Transcript Fall Semester Review - mychandlerschools.org

Fall Semester Review
AP/IB Biology
The Discovery of Plant Hormones
• Any growth response
– That results in curvatures of whole plant organs
toward or away from a stimulus is called a tropism
– Is often caused by hormones
Auxin
– Is used for any chemical substance that promotes
cell elongation in different target tissues
• Auxin transporters
– Move the hormone out of
the basal end of one cell,
and into the apical end of
neighboring cells
• Auxin
– Is involved in the formation and branching of roots
Other Effects of Auxin
• Auxin affects secondary growth
– By inducing cell division in the vascular cambium
and influencing differentiation of secondary xylem
• Developing seeds synthesize auxin
• tomatoes grown in greenhouse conditions sprayed with auxin
induce fruit development without a need for pollination
• This allows for seedless tomatoes
• Charles Darwin and his son Francis
– Conducted some of the earliest experiments on phototropism, a plant’s
response to light, in the late 19th century
EXPERIMENT
In 1880, Charles Darwin and his son Francis designed an experiment to determine what part of the
coleoptile senses light. In 1913, Peter Boysen-Jensen conducted an experiment to determine how the signal for
phototropism is transmitted.
RESULTS
Control
Boysen-Jensen (1913)
Darwin and Darwin (1880)
Shaded
side of
coleoptile
Light
Light
Light
Illuminated
side of
coleoptile
CONCLUSION
Tip
removed
Tip covered
by opaque
cap
Tip
covered
by transparent
cap
Base covered
by opaque
shield
Tip separated
by gelatin
block
In the Darwins’ experiment, a phototropic response occurred only when light could
reach the tip of coleoptile. Therefore, they concluded that only the tip senses light. Boysen-Jensen
observed that a phototropic response occurred if the tip was separated by a permeable barrier (gelatin)
but not if separated by an impermeable solid barrier (a mineral called mica). These results suggested
that the signal is a light-activated mobile chemical.
Tip separated
by mica
• In 1926, Frits Went
– Extracted the
chemical
messenger for
phototropism,
auxin, by
removing the
coleoptile tip &
placed it on a
block of agar. This
will allow the
chemical to travel
through.
EXPERIMENT
In 1926, Frits Went’s experiment identified how a growth-promoting chemical
causes a coleoptile to grow toward light. He placed coleoptiles in the dark and removed their tips,
putting some tips on agar blocks that he predicted would absorb the chemical. On a control
coleoptile, he placed a block that lacked the chemical. On others,
he placed blocks containing the chemical, either centered on top of the coleoptile to distribute the
chemical evenly or offset to increase the concentration on one side.
RESULTS
The coleoptile grew straight if the chemical was distributed evenly.
If the chemical was distributed unevenly, the coleoptile curved away from the side with
the block, as if growing toward light, even though it was grown in the dark.
Excised tip placed
on agar block
Growth-promoting
chemical diffuses
into agar block
Control
Control
(agar block
lacking
chemical)
has no
effect
Agar block
with chemical
stimulates growth
Offset blocks
cause curvature
CONCLUSION
Went concluded that a coleoptile curved toward light because its dark
side had a higher concentration of the growth-promoting chemical, which he named auxin.
Photoperiodism
• plant's ability to flower in response to changes in the
photoperiod: the relative lengths of day and night.
• research has shown that the dark period is more
important than the light period. For example, if SDPs
are grown under short-day conditions but the dark
period is interrupted by a flash of light, the SDPs will
not flower. The long night that normally accompanies a
short day is interrupted by the flash. An interruption of
the light period with dark has no effect.
Animal Behavior
Fixed Action Patterns (FAP)
• FAP is an instinctive behavioral response
triggered by a very specific stimulus.
• Once triggered, the FAP behavior can’t be
stopped ‘midstream’, but must play out to
completion.
Egg Rolling and the Greylag Goose
If one of the gooses' egg rolls away from the nest, the
goose automatically rolls the egg back to the nest with a
repeated, specific action. When the female notices an egg
outside the nest (sign stimulus), she begins this repeated
movement to drag the egg with her beak and neck.
