMOSIS

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FACILITATED DIFFUSION:
-Solute moves down the lipid bilayer
through a membrane channel
-Most are ION channels
GATED Channel
- When a part of the channel protein
acts as a”plug” or “gate

CHANNEL-MEDIATED

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FACILITATED DIFFUSION:
-A carrier (transporter) moves a solute down
its concentration gradient
-Has transport maximum (upper limit of
carriers available for transport)

CARRIER-MEDIATED

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OSMOSIS: SOLVENT

- water moves from..

an area of
high water concentration to an area of
low water concentration

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OSMOSIS: SOLUTE

-water moves from..

an area of low
solute concentration to an area of high
solute concentration.

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OSMOSIS:

Water movement is through:

○ Simple diffusion

○ Through aquaporins (AQPs)

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Osmosis occurs only when..

membrane is permeable to water but impermeable to certain

solutes

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2 forces governing osmosis, maintaining equilibrium: (pressure)

○ HYDROSTATIC PRESSURE

○ ONCOTIC PRESSURE

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OSMOSIS:

-pressure exerted by liquid

Hydrostatic pressure

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OSMOSIS:

-pressure exerted by impermeable solutes

Oncotic pressure

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OSMOSIS:

- the amount of pressure needed to restore equilibrium

OSMOTIC PRESSURE

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OSMOSIS:

● Under normal conditions:

osmotic pressure of the extracellular fluid is the same with the cytosol, therefore
there is no change in the cell volume

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OSMOSIS:

● When a cell placed in a solution with different osmotic pressure

→ changes in cell size,

shape, and volume

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is the measure of the solution’s ability to change the volume of cells by
altering the water content

TONICITY

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Types of Tonicity Solutions-

Isotonic
Hypotonic
Hypertonic

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Tonicity Solutions:
-EQUAL Concentration of
solutes inside &
outside cell
-Water enters in and out of
the cell w/o change in
cell size and shape
-cells: normal size and shape

ISOTONIC SOLUTION

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Tonicity Solutions:
-The solutes are greater
inside than outside the cell
-OUTSIDE → INSIDE the
cell
-Cells may SWELL or
BURST

HYPOTONIC SOLUTION

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Tonicity Solutions:
-The solutes are lesser inside
than outside the cell
-INSIDE → OUTSIDE THE
CELL
-Cell will shrink (crenated)

HYPERTONIC

SOLUTION

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what type of TRANSPORT?
○ POLAR or CHARGED molecules that need to
move “uphill” or against the concentration
gradient
○ carrier proteins need energy

ACTIVE TRANSPORT

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ACTIVE PROCESS:

Two sources of cellular energy

primary active transport

- secondary active transport

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What type of active process?

source of cellular energy that is taken via HYDROLYSIS of ATP

PRIMARY ACTIVE TRANSPORT

What type of active process?

source of cellular energy that is taken from energy stored in an IONIC CONCENTRATION GRADIENT

SECONDARY ACTIVE TRANSPORT

What type of active process?
Aka PUMPS
- energy is derived from ATP hydrolysis that changes the shape of carrier protein → pumps
the substance against its concentration gradient.

PRIMARY ACTIVE TRANSPORT

■ Most prevalent primary active transport
■ Maintains low concentrations of Na (pumping out against C.G) and high concentration of K (by moving inside against C.G) in the cytosol
■ Importance:
● Maintains cell shape and volume
● Generate electrical signals for action
potential

SODIUM-POTASSIUM PUMP (aka Na-K ATPase)

● type of active transport where energy stored in a Na+ or H+ gradient is
used to drive other substances across the
membrane against the C.G
● INDIRECTLY uses the hydrolysis of ATP
● A carrier protein simultaneously binds to Na+ and
another substance and changes in shape so that
both substances can cross the membrane at the
same time.

