enzymes as catalysts

terms: substrates, active site, products, lock and key, induced fit

-ase as an ending

isoenzymes and their role in diagnosis

(measurement in the blood or secretions. Any cell product including enzymes)

factors that affect enzyme activity:

temperature, pH

coenzymes, derived from vitamins, example: NAD and FAD

endergonic and exergonic reactions

ATP and ADP

redox reactions

gain and loss of electrons can be gain and loss of hydrogens

role of NADH and FADH₂ as electron shuttles

glycolysis (Arobic)

formation of two molecules of pyruvic acid from glucose

NAD to pick up the H's

end products: 2 pyruvic acid, 2 NADH and 2 ATP (net) per glucose molecule

2 ATPs used initially to energize glucose (the first one fixes glucose in the cell) and 4 ATPs produced total; therefore 2 ATPs net

glycolysis anaerobic

under anaerobic conditions pyruvic acid à lactic acid to regenerate NAD

alcohol fermentation

cardiac muscle: lactic acid à angina pectoris under ischemic conditions

glycogenolysis

glycogenolysis to release glucose for cell use

liver, having glucose-6-phosphatase, can provide glucose to increase blood sugar

glycogenesis to synthesize glycogen from excess blood glucose

gluconeogenesis: the synthesis of glucose from non-carbohydrate sources

occurs in the liver

is a good source of blood glucose, especially as liver glycogen is being depleted

brain depends on glucose as its sole energy source

in the presence of O₂ pyruvic acid can be completely oxidized to CO₂ and H₂ O

aerobic respiration yields 30 ATPs total (including glycolysis) vs. 2 for glycolysis alone

takes place in the mitochondrion

first step prepares pyruvic acid to enter the Krebs cycle

pyruvic acid à acetyl CoA + NADH + CO₂

CO₂ is exhaled

acetyl CoA is how acetyl (2-C molecule) enters the Krebs cycle

processes of cell respiration: glycolysis, Krebs cycle, electron transport and chemiosmosis

oxidative phosphorylation involves electron transport and chemiosmosis

oxaloacetic acid (a C-4 molecule) combines with acetyl (a C-2molecule) from acetyl  CoA the C-6 molecule is changed to a C-5 molecule and then to a C-4 molecule per turn of the cycle, two molecules of CO₂ are produced, three molecules of NADH, and one molecule of FADH ₂ and one ATP are produced oxaloacetic acid is regenerated occurs in the matrix of the mitochondrion

electron transport

takes place on the inner mitochondrial membrane

NADH and FADH ₂ give up their two (high energy) electrons to members of the chain the electrons and H's of NADH have different pathway selectrons are passed from one carrier (such as a cytochrome) to another and finally to oxygen

the energy released as the electrons are passed down the chain is used to make ATP by chemiosmosis

chemiosmosis

the electron transport chain is set up as 3 complexes each complex passes electrons and also pumps H+ into the intermembrane space the hydrogen ions can only leave the intermembrane space through respiratory assemblies that contain ATP synthase as the hydrogen ions stream through the ATP synthase, their energy enables ATP synthase to form ATP 4 H+ are needed to make one ATP each NADH pumps 10 H+ and makes 2.5 ATP FADH₂ makes 1.5 ATP 30 ATPs are produced from the aerobic respiration of glucose, 32% efficiency

water as a product of cell respiration is derived from oxygen, plus electrons plus H+

excess glucose stored as glycogen, and then fat

acetyl Co A can generate fatty acids, two carbon atoms at a time fat can be broken down to provide energy as an alternative to glucose (except for the

brain (which can only use glucose)

protein can be used for energy, but is a last choice

fat is an efficient energy storage form

Ch. 6 Interactions Between Cells and Their External Environment

external environment

fluid compartments: intracellular (66% of body water) extracellular: plasma (20% of the 33%), interstitial (80% of the 33%) plasma membrane, composition (review); selectively permeable categories of passage of materials through the plasma (cell) membrane:non-carrier mediated: simple diffusion, osmosis (a type of simple diffusion) carrier-mediated: facilitated diffusion, active transport and passive transport, uses kinetic energy from molecules active transport, against a concentration gradient: requires ATP

factors affecting diffusion: concentration gradient, surface area of membrane

carrier-mediated transport in general

requires protein carriers, which are usually specific for the molecules they transport carriers exhibit a transport maximum in diabetes this results in glucose being left in the urine instead of being reabsorbed

facilitated diffusion

from high concentration to low concentration

requires protein carrier example: glucose entry into cells problem, hypoglycemia doesn't result in sufficient glucose diffusing into brain cells

from low concentration to high concentration (against a concentration gradient)

requires ATP requires a protein carrier

Example:Na+/K+ pump

primary active transport

ATP directly involvedexample: Ca ²⁺ extrusion from cells example: Na⁺ -K⁺ pump, pumps : Na⁺ out of cells and K⁺ into cells. Moves 3 Na⁺ for 2 K⁺

molecules are moved against a concentration gradient energy comes from a concentration gradient set up by primary active transportexample: kidney tubule cell reclaiming glucose from the filtrate, made possible by the inward diffusion of Na+ from the filtrate

motor neurons can be somatic or autonomic ( and these can be sympathetic or

parasympathetic)