If, while the goose is rolling the egg back to the nest, the
egg slides off to the side, or is removed by an observer, the
goose continues to repeat the stereotypic movements,
until she reaches the nest. She'll then relocate the missing
egg and begin the process all over again.
GREYLAG GOOSE SHOW VIDEO
Innate Behavior
Habituation
An organism decreases or ceases to respond to a stimulus
after repeated presentations.
Operant Conditioning
a method of learning that occurs through rewards and
punishments for behavior. Through operant
conditioning, an association is made between a
behavior and a consequence for that behavior.
Classical Conditioning
A learning process that occurs through associations
between an environmental stimulus and a naturally
occurring stimulus.
It's important to note
that classical
conditioning involves
placing a neutral signal
(bell) before a naturally
occurring reflex
(salivating in response
to food).
Classical conditioning basically involves forming an association
between two stimuli resulting in a learned response.
Taxis and Kinesis
Taxis has a specific and directed motion while kinesis
has a random and undirected motion.
Woodlice prefer moist areas so
they will move around less than in
dry areas. In dry areas they will
move around a lot (randomly) until
they hit upon a moist area
Magnification and scales
2. In Figure 12 the actual length of the mitochondrion is 8µm.
(a) Determine the magnification of this electron
micrograph.
(b) Calculate how long a 5 µm scale bar would be on
this electron micrograph.
(c) Determine the width of the mitochondrion.
Magnification =
size of image
actual size of specimen
a) Magnification = image size =
actual size
b) 8000 =
X__
5µm
63mm
8µm
63000µm
8µm
= 7875x ~ 8000x
8000 x 5 = 40,000µm = 40mm
c) Depending on your measurement location the image width is b/w 20mm & 23mm.
We will use 20mm.
magnification (8000) = 20,000 µm = 20,000 / 80000 = 2.5µm
X
Ionic and Covalent Bonds
Ionic Bonding
• A strong bond
• Opposite charge atoms bond & an electron is lost
by one atom & gained by the other.
– Cation: when the charge of an atom is positive
• The atom lost an electron
– Anion: when the charge of the atom is negative
• The atom gained an electron
Ionic Bonds
Everyday
tablesalt
NaCl
Crystal
The formation of the ionic bond in table salt
Covalent Bonding
VERY STRONG BOND
pH
pH
• A convenient way to express the hydrogen ion
concentration of a solution
pH = _ log [H+]
The pH scale is logarithmic
A difference of one unit represents a ten-fold change in H+
concentration
Acid
Dissociates in water to increase H+ concentration
Base
Combines with H+ when dissolved in water
Buffers
• Hydrogen ion reservoirs that take up or release H+
as needed
• The key buffer in blood is an acid-base pair
(carbonic acid-bicarbonate buffering system)
Response to a rise
in pH
–
+
+
H2O
Water in
blood plasma
CO2
Carbon dioxide
H2CO3
Carbonic acid
HCO3–
Bicarbonate
ion
Response to a drop
in pH
+
H+
Hydrogen
ion
Importance of Water
Hydrogen Bonds Give Water Unique
Properties
• Water molecules are polar molecules
• Unequal sharing of electrons & V-like shape
– They can thus form hydrogen bonds with each other
and with other polar molecules
• Each hydrogen bond is very weak
– However, the cumulative effect of enormous
numbers can make them quite strong
• Hydrogen bonding is responsible for many of the
physical properties of water
COHESIVE PROPERTIES
THERMAL PROPERTIES
High Specific Heat
Water can absorb or release a
lot of heat without changing
its own temperature by very
much.
High Heat of Vaporization
Water absorbs a lot of heat,
hydrogen bonds break, then water
turns to vapor & then evaporates.
WATER AS ICE, FLOATS
Ice
Liquid water
SOLVENT PROPERTIES
Water is a versatile
solvent because of its
polarity
Most of the important molecules in and out of
the cell are polar molecules. These molecules
create solutions that enable for biochemical
processes to occur.
Protein synthesis & glycolysis
Gas Exchange
Salt dissolves when all
ions have separated
from the crystal
Water forms a hydration shell
around each solute ion.
