Biology 10 Lecture
Chapter 6 – Metabolism - Energy & Enzymes
I.
Overview
A. Cells & the Flow of Energy
B. Metabolic Reactions & Energy Transformations
C. Metabolic Pathways & Enzymes
D. Oxidation-Reduction and the Flow of Energy
II. Cells and the Flow of Energy
A. ______ - capacity to do work; occurs as light, chemical, electrical, heat, etc.; energy
initially comes from the ___. Forms of energy are
1. __________ Energy - stored energy (e.g.: book held above desk; chemical energy
stored in glucose and ATP ______).
2. __________ Energy - energy of motion (e.g.: book dropped on desk; ____ phosphate
bonds broken to energize Na+/K+ pump).
3. __________ Energy is in the interactions of atoms in a molecule. Molecules have
different amounts of ___________ energy (e.g.: glucose - C6H12O6 - has more energy
than its breakdown products CO2 and H2O)
B. Two Laws of Thermodynamics:
1. ______ is neither created nor destroyed, but can be __________ from one form to
another (e.g.: plants absorb light energy and convert it to chemical energy in
carbohydrates)
2. One usable form of energy can’t be ___________ converted to another usable form
(e.g.: only about 40% of glucose bond energy is converted to ATP bond energy, the
rest is lost as ___).
E. Cells & __________ (a measure of disorder)
1. Molecules naturally go from ordered to ___________ states.
2. Living things need constant ________ input to maintain their organization.
F. Energy is measured in Joules or _____________ (1 Kcal = amount of energy needed to
raise the temperature of one kilogram of water one degree Celcius).
III. Metabolic Reactions & Energy Transformations
A. ______________ - sum of all chemical reactions in an organism’s cells; includes
anabolic and catabolic processes such as:
1.
_______________ in plants; autotrophs absorb _______ energy and convert it (via
reduction) to chemical energy in the covalent _______ of carbohydrates (glucose).
Light Energy
6CO2 + 6H2O  C6H12O6 + 6O2
Chloroplast
2. Cellular _____________ in plants and animals (heterotrophs); break down (oxidation)
of glucose to convert the unusable glucose bond energy to usable _____ energy.
C6H12O6 + 6O2  6CO2 + 6H2O + 38ATP + Heat
2
Enzymes
B. _____________ Reactions (e.g.: cellular respiration)
1. __________ (beginning molecules) start at higher energy level than ____________
(end molecules).
2. Often the breakdown (____________) of larger molecules.
3. Reaction occurs _____________ (needs no input of energy)
4. Results in release of _________.
C. ______________ Reactions (e.g.: photosynthesis)
1. End __________ are at higher energy level than reactants.
2. Often the build-up (____________) of larger molecules.
3. Requires an input of _________ for reaction to occur.
D. _____________ Reactions
1. Energy released by _________ reactions are used to drive endergonic reactions.
2. Exergonic break down of _____ is often coupled to endergonic cell reactions
requiring energy.
E. ____ (adenosine triphosphate) - a nucleotide composed of adenine, ribose sugar, and
three phosphates bonded with high energy _____ that can be broken for energy.
1.
2.
___________ bond energy cannot be used directly by cell
3.
___ Kcal/mole is released when 1 mole of ATP is broken down to ADP + Pi
(compared to ____ Kcal/mole Glucose)
4.
5.
ADP + Pi is recycled back to ____ during cellular respiration.
6.
Cellular _____ of ATP energy:
Glucose energy is broken down to smaller ____ energy packets during cellular
_____________
_____________ of ATP as cellular energy source:
a. Common energy currency used in many ________
b. Amount of energy is just enough; little ______
c. Exergonic ATP reaction coupled to ___________ reactions minimizes energy
loss.
a.
b.
c.
___________ work to synthesize cell molecules
_________ work to pump substances across cell membranes
__________ work for muscle contraction, chromosome movement, etc.
IV. Metabolic Pathways & Enzymes
A. Metabolic ___________ - organized series of chemical reactions.
1. Begins with a _________ and ends with a __________.
2. Reactants are called ____________ in enzymatic reactions
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3. Involves many small ______.
