A&P: The Cell
The Plasma Membrane
How was it discovered?
http://ed.ted.com/lessons/insights-into-cellmembranes-via-dish-detergent-ethanperlstein#watch
The Plasma Membrane
What is the
plasma
membrane?
• Flexible, sturdy barrier of the cell.
• Fluid mosaic model: proteins float
freely in sea of lipids.
• Lipid bilayer: phospholipids,
cholesterol, glycolipids.
• Phospholipids are amphipathic (have
both polar and nonpolar parts)
• Fluidity depends on double bonds in
lipids, and amount of cholesterol
The Plasma Membrane
What is it
made of?
• Integral proteins extend through
membrane- nost are transmembrane
(go all the way through)
• Peripheral proteins are not firmly
imbedded in membrane
• Many of these proteins are
glycoproteins (have carbohydrate
groups)
The Plasma Membrane
What do the
membrane
proteins do?
• Ion channels: pores which selectively
allow ions in or out
• Transporters: selectively move a
substance in or out
• Receptors: cell recognition site (binds to
ligand)
• Enzymes: catalyze reaction
• Linkers: anchor to proteins inside or
outside cell, or to proteins of neighbor
cell
• Cell Identity Marker- allows cells to
recognize each other, tells identity.
The Plasma Membrane
Permeability
• Permeability: the ability of substances
to pass through
• The plasma membrane is selectively
permeable.
• Permeable to nonpolar, uncharged
molecules such as O2, CO2, steroids.
• Impermeable to ions and large,
uncharged polar molecules such as
glucose.
• Slightly permeable to small uncharged
polar molecules such as water.
The Plasma Membrane
• Gradients
• Concentration gradient: difference in
concentration of a substance inside
and outside the cell.
• Substances will move from area of
high concentration to low.
• Electrical gradient: difference in
electrical charge. The inner surface of
the membrane is negatively charged,
the outside is positive.
• Positively charged substances will
move toward negative area, and vice
versa.
Homework
Read pages 60-65. Do page 65 #1-7
Article (Sleep deprivation) summary due Friday.
Include in your summary a personal angle (personal
story about sleep, how reading the article
changed/may change your sleeping habits, etc)
The Plasma Membrane
https://www.youtube.com/watch?v=kfy92hd
aAH0
The Plasma Membrane
Passive
Transport
• no energy or ATP needed.
• Substances move with gradient.
• Osmosis, dialysis, facilitated difuusion are
examples.
• Facilitated diffusion involves proteins
The Plasma Membrane
Active
Transport
• Material is moved through the membrane using a
protein carrier using ATP.
• Examples: uptake of iodine into the thyroid,
sodium/potassium pump.
https://www.youtube.com/watch?v=P-imDC1txWw
The Plasma Membrane
Endocytosis
• Endocytosis needs ATP, and brings materials in by
forming vesicles around large particles.
• A lysosome will join with the vesicle to break down
the particles.
• Phagocytosis is intake of solids.
• Pinocytosis is intake of liquids.
https://www.youtube.com/watch?v=-ZFnO5RY1cU
https://www.youtube.com/watch?v=hacbn_xcZdU
The Plasma Membrane
Receptor
mediated
endocytosis
• Receptor mediated endocytosis- molecules
bind to receptors, a vesicle forms as the
membrane sinks in
• A lysosome joins with the vesicle, enzyme
break down the substance so it can be
absorbed.
• The receptor returns to membrane.
The Plasma Membrane
Exocytosis
Exocytosis releases materials from the cell.
Secretory cells release enzymes, hormones, mucus.
Nerve cells release neurotransmitters.
http://science.education.nih.gov/supplements/nih2/addic
tion/activities/lesson2_neurotransmission.htm
The Plasma Membrane
Homework: Read pages 69-74, do page 74 #12
and #15
Organelles and human
disorders
Tay-Sachs Disease
• Inherited condition
• Absence of Hex A (a lysosomal
enzyme)
• Hex A breaks down a membrane
glycolipid found abundantly in nerve
cells.
• Effects: seizures, muscle rigidity,
blindness, dementia, death
http://vimeo.com/62446736
Lily Foundation Mitochondrial Disease
Organelles and human
disorders
Mitochondrial
Disease
• Results from failures of the
mitochondria.
• Less energy is generated for the cell.
• Cell injury or death occurs.
• Organs and organ systems may fail.
• Symptoms include loss of motor
control, muscle weakness/pain,
gastrointestinal disorders, poor
growth, cardiac disease, liver disease,
vision/hearing problems,
developmental delays.
https://www.youtube.com/watch?v=F8Xg8sO5AM&list=PLio7GaXoQ3Sg14ms4m2wKJNLtaw
J-diBO
The Triumphant Story of Sam Berns, Progeria
Organelles and Human
Disorders
Progeria
• Caused by a mutation for a protein (Lamin A) which
is the structural scaffolding that holds the nucleus
together.