SECONDARY ACTIVE TRANSPORT

SECONDARY ACTIVE TRANSPORT - TWO

TYPES

SYMPORTERS

ANTIPORTERS

type of SECONDARY ACTIVE TRANSPORT THAT

moves substances in SAME direction
more on ABSORPTION

SYMPORTERS

type of SECONDARY ACTIVE TRANSPORT THAT
-Moves substances in the OPPOSITE
direction
-More on REGULATION of ions and pH

ANTIPORTERS

TYPES OF TRANSPORT IN VESICLES

ENDOCYTOSIS
EXOCYTOSIS
TRANSCYTOSIS

TYPES OF TRANSPORT IN VESICLES:

-materials move into a cell in a vesicle formed from the plasma membrane

ENDOCYTOSIS

TYPES OF TRANSPORT IN VESICLES:
-Materials move OUT of a cell by fusion
with the plasma membrane of vesicles
formed within the cell

EXOCYTOSIS

TYPES OF TRANSPORT IN VESICLES:
-Movement of substance into, across, and out of the cell
Vesicles undergo endocytosis on one
side, move across, then undergo exocytosis on the other side.
-Occurs in: endothelial cells

TRANSCYTOSIS

what form of endocytosis?
● Highly-selective type of endocytosis by
which cells take up specific ligands
● Uptake of LDL, transferrin,
vitamins, antibodies and hormones
● STEPS:
○ Binding
○ Vesicle formation
○ Uncoating
○ Fusion with endosome
○ Recycling of receptors to plasma membrane
○ Degradation in lysosomes

RECEPTOR-MEDIATED

ENDOCYTOSIS

what form of endocytosis?
● Aka CELL EATING
● cell
engulfs large solid particles (worn-out
cells, whole bacteria, or viruses)
●Undigested materials are excreted or
turned into lipofuscin granules

PHAGOCYTOSIS

○ Are cells capable of performing
phagocytosis
○ Examples:
■ Macrophages
■ Neutrophils

PHAGOCYTES

what form of endocytosis?
● Aka PINOCYTOSIS or cell-drinking
● droplets of extracellular fluid are taken up
● Mostly occurs in intestines and kidneys

BULK-PHASE ENDOCYTOSIS

part of cell that
● Consists of all cellular
contents between the
plasma membrane and
the nucleus

CYTOPLASM

Components of Cytoplasm

○ CYTOSOL

○ ORGANELLES

● Aka INTRACELLULAR FLUID
● The fluid portion of cytoplasm surrounding the organelles
● 55% of cell volume
● Site of many chemical reactions (eg. Glycolysis)
● Composition:
○ 75-90% water, the remaining are dissolved and suspended components
○ Some have aggregations
■ Examples (lipid droplets, glycogen granules)

CYTOSOL

CYTOSOL - components:

CYTOSKELETON

■ Network of protein filaments that extends throughout the cytosol
● Contributes to the cytoskeleton and other organelle’s structure
○ Microfilaments, intermediate filaments, and microtubules
● Serves as a scaffold (helps determine a cell’s shape and organize the cellular
components)
● Aids movement of organelles within the cell, of chromosomes during cell division,
and of whole cells such as phagocytes.

CYTOSKELETON

TYPES OF CYTOSKELETON (from smallest to largest)

Microfilaments
Intermediate filaments
microtubules

what type of cytoskeleton?
-Thinnest elements of the cytoskeleton
-Composed of ACTIN and MYOSIN
-Most prevalent at the cell edge
Functions:
- Help generate movement

Provide mechanical support ( microvilli)

MICROFILAMENTS

what type of cytoskeleton?

