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

lipid with carbohydrate attached

Glycolipid

Plasma Membrane proteins:

- Integral Proteins | - Peripheral Proteins

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

INTEGRAL PROTEINS

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

PERIPHERAL PROTEINS

● Formed by the carbohydrate portions of | glycoproteins and glycolipids

GLYCOCALYX

``` 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

FUNCTIONS OF MEMBRANE PROTEINS

1. Forms an Ion channel 2. Acts are carriers 3. Acts as receptors 4. Acts as Enzymes 5. Serves as linkers 6. Serves as cell-identity markers

MEMBRANE FLUIDITY depends on..

the NUMBER OF DOUBLE BONDS in the fatty acid tails ○ ↑double bond = ↑ fluidity

makes the membrane less fluid in normal temperature

Cholesterol ○ ↓ temperature = ↑ fluidity

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

what part of the cell is SELECTIVELY PERMEABLE?

Plasma membrane

● LIPID BILAYER | ○ Permeable to...

``` nonpolar molecules (oxygen, carbon dioxide, and steroids ```

● LIPID BILAYER | ○ Moderately permeable to...

small uncharged molecules | water and urea

● LIPID BILAYER | ○ impermeable to...

ions and large, uncharged polar | molecules (glucose)

MEMBRANE PERMEABILITY: | ○ Acts as channels or carriers

TRANSMEMBRANE PROTEINS

MEMBRANE PERMEABILITY: | the more hydrophobic or lipid-soluble the substance is

more it readily passes through the plasma membrane

TYPES OF GRADIENT ACROSS THE PLASMA MEMBRANE:

● CONCENTRATION GRADIENT ● ELECTRICAL GRADIENT ● ELECTROCHEMICAL GRADIENT

○ 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

aka MEMBRANE POTENTIA

ELECTRICAL GRADIENT

○ 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

- combination of concentration and | chemical gradient

ELECTROCHEMICAL GRADIENT

○ This contributes to the movement of substances across the | plasma membrane

ELECTROCHEMICAL GRADIENT

TRANSPORT ACROSS THE | MEMBRANE occur via

ACTIVE / PASSIVE PROCESS

What type of transport: - requires ATP - movement of substances is UPHILL (lower solute concentration→ higher)

Active transport

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

Active transport

What type of transport: - does not require ATP - movement of substances is DOWNHILL (higher solute concentration→ lower)

Passive transport

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

Passive transport

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

DIFFUSION

what is SOLUTE

the dissolved particles

what is SOLVENT

- liquid that does dissolving

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

FACTORS THAT INFLUENCE DIFFUSION RATE

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

TYPES OF PASSIVE DIFFUSION

- simple - facilitated - osmosis

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

SIMPLE DIFFUSION

what type of passive diffusion? - Nonpolar, hydrophobic molecules - Small, uncharged polar molecules

SIMPLE DIFFUSION

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

FACILITATED | DIFFUSION

what type of passive diffusion? - channel mediated (ions) - carrier mediated (sugars, vitamins)

FACILITATED | DIFFUSION

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

OSMOSIS

``` 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

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

CARRIER-MEDIATED

OSMOSIS: SOLVENT | - water moves from..

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

OSMOSIS: SOLUTE | -water moves from..

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

OSMOSIS: | Water movement is through:

○ Simple diffusion | ○ Through aquaporins (AQPs)

Osmosis occurs only when..

membrane is permeable to water but impermeable to certain | solutes

2 forces governing osmosis, maintaining equilibrium: (pressure)

○ HYDROSTATIC PRESSURE | ○ ONCOTIC PRESSURE

OSMOSIS: | -pressure exerted by liquid

Hydrostatic pressure

OSMOSIS: | -pressure exerted by impermeable solutes

Oncotic pressure

OSMOSIS: | - the amount of pressure needed to restore equilibrium

OSMOTIC PRESSURE

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

OSMOSIS: | ● When a cell placed in a solution with different osmotic pressure

→ changes in cell size, | shape, and volume

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

TONICITY

Types of Tonicity Solutions-

- Isotonic - Hypotonic - Hypertonic

``` 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

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

HYPOTONIC SOLUTION

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

HYPERTONIC | SOLUTION

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

ACTIVE TRANSPORT

ACTIVE PROCESS: | Two sources of cellular energy

- primary active transport | - secondary active transport

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)

1. Microfilaments 2. Intermediate filaments 3. 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:

1. centrosome 2. cilla and flagella 3. ribosomes 4. endoplasmic reticulum 5. golgi complex 6. lysosome 7. perixosome 8. proteasome 9. 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:

1. nuclear envelope 2. nuclear pore 3. nuclei/nucleolus 4. 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

1. 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:

1. Initiation 2. Elongation 3. 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

1. Prophase 2. Metaphase 3. Anaphase 4. 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

1. To remain alive and functioning without dividing 2. To grow and divide 3. 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

1. Interphase I 2. Prophase I, II 3. Metaphase I, II 4. Anaphase I, II 5. 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