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Ch. 3 Cell metabolism


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Cell Metabolism
study of energy of related concepts as they effect cells

The sum of all chemical reactions that occur in cells
Energy metabolism
set of reactions involved in energy storage and use

AKA energy exchange
transformation of materials that enter the reaction
A substance resulting from a chemical reaction.
goes in both directions at the same time
A reaction that involves the breakdown of larger molecules into smaller ones.
A reaction that involves the production of larger molecules from smaller reactants.
Metabolic reactions
"splitting of water"
catabolic reaction

The breakage of a chemical bond through the addition of a water molecule
involves joining together of 2 or more smaller molecules to form a larger one, as when amino acids are joined together to form proteins.
The addition of a high-energy phosphate group to a molecule
The removal of a phosphate group from a molecule.
Oxidation-reduction reaction
Any reaction in which elelctrons are removed from one reactant molecule and transferred to another.
The loss of electrons or hydrogen atoms or the acceptance of an oxygen atom.
Once electrons have been removed from a molecule, molecule is said to be ______.
Oxidative phosphoralation
a process occuring in mitochondria that is crucial to energy metabolism
Laws of mass action
an INCREASE in the CONCENTRATION of REACTANTS tent to move the reaction towards the PRODUCTION of MORE PRODUCT.

An INCREASE in the conc. of products tends to push the reaction in reverse.
Translation state
Reacting molecules go into a high-energy intermediate form which then breaks down into the products.
Activation energy barrier
The "hump" in the middle of the curve, is known as _______ ______ ______, is due to the fact that potential energy of the transition state is greater than that of either the reactants or the products.
Activation energy
Energy that must be added to the REACTANTS to allow then to overcome the ACTIVATION ENERGY BARRIER and move through the TRANSITION STATE to produce the PRODUCTS.
How does activation energy get the extra energy it needs?
1. collisions from other molecules
a. adds energy to the molecules
b. increased molecular motion due to increases in temp. can act to add more energy to tmolecules via collision btwn molecules
a chemical reaction is a measure of how fast it comnumes reactants and generates products

expressed as moles/liter-second, or some equivalent
Net rate
difference btwn the rate of the forward reactants (reactants → products) and the rate of the reverse (products → reactants)
Any _______ in the conc. of reactants will bring about an _______ in the forward rate without affecting the reverse rate.
increase; decrease
An _______ in the concentration of products relative to reactants wil _______ the net forward rate, and can even make the reaction go in reverse if the change in conc. is large enough.
decrease; increase
As the height of the activation energy barrier _________, rates of both the reverse reaction and forward reaction ________ because the activation energy of both reaction becomes lower.
______only react w/only a certain molecule type, and a related group of molecules.
How do enzymes work?
1. Enzymes have enzyme sites at which reactant(s) can bind.
2. Binding will allow the reaction to occur thus producing the products.
3. Product is released from the active site.
4. Enzyme can now interact with a new reactant.
A participant (product or reactant) in an enzyme-catalyzed reaction.
Catalytic Rate
Enzyme Concentration
Substrate Concentration
The rate at which an enzyme can catalyze a reaction is affected by several factors. (4)
Catalytic Rate
a maeasure of how many product molecules it can generate per unit time, assuming that the active site is always occupied by a substrate molecule.

influences how fast enzyme molecules can convert substrates into products
Enzyme Concentration
The rate of an enzymatic reaction also increases in direct proportion to the _______ _________ based on the law of mass action.

More enzymes molecules, the more product.
Substrate Concentration
increases when enzymatic reaction increases based on law of mass action

When __________ ___________ is low, more time will pass bofore the next substrate molecule binds to the enzyme, and as a result its active site wil remain unoccupied for a greater percentage of the time.

When high __________ _________, less time will pass before the next substrate molecule comes along.
a measure of how tightly substrate molecules bind to its active site.

tightness of binding btwn any two molecules
allosteric regulation
covalent regulation
Two common mechanisms for altering the activity of existing enzymes are ________and_________.
allosteric regulation
regulatory mechanism in which a modulator bonds reversibly to the regulatory site on an enzyme, inducing a change in its conformation and activity.
covalent regulation
regulatory mechanism in which changes in an enzyme's activity are brought about by the covalent bonding of a specific chemical group to a site on the enzyme molecule

usually involves bonding of a phosphate group.
induces a change in an enzyme's conformation that alters the shape of the active site, causing a change in the enzyme's activity by altering its catalytic rate, it affinity for substrate, or both.
A modulator that increases the activity of an enzyme
a modulatory that decreases the activity of an enzyme
Regulatory site
enzyme binding site