Found in parts of cells subject to mechanical stress
Helps stabilize the position of organelles
Help attach cells to one another

INTERMEDIATE

FILAMENTS

what type of cytoskeleton?
-Largest of the cytoskeletal components
-Long, unbranched hollow tubes
-composed mainly of TUBULIN
-Begins in CENTROSOME → grows
outward
Functions:
- Helps determine shape
- Helps in movement of organelles
- Secretory vesicles
- Chromosomes during cell
division
- Specialized cell projections
(CILIA and FLAGELLA)

MICROTUBULES

what part of cell?
● Are specialized structures within
the cell
● Performs different functions with
one goal: PROMOTE
HOMEOSTASIS within the cell

ORGANELLES

types of organelles:

centrosome
cilla and flagella
ribosomes
endoplasmic reticulum
golgi complex
lysosome
perixosome
proteasome
mitochondria

what type of organelle:
-Aka MICROTUBULE ORGANIZING CENTER
-Located near the nucleus
Components:
>two centrioles 
>One pericentriolar matrix
Function:
-Builds microtubules in non-dividing cells
-Forms the mitotic spindle during cell division

CENTROSOME

CENTROSOME:
-9 clusters of 3 microtubules
arranged in a circular pattern

two centrioles

CENTROSOME:
-Surrounds the centrioles
-Composed of ring-shaped complexes
(tubulin)

One pericentriolar matrix

what type of organelle:
● Motile projections of the cell surface
● Made up of microtubules

CILIA AND FLAGELLA

what type of organelle:
○ Numerous, short, hair-like projections
that extend from the surface of the cell
○ Function - moves fluids along a cell’s
surface
■ Found in: respiratory tract

CILIA

what type of organelle:
○ Longer
○ Usually moves an entire cell
■ Generates a forward motion
along its axis by rapidly wriggling
in a wavelike pattern
■ Example: SPERM

FLAGELLA

what type of organelle:
● Site of protein synthesis
● Contains high content of rRNA (ribosomal
RNA)
● has 2 subunits
● Types of ribosomes:
○ attached to the nuclear membrane
and to the endoplasmic reticulum (Synthesizes proteins for insertion in membrane or secretion)
○ Free ribosomes (Synthesizes proteins used in cytosol)

RIBOSOMES

what type of organelle:

● Network of membranes in the form of flattened sacs or tubules.

ENDOPLASMIC RETICULUM

what type of E.R?
Continuous with the nuclear membrane
Outer surface is studded with RIBOSOMES

ROUGH ENDOPLASMIC RETICULUM

what type of E.R?
Produces PROTEINS:
- Secretory proteins
- Membrane proteins
- Organellar proteins

ROUGH ENDOPLASMIC RETICULUM

what type of E.R?
Synthesizes glycoproteins and phospholipids →
transferred to cellular organelles → inserted to
plasma membrane or secreted

ROUGH ENDOPLASMIC RETICULUM

what type of E.R?

Not studded with ribosomes

SMOOTH ENDOPLASMIC RETICULUM

what type of E.R?
Produces:
- Fatty acids and steroids

SMOOTH ENDOPLASMIC RETICULUM

what type of E.R?

Other functions:
Releases glucose in liver cells
Inactivate or detoxify lipid-soluble drugs
Releases calcium during muscular contraction (sarcoplasmic reticulum)

SMOOTH ENDOPLASMIC RETICULUM

what type of organelle:
● More extensive in cells that secrete proteins
● Consists of 3-20 cisterns (small, flattened membranous sacs with bulging edges)
-Entry (cis) face
-Exit (trans) face
-Medial cisterns

GOLGI COMPLEX

what type of organelle:
● Functions
○ Modifies, sorts, packages, and transports proteins received from the ER
○ Forms secretory vesicles - discharges substances via exocytosis
○ Forms membrane vesicles - carries new molecules to the plasma membrane
○ Forms transport vesicles - carries molecules to other organelles

GOLGI COMPLEX

what step in golgi complex?
Proteins synthesized
from the RER are
surrounded by ER
membrane → buds
off to form
TRANSPORT
VESICLES

1st

what step in golgi complex?
Transport vesicles
move towards the
entry face of golgi
complex

