Last of Cellular function: 9/2
What mechanisms help cell undergo bulk transport?
How do membrane proteins facilitate bulk transport?
How do exocytosis and endocytosis differ?
Review of membrane proteins and their functions.
Why is the Na+/K+-ATPase one of the most important
transmembrane proteins on a plasma membrane?
This ubiquitous enzyme is a transmembrane, primary active, and an
antiport. Check out this Great Review Animation:
Review of Na+/K+-ATPase Functions:
1) Regulation of intracellular Na+ and K+ content/water volume.
Na+ sphere of hydration > K+ sphere of hydration
2) Pump itself is Primary Active, other secondary active pumps depend a
pre-existing Na+ concentration gradient. Consider glucose transport.
3) Maintaining membrane potential (voltage). All cells have a
membrane potential, neurons modify potential to exchange
4) Heat Production: Some cells create “futile cycles” where they just
oxidize ATP to run the Na/K-ATPase and let the ions leak back in/out.
Net result is HEAT production by a cell and for the body.
Review: 1) Simple Diffusion (no transmembrane protein required) and 2)
Membrane transport methods that use transmembrane proteins with a
high degree of substrate specificity to move things across the Pl bilayer.
What is it called when materials in
a vesicle leave a cell? “Exocytosis”
• “Exocytosis” is critical for the release of materials from
within a cell!
– Beta-cells in the pancreas release insulin contained in
tiny membrane bound inclusions (vesicles) into the
blood after you eat a meal!
– Neurons release the contents of vesicles
(neurotransmitters) at nerve ending too to cause
muscle contraction and many other activities!
Fusion of the vesicular PL bilayer with the plasma membrane PL bilayer
allows the materials enclosed in a vesicle to leave the cell!
This could be insulin or
growth hormone or even
things that are not proteins
like acetylcholine of
epinephrine from neurons.
What is it called when vesicles enter and bring extracellular
materials or parts of the plasma membrane into the cytosol?
Endocytosis- movement of materials “into the cell” :
There are Three Types of Endocytosis:
1) Large Volume Endocytosis: “Phagocytosis”
Used by a macrophage to engulf a bacteria
2) Smaller Volume Endocytosis: “Pinocytosis”
Often called cell drinking
3) “Receptor Mediated Endocytosis”: entry via special
protein receptors on membrane that detect, bind to, and
mediate transport of only specific kinds of molecule
(remember key-lock idea!) Very Important!
How does these differ from Osmosis?
Receptor-mediated endocytosis: after particles bind to receptor proteins
that line „clathrin coated pits‟ they can be pulled into the cell!
This is how most cholesterol (in LDL) enters the cells of an artery!
TRANSCYTOSIS: vesicular passage “across” a cell (one side to other)
Specialization of Transmembrane proteins: 1) Glycoproteins help cells
contact and communicate with each other, 2) Receptors permit
hormones to send information into a cell, and 3) Channels permit the
regulated transport of ions/small molecules into/out of a cell.
Hormones are often present at mico or nanogram/liter quantities in
the blood. Amplification creates massive effects in the target cell!
Second messengers inside the cytosol make this possible.
• Please be sure to review the organelles
and cellular structures listed on pages
• Know These: Nucleus, nucleolus,
mitochondria, endoplasmic reticulum,
lysosome, peroxisome, Golgi apparatus,
plasma membrane bilayer, and cytosol.
Introduction to genetics:
What bases are used to make DNA and RNA?
How does a complimentary base pairing stabilize the
DNA double helix?
How is DNA structurally organized in a cell?
What is “semiconservative” DNA replication?
Review of organelles that make it possible to produce a
functional protein from DNA.
How is your Genetic Info turned into your unique proteins? Genetic Info
is contained in a the DNA double helix of chromosomes located in the
nucleus that is “transcribed” into mRNA. The mRNA is “translated” into
protein in the cytosol after associating with ribosomes.
• RNA and DNA are made of 5 kinds of “nucleotide”.
• Each nucleotide is characterized by its unique nitrogenous “base”:
– 5 bases: A, T, C, G or U
– Who Gets What? ATGCDNA AUGCRNA
• DNA forms a double helix that holds your genetic information
– (“genes” are sections of DNA that code for specific proteins)
• DNA is converted to mRNA (transcription)
• mRNA is translated to protein (amino acids)
– Proteins create “traits”-what you look like
• RNA is single stranded because it contains Uracil not Thymine and
because the ribose has a full hydroxyl:
-Uracil can‟t hydrogen bond very well and hydroxyl-group also
prevents double helix
• Three RNA types: mRNA, tRNA, rRNA
What do the bases that make up DNA and RNA look like?
Remember that RNA has Uracil not Thymine!
DNA forms a double helix when complimentary bases on two strands
hydrogen bond to each others bases. RNA cannot form a double helix
because uracil can‟t form hydrogen bonds to adenine and the hydroxyl-
group of Ribose (RNA) blocks the formation of a RNA double helix !
Watson and Crick elucidated the double helix DNA structure in 1953
DNA is a huge molecule. All the DNA in the 10 trillion cells
of your body put end to end would reach to the sun and
back 65 times!
How does all the DNA fit inside a tiny nuclei of a cell?
DNA Helix: wound onto histone proteins Degrees of DNA
Histones: wound into nucleosomes Organization:
– Helix must also be “unwound” to make new 1) Primary base
DNA or RNA sequence
DNA on nucleosomes: wound into chromatids, 2) Histones
supercoiled, and wound onto chromatin 3) Nucleosomes
– Chromatids and Chromatin must be 4) Chromatin
unwound to make new DNA or RNA 5) Supercoiled
Chromosome is a massive structure of tightly nucleosomes
– Chromosomes must be unwound at cell
replication 7) Chromosome
– Parts of chromosomes must be unwound for
RNA to be produced
How do we organize this long strand into a structure that
will fit inside a cell? Could you describe these structures
from DNA to Chromosome (from smallest to largest)?
The chromosomes on my son Dirk’s FISH Analysis looked fine
What will the next kid look like????
“FISH= Fluorescence In Situ Hybridization”
Full Chromosomal Analysis: My Kid Dirk’s Karyotype Looked
Good! Good=23 pairs and each chromosome had normal size
How is DNA reproduced in the cell?
• DNA is replicated in semi-conservative fashion.
• This means it is unwound such that each original strand
becomes the template for each new strand of DNA.
• Therefore two new DNA strands and two new double-
helices result from the original helix.
• DNA Polymerase is the enzyme that replicates the DNA.
• DNA is only replicated when needed during cell division.
Original cell with one ds DNA
Shown in blue. This cell is
undergoing cell division into
two new cells. The new DNA in
the two new cells is shown in
Semiconservative DNA replication in original cell!
Each strand of DNA is used as a “template” to make
the next strand of new DNA that becomes a new ds DNA helix.
Two new cells, each with
a ds DNA (1old/1new)
Four new cells:
Two cells contain
the original two DNA
strands (blue), two
contain entirely new
DNA mRNA protein
• DNA mRNA: organelle?
• mRNA protein: organelle?
• Nascent (new) protein final protein: