2. Passive Transport
• Diffusion refers to a natural phenomenon caused by the
tendency of small particles to spread out evenly within any
given space.
• Dialysis is a form of diffusion in which the selectively permeable
nature of a membrane causes the separation of smaller solute
particles from larger solute particles.
• Osmosis is the diffusion of water through a selectively
permeable membrane.
• Facilitated Diffusion is when the movement of molecules of
molecules is facilitated or made more efficient by the action of
carrier mechanisms in a cell membrane.
• Filtration involves the passing of water and permeable solutes
through a membrane by the forces of hydrostatic pressure.
3. Active Transportation
• One type of active transport pump, the sodium-
potassium pump, operates in the plasma
membrane of all human cells.
• it actively transport sodium ions and potassium ions but in
opposite directions.
it actively transport sodium ions and
• In endocytosis the plasma membrane “traps”
potassium ions but in opposite directions.
some extra cellular material and brings it into the
cell
• Exocytosis is the process by which large
molecules notably proteins, can leave the cell
even though they are too large to move through
the plasma membrane.
4. Cell Metabolism
• Catabolism includes
– Cellular respiration
– Glycolysis
– Citric acid cycle
– Electron transport system
• Anabolism
– DNA
– RNA
– mRNA
– tRNA
5. Cell Metabolism
• Enzymes are classified as functional proteins; they regulate cell
functions by regulating metabolic pathways.
– Enzymes are proteins and have the chemical properties of
proteins
– Enzymes are usually teritary or quanternary proteins of
complex shapes.
– The active site is the portion of the emzyme molecule that
chemically “fits” the sunstrate molecule(s).
– Enzymes fall into several groups
• Oxidation-reduction enzymes
• Hydrolyzing enzymes
• Phosphorylating enzymes
• Enzymes that add or remove carbon dioxide
• Enzymes that rerange atoms within a molecule
• Hydrases
6. Protein Synthesis
• Transcription
1. A strand of RNA forms along a segment of one
strand of a DNA molecule
2. Uracil attaches to adenine and guanine attaches
to cytosine (Complementary paring). mRNA is
formed.
3. Introns , of mRNA, are removed by enzymatic
process; which leaves behind segments that are
copies of the DNA’s exon.
4. The mRNA leaves the nucleus therefore
completing transcription.
7. Protein Synthesis
• Translation
1. In the cytoplasm, the edited mRNA molecule
attracts ribosome subunits that come together
around the mRNA molecule.
8. DNA Transcription
• DNA must be copied to messenger RNA
(mRNA)
• mRNA goes from nucleus to the ribosomes in
cytoplasm
• mRNA complements known as codons
– Only 3 nucleotide “letters” long
• Remember RNA has uracil (U) instead of
thymine (T)!
9. Transcription – Step I
A C G T A T C G C G T A
T G C A T A G C G C A T
Template DNA Strands
10. Transcription – Step II
A C G T A T C G C G T A
U G C A U A G C G C A U
Template DNA is Matched Up with
Complementary mRNA Sequences
11. Transcription – Step III
A C G U A U C G C G U A
U G C A U A G C G C A U
mRNA leaves nucleus
and goes to ribosomes
A new complementary RNA strand is
made (rRNA)
12. Protein Translation
• Modified genetic code is “translated” into
proteins
• Codon code is specific, but redundant!
– 20 amino acids
– 64 triplet (codon) combinations
14. tRNA structure
• 3-base code (triplet) is an “anticodon”
• Protein molecule
• Attached amino acid that is carried from
cytoplasm to ribosomes
15. Protein Synthesis
• Start: Ribosome binds to mRNA at start codon
(AUG)
• Elongation:
– tRNA complexes bind to mRNA codon by forming
complementary base pairs with the tRNA anticodon
– The ribosome moves from codon to codon along the
mRNA.
– Amino acids are added one by one
• Release: release factor binds to the stop codon
18. Growth
• Mitosis is the process of organizing and distributing nuclear
DNA during cell division.
1. Interphase is when a cell is not experiencing mitosis.
2. Prophase (“before phase”) is when the cell begins to divide,
usually before cytokines( “pinching in half”) become apparent.
The nucleus envelope falls apart as the paired chromatids coil
up to form dense, compact chromosome.
3. Metaphase is when the chromosomes are lined along a plane
at the “equator” of the cell.
4. Anaphase is when the centromere of each chromosome splits
to form two chromosomes, each consisting of a single DNA
molecule.
5. Telophase is the end phase and during this phase that the DNA
is returned to its original form and location within the cell.
19. Growth
• Meiosis is the type of cell division that occurs only in
primitive sex cells during the process of their becoming
mature sex cells.
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