2nd

what step in golgi complex?
Fusion of several
transport vesicles
creates the entry
face of golgi
complex → release
of substances to the
lumen

3rd

what step in golgi complex?
-Proteins move from
entry phase →
medial cisterns
-Enzymes modify the
proteins, forming
glycoproteins,
glycolipids, and
lipoproteins
-Transfer vesicles
move enzymes back
to the entry face and
modified proteins to
the exit face

4th

what step in golgi complex?
Products of the
medial cisterns
move into the lumen
of the exit face

5th

what step in golgi complex?
Products are further
modified, sorted,
and packaged at the
exit face

6th

what step in golgi complex?
Some of the process proteins leave the exit face and stored
in secretory vesicles
→ proteins are delivered to plasma membrane and
discharged via exocytosis
Ex. release of insulin
hormone from the
pancreatic cell

7th

what step in golgi complex?
Others leave in
MEMBRANE
VESICLES →
plasma membrane
→ incorporated to
the membrane

8th

what step in golgi complex?
Some will exit in
TRANSPORT
vesicles that will
carry the proteins to
another cellular
destination.
Ex. transport of
enzymes to
lysosomes

9th

what type of organelle?
● Membrane-enclosed vesicles that form from the golgi complex
● Contains as many as 60 kinds of powerful digestive and hydrolytic
enzymes (lysosomal enzymes)
○ Lysosomal enzymes works best in acidic pH (lysosome pH = 5;
cytosol pH = 7)

LYSOSOME

what type of organelle?
Components:
○ Transport pumps (imports H+)
○ Transporters that moves products of digestion (glucose, fatty
acids, and amino acids) into the cytosol

LYSOSOME

what type of organelle?
functions:
○ Digest substances that enter the cell via endocytosis and
transport final products of digestion into the cytosol
○ AUTOPHAGY - digestion of worn-out organelles
○ AUTOLYSIS - digestion of entire cell
○ Extracellular digestion

LYSOSOME

what type of organelle?
Aka microbodies
Contains OXIDASES
- Enzymes that oxidize (remove H+ atoms)
various organic substances
- By-products: H2O2 and superoxide
- H2O2 - decomposed by
CATALASE
- Superoxide - decomposed by other
enzymes

PEROXISOME

what type of organelle?
Functions:
- Detoxification of alcohol and other
damaging substances
- Prevents accumulation of by-products of

PEROXISOME

what type of organelle?
Function:
- Destroys unneeded, damaged, or faulty
proteins
Contains PROTEASES
- Enzymes that cut proteins into small
peptides
Capable of self-replications

PROTEASOME

what type of organelle?
● Functions:
○ “POWERHOUSE” of the cell
■ Generates most of the ATP through AEROBIC (oxygen-requiring) respiration
○ Plays a role in APOPTOSIS
(Aka programmed cell death)
-In response to stimuli, mitochondria releases chemicals (cytochrome c) to the cytosol initiating cascade of activation of protein-digesting enzymes → cell
death

MITOCHONDRIA

what type of organelle?
● Capable of self-replication
● Has ribosomes attached in the mitochondrial matrix
● Has their own DNA (multiple copies of circular DNA that contains 37 genes)
○ For synthesis of 2 rRNA, 22 tRNA, 13 proteins
● Mitochondrial genes are inherited from the MOTHER ONLY

MITOCHONDRIA

What part of cell?
Contains most of the cell’s GENES.
Functions:
- Controls cellular structure
- Directs cellular activities
- Produces ribosomes in nucleoli

NUCLEUS

parts of the nucleus:

nuclear envelope
nuclear pore
nuclei/nucleolus
chromosomes

what part of nucleus?