Light independent processes of photosynthesis
Functional Groups and
Macromolecules
WHAT IS THE DIFFERENCE BETWEEN A MONOMER & A POLYMER?
SYNTHESIS AND BREAKDOWN
OF POLYMERS
 Enzymes help
Dehydration (Condensation) reaction
To connect monomers together
A water molecule is released
One molecule gives up a hydroxyl group
& the other a hydrogen
 Hydrolysis
Polymers are broken apart to monomers
A water molecule is added to split apart
the monomers
EX: Digestion
VARIOUS MONOSACCHARIDES
What do all of these
sugars have in
common?
They are made of
one carbonyl group
and several hydroxyl
groups.
What’s the difference
between the top row
of sugars compared
to the bottom row?
The top sugars have their
carbonyl group at the end
of the carbon skeleton &
the bottom ones have their
carbonyl group in the
middle
Identify the difference between glucose & galactose.
Lipids
• Large nonpolar molecules that are insoluble in
water
• They are NOT polymers but they are large
molecules assembled from smaller molecules.
• Three major types
– Triglycerides
– Phospholipids
– Steroids
Phospholipids
• A modified fat
– One of the three fatty acids is replaced by a
phosphate and a small polar functional group
Essential to cells: they
make up the cell
membrane.
Nucleic Acids
• Serve as information storage molecules
• Store, transmit and help express hereditary
information
• Long polymers of repeating subunits termed
nucleotides
• A nucleotide is composed of three parts
– Five-carbon sugar
– Nitrogen-containing base
– Phosphate
Protein Structure
• Primary structure
– The specific amino acid sequence of a protein
• Secondary structure
– The initial folding of the amino acid chain by hydrogen
bonding
• Tertiary structure
– The final three-dimensional shape of the protein
• Quaternary structure
– The spatial arrangement of polypeptides in a multicomponent protein
Enzymes
• Influence the rate of reaction
• A set of reactants present with enzymes will
form products at a faster rate than without
enzymes.
• Enzymes cannot force reactions to occur that
would not normally occur
• The enzymes role is to lower the energy level
needed to start the reaction.
– Enzymes lower the activation energy of reactions
• Enzymes are not used up during the reaction
Prokaryotic and Eukaryotic Cells
PROKARYOTIC
• Smaller & simpler
• Less than 10µm in diameter
• DNA in ring form without
protein
• DNA is free floating
• No mitochondria
• 70S ribosomes
• No internal
compartmentalization to form
organelles
• Thought to be the 1st cells on
Earth.
• Reproduce by Binary Fission
• EX: BACTERIA
• EUKARYOTIC
• Bigger & more complex
• More than 10µm
• DNA with proteins as
chromosomes/chromatin
• DNA enclosed in nucleus
• Mitochondria is present
• 80S ribosomes
• Internal compartmentalization
present to form many types of
organelles.
• EX: EVERYTHING EXCEPT
BACTERIA
Variations among Eukaryotic Cells
• Plant cells
• Exterior of cell includes
cell wall
• Have chloroplasts
• Possess large vacuole
that’s centrally located
• Store carbohydrates as
starch
• Do not contain centrioles
• Has a fixed often angular
shape
• Animal cells
• Exterior of cell includes
plasma membrane
• No chloroplasts
• Vacuoles are usually not
present or are very small
• Store carbohydrates as
glycogen
• Have centrioles
• Is flexible and more likely
to be rounded in shape.
HOW ARE THE MITOCHONDRIA AND
CHLOROPLASTS SIMILAR TO PROKARYOTIC
CELLS?
SIZE
BOTH HAVE THEIR OWN DNA
THEY ARE NOT PART OF THE
ENDOMEMBRANE SYSTEM
THEY REPRODUCE IN A
SEMIAUTONOMOUS
MANNER
SOME PROTEINS NEEDED ARE MADE BY THEIR RIBOSOMES
LOCATED IN THEIR MEMBRANE & OTHER PROTEINS ARE BROUGHT
IN FROM THE CYTOSOL
Why do mitochondria & chloroplasts have
so many membranes in them?
