Biology 151 VCU Merk Exam 2

What happens in a chemical reaction?

chemical bonds between atoms are broken and new ones are formed producing one or more different substances

Reactants

substances that start a chemical reaction

Products

The elements or compounds produced by a chemical reaction.

potential energy

stored energy

kinetic energy

energy of motion

anabolic reactions

build large molecules from small ones; requires an input of energy

catabolic reactions

break down of large molecules into small ones; release the energy

first law of thermodynamics

the total amount of energy in the universe is constant ( enrgy cannot be createde nor destroyed)

second law of thermodynamics

a small amount of energy is lost as heat in each energy conversion

what is delta G?

the change in usable energy

What does it mean when delta G is positive?

energy must have been added from somewhere and requires an energy input

What type of reaction is it when delta G is positive?

endergonic reaction

What does it mean when delta G is negative?

energy was lost and give off energy

what type of reaction is it when delta G is negative?

exergonic reaction

How does anabolic reactions relates to endergonic processes?

anabolic reactions requires an input of energy therefore it is endergonic where energy is put in

How does catabolic reactions relate to exergonic processes?

catabolic reactions is the brealdown of large molecules therefore it is a release of energy

Entropy

A measure of disorder or randomness.

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

What does ATP do in the cell?

it picks up free energy from exergonic reactions and then stores it and releases it elsewhere to help run endergonic reactions

How does ATP store chemical energy?

atp is stored in its phosphate bonds

How is the energy from ATP released?

hydrolysis reaction ehich breaks the bond and reforms ADP and releases a phosphate

How is ATP different from ADP?

ATP has 3 phosphate groups while ADP has 2.

What is Activation Energy?

the input of energy required to get a reaction going

Where does the Activation Energy come from?

random molecular motion

What is activation energy used for?

it is used to destabilize the reactants, making them more reactive

transition state intermediates

reactants in their unstable state

what are enzymes?

are proteins that function as catalyst

catalyst

substance that speeds up the rate of a chemical reaction

How do enzymes speed up chemical reactions?

by lowering the activation energy

How do enzymes work?

enzymes bring reactants together now called substrates that binds to the active site forming an enzyme substrate complex. then the reaction takes places and the products are released

How do enzymes lower activation energy?

3 ways:

1. Enzymes move substrates into the right orientation to react

2. Enzymes strain substrate bonds, putting them in unstable transition state

3. Enzymes can temporarily add chemical groups to the substrates, destabilizing its bonds

How is an enzyme's structure/ shape related to its function?

active sites on enzymes are specific to their substrate and some enzymes change their shape after binding the substrate

induced fit

enzyme changes shape when it binds the substrate, which alters the shape of the active site

Why is there a limit to how much enzymes can speed up a reaction?

once all the enzymes are occupied and working as fast as they can, adding more substrate does not increase the rate any further.

Why is it important for the cells to regulate enzyme activity?

to conserve energy

what are different types of inhibitors?

irreversible inhibitors, reversible inhibitors and competitive inhibitors

How do irreversible inhibitors work?

they covalently bind to the enzymes active site which permanently disables the enzymes

How are reversible inhibitors different from irreversible inhibitors?

reversible inhibitors binds to the enzyme non-covalently and irreversible inhibitors binds to covalently

Which type does a cell tend to use?

reversible inhibitor

What are the different types of reversible inhibitors?

Competitive inhibitors and allosteric inhibitors

How do reversible inhibitors work?

they bind to the enzyme non-covalently and they prevent the enzyme activity while they are bound. Omce they are released, the enzyme can resume its function.

How does substrate concentration affect competitive inhibitors?

adding more substrate can overcome the inhibition

How does allosteric regulations work?

an inhibitor or activator binds to the enxyme somewhere other than the active site, causing it to change its shape.

what is the feedback inhibition?

The final product acts as an inhibitor for the first enzyme in the pathway. So if theres lots of products, the pathway stops

How is feedback inhibition useful in regulating metabolic pathways?

What is the role of phosphorylation in regulating enzyme activity?

is can deactivate the enzyme

Kinase

An enzyme that transfers phosphate ions from one molecule to another

Phosphatase

removes phosphate

How do pH and temperature affect enzyme activity?

