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BSCI170 exam 3

Entropy: measurement of disorder; how spread out energy is

System: whatever is being studied

Surroundings: whatever is NOT in the system

Thermodynamics: study of energy transformation in a collection of matter

1st Law of Thermodynamics:
- Energy can not be created or destroyed
- Energy can be converted from one form to another
- Conservation of energy

2nd Law of Thermodynamics:
- Increase in entropy(how spread out energy is) when energy transformation
occurs
- After each energy transformation, some of the energy system becomes
unavailable to do work

Gibbs Free Energy:

Thermodynamic potential that can be used to calculate the maximum amount of

work performed by a thermodynamically closed system(Energy available to do

work).

Formula for Gibbs Free Energy:

ΔG = ΔH-TΔS

G: free energy

H: enthalpy(total energy in system

T: temperature(Kelvin)

S: entropy

Characteristics of negative and positive ΔG?

Negative ΔG Positive ΔG
Spontaneous Non-spontaneous
Release energy Requires energy
TΔS > ΔH TΔS < ΔH
Exergonic Endergonic

Characteristics about anabolism:

- Building up

- Creates bonds

- Energy required to form chemical bonds

Characteristics about catabolism:

- Breaking down

- Breaks bonds

- Energy is released when bonds are broken

How do chemical transformations get started?

Need activation energy(Ea) to get started

Exergonic:

A reaction that breaks down molecules and releases energy

Metabolic Pathway:

Living cells rely on this to run complex chemical reaction through a sequence of intermediate steps

Metabolism:

The sum of all bichemical reactions in every cell

Endergonic:

A reaction that makes molecules and uses energy

Energy:

The capacity to do work

Potential energy:

Stored energy that can be used in the future, stored in bonds in living cells, extracted by breaking molecular bonds

Kinetic energy

Energy of movement

Covalent bonds:

Through shared unpaired valence electrons

Ionic bonds:

Through electrostatic attraction

Structure-function relationships of ATP:

Allows for covalent phosphate bonds that unstable and easily broken therefore the subsequent energy released is significant.

Direct exchange:

Substrate direct with indirect. Some molecules can directly exchange electrons through reduction-oxidation.

Endergonic vs. Exergonic:

Elements combine Elements seperate

Bonds are made Bonds are broken

Uses energy Releases energy

Entropy decreases Entropy inscreases

High free energy Low free energy

Reduce disorder Increases disorder

Ananbolic Catabolic

Non-spontaneous Spontaneous

A + B —> C A —> B + C

+ΔG -ΔG

Enzymes:

Have an active site whose shape is complementary to the shape of the specific substrate, fitting like puzzle pieces

Activity of enzymes are influences by:

Temperature, pH, and Co-factors: metal ions and coenzymes

Steps of enzyme binding:

1- substrates enter active site

2- substrates stay in active sites through weak interactions

3- active site can lower activation energy to speed up reaction

4- substrates convert to poducts

5- products are released

6- active site is avaliable fore new substrates

Induced fit:

What forms when the substrate and enzyme interact to create an enzyme-substrate complex

Enzyme-substrate complex:

Formed through induced fit, activation energy is lowered.

Inhibitors:

Turn off enzyme, lower enzyme activity

Competitive inhibitors:

Slow down or block the enzyme by preventing substrate binding through insertion into the active site of the enzyme

Non-competitive inhibitor:

A molecule that binds to an enzyme regardless of whether the substrate is present

Allosteric inhibitor:

A molecule that binds to a site other than the active site and reduces enzyme activity, causing a change in the shape of the active site

Feedback inhibition:

Inhibits the activity of the first enzyme in the pathway

Activators:

Turn on enzyme, increase enzyme activity

Allosteric regulation:

Allosteric activators stabilize the enzyme in its active conformation

Reaction coupling:

Makes a positive delta G reaction into a net negative delta G, the negative delta G has to be greater in magnitude than the required positive delta G

Light reactions:

  • Light reactions of photosynthesis take place in the thylakoid membrane of the chloroplast

  • Its primary function is to capture light energy and use it to produce ATP and NADPH to power the Calvin cycle

  • The final electron carrier is NADP+, which gets reduced to NADPH

  • Major products: ATP provides energy and NADPH provides electrons

Photosystem II (PSII): electrons are replaced through photolysis, which splits water molecules, releasing oxygen and hydrogen ions

Plastoquinone (PQ): carries high-energy electrons from PSII to the cytochrome complex while picking up H+ ions from the stroma

Cytochrome complex: transfers electrons while pumping H+ ions into the lumen, creating a proton gradient for ATP synthesis

Photosystem I (PSI): Electrons get re-excited by light and passed to the ferredoxin (FD) before reaching NADP+ reductase (FNR)

NADP+ reductase: Not considered a part of an electron transport chain because it doesn’t actively pump protons, just simply transfers high-energy electrons to NADP+

Calvin Cycle

  • Carbon Fixation

    • Enzyme responsible: Rubisco

    • RuBP reacts with CO2

  • Reduction

    • Final product: G3P, which makes glucose and other organic molecules

    • ATP provides energy, and NADPH provides electrons

  • Regeneration

    • 5 out of 6 G3P molecules make RuBP to fix more CO2

    • Glucose is not a direct product of photosynthesis because it is synthesized from G3P in other pathways

  • G3P can be synthesized to make:

    • Starch, fatty acids, and amino acids

Phosphorylated inermediates:

Made by non-spontaneous reaction being coupled to the hydrolysis of ATP. They are more unstable and chemically reactive than the original reactants.