For increased surface area used for the energy
conversion processes that occur in these
organelles.
Cellular Respiration
Oxidation and Reduction
Oxidation
Reduction
Loss of electrons
Gain of electrons
Gain of oxygen
Loss of oxygen
Loss of hydrogen
Gain of hydrogen
Results in many C – O bonds
Results in many C – H bonds
Results in a compound with
lower potential energy
Results in a compound with
higher potential energy
A useful way to remember: OIL = Oxidation Is Loss (of electrons)
RIG= Reduction Is Gain (of electrons)
These two reactions occur together during chemical reactions= redox reactions.
One compound’s or element’s loss is another compound’s or element’s gain.
Respiration
• Glycolysis
– Breaks down glucose into two molecules of
pyruvate
• The citric acid cycle (Krebs Cycle)
– Completes the breakdown of glucose
• Oxidative phosphorylation
– Is driven by the electron transport chain
– Generates ATP
Glycolysis
• Harvests energy by oxidizing
glucose to pyruvate
Glycolysis
ATP
Citric
acid
cycle
Oxidative
phosphorylation
ATP
ATP
Energy investment
phase
Glucose
• Glycolysis
– Means “splitting of sugar”
– Breaks down glucose into
pyruvate
– Occurs in the cytoplasm of
the cell
2 ATP + 2 P
2 ATP
used
Energy payoff phase
4 ADP + 4 P
2 NAD+ + 4 e- + 4 H +
4 ATP formed
2 NADH + 2 H+
2 Pyruvate + 2 H2O
• Two major phases
– Energy investment phase
– Energy payoff phase
Figure 9.8
Glucose
4 ATP formed – 2 ATP
used
2 NAD+ + 4 e– + 4
H+
2 Pyruvate + 2 H2O
2 ATP + 2 H+
2 NADH
Glycolysis Summary
At the end
you get
these
Before the Krebs cycle can
begin….we have the link reaction
–Pyruvate must first be converted to acetyl CoA, which
links the cycle to glycolysis
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+
O–
S
CoA
C
O
2
C
C
O
O
1
3
CH3
Pyruvate
Transport protein
Figure 9.10
CH3
Acetyle CoA
CO2
Coenzyme A
The Krebs Cycle
•6 NADH's are generated
•2 FADH2 is generated
•2 ATP are generated
•4 CO2's are released
Two turns for each molecule of glucose because each glucose is converted to 2
molecules of acetyl CoA.
ETC
–Electron transfer causes protein complexes to pump H+
from the mitochondrial matrix to the intermembrane
space
•The resulting H+ gradient
–Stores energy
–Drives chemiosmosis in ATP synthase
–Is referred to as a proton-motive force
How does electronegativity play a part in the electron transport chain?
Because each electron acceptor in the chain is more electronegative than the previous, the
electron will move from one electron transport chain molecule to the next, falling closer
and closer to the nucleus of the last electron acceptor.
Where do the electrons for the ETC come from?
NADH and FADH2 which got theirs from glucose.
What molecule is the final acceptor of the electron?
Oxygen, from splitting O2 molecule & grabbing 2 H+ .
What’s consumed
during this process?
O2
What’s gained by this
process?
H+ inside the inner
membrane space
• FADH2 enters the ETC at a
lower free energy level than
the NADH.
– Results in FADH2 produces 2
ATP’s to NADH’s 3
• Oxygen is the final electron
acceptor
– The electrons + oxygen + 2
hydrogen ions = H2O
• Important to note that low
amounts of energy is lost at
each exchange along the ETC.
Chemiosmosis:
The Energy-Coupling Mechanism
INTERMEMBRANE SPACE
H+
H+
H+
H+
•ATP synthase
H+
H+
H+
A stator anchored
in the membrane
holds the knob
stationary.
–Is the enzyme
that actually
makes ATP
H+
32-34 ATP
ADP
+
Pi
Figure 9.14
A rotor within the
membrane spins
clockwise when
H+ flows past
it down the H+
gradient.
MITOCHONDRIAL MATRIX
ATP
A rod (for “stalk”)
extending into
the knob also
spins, activating
catalytic sites in
the knob.
