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.