Enzymes work best under optimal conditions PH(2-6) temp (37-81) can denature them

What are fuel molecules used for?

for energy storage in the covalent bonds

What is the most common/ .abundant molecule?

glucose

How do cells obtain energy from glucose?

They break it down in a number steps

chemosynthesis

process in which chemical energy is used to produce sugars

What is the overall reaction of glucose breakdown (aerobic respiration)?

C6H12O6-> 6H2)+^CO2+energy

What is glycolysis?

The first step in glucose catabolism where glucose is converted into two molecules of pyruvate

Pyruvate

Three-carbon compound that forms as an end product of glycolysis.

What is the starting material for glycolysis?

glucose

What are the ending products for glycolysis?

2 pyruvate, 4 ATP and two NADH

What is NADH?

electron and H+ ion carrier

Where in the cell does glycolysis occur?

cytoplasm/cytosol

What is a redox reaction?

reactions that transfer electrons between reactants (involved in glucose catabolism)

How can you tell if a molecule is reduced or oxidized?

the form with more H is reduced

reduced

gains electrons

oxidized

loses electrons

Does a molecule have more energy when it is reduced or when its oxidized?

Reduced

How does oxygen affect what happens to the pyruvate after glycolysis?

is oxygen is not present, the pyruvate is converted into lactate and no ATP is produced?

What are the four steps in aerobic respiration?

Glycolysis, pyruvate oxidation, citric acid cylcle (krebs cycle) and ETC (ATP Synthesis)

Where does pyruvate oxidation occur?

mitochondria

Where does the Krebs cycle occur?

mitochondria

Where does ATP synthesis occur?

inner mitochondrial membrane

In aerobic respiration, what happens to pyruvate once it enters the mitochondria?

pyruvate oxidation forms acetate

How many carbons does Acetyl CoA have?

2 carbons

What is the first step in the krebs cycle?

acetyl group + oxaloacetate -> citrate

(2 carbons) (4 carbons) (6 carbons)

What is the last step of the krebs cycle?

oxaloacetate is regenerated

What is the purpose of the Krebs Cylcle if it only produces 2 ATP?

to break down Acetyl CoA into individual CO2 molecules

What is the role of NAD(H) and FAD(h2) in aerobic respiration?

reduce electron carries

What are the products of the Krebs Cycle?

3 NADH, 1 FADH2, 1 GTP, 2CO2

Which step in respiration produces the most ATP?

ETC

Where do the electrons for the ETC come from?

NADH and FADH2

Where do the electron for the ETC end up?

inner mitochondrial membrane

When electons get passed down the ETC, energy is released. What is the energy used for?

to establish a H+ gradient across the membrane.

H+ gradient

proton motive force that drives the ATP synthase to make ATP

Why would the mitochondrion want to build a H+ gradient across its inner membrane?

protons are pumped from the matrix to the inter membrane space

What is the name of the enzyme that produces ATP at the end of the ETC?

ATP Synthase

What provides the energy for ATP at the end of the ETC?

NADH and FADH2

Why is oxygen essential for aerobic respiration?

its the final electron acceptor

Why do we exhale water along with CO2?

in ETC the electrons bind to the oxygen and water is formed in the process

How many ATP does respiration produce per molecule of glucose that is broken down?

32+ ATP

How many ATP per glucose are produced in fermentation?

2

Why would a cell ever do fermentation if respiration so much more efficient?

theres not enough oxygen present

What is the first step of fermentation?

glycolysis which happens in to cytoplasm

Where does fermentation take place?

cytoplasm

What are two possible products of fermentation?

lactate and ethanol (and CO2)

If fermentation doesn't produce ATP, why do it?

to regenerate NAD+ which allows glycolysis to continue indefinitely

What is photosynthesis?

the process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.

what is the chemical reaction of photosynthesis?

6CO2 + 6H2O ------> C6H12O6 + 6O2

Is photosynthesis endergonic or exergonic?

endergonic because it requires energy

where does the plant obtain the energy to run the anabolic reactions of photosynthesis?

water through roots and CO2

Stomata

Small openings on the underside of a leaf through which oxygen and carbon dioxide can move

Chloroplast

An organelle found in plant and algae cells where photosynthesis occurs