Three catalytic
sites in the
stationary knob
join inorganic
Phosphate to ADP
to make ATP.
Oxidative
phosphorylation.
electron transport
and chemiosmosis
Glycolysis
ATP
Inner
Mitochondrial
membrane
ATP
ATP
H+
H+
H+
Intermembrane
space
H+
Cyt c
Protein complex
of electron
carners
Q
I
Inner
mitochondrial
membrane
IV
III
ATP
synthase
II
FADH2
FAD+
NADH+
2 H+ + 1/2 O2
NAD+
H2O
ADP +
(Carrying electrons
from, food)
Mitochondrial
matrix
Figure 9.15
ATP
Pi
H+
Electron transport chain
Electron transport and pumping of protons (H+),
which create an H+ gradient across the membrane
Chemiosmosis
ATP synthesis powered by the flow
Of H+ back across the membrane
Oxidative phosphorylation
Is cellular respiration endergonic or exergonic?
Is it a catabolic or anabolic process?
exergonic
catabolic
If one ATP molecule holds 7.3kcal of potential energy, how
much potential energy does 1 glucose molecule produce in
cell respiration?
At its maximum output, 38 x 7.3kcal = 277.4kcal
One molecule of glucose actually contains 686 kcal/mol of
potential energy. Where does the remaining energy go when
glucose is reduced?
It’s lost as heat-which is why our bodies are warm
right now.
What is the net efficiency of cell respiration if glucose
contains 686kcal and only 277.4kcal are produced?
277.4/ 686 x 100 = 40% energy recovered from aerobic respiration
Anaerobic Respiration
•Fermentation enables some cells to produce ATP
without the use of oxygen
•Glycolysis
–Can produce ATP with or without oxygen, in aerobic or
anaerobic conditions
–Couples with fermentation to produce ATP
Anaerobic Respiration
•Fermentation consists of
–Glycolysis plus reactions that regenerate NAD+, which can
be reused by glyocolysis
•Alcohol fermentation
–Pyruvate is converted to ethanol in two steps, one of
which releases CO2
•Lactic acid fermentation
–Pyruvate is reduced directly to NADH to form lactate as a
waste product
Stage 2: If oxygen is absentFermentation
-Produces
organic molecules, including alcohol and
lactic acid, and it occurs in the absence of oxygen.
Cells not getting enough
oxygen, excess pyruvate
molecules are converted into
lactic acid molecules, raising
the pH in the cells.
Yeast uses alcoholic
fermentation for ATP
generation.
Cell Communication
• Animal and plant cells
– Have cell junctions that directly connect the
cytoplasm of adjacent cells
Plasma membranes
Gap junctions
between animal cells
Figure 11.3
Plasmodesmata
between plant cells
(a) Cell junctions. Both animals and plants have cell junctions that allow molecules
to pass readily between adjacent cells without crossing plasma membranes.
• In local signaling, animal cells
– May communicate via direct contact
–EX: immune system & embryonic development
(b) Cell-cell recognition. Two cells in an animal may communicate by interaction
between molecules protruding from their surfaces.
Cell to Cell Communication
(no distance; passing a note)
Cell to Cell Communication
(short distance…on the board message)
Neurons
Local regulator =
neurotransmitters
• In other cases, animal cells
– Communicate using local regulators
Local signaling
Target cell
Electrical signal
along nerve cell
triggers release of
neurotransmitter
Neurotransmitter
diffuses across
synapse
Secretory
vesicle
Local regulator
diffuses through
extracellular fluid
(a) Paracrine signaling. A secreting cell acts
on nearby target cells by discharging
molecules of a local regulator (a growth
factor, for example) into the extracellular
fluid.
Growth factors
Target cell
is stimulated
(b) Synaptic signaling. A nerve cell
releases neurotransmitter molecules
into a synapse, stimulating the
target cell.
Neurotransmitters
Cell to Cell Communication
(long distance; hit a lot of cells…advertisement in local paper)
Message gets sent to a
lot of different cells.
Some will act on it and
some won’t.
The ones that do act
may not all act in the
same way.
