CELLULAR ORGANIZATION
CELL THEORY
• All Living Things Are Composed of
Cells
• Cells Are the Functional Unit of the
Body
• Complementarity: Subcellular
structures control biochemical activities
• Continuity of Life: Cells come from
other cells
CELL DIVERSITY
• Human Body contains 50-106 trillion
cells
• 200 different cell types
• Range from 2 micrometers to 1 meter
in length
TYPICAL COMPOSITE CELL
• Cell membrane
• Nucleus
• Cytoplasm
• Organelles
CELL MEMBRANE
• Gives form to the cell, forms
outermost limits of the cell
• Controls what enters and leaves the
cell
• Selectively permeable
• FLUID MOSAIC MODEL
–Phospholipid bilayer
–Proteins
LIPID BILAYER
• 2 Layers of phospholipids
–Heads
• Polar (charged)
• Hydrophilic
–Tails
• Nonpolar (uncharged)
• Hydrophobic
• Glycolipids - have attached sugar groups
PROTEINS - responsible for
specialized functions
• Integral embedded
– Channels / Pores
– Transporters /
Carriers
– Receptors
• Peripheral attached
– Enzymes
– Glycocalyx “sugar coating”
– Cell ID markers
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NUCLEUS
Cell control center- directs activities
Bounded by a double membrane, the
nuclear envelope
Contains genetic information (DNA) in
the form of genes
Nucleolus - site of ribosome assembly
Multinucleate - many nuclei
Anucleate - no nucleus
CYTOPLASM
• Cell forming material
–cytosol - viscous transparent fluid
–cytoplasmic organelles - “little
organs”
–inclusions - chemical substances
that may be stored in the cytoplasm
ORGANELLES
• Endoplasmic reticulum
– rough ER - transport & membrane synthesis
– smooth ER - lipid synthesis & drug
detoxification
• Ribosome - synthesize proteins
• Golgi apparatus - series of flattened
membrane sacs that process, sort and
modify proteins and lipids for export or
cell use
ORGANELLES
• Mitochondria - ATP formation
• Lysosome - contains hydrolytic enzymes
to break down molecules, digest bacteria
• Microtubules / Microfilaments - form part
of the cytoskeleton that serve as support
structures and assist with cell movement
–Cilia -numerous, short, transport
substnces across the membrane
–Flagella - often single, propels the cell
ORGANELLES
• Peroxisomes - contain enzymes that
oxidize toxic substances (neutralize
free radicals)
• Centrosomes/centrioles - function in
cell division
• Storage organelles - Vacuoles,
Vesicles, may contain:
–fats, oils, melanin
CELL PHYSIOLOGY
Membrane Transport
PASSIVE PROCESSES
• Do not require energy
–simple diffusion
–facilitated diffusion
–osmosis
• isotonic
• hypotonic
• hypertonic
– bulk flow/filtration
ACTIVE PROCESSES
• REQUIRE ENERGY / ATP
• Goes against the concentration
gradient
–active transport using carrier proteins
–vesicular transport
• endocytosis - phagocytosis
pinocytosis
• exocytosis - cell export
Source of Cell Energy
ATP Catabolism
• Adenosine triphosphate (ATP)
• ATP - 5 carbon sugar (ribose)
nitrogen containing base (adenine)
3 phosphate groups
• ATP---P ~ P ~ P
• ATP---ADP + P + Energy
CELL DIVISION
• Process by which a cell reproduces itself
• Nuclear division - mitosis, meiosis
–Mitosis - somatic cell division in which
the cell retains the same number of
chromosomes
–Meiosis - reductional division in which
the chromosome number is reduced
• Cytoplasmic division - cytokinesis
CELL CYCLE
• Growth Phase 1 - synthesis of lipids,
proteins and carbohydrates
• S Phase - DNA synthesis
• Growth Phase 2 - formation of spindle
fibers for cell division, centrioles
divide
• Mitosis / Meiosis
• INTERPHASE
STAGES OF MITOSIS
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE
PROPHASE
• Chromatin condenses into
chromosomes
• Spindle Fibers appear
• Nuclear membrane disappears
• Nucleolus disappears
• Centrioles move to opposite poles
• Chromosomes begins to migrate
toward equator
METAPHASE
• Chromosomes
line up along
equator
• centromere of
each pair
attached to a
spindle fiber
/
ANAPHASE
• Centromeres
split; sister
chromatids
separate
• Chromatids
migrate to
opposite poles
TELOPHASE & CYTOKINESIS
• Opposite of Prophase
• Chromosomes elongate forming
indistinct chromatin
• Nuclear membrane reappears
• Nuclear reorganization occurs
• Two new daughter cells formed
NUCLEIC ACID STRUCTURE
DNA - forms genetic code
RNA - functions in the process of
protein synthesis
DNA - DEOXYRIBONUCLEIC ACID
• Double stranded helix; nucleus
• Contains: 5 carbon sugar, phosphate
group, nitrogenous base
• Nitrogenous bases
–adenine-thymine
–cytosine- guanine
• Base pairing occurs
DNA RELICATION
• DNA makes an exact duplicate of itself
• DNA strands separate into separate
strands and each one is used as a template
for a new strand of nucleotides
• Two double- helix molecules are formed,
each contains an original strand and a
newly synthesized strand
RNA
RIBONUCLEIC ACID
• Single stranded
• Uracil substitutes for thymine
• consists of 5 carbon sugar ribose,
phosphate group, nitrogenous base
• Bases: adenine, guanine, cytosine,
uracil
• RNA types: mRNA, tRNA, rRNA
GENETIC CODE
What are genes?
GENE
• Is a segment of a DNA molecule that may
consist of 1,000 pairs of nucleotides that
code for a specific protein
• ONE GENE=ONE POLYPEPTIDE=ONE
PROTEIN
AMINO ACIDS
• Each amino acid is coded for by a
triplet of bases
• Codon - triplet of bases that codes
for a single amino acid
TRANSCRIPTION
RNA SYNTHESIS
• mRNA is synthesized using a DNA
molecule as a template
• mRNA carries MESSAGE out of the
nucleus to the ribsome in the
cytoplasm
TRANSLATION
PROTEIN SYNTHESIS
• Genetic code is translated forming a specific
sequence of amino acids
• mRNA attaches to ribosomes in cytoplasm
• tRNA molecules bring specific A.A. to the
ribosome for placement in the dictated
sequence
• Ribosome bonds amino acids together to form
proteins / polypeptides
• Protein is released
Cell Aging
• Wear & Tear Theory - cell damage by
chemicals and free radicals have cumulative
effect
• Immune Theory - weakening of immune
response or auto-immune disorders
• Genetic Theory - “Telomere Clock”
– Telomere = string of nucleotides on the end
of chromosomes; (TTAGGG) repeated
>1000X
– 50-100 nucleotides lost each division.