Double membrane
Separates the nucleus from the cytoplasm
Lipid bilayer
Outer envelope is continuous with the RER

NUCLEAR ENVELOPE

what part of nucleus?
- Consists of a circular arrangement of proteins
surrounding a large central opening
- Controls the movement of substances between
the nucleus and cytoplasm

NUCLEAR PORE

what part of nucleus?
- Located inside the nucleus
- Produces ribosomes (site of synthesis and assembly of
rRNA and proteins)
- Prominent in cells that synthesize large amount of proteins

NUCLEOLI/NUCLEOLUS

what part of nucleus?
● The GENES housed within the nucleus controls
cellular structure and direct cellular activities.
○ Arrange along CHROMOSOMES
○ Somatic cells - 46 chromosomes
● GENOME - the total genomic information
carried in a cell/organism
● DNA helix + Histones → nucleosome → further
coiling → chromatin → 2 chromatids +
centromere → chromosome

chromosomes

- Double stranded DNA wrapped twice
around histone (core of eight proteins)

Nucleosome

______ is used as a template for protein

synthesis

A gene’s DNA

process of Protein Synthesis

TRANSCRIPTION (nucleus)

2. TRANSLATION (cytoplasm)

Genetic expression are stored in….

sets of three
nucleotides
(base triplets)

three set of nucleotides in DNA

Base triplets

complementary sequence of base

triplets; it codes for a specific amino acid

Codon

what process of Protein Synthesis: 
● Occurs inside the nucleus
● The sequence of base triplets in DNA is copied to produce a complementary
sequence of RNA (codons)
● Three types of RNA are made

TRANSCRIPTION

the types of RNA made in transcription:

messenger RNA (mRNA)
Ribosomal (rRNA)
Transfer RNA (tRNA)

type of RNA that

■ Directs protein synthesis

mRNA

type of RNA that

■ Joins with ribosomal proteins to form ribosomes

rRNA

type of RNA that
■ Binds to amino acids and incorporates it into the protein during
translation

tRNA

○ Enzyme that catalyzes the transcription of

DNA

RNA polymerase

TRANSCRIPTION PROCESS:

Initiation
Elongation
Termination

what process of Protein Synthesis:
● Occurs in CYTOPLASM
● The nucleotide sequence of mRNA is translated
into a sequence of amino acids, forming a new
protein molecule
● Ribosomes: organelle responsible

TRANSLATION

binds the tRNA
carrying the next amino acid to be
added

aminoacyl site

binds to tRNA

carrying the growing peptide chain

peptidyl site

binds to tRNA before

release to ribosome

exit site

The process by which cells reproduce themselves

CELL DIVISION

TWO TYPES of CELL DIVISION

Somatic

- Reproductive

(any cell of the body except the gametes/

germ cell)

Somatic cells

SOMATIC CELL DIVISION undergoes?

Mitosis

Product of somatic cell division

Diploid cell

normal number of chromosomes (46)
has both members of chromosome pair

Production of germ cells/gametes (egg cell and sperm

cell)

REPRODUCTIVE CELL DIVISION

REPRODUCTIVE CELL DIVISION undergoes?

Meiosis (2-step nuclear division)

product of reproductive cell division

Haploid cell

23 chromosomes
1 member of chromosome pair

An orderly sequence of events in which a somatic cell

duplicates its contents and divides in two.

CELL CYCLE

Two chromosomes that make up one pair of

chromosomes

Homologous chromosomes

CELL CYCLE

- Consists of two major periods:

INTERPHASE
The cell is not dividing
MITOTIC (M) PHASE
The cell is dividing

Summary of sequence of events in cell cycle:

G1 → S PHASE → G2 → MITOSIS →

CYTOKINESIS

A state of “high metabolic activity”
The cell undergoes growth
The cell replicates DNA in preparation
for cell division
Undergoes production of additional
organelles and cytosolic proteins

INTERPHASE

Interphase Three phases:

G1 ,S, and G2

WHAT PHASE IN INTERPHASE?
- Cell is metabolically active
- The cell replicates most of its organelles
EXCEPT DNA

G1 (GAP) PHASE (46 chromosomes)

WHAT PHASE IN INTERPHASE?
- Cells that remain in G1 for a long time or
does not divide

G0 PHASE

WHAT PHASE IN INTERPHASE?
- Cell undergo DNA REPLICATION
- DNA uncoils, the old DNA strand pairs with
the newly formed DNA strand

S PHASE (92 chromosomes)

WHAT PHASE IN INTERPHASE?

