Review Questions
According to the figure
which abdominopelvic
region(s) is/are cranial to
the ascending colon of the
large intestine?
a) Umbilical
b) Right hypochondriac
c) Left Lumbar
d) Two of these options
e) None of these options
B) Right hypochondriac
• In what regions are the liver?
– Right hypochondriac and epigastric regions
The cell
Ultrastructure
Ch. 3
The Cell
• Cell – basic structural & functional unit
of the body
• Cytology
– Prokaryotic- simple, no membranebound organelles
– Eukaryotic- complex, organelles
Specialized Cells
– Red Blood Cell
• small, no nucleus
– Skeletal muscle cell
• Cylindrical, multi-nucleated, long
– Neuron
• Cell body with axon and dendrites
• AXONAL PROCESS 1 METER LONG
– Sperm Cell
• Flagellated
– MANY OTHER DIFFERENT CELL TYPES (over 200)
Basic Structural Similarities of Cells
– all cells have to metabolize to stay alive
•
results in structural similarities
1. Plasma/Cell Membrane
– Separates inside of cell (intracellular) from
outside of cell (extracellular)
– Control what enters/exits cell
– Very thin (5 to 10 nanometers)
Fluid mosaic model of plasma membrane
S. J. Singer & Garth Nicholson 1972
Composition of Plasma Membrane
1. Lipid bilayer
a. Largely phospholipids
• Polar “head” – hydrophilic =
attracted to water
• Non-polar “tails” –
hydrophobic = repelled by
water
b. Glycolipids (~5%)- lipids
with sugar groups attached
c. Cholesterol (20%)
• polar and non-polar regions
• stabilizes membrane
(decreases fluidity
glycerol
Composition continued…
2. Lipid Rafts (20%)
•
•
•
On outer membrane surface
Dynamic assembly of saturated phospholipids,
sphingolipids and cholesterol
Important for various functions (receptors, etc)
3. Plasma membrane proteins (50% by mass)
• Integral proteins
• Peripheral proteins
• cell signaling, or endocytosis
Integral plasma membrane proteins
• Embedded in lipid
bilayer
• Most are
transmembrane
Functions of integral plasma membrane proteins
1. Transport
a. cluster of transmembrane proteins can form channels
(pores)
b. let certain substances pass in/out of cell; small, watersoluble molecules or ions (like Na, K)
c. Carrier proteins- substance binding induces
conformational change
2. Receptor
a. Bind substances - relay messages to cell interior
3. Enzyme
Functions of integral plasma
membrane proteins
1. Cell junctions
a. Tight junctions - integral proteins of neighboring cells
fuse together
a.
between epithelial cells of digestive tract)
b. Desmosomes - like ‘velcro’: protein filaments extend from
adjacent cells and link together (heart, skin)
c. Gap junctions - channels of adjacent cells connect
(smooth muscle, heart)
Functions of integral plasma membrane proteins
5. Cell Identity – signatures on cell that give it specific
identity via glycoproteins
Glycoproteins- short chain sugars attached to protein
Peripheral plasma membrane proteins
1. Loosely attach to
integral proteins
2. Transport
3. Receptor
4. Enzyme
5. Cell identity
6. Cell junctions
Basic Structural Similarities of Cells
1. Plasma/Cell Membrane
2. Cytoplasm/cytoskeleton
• Cytoplasm - material
between plasma
membrane and nucleus
• Contains
- Cytosol
- Organelles
Cytosol - thick , semi-transparent, jelly-like fluid
Mostly water but also contains:
•
•
•
Proteins
Salts/ions
Sugars
Basic Structural Similarities of Cells
3. Organelles “small organs”
Organelle
Function
Nucleus
Contains DNA
Mitochondria
Cellular respiration; contain own DNA
Ribosomes
Make protein
Endoplasmic reticulum
-Rough
-Smooth
Site of protein synthesis, packaging
Many functions
Golgi apparatus
Processing center: modify/package proteins
Lysosomes
“Cleaning crew”
Cytoskeleton (microtubules, microfilaments) Structural support, cell movements
Mitochondrial diseases - many different types; symptoms from muscle weakness
to poor growth, seizures, organ failure
• nucleus- largest structure in cell; red blood
cells (no nucleus)
– skeletal muscle cells (many nuclei)
– contains chromosomes (genes) controlling cell
structure and function
• mitochondria - involved in cellular respiration
(producing energy or ATP)
– contain their own DNA apart from that contained
in nucleus (DNA inherited from only mom)
• endoplasmic reticulum
– rough (has ribosomes); protein synthesis occurs
– packaging of newly formed protein into vesicles
which then go to Golgi apparatus
– smooth - most cells contain relatively little if any;
enzymes involved in many functions, storage site
of calcium in skeletal and cardiac muscle cells
• Golgi - proteins undergo modification (sugars,
phosphate groups added) packaged to be sent
• Lysosomes- contain enzymes to digest
particles, bacteria, viruses, broken-worn-out,
non-functional organelles
• -cytoskeleton - network of rods like
microtubules and microfilaments- provide
support and function in cell movement,
moving organelles/molecules within cell
• Tay Sachs disease - affects specific enzyme
found in lysosomes
– mutation in gene encoding for enzyme in
lysosome that breaks down lipids in brain and
nerve cells. Without enzyme lipids build up and
damage nerve cells
– Children rarely live beyond 4-5 years; no cure or
treatment
What 3 structures are common among
all animal cells?
Plasma/cell membrane
Cytoplasm/cytoskeleton
Organelles
What is the fluid mosaic model of the
plasma membrane?
What are the 2 types of plasma
membrane proteins?
