Introduction to Biology

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Introduction to Biology
September 17th 2004 Nancy Van Driessche (email
nv993804_at_bcm.tmc.edu)
Overview of What is a cell? http//www.ncbi.nlm
.nih.gov/About/primer/genetics_cell.html
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What is a cell?

• structural and functional units of all living
  organisms
• unicellular and multicellular organisms
• bacteria vs. human

specialized functions
nutrients
energy source
reproduce
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Eukaryote vs. Prokaryote
eg. bacteria
eg. fungi animals plants
unicellular organisms yeast, Dictyostelium etc.
Biggest differences Prokaryotes lack a nuclear
membrane! Prokaryotes don't have intracellular
organelles! Prokaryotes about 10X size of
Eukaryotes.
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Plasma membrane a cell's protective coat
outside the cell
double layer of lipids
proteins
inside the cell
Several functions of membrane proteins
outside the cell
inside the cell
inport and export of molecules
cross-linking of membrane proteins
amplification of extracellular signal
convertion of product X into product Y
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The cytoskeleton a cell's scaffold

• very complex and dynamic cell component!
• organizes and maintains the cell's shape (e.g.
  epithelial cells of the gut)
• anchors the organells in place
• helps during the uptake of external material
  (endocytosis)
• involvement in cell movement
• growth

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The cytoskeleton a cell's scaffold
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The cytoplasm (cytosol) a cell's inner space
Plasma membrane
Cytoskeleton cytosol
large fluid-filled space (mostly water proteins
that control most of the cell metabolisms) glyc
olysis, transcription factors, intracellular
receptors etc.
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Organelles

• Nucleus
• Protein production machine the ribosomes
• Mitochondria and Chloroplasts
• Endoplasmic Reticulum and the Golgi apparatus
• Lysosomes and Peroxisomes

Adapted and/or specialized for carrying out one
or more vital functions. Reminder! Are only found
in eukaryotes.
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Nucleus a cell's center
Function of the nucleus
Structure of the nucleus
- Stores the chromosomes (genetic material) -
production of ribosomes in nucleolus - protection
of DNA from damaging molecules of molecules that
interfere with its processing - DNA replication
and synthesis of messenger RNA (mRNA)
Note 2 kinds of genetic material deoxyribonuclei
c acid (DNA) ribonucleic acid (RNA)
source http//cellbio.utmb.edu/cellbio/nucleus.ht
ml
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Endoplasmic Reticulum and the Ribosomes protein
production machine
Endoplasmic Reticulum (ER)
source http//cellbio.utmb.edu/cellbio/ribosome.h
tm
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Endoplasmic Reticulum
ER is a continuation of the outer nuclear
membrane. ER has smooth regions (responsible for
lipid and membrane protein modifications) and
rough regions (associated with ribosomes
responsible for the synthesis of other proteins)
source http//www.cellsalive.com/cells/er.htm
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Golgi apparatus

• Function
• - modification of lipids and proteins
• storage and packaging of materials that will be
  exported from the cell.

source http//cellbio.utmb.edu/cellbio/golgi.htm
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Mitochondria

• Contain their own genome (distinct from nuclear
  genome)
• Self-replicating
• Critical role in generation of energy (called
  ATP)
• Glycolysis (without oxygen use)
• Krebs cycle (in presence of oxygen)

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Lysosomes

• Rich in digestive enzymes (that work at low pH)
• Digest fforeing bacteria that invade a cell
• Recycling of membrane components
• Repair damage to plasma membrane

Peroxisomes

• Get rid of toxic substances
• Many in the liver

lysosome
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Making new Cells and Cell types
(1) Making New Cells
Unicellular organisms Asexual reproduction
replication of genetic material and splitting 1
cell Into 2 identical cells Multicellular
organisms Mitosis to produce for example new
skin cells and liver cells. Meiosis or sexual
reproduction to create a whole new organism
(gametes)
Human chromosomes
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Overview of the major events in mitosis
Interphase prophase metaphase
anaphase telophase
In case of DNA damage or failure of critical
processes
P53 stimulates induction of inhibitory proteins
that halt DNA replication
Defects in p53 are associated with a variety of
cancers
DNA damage repair or initiation of programmed
cell death (apoptosis)
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Overview of the major events in meiosis
Production of gametes 2 cell divisions in sequence
Big difference between mitosis and meiosis
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The Working Cell

• DNA, RNA and Protein Synthesis

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DNA structure base pairs
adenosine
thymine
cytosine
guanine
Source http//www.blc.arizona.edu/Molecular_Graph
ics/DNA_Structure/DNA_Tutorial.HTML
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DNA The code of life
Side view
5 end
3 end
Double stranded AT GC basepairs Right handed
spiral
View down helix axis
3 end
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Source http//www.blc.arizona.edu/Molecular_Graph
ics/DNA_Structure/DNA_Tutorial.HTML
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DNA replication
Occurs during cell division. Requires -
Helicases (unwind DNA) - DNA polymerases (can
bind single Stranded DNA and can move only In 3
to 5 direction. - DNA ligase stitches Okazaki
fragments
Source http//users.rcn.com/jkimball.ma.ultranet/
BiologyPages/D/DNAReplication.html
Animation
http//www.phschool.com/science/biology_place/bioc
oach/dnarep/repstrands.html?blahstep6
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Transcription RNA synthesis
Basic structure of a protein encoding gene
DNA
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Transcription RNA synthesis
(1) Initiation
- Involves transcription factors (TFs) and RNA
polymerase - Recognition of TATA box (located
20 to 30 bp of transcription initiation site)
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Transcription (elongation) (2)
/antisense strand
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Transcription (termination) (3)
RNA polymerase falls off
terminator
Animation
http//www.phschool.com/science/biology_place/bioc
oach/images/transcription/tcani.gif
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DNA vs. RNA
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Post-transcriptional modifications
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Protein synthesis Translation initiation
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Protein synthesiselongation (2)
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Protein translationtermination (3)
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Protein translation summary
Elongation
Initiation
Termination
http//www.phschool.com/science/biology_place/bioc
oach/translation/init.html
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Summary