CELLS

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CELLS

• Basic unit of life (except virus)
• Prokaryotic, w/o nucleus, bacteria
• Eukaryotic, w/ nucleus
• Various cell types specialized for particular
  function. Differentiation.
• Over 200 human cell types

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Cells

• 56 of body is fluid
• Similar to sea water
• Intracellular extracellular
• Exchange regulated by cell membrane (plasma
  membrane)
• Passive transport (with gradient)
• Active transport (requires energy)

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Cells

• Cell life supported by extracellular fluid
  containingIons Calcium, Potassium, Sodium,
  Nutrients Glucose, Oxygen, Amino Acids,
  Vitamins, ...Regulatory chemicals Steroids,
  Hormones, Paracrin/Autocrin factors, ...

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Biochemistry
Monomer Nucleic Acid Amino Acid Fatty Acid Sugar
Polymer RNA, DNA Peptide, Protein Lipid Polysaccha
ride, Carbohydrate
Genes Gene products Not coded by genes
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Biochemistry

• Molecules or molecular regions (domains) are
  hydrophilic/hydrophobic
• Water is polar ( and - charged sides)
• Charged and polar molecules are soluble in water
• Nonionic, nonpolar molecules are insoluble in
  water

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Fig 1
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Biochemistry

• C-C and C-H (hydrocarbons) bonds are nonpolar
  hydrophobic
• In water, hydrophobic molecules and nonpolar
  regions of molecules aggregate to hide from
  water

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Biochemistry
Amino Acid
H
O
C
H2N
C
OH
Carboxyl
Amino
R
Side Chain (20)
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Biochemistry
Biochemistry
H
O
H
O
C
H2N
C
OH
C
H2N
C
OH
R
R
H2O
H
O
H
O
H
C
H2N
C
C
N
C
OH
Amino endN-Terminus
Carboxyl end C-Terminus
R
R
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Biochemistry

• Enzymes - Catalyze reactions (not metabolized).
• All enzymes are proteins, but not all protein are
  enzymes.
• Structural proteins provide physical rather
  than chemical function.

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Cells

• Cellular substructures called organelles made
  from membranes with similar structure floating in
  cytoplasm
• Membranes consist of bi-layer of phospholipid.

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Membranes
Phosphate rich protein head Charged - hydrophilic
Lipid tail Hydrophobic
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Membranes

• 2D Fluid, oil slick
• Semipermeable depending on size charge
• Suspended proteins float in membranes.
  Hydrophobic regions w/in membrane, hydrophilic
  regions exposed
• Ion channels, pumps, transporters, exchangers,
  receptors

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Organelles

• Endoplasmic Reticulum, smooth rough
• SER - Site of lipid metabolism
• RER - Contiguous with outer nuclear membrane.
  Site of protein synthesis (translation), storage,
  post-translational modification, sorting, and
  transport. Many tubular and vesicular membranes.

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Organelles

• Ribosomes - Contained in RER
• Responsible for translation of mRNA into protein.
• Made up of protein and specialized structural RNA
  called ribosomal RNA (rRNA)

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Organelles

• Golgi Complex - Specialized portion of RER.
  Storage and sorting of protein vesicles prior to
  transport to membrane secretion.

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Organelles

• Mitochondria - Engines of the cell. Convert
  glucose to ATP. Number in the hundreds to
  thousands. Contain own DNA.

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Organelles

• Lysosome - Lytic enzymes breakdown organic
  compounds and are sequestered lysosomes from rest
  of cell for protection. Proteins ? Amino
  AcidsCarbohydrates ? Sugars

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Cytoskeleton

• Give cell structure, motility, intracellular
  vesicular trafficking, and ability to replicate.
• Microfiliments 7-9nm
• Intermediate filiments 10nm
• Microtubules 24nm

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Cytoskeleton
Monomer Role Motor MF Actin Stiffen plasma
membrane Myosin Provides motility
by depolymerizing A-M interaction IF V
imentin Strictly structural None Keratins One
end attached membrane Others Integrates cells
w/ other cells and into tissues MT Tubulin
Track for vesicle transport Dynein Cilia and
flagella motion Kinesin Alignment/separation
of chromosomes
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Organelles

• Nucleus - Repository of DNA. Site of RNA
  synthesis (translation). Double membrane, outer
  continuous with RER. Large channels for export of
  mRNA to cytoplasm. Nuclear matrix proteins give
  nucleus structure.
• Nucleolus - Large nuclear organelle where rRNA is
  synthesized and coupled with protein to form
  partial ribosomes.

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Protein Synthesis

• RNA polymerase bind to gene promoter and converts
  DNA to complementary mRNA (transcription).
  Binding to promoter regulated by transcription
  factors.
• Non-coding mRNA is cleaved. Alternative splicing.
  Export of mature mRNA to ER
• Ribosome converts mRNA sequence to AA sequence by
  attaching tRNAAA subunits in groups of three
  mRNA bases (codons).

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Protein Synthesis

• Multiple ribosomes may be translating each mRNA
  over time or simultaneously
• This cannot occur for rRNA, so 80-90 of DNA
  codes for rRNA.
• Post-translational modification - addition of
  lipids carbohydrates, assembly of subunits.
  Intracellular and extracellular.

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Translation
AA
tRNA
AA
AA
AA
AA
C
U
A
G
C
T
G
U
A
G
A
C
C
G
U
C
A
U
C
U
G
G
A
U
mRNA
Ribosome (rRNAProtein)
ER
Transcription
Nucleus
Export
RNA Polymerase
mRNA
C
G
U
C
A
U
C
U
G
G
A
G
C
A
G
T
A
G
A
C
C
T
G
G
G
G
C
DNA