physiology of cells
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Physiology of CellsCellular Processes
Membrane Transport
• Passive Transport– Simple diffusion down
concentration gradient– Facilitated Diffusion
occurs through channel proteins
• Active Transport– Requires energy
Permeability
• Plasma membrane allows only certain substance to diffuse across.
• Non-polar lipid based substances, steroids, diffuse quickly through membrane
Diffusion
• Molecules always move from high to low concentrations
• Occurs down a concentration gradient
• Effective only across small distance.
Facilitated Diffusion
• When a molecule either passes through or binds to an channel protein to cross a membrane.
Carrier Proteins
• When substance being transported binds to protein
Osmosis
• Diffusion of water
• Occurs easily through bi-lipid layer
• Aquaporins allow for quicker movement of water
Solute Concentrations
• Isotonic- equal amount of solutes
• Hypotonic- solution has lower solute concentration
• Hypertonic- solution has higher concentration of solutes
Active Transport
• Moves substances against concentration gradient
• Sodium-Potassium pump
Bulk Transport
• Endocytosis– Phagocytosis
movement of large molecules into the cell
– Pinocytosis is the ingestion of extracellular fluid
• Exocytosis moves large molecules out of cell– Ex: proteins,
waste
Cell Transport
Cellular Respiration
• Metabolism happens in a series of separate reactions
• Each step is catalzyed by a separate enzyme
• Cellular respiration occurs inside the mitochondria(except glycolysis)
Steps of Cellular Respiration
• Glycolysis• Pyruvate Oxidation• Kreb Cycle• Electron Transport Chain
• Net gain of 36 ATP• Waste products CO2 & H2O
http://biology.clc.uc.edu/courses/bio104/atp.htm
Relationships between Metabolic Pathways
• Catabolic interconversions:– Polysaccharides are hydrolyzed
into glucose, which passes on to glycolysis.
– Lipids are converted to fatty acids, which become acetate (then acetyl CoA), and glycerol, which is converted to an intermediate in glycolysis.
– Proteins are hydrolyzed into amino acids, which feed into glycolysis or the citric acid cycle.
Relationships between Metabolic Pathways
• What happens if inadequate food molecules are available?– Glycogen stores in muscle and
liver are used first.– Fats are used next. But the
brain can only use glucose, so it must be synthesized by gluconeogenesis which uses mostly amino acids.
– Therefore, proteins must be broken down.
– After fats are depleted, proteins alone provide energy.
Diseases of Cell Membrane
• Cystic Fibrosis– does not allow Cl- to pumped
across the membrane– Mucus and secretions in lungs,
pancreas thicken• Duchenne Muscular Dystrophy
– “leaky” Ca++ channels
• Type II Diabetes– Cells become less sensitive to
insulin
TT AA
CC
TT
GG CC
GG
AA
GG
CC
TT AA
GGCC
TT
AA
GG
CC
Replication
Replication
DNA is doubled so
DNA is doubled so
each cell will have an
each cell will have an
exact copy of DNA.
exact copy of DNA.
Cell Growth and Cell Growth and “Everyday Activity” “Everyday Activity”
~ Protein Synthesis ~ Protein Synthesis ~~
Transcription Transcription
TranslationTranslation
““Replic
ated D
NA”
Replicate
d DNA”
is given to
each ce
ll.
is given to
each ce
ll.
Cell Division and Cell Division and Protein SynthesisProtein Synthesis
Cytokinesis Cytoplasm is
divided up into each cell.
MET LEUTHRARG
DNADNA
RNARNA
RNARNA
DNADNA
TT
CC
GG
AA
GG
TT
CC
AA
GG
AA
TT
CC
GG
CC
AA
GG
TT
CC
TT
CC
GG
AA
GG
TT
CC
AA
GG
AA
TT
CC
GG
CC
AA
GG
TT
CC
TranscriptionTranscription
ReplicationReplication
TranslationTranslation
When cells divide, they must make a copy of the DNA so the two resulting cells each have the exact same copy
of genetic code.
Mitosis:Mitosis:Dividing the DNADividing the DNA
Cytokinesis:Cytokinesis:Dividing of the cellDividing of the cell
Cell Division: MitosisCell Division: Mitosis
Cell DivisionThe newly formed cell receives the replicated copy of DNA.
TT AA
CC
TT
GG CC
GG
AA
GG
CC
TT AA
GGCC
TT
AA
GG
CC
TT
CC
GG
AA
GG
TT
CC
AA
GG
AA
TT
CC
GG
CC
AA
GG
TT
CC
The free-floating nucleotides in the nucleus attach themselves to each side of the ladder.
AA TT
GG CC
CC GG
TT AA
CC GG
AA TT
GG CC
TT AA
CC GGOnce replication has occurred,
the cell can divide into 2.
-Creates 2 IDENTICAL DAUGHTER CELLS.
-Process that all body (somatic) cells go through
-Replace old cells, repair damage
Protein Synthesis: Using DNA to make proteins
TranscriptionTranscription
TranslationTranslation Protein SynthesisProtein Synthesis
DNA makes messenger RNA (mRNA), and then it is sent to the ribosome.
mRNA serves as the code sotransfer RNA (tRNA) can placethe amino acids in sequence.
The protein is made from the coded message.
11
22 33
MET
LEU
THRARGMET ARG
THR
LEU
TTTTTTTT
TT TTTT
TranscriptionDNA writes its code to make mRNA.
TT TTTT
DNA
RNA
mRNA
message sent
toTTTTTTTT
DNA
RNA
Next is translation
UU
GGAACC
AACCUUGG
AACCUU
GG
AACC
UU
GG
AACCUU
GG
UUGGAA CC UU
GG AACC
UU
GGAA
CC
UU
GGAA
CC
AACCUU
GG
AACC
UU
GG
AACC UU
GG
AA CC UUGG AA CC UU
GG
AACCUU
GG
AACCUU
GG
AACC
UU
GG
AACC
UU
GG
AACC
UU
GG
AACCUU
GG
AACCUUGG
TyptophanTyptophan
Proline
Proline
StopStop
Tyrosine
Tyrosine
Serine
Serine
Leuci
ne
Leuci
ne
Phenyla
l-
Phenyla
l-anin
eanin
eG
lycin
eG
lycin
e
Glu
tam
ic
Glu
tam
ic
Acid
Acid
Aspartic
Aspartic
Acid
Acid
Alanine
Alanine
ValineValine
LeucineLeucine
Thre
onin
e
Thre
onin
e
Aspar
agin
e
Aspar
agin
e
ArginineArginine
Histdine
Histdine
Isole
ucin
eIs
ole
ucin
e
Glu
tam
ine
Glu
tam
ine
SerineSerine
LysineLysine
Meth
ionin
e
Meth
ionin
e Arg
inin
eA
rgin
ine
mRNA CodonmRNA Codon
mRNA CodonmRNA Codon mRNA CodonmRNA Codon
mRNA CodonmRNA Codon
anticodonanticodon
tRN
AtR
NA
VAL
anticodonanticodon
tRN
AtR
NA
LEU
anticodonanticodon
tRN
AtR
NA
PRO
anticodonanticodon
tRN
AtR
NA
MET
This Is the “start” codon and begins the amino
acid chain.
TranslationThe ribosome and tRNA helps assemble the protein chain of amino acids.
MET LEUTHRARG
The amino acids are bonded together to start the protein chain.
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