associated w/allosteric regulation
Protein Kinase
a type of enzyme that catalyzes phosphorylation of a target protein.
enzyme that catalyzes the dephosphorylation of a target protein
Feedback Inhibition
Regulatory mechanism is which an enzyme in a metabolic pathway is inhibited by an intermediate appearing DOWNSTREAM
Feedforward activation
Regulatory mechanism which involves the activation of an enzyme by an intermediate appearing UPSTREAM in a metabolic pathway
Substrate specificity
Enzymes are generally able to catalyze one particular reaction because they have the ability to "recognize" and bind to only one particular type of substrate, a phenomenon known as ___________ ________.
serves as temporary energy storage
comes from ADP & Pi
synthesis occurs in two ways:
substrate-level phosphorylation
oxidative phosphorylation
substrate-level phosphorylation
a mechanism of ATP synthesis, in which an enzyme transfers a phosphate group from a substrate to ADP

Occurs in 7 & 10 steps of Glycolysis & 5 step of Krebs cycle
oxidative phosphorylation
a mechanism where ADP binds with a free inorganic phosphate (Pi) to form ATP

needs electron transport & oxygen
ATP breakdown
A process where an ADP and a free phosphate (Pi) releases stored energy that can be used to overcome the Activation Energy Barrier & allow a reaction to occur.
ATP Hydrolysis
Process that releases energy and involves the splitting of a single bond- the bond btwn ATP and one of the attached phosphate groups
Glucose Oxidation
Krebs cycle
Oxidative phosphorylation
"spitting of sugar"
occurs in cytosol
O2 not necessary (anerobic)
Requires initial input of energy
Produces a net of 2 ATPs for each glucose entering glycolysis
Produces 2 reduced NADs for each glucose
Final products are 2 pyruvates
Krebs cycle
has no starting or ending points because its circular

Occurs in mitochondria when O2 is present
Uses acetyl-CoA or breakdown products from proteins or fats
Produces many reduced molecules (NAD2, FADH2, CO2, & a little ATP)
Chemiomotic coupling
The use of energy released during electron transport to pump ions across a membrane against a conc. gradient

The energy "stored" by this gradient & a special type of enzyme are used to make ATP.
Lactid Acid
For pyruvate production by Glycolysis to enter the linking reaction & Kreb's chemistry there must be sufficient O2 available to the mitochondria to accept all the electron and H+ produced

If not enough O2 is delivered to cell then some of the pyruvate must be converted to another compound, ______ ____.
Purpose of Lactaid Acid
1. ↑ the NADox available in the cytosol, it must be available for glycolysis to occur
2. Stops an ever increasing conc. of pyruvate in the cytosol (law of mass action)
3. Allows Glycolysis to cont. as to PRODUCE ATP even when cell has limited O2 available
4. Lactate can exit a cell, go to liver, and be converted to glucose, pyruvate cannot.
Cell membrane transport
Molecules must be able to pass into or out of cells through the cell membrane.

Lactate acid
______ acid like muscle cells the best.

Lactate can be ______, so needs to be converted back to pyruvate.

Passive Transport
Molecular motion across a cell membrane not requiring cell energy
motion is due to the kinetic (thermal) energy of the molecules.

Active transport
Molecular motion across a cell membrane that requires the use of cell energy (ATP) and transport proteins often called carriers or pumps.


(factor to produce molecular motion)
The existance of a conc. gradient for a given type of a molecule across a cell membrane.

Molecules always moves from areas of high concentration to areas of lower conc. The greater the conc., the more molecules will move.


(factor to produce molecular motion)
1. Ions are affected by differences in charge found inside & outside of cell membranes.
2. Is in fact, an unequal distribution of charged particles across a cells membrane
A. more - ions inside a cell
B. more + ions outside a cell
3. Creates an electrical charge differences across a cell membrane, measured in millivolts
A. called the Membrane Potential, often about 70 millivolts inside composed to outside
4. Charge difference can affect ion movement across membranes.
a. like charges repel
b. unlike charges attract

When ______ is scarce, the body can breakdown proteins and fats for energy.
A polysaccharide that is an important energy reserve; a polymer consisting of a long chain of glucose molecules.
The synthesis of glycogen from glucose molecules.
Glycogen breakdown and the liberation of glucose molecules
The synthesis of new glucose from protein or lipid precursors which usually takes place in liver.
The first stage of fat breakdown which sep. of fatty acids from glycerol molecule.

The catabolism of lipids as a source of energy
The synthesis of lipids from nonlipid precursors.
metabolic breakdown of proteins to A.A.s
Essential nutrient
any biomolecule necessary for proper body function that cannot by synthesized in cells and therefore must be obtained from dietary sources.
Goes to liver and turns into UREA and then goes to kidneys
What happens to ammonia that is produced when A.A.s are broken down for energy?

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