• In long-distance signaling
– Both plants and animals use hormones
Long-distance signaling
Blood
vessel
Endocrine cell
Hormonal signaling
AKA: endocrine signaling
Hormone travels
in bloodstream
to target cells
Target
cell
(c) Hormonal signaling. Specialized
endocrine cells secrete hormones
into body fluids, often the blood.
Hormones may reach virtually all
body cells.
Plant hormones
• Sometimes travel through vessels but more
often travel through the air as gas (ethylene).
What are theses types of signals? Are they
short/local or long distance? Are they specific or
general?
Paracrine
signaling
Short/local & general
Synaptic
signaling
Short/local
and specific
Hormonal
signaling
Long distance and
general or specific
The Stages of Cell Signaling: A Preview
• Earl W. Sutherland
– Established that epinephrine causes glycogen
breakdown without passing through the membrane.
– Discovered how the hormone epinephrine acts on
cells
•Sutherland suggested that cells receiving signals went through
three processes
–Reception
–Transduction
–Response
Reception- target cells detection of a signaling
molecule (ligand) that binds to a receptor protein,
causing it to change shape
Transduction-several steps where each molecule
brings about a change in the next molecule
Response occurs with the last molecule in the
transduction pathway & triggers the cell’s
response.
• Plants have cellular receptors
– That they use to detect important changes in their
environment
• For a stimulus to elicit a response
– Certain cells must have an appropriate receptor
• The potato’s response to light
– Is an example of cell-signal processing
CYTOPLASM
CELL
WALL
1 Reception
2 Transduction
Relay molecules
Receptor
Hormone or
environmental
stimulus
Plasma membrane
Figure 39.3
3 Response
Activation
of cellular
responses
Other Type of Intracellular Receptors
• Intracellular receptors
– Are cytoplasmic or
nuclear proteins
• Signal molecules that are
small or hydrophobic
– And can readily cross the
plasma membrane use
these receptors
Like undercover cops hidden in a
crowd
• Receptor tyrosine kinases (insulin uses these)
Can trigger more than 1 signal transduction pathway
-coordinates many aspects of cell growth & reproduction
-abnormal tyrosine receptors (function w/o signal molecules) may contribute to
some cancers.
Signal-binding sitea
Signal
molecule
Kinase is an enzymeHelix in the
that catalyzes the Membrane
transfer of
phosphate groups Tyrosines
Signal
molecule
Tyr
Tyr
Tyr
Figure 11.7
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Receptor tyrosine
kinase proteins
(inactive monomers)
CYTOPLASM
Like a friend who
brings together 2
people who
otherwise don’t
hang out (unless it’s
with this friend); the
3 have a greater
time whenever they
are together.
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Dimer
Activated
relay proteins
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
6 ATP
Activated tyrosinekinase regions
(unphosphorylated
dimer)
6 ADP
P Tyr
P Tyr
P Tyr
Tyr P
Tyr P
Tyr P
Fully activated receptor
tyrosine-kinase
(phosphorylated
dimer)
P Tyr
P Tyr
P Tyr
Tyr P
Tyr P
Tyr P
Inactive
relay proteins
Cellular
response 1
Cellular
response 2
SIGNAL TRANSDUCTION PATHWAYS
• A phosphorylation cascade
Signal molecule
Like flipping the
switch of a
mechanical toy
which goes full
speed when it is
turned on and is
completely still when
turned off.
Receptor
Activated relay
molecule
Inactive
protein kinase
1
1 A relay molecule
activates protein kinase 1.
2 Active protein kinase 1
transfers a phosphate from ATP
to an inactive molecule of
protein kinase 2, thus activating
this second kinase.
Active
protein
kinase
1
Inactive
protein kinase
2
ATP
Pi
PP
Inactive
protein kinase
3
5 Enzymes called protein
phosphatases (PP)
catalyze the removal of
the phosphate groups
from the proteins,
making them inactive
and available for reuse.
P
Active
protein
kinase
2
ADP
3 Active protein kinase 2
then catalyzes the phosphorylation (and activation) of
protein kinase 3.