• Integral and peripheral
Transport Processes
• Plasma membrane is selectively (differentially)
permeable
– some substances can pass through and others are excluded
• The way substances move across membrane
depends on electrochemical gradient =
concentration gradient + electrical gradient across
plasma membrane & which direction substance
needs to go
• Substances move from areas of high concentration to
areas of low concentration
Main Types of Transport
1. Passive transport – no ATP needed; 4 types
– down their concentration gradient (from high to
low)
2. Active transport - ATP needed; 3 types
– against their concentration gradient (from low to
high)
Passive transport
– Diffusion 1. Simple diffusion –
substances pass
through lipid bilayer
a.
b.
Lipid soluble
molecules
Small molecules (O2
and CO2)
2. Facilitated diffusion substances move
across membrane by
protein channels or
carrier proteins
a.
b.
c.
Glucose
Amino acids
Ions
Passive transport
3. Osmosis – water moving
through a semipermeable membrane
Osmolarity - total concentration
of solutes in solution
Osmosis- water moves, solutes don't
ie. Cell relative to environment
Which of these is used for most intravenous solutions?
Passive Transport
4. Bulk Flow (Filtration) – movement of solutes
& water from high pressure to low pressure
– E.g. Kidney
*Faster rate than diffusion & osmosis
Active Transport
1. Bulk (Vesicular) transport - large substances
transported in vesicles (w/ ATP)
a. Endocytosis – bringing substance into the cell
1)
2)
Phagocytosis – engulfing molecules/bacteria (“ cell
eating”)
Pinocytosis – engulfing water (“cell drinking”)
b. Exocytosis – removing substance from the cell,
fuses with membrane and erupts
Active Transport
2. Primary Active Transport – involves ATP and
transport proteins to move substances
against concentration gradient
– Ex: Na+/K+ ATPase pump (3 Na+ out for every 2 K+ in)
http://www.youtube.com/watch?v=yz7EHJFDE
Active Transport
3. Secondary Active Transport – simultaneous
movement of 2 substances through transport
protein.
• 1 leaking through provides energy to move
other
a. Co-transport (symport) – substances going in
same direction
b. Counter transport (antiport) – substances going
in opposite direction
Membrane potential - difference in electrical charge across
plasma membrane
Resting membrane potential - at rest; ~-70 mV
- inside of cell has overall negative charge relative to
outside
Extracellular
High Na+
Low K+
High Ca++
High ClLow Protein-
Intracellular
Low Na+
High K+
Low Ca++
Low ClHigh Protein-
• The resting membrane potential determined
by differential permeability of membrane to K
and concentration gradient of K
• passive process of K+ and Na+ moving across
membrane would continue until their
concentrations are equal across the
membrane (electrochemical equilibrium).
– this would be a problem!!!! Need voltage
difference because a change in membrane
potential is what causes muscles to contract and
what propagates nerve impulses!!!!
Establishing the potential
④ Na+ also enters cell through
leaky channels bringing
resting membrane potential to
~-70 mV
Maintaining the potential
Na+/K+ pumps (Active
transport) maintains
the resting membrane
potential
-3 Na+ out for
every 2 K+ in
Na+
K+
2 K+
2 K+
3 Na+
3 Na+
Inclusions
• 1. Chemical substances produced by the cell
(usually organic and recognizable)
– Examples: melanin, glycogen, lipids
• Melanin - protein pigment giving skin color
• Glycogen - an animal starch - the storage form
of glucose in liver & muscles
• Lipids - energy storage in specialized cells and
in others as components
Protein Synthesis
• Proteins made by translating the DNA code
into specific proteins
• a. Transcription - genetic code passed from
DNA to RNA (messenger RNA)
– 1] Ribosomal RNA - formed on DNA strand to
direct peptide chain start and stop codons
– 2] Transfer RNA – reads mRNA to add amino
acids
• Translation - mRNA nitrogenous base sequence
specifies the amino acid sequence in the protein
• 1] mRNA associates with ribosome (composed of
proteins & rRNA)
• 2] tRNA attracts specific amino acids to the
anticodon (triplet of nitrogenous bases as mirror to
the sequence of bases on mRNA called codon)
• 3] tRNA delivers the amino acids to the codon with
the ribosome moving along the mRNA strand
stimulating the amino acids to form peptide bonds
(polypeptide).
Cellular reproduction
• Mitosis - nuclear division of progressing through a series of specific steps
toward development of a pair of genetically identical nuclei.
• a. DNA replicates during cell S-phase - part of interphase
• b. Chromosomes organized into duplicates during the cell G2 phase
providing genetic replicates (have the same hereditary information) part
of interphase
• c. Prophase - chromosomes condense - with the decomposition of the
nuclear membrane nucleoli disappears, centrioles migrate to form poles
and chromosomes become visible.
• d. Metaphase - spindle appears and chromosomes align vertically along
the equator of the cell.
• e. Anaphase - centromeres (attachment points of chromosomes to the
spindle) divide and single chromosomes move along toward the opposite
poles.
• f. Telophase - chromosomes stretch out and unwind, a new nuclear
membrane forms and nucleoli reappears forming new nuclei.
Cytokinesis
• -division of the cytoplasm and organelles
resulting in two genetically identical individual
cells
• beginning during anaphase a cleavage furrow
begins at the cell’s equatorial plane and
progresses inward during telophase effectively
developing two genetically daughter cells.
Meiosis
• the production of gametic (sex) cells from
specialized tissues resulting in the product cells
possessing ½ of the chromosomes of the parent
cells.
• Abnormal Cell Division
– Neoplasms: normal cell’s internal reproductive controls fail
resulting in excessive cellular division and potential spread
(metastasis).
– correlated with virus and environmental triggers.