Ch. 7 Neurons and Synapses

CNS, PNS

neurons: cell body, dendrites, axon hillock, axon, axonal transportsensory, motor and association neuronsmotor neurons can be somatic or autonomic ( and these can be sympathetic or parasympathetic)

nerve vs. neuron

neurons:

sensory, motor and association neurons

motor neurons can be somatic or autonomic ( and these can be sympathetic or

parasympathetic)

Neuron: a cell that conducts impulses

supporting cells:

Schwann cells and oligodendrocytes form meylin sheaths in the PNS and CNS

respectively

Schwann cells

Schwann cells wrap around an axon many times, forming the myelin sheath; the

outer part of the cell is the neurilemma (sheath of Schwann)

gaps between adjacent Schwann cells are the nodes of Ranvier, which allow

transmission of impulses to speed down the axon

Gray matter is unmyelinated material - soma, unmyelinated axons

White matter is myelinated material

Schwann cells

regeneration of axons: may occur in the PNS, but not the CNS

aided by Schwann cells which form a growth tube and secrete growth factors

(neurotrophins)

clean up and maintain the neuron environment, by removing K+ and helping recycle some neurotransmitters contribute to the formation of the blood-brain barrier: end-feet attach to capillaries and result in capillary cells having tight junctions. Keeps many undesirable substances

out of the brain, but does make it more difficult to administer meds. to combat brainproblemsneed for the use of L-dopa, which does cross the blood-brain barrier, in place of dopamine, which doesn't, in the treatment of Parkinson's disease

resting membrane potential is altered by neurons (and muscle cells) to send an action potential depolarization: positive charges move into the cell; repolarization: positive charges leave the cell; hyperpolarization: an extension of repolarization

gated ion channels allow ion influx (entry) and efflux(exit) at specific times Na+ channels can be closed (usually), open (during stimulation), or inactivated (right after stimulation) by the "ball and chain"Na+ channels allow Na+ to enter the cell K+ channels allow K+ to leave the cell when neuron is depolarized to threshold, -55 mV, Na+ voltage gated channels open

 Action potential

Na+ enters at depolarization

K+ leaves (repolarization) due to the opening of K+ gated channels positive feedback scheme for Na+entry, overall negative feedback cycle at

repolarizationNa+-K+ pump to maintain ion concentration

Na+ enters, Na+ diffuses, depolarizes next patch of membrane to produce another action  potentialall-or-none law for action potential, all action potentials in a neuron are the same regardless of stimulus coding for stimulus intensity by frequency not amplitude of action potential stimulus intensity also communicated by recruitment of more neurons in a nerve refractory periods: absolute and relative

saltatory conduction MS

synapses

presynaptic and postsynaptic cells

electrical synapses chemical synapses: terminal bouton, synaptic cleft, synaptic vesicles

Ca²⁺ voltage regulated gates and the entrance of Ca²⁺

Ca²⁺ promotes exocytosis of neurotransmitter neurotransmitter binds to receptors on the postsynaptic membrane opening of chemically regulated gatesif it's a Na+ channel, this produces a depolarization which is excitatory and called an EPSP if it's a Cl ^- channel, Cl ^- would enter and hyperpolarize cell (K+ channels opening would hyperpolarize also)produces an IPSP

comparison of chemically regulated gates and voltage-regulated gates in

terms of what makes them open:neurotransmitter vs. voltage change; where they are located: cell body and dendrites vs. axon; and the result of their opening: EPSPs/IPSPs vs. action potentials. events in neuron transmission (see handout)

acetylcholine (ACh).

in the CNS and the autonomic nervous system

muscarinic, on smooth and cardiac muscle, and nicotinic

on neurons and skeletal muscle

receptors are part of ligand-operated channels

binding of ACh causes channel to open

Na+ enters and K+ leave through the same channels

more Na+ enters than K+ leaves and this depolarizes the cell

receptors are separated from the ion channel they control

a G-protein connects the receptor with the channel

binding of ACh to receptor causes beta and gamma subunits of the

G-protein to dissociate, and open the ion channel

example: heart muscle has K+ channels that open this way

is the enzyme that degrades ACh

choline is taken back into the presynaptic neuron

catecholamines, based on the amino acid tyrosine includes norepinephrine, epinephrine (a hormone) and dopamineserotonin, based on the amino acid tryptophan all are "feeling good" neurotransmitters inactivated by reuptake into the presynaptic neuronuse of meds in clinical depression: SSRIs, serotonin-specific reuptake inhibitors, to increase the amount of serotonin at synapses

dopamine:

Diffusion of neurotransmitter to postsynaptic neuron, binding to receptor.

Opening of chemically gated channels.

Diffusion of positive ions (Na+) into postsynaptic neuron. EPSP (excitatory postsynaptic potential) produced in the postsynaptic neuron.

Na+ diffuses in the cell body.

If enough Na+ is present at the axon hillock to depolarize the cell to threshold, voltage-gated channels open and an action potential starts.

Na+ enters these channels and causes depolarization.

Na+ voltage-gated channels close.

K+ voltage-gated channels open.

K+ leaves the axon and results in repolarization.

K+ voltage-gated channels close.

This starts another action potential.

These events continue down the axon until the terminal bouton is reached.

Here, Ca²⁺ gates open due to the depolarization and Ca²⁺ enters.

Ca²⁺ promotes exocytosis of neurotransmitter from synaptic vesicles.

This neurotransmitter can now diffuse to and stimulate another neuron.