ATP
ADP
Pi
Active
protein
kinase
3
PP
Inactive
protein
P
4 Finally, active protein
kinase 3 phosphorylates a
protein (pink) that brings
about the cell’s response to
the signal.
ATP
ADP
Pi
PP
P
Active
protein
Cellular
response
Transduction
Changing the chemical message outside the cell to a message
inside the cell.
Inactive until g-protein
attaches
Converts ATP into cAMP
Response
Has regulatory factors and
catalytic factors
cAMP attaches & breaks
regulatory factors away &
catalytic factors become
energized with the help of
ATP (phosphorylation)
Activate phosphorylase to breakdown glycogen into glucose in liver cells & muscle cells.
How long does it last?
• The cAMP boost does not last without
another surge of epinephrine.
• If there is no epinephrine another enzyme,
phosphodiesterase, converts cAMP to AMP.
Like the trigger on a water gun, each time the trigger is pulled the reaction is
immediate and temporary; cAMP is produced each time there is a cell signal
stimulant (such as epinephrine) but the cAMP does not stay present long.
WHAT INSULIN DOES…
Maintaining blood glucose levels.
Feedback inhibition (negative)
Cell Membrane &
Water potential
What mechanisms drive molecules
across the membrane?
• Passive Transport
– Diffusion
– Osmosis
– Facilitated diffusion
• Active Transport
– Sodium Potassium Pump/Electrogenic pump
– Cotransport
– Exocytosis
– Endocytosis
Solutions of Osmosis
•HYPERTONIC:
•Has a higher solute concentration and a lower water
potential compared to the solution on the other side of
the membrane.
•HYPOTONIC:
•Has a lower solute concentration and a higher water
potential than the solution on the other side of the
membrane
•ISOTONIC:
•Have equal water potentials
Turgor Pressure
• most plant cells live in hypotonic environment
• water moves into cells, pushing cell membrane
against cell wall
• cell wall is strong enough to resist pressure
• pressure from the water is called turgor pressure
Plasmolysis
•
•
•
•
plant cells in hypertonic environment
water leaves cells
cell membrane moves away from cell wall
loss of turgor pressure (wilting in plants)
FACILITATED DIFFUSION
CHANNEL
PROTEIN
EX: aquaporins
MOVE CHARGED POLAR
MOLECULES ACROSS
MEMBRANE
CARRIER
PROTEIN
EX: Cysteine transporter
Hydrophillic
passageway
ACTIVE TRANSPORT
• Where free energy (often provided by ATP) is
used by proteins embedded in the membrane
to “move” molecules &/or ions across the
membrane & to establish or maintain
concentration gradients.
• Membrane proteins are necessary
WHICH MEMBRANE PROTEINS ARE
USED?
CARRIER PROTEINS
AN EXAMPLE OF ACTIVE TRANSPORT
SODIUM-POTASSIUM PUMP
•Contributes to the membrane potential
•Pumps 3 Na+ out of cell for every 2 K+.
•Creates a positive charge from
cytoplasm to extracellular fluid.
•Stores energy in the form of voltage
•Major electrogenic pump of animals
•Proton pump for plants, fungi, &
bacteria.
What is a nerve impulse?
• Nerve impulse is misleading. We will call it an
action potential instead
• Can be measured in the same way as
electricity is measured
– Voltage
• Millivolts
• The conductor of a neuron is the axon
– Is covered by a myelin sheath
• Increases the rate at which an action potential passes
down an axon.
Resting potential
• Area of a neuron that is ready to send an action
potential but is not currently sending one.
• This area is considered polarized
– Characterized by the active transport of sodium ions
(Na+ ) out of the axon cell & potassium ions (K+) into
the cytoplasm.
– There are negatively charged ions permanently
located in the cytoplasm
– This collection of charged ions leads to a net positive
charge outside the axon membrane & negative charge
inside.
Action Potential
• Described as a self-propagating wave of ion movements in and
out of the neuron membrane
• This is the diffusion of the Na+ & the K+ .
– Sodium channels open & then potassium ones do to.
• This is the “impulse” or action potential
• It is a nearly instantaneous event occurring in one area of the
axon = depolarization
– This area initiates the next area on the axon to open up the channels.