Cell growth continues
Replication of centromere is completed

G2 PHASE (92 chromosomes)

Phases in Mitotic Phase

Prophase
Metaphase
Anaphase
Telophase

what phase in mitosis?
- Chromatin fibers condense and
shorten into chromosomes
- Each chromosomes contain
chromatids held together by
centromere

EARLY PROPHASE (92 CHROMOSOMES)

what phase in mitosis?
- Pericentriolar material of
centrosomes start to form mitotic
spindle

LATE PROPHASE

what phase in mitosis?
- Microtubules of the mitotic spindle
align the centromeres of chromatid pairs at metaphase plate

METAPHASE (92 CHROMOSOMES)

what phase in mitosis?
-The centromeres split, separating
each chromatid pair, moving towards
the opposite poles of the cell
- Each chromatid are now termed as CHROMOSOMES

ANAPHASE (46 CHROMOSOMES

what phase in mitosis?

begins after chromosomal movement stops
chromosomes uncoil and revert to chromatin form
nucleoli reapper
mitotic spindle breaks up

TELOPHASE (46 CHROMOSOMES/CELL)

● AKA CYTOPLASMIC DIVISION
○ Division of cell’s cytoplasm and organelles into separate and equal portions
○ Usually begins in LATE ANAPHASE with the formation of cleavage furrow

CYTOKINESIS

○ Appears midway between centrosomes
○ Always perpendicular to the mitotic spindle
○ Actin microfilaments form a contractile ring that pulls the plasma membrane inward

● CLEAVAGE FURROW

THREE (3) POSSIBLE DESTINIES OF THE CELL

To remain alive and functioning without dividing
To grow and divide
To die

■ Crucial in the regulation of DNA replication, mitosis, and cytokinesis
■ Regulated by CYCLINS (activates or deactivates CDKs)

○ CYCLIN-DEPENDENT PROTEIN KINASES (CDK’s)

● The reproductive division that occurs in the gonads (ovaries and testes), that
produces gametes (egg cell and sperm cell) in which the number of chromosomes
is reduced by half.
○ Produced HAPLOID (n) cells - single set of 23 chromosomes

MEIOSIS

MEIOSIS Occur in two successive stages:

○ Meiosis I (REDUCTIONAL division)

○ Meiosis II (EQUATORIAL division)

what stage in meiosis?

Begins with diploid cells, ending with two daughter haploid cells

Meiosis I (REDUCTIONAL division)

what stage in meiosis?
Similar to process to mitosis
● Note: Begins with two haploid cells, ending with four haploid
daughter cells

Meiosis II (EQUATORIAL division)

stages of meiosis

Interphase I
Prophase I, II
Metaphase I, II
Anaphase I, II
Telephase I, II

TYPES OF CELLULAR

DEATH

APOPTOSIS

- NECROSIS

Orderly, genetically programmed cell death

Normal process

APOPTOSIS

Cell death resulting from a tissue injury
Pathologic (abnormal) type of cell
death

NECROSIS

A normal process accompanied by progressive alteration of the body’s homeostatic
responses
○ Produces observable changes in structure and function, and increases vulnerability
to environmental stress and disease

AGING

Branch of medicine that deals with medical problems and care of elderly person

GERIATRICS

Scientific study of the process and problems associated with aging

GERONTOLOGY

Factors relating to cell aging:

“Aging genes” as part of the genetic blueprint
Erosion/shortening of telomeres
Glucose
Autoimmune response

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