4. Proceeds in an __________ step-by-step manner.
A → B → C → D → E → F →G
E1
E2
E3 E4
E5
E6
(A-F are substrates, B-G are products, E1, E2…are enzymes)
5. One pathway may lead to ________ pathways if they have molecules in common.
6. Allows easier capture & use of _______ because it is released in small increments.
B. ___________ - protein catalysts that speed up the rate of chemical reactions.
1. Enzyme names often formed by adding “____” to substrate (e.g.: lipase) or by the
action they perform (e.g.: phosphatase)
2. Every chemical reaction in a cell requires a ________ enzyme.
3. Enzymes lower the _______ of ________ so chemical reactions can take place with
less heat in the cell.
4. Enzymes form an __________-_________ complex
a. Substrate attaches to a specific enzyme at its ___________ (Lock & Key Model
vs. Induced Fit Model).
b. Enzyme helps to split substrate (______________) or to join substrates together
(____________) to form product(s).
c. ___________(s) detach from enzyme, which returns to its original shape, ready for
another substrate.
5. The presence or absence of specific _________ determines what reactions take place in
a given cell.
C. Factors that Affect Enzymatic _______
1. ______________
a. As temperature increases to an _________ point, the reaction speed increases (in
humans, optimal temp. is _____oF).
b. Beyond the optimal point, the speed levels off, then decreases sharply as enzyme is
_____________ (inactivated)
2. ____ (acidity or basicity)
a. Each enzyme has an _________ pH, which helps it maintain its functional shape.
b. Change in pH alters bonding of amino acid “_” groups, results in a change in shape
(_________) that inactivates the enzyme.
3. Substrate & Active Enzyme ______________
a. Greater __________ concentration, more chances to bind with enzyme active sites,
faster reaction speeds.
b. Greater active _________ concentration, more active sites for substrates to bind
with, faster speeds.
c. Enzymes are often activated by ____________________ (via a kinase and ATP) or
dephosphorylation (via a phosphatase).
D. Enzyme Inhibition
1. Inhibitor - a molecule that binds to an enzyme and __________ the chemical reaction.
2. Inhibition is used by cells to ___________ enzyme activity.
a. Competitive Inhibition - inhibitor with shape similar to that of the substrate
___________ for the enzyme’s active site.
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b. Noncompetitive Inhibition - inhibitor binds to an _________ site and alters the
_____ site shape so the substrate can’t bind.
c. ____________ Inhibition - product produced by an enzymatic reaction
___________ the enzyme
1) An end _________ can also bind to the first enzyme in a pathway and shut down
the pathway.
2) When the product is low, inhibition is ____________ and more product is
produced.
E. Cofactors and Coenzymes Help Enzymes Function
1. ___________ - nonprotein __________ molecule or ion required by some enzymes to
function (e.g.: magnesium, potassium, calcium ____).
2. ______________ - nonprotein _________ molecules that bind to enzymes and serve as
carriers for chemical groups or electrons (e.g.: NAD+, FADH, and CoA).
3. _____________ such as niacin, riboflavin and pantothenic acid are used to make
__________ such as NAD+, FADH, and CoA.
V. Oxidation-Reduction & the Flow of Energy
A. ________ flows through all organisms, involving energy transformations from one
molecule to another. This usually involves oxidation-reduction (_______) reactions
1.
___________ is the ____ of electrons (or H atoms); molecules that lose electrons
are at a _______ energy level
2.
__________ is the _____ of electrons (or H atoms); molecules that gain electrons
are at a ______ energy level
3.
________ reactions always take place simultaneously
a.
b.
One molecule accepts the _________ given up by another
Redox reactions take place during photosynthesis and cellular __________
B. Metabolic pathways of photosynthesis and cellular respiration convert one form of
________ to another.
1.
2.
During _______________ in plant chloroplasts:
a.
_________ energy is used to convert CO2 and water to ______________, which
serve as food for other organisms; oxygen is released
b.
Solar energy is partially converted into the covalent ______ energy of the
carbohydrates.
During aerobic cellular ______________ in mitochondria:
a.
b.
3.
The carbohydrates are “burned” with oxygen to form _____ and water
Some of the carbohydrate’s covalent bond energy is converted to _____ bond
energy.
ATP bond energy is used to fuel cellular activities that require __________
C. Eventually, all solar energy is lost as _______, a nonusable energy, so living things must
have a constant input of _________.