• This action continues down the axon.
• Once an impulse is started at the dendrite end that action
potential will self-propagate itself to the far axon end of the
cell.
Return to Resting Potential
• Remember that one neuron may send dozens of
action potentials in a very short period of time.
• Once an area of the axon sends an action
potential it cannot send another until the Na+ &
K+ have been restored to their positions at the
resting potential.
• Active transport is required to move the ions =
repolarization
– The time it takes for a neuron to send an action
potential & then repolarize is called: the refractory
period of that neuron.
So… what causes diffusion of ions?
• Electrochemical gradient
– Electrical force
– Concentration gradient
• EX: Na+ concentration inside a resting nerve is much
lower than the concentration outside it.
– When the cell is stimulated gated channels open & Na+
“fall” down their electrochemical gradient driven by the
concentration gradient of the Na+ & the attraction of the
cations to the negative side of the membrane.
Human Systems
Villi of the small intestine
Why is your small intestine infested with villi?
Function of villi
• Location of absorption of molecules
– All but the fatty acids are absorbed into the
capillaries.
– Fatty acids are absorbed into the lacteal.
• Lacteal is a vessel that is part of the lymphatic system
• Villi are thin for easy absorption & has an abundance of
capillaries and lymph vessels.
• All absorbed molecules are taken to body cells by the
circulatory system
• Nutrient molecule can be used for energy (glucose) or as a
component to build a larger molecule (amino acids).
– The process of building a bigger molecule is called:
assimilation
Absorption vs Assimilation
• Absorption occurs when the food enters the
body as the food molecules pass through a
layer of cells and into the bodies tissues. This
occurs in the small intestine which has many
villi that are specialized for absorption.
• Assimilation occurs when the food molecules
becomes part of the bodies tissue. Therefore,
absorption is followed by assimilation.
The Human Heart
“Pumps Your Blood”
Valves close to
prevent backflow
venules
arterioles
Closing of the valves
produces the “lub dub”
sound of you heart
Why is the muscle thicker at the left ventricle?
Where would you suppose the
highest blood pressure is and
why?
The aorta because this is the
first place blood travels from
the heart pumping it out.
Where would you suppose the
lowest blood pressure is and
why?
Veins- this is the last area blood travels
before entering the heart again. They
have valves to prevent back flow
Control of your heart rate
• Hearts are made of muscle tissue; cardiac muscle.
– Contracts & relaxes = myogenic muscle contraction
• Mass of tissue in the right atrium known as the
sinoatrial node (SA node)
– Acts as a pacemaker by sending electrical signals for the
artrias to contract (aka stimulate the myogenic
contraction)
• 2nd mass is known as the atrioventricular node (AV
node)
– On a 0.1 second delay from the SA node in which it sends
a signal for both ventricles to contract.
What happens during exercise?
• Increased demand for oxygen so heart beat
speeds up.
• Also an increased build up of CO2 in the
bloodstream.
• The medulla chemically senses the rise of CO2
– sends signal through the cardiac nerve to the SA
node to increase your heart rate
– Later sends another signal to decrease heart rate
through the vagus nerve
Adrenaline
• Chemical that is able to influence your heart
rate.
• High stress times and times of excitement
triggers the adrenal glands to release
adrenaline into your bloodstream.
• The SA node “fires” more frequently causing
an increase in your heart rate.
Pump, pump, pumps your blood.
The right atrium's where the process
begins,
Where the C02 blood enters the heart
Through the tricuspid valve to the right
ventricle
The pulmonary artery and lungs.
Once inside the lungs it dumps its
carbon dioxide
And picks up its oxygen supply
Then it's back to the heart through the
pulmonary vein
Through the atrium and left ventricle."
"Pump, pump, pumps your blood.
"The aortic valve’s where the
blood leaves the heart
Then it's channeled to the rest of the
bod
The arteries, arterioles, and capillaries
too
Bring the oxygenated blood to the cells
The tissues and the cells trade off waste
and CO2
Which is carried through the venules
and the veins
Through the larger vena cava to the
atrium and lungs
And we're back to where we started in
the heart.
Pump, pump, pump, pumps your blood