• This change in the protein makes the nucleus
unstable, and leads to premature aging.
• Symptoms include growth failure, loss of body fat
and hair, stiffness of joints, heart disease/stroke.
• Life expectancy is 14 years.
https://www.youtube.com/watch?v=Twjg7v-pTO4
Current TV presents ‘Dying Young’
Organelles and human
disorders
Cystic Fibrosis
• Defect in protein channels in the cell
membrane leading from certain glands.
• The channel transports Cl- into and out
of cells, controlling the movement of
water.
• Water is needed to thin the mucus.
• Thick mucus in the lungs, leading to
infection.
• Clogged pancreas, prevents digestive
juices from reaching intestines.
• Salty sweat.
Continue the Tonicity Experiment
Homework: Read pages 74-84. Complete worksheet
(glue into notebook). Also make sure notebook is
ready for check.
Tonicity Lab is complete.
Homework: Complete the lab write-up. It should include:
•
Introduction paragraph (you did this Friday)
•
Data tables
•
Conclusion paragraph
Also: read pages 85-87, do page 86 #20-22
The nucleus
The
structure of
the nucleus
• Large and spherical
• Most human cells have a single nucleus
• Exceptions: mature blood cells have none, skeletal
muscles have several.
• Nuclear envelope is a double membrane to
separate the nucleus from the cytoplasm
The nucleus
The
structure of
the nucleus
• Nucleoli are clusters of protein, DNA, and RNA
inside the nucleus. The control the creation of the
ribosomes.
• Nuclear pores are transmembrane proteins that
control the movement of molecules in and out of
the nucleus.
The nucleus
The function
of the
nucleus
• Controls cellular structure and directs cellular
function.
• Genes contain instructions for the cell structure and
function- located on chromosomes.
• Chromosomes are made of chromatin- a complex
of DNA, proteins, and RNA.
http://www.dnalc.org/resources/3d/12-transcriptionbasic.html
Transcription basic video
The nucleus
Transcription and Translation
Transcription
• DNA and RNA store information as sets of three
nucleotides called codons.
• RNA polymerase catalyzes transcription of DNA.
• Three types of RNA are made from the DNA
template:
1. Messenger RNA (mRNA)- directs the synthesis of a
protein.
2. Ribosomal RNA (rRNA)- joins with ribosomal
proteins to make ribosomes
3. Transfer RNA (tRNA)- involved in protein synthesis.
http://www.dnalc.org/resources/3d/15-translationbasic.html\
Translation basic video
The nucleus
Transcription and Translation
Translation
• Ribosomes and tRNA use the sequence of the
mRNA to assemble amino acids into proteins.
• Steps:
1. Initiator tRNA with anticodon UAC attaches to the
start codon AUG on the mRNA.
2. Large and small ribosomal subunits attach.
3. The next tRNA attaches to the next codon.
4. The large RNA subunit catalyzes the formation of a
bond between the two amino acids.
5. The first tRNA detaches, the ribosome shifts down
the mRNA. Steps 3-6 repeat.
6. Synthesis ends at the stop codon, the protein is
freed and the ribosome detaches.
https://www.youtube.com/watch?v=eWVuCDQKB5k
https://www.youtube.com/watch?v=cZEPQ3kkwHo
https://www.youtube.com/watch?v=LelFL9CrqQs
Recombinant DNA
Recombinant
DNA
Recombinants
Genetic
Engineering
• DNA combined from different sources
• Organisms with recombinant DNA
• The manipulation of genetic material and creation
of recombinants.
• Medical uses: human proteins produced in bacteria
in large quantities, then harvested and purified for
distribution to patients.
• Examples: human growth hormone, insulin,
interferon, and erythropoietin
Recombinant DNA
Restriction
enzymes
• Molecular tool used to cut DNA- cuts the DNA at a
specific point.
• Examples: Eco RI, Bam HI
• Some restriction enzymes create “sticky ends”
• DNA can be inserted- like a puzzle piece.
• DNA ligase ligates (“glues) the pieces together.
• http://www.hhmi.org/biointeractive/geneticengineering
Recombinant DNA
How does the
engineered
DNA get into
the bacteria?
• Antibiotic sensitive bacteria are treated with
CaCl2.
• Engineered DNA (which has both the gene
wanted and also a gene for antibiotic
resistance) is added, taken in by bacteria
• Bacteria are grown on media containing the
appropriate antibiotic.
• Only the bacteria with the engineered DNA will
grow.