Enzymes
What class of macromolecules do enzymes belong to, and what is their primary catalytic function?
Proteins; catalyze (speed up) chemical reactions by lowering activation energy
What term describes the complete loss of structure and function when an enzyme unfolds?
Denaturation
State the 1st Law of Thermodynamics.
Energy cannot be created or destroyed
Energy can be transferred or transformed
Which early prokaryotes were the first to perform photosynthesis and oxygenate Earth's atmosphere?
Cyanobacteria
What is missing from the balanced chemical equation for cellular respiration?
C6H12O6 + 6___ --> 6CO2 + 6___ + energy (ATP & heat)
C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy (ATP & heat)
What is the specific region of an enzyme where the substrate binds?
Active site
Under what specific condition can enzyme denaturation be reversed?
When primary structure remains intact and the environment returns to optimal conditions before further damage occurs
According to the 2nd Law of Thermodynamics, every energy transformation increases what property of the universe?
Entropy (the measure of disorder)
What leaf pores allow CO₂ to enter and O₂ to exit during gas exchange?
Stomata
In what specific part of the cell does glycolysis occur?
Cytosol (the fluid part of the cytoplasm; aqueous solution of water, salts, dissolved molecules around the organelles
NOT CYTOPLASM (cytoplasm includes cytosol and the suspended organelles besides the nucleus)
According to the induced fit model, what happens to both the enzyme and substrate when binding occurs?
Both change shape to position the substrate, meaning bonds can be broken or formed easily
How do high temperatures outside the optimal range cause denaturation?
High heat breaks hydrogen and ionic bonds holding 3D shape
Why is heat considered "less usable" energy during cellular thermodynamic conversions?
Heat is disorganized
Where do the light reactions and Calvin cycle occur within the chloroplast?
Light reactions = thylakoids
Calvin Cycle (light independent reactions) = stroma
List the four stages of cellular respiration in sequential order.
1. Glycolysis
2. Pyruvate oxidation
3. Citric Acid Cycle (Krebs Cycle)
4. Oxidative phosphorylation
Name at least one of three distinct mechanism strategies enzymes use at the active site to lower activation energy.
1. Bring reacting molecules close together in correct orientation
2. Altering active site charges to promote catalysis
3. Changing/straining the substrate's shape
Why does reaction rate level off as substrate concentration increases to high levels?
As substrate concentration increases, reaction rate increases until the enzyme is saturated
Increases collision with enzymes
What evolutionary conclusion is drawn from the fact that metabolic pathways like glycolysis are necessary to extract energy and convert it to usable forms?
This is evidence of common ancestry among all living organisms
What are the primary and accessory pigments in plants, and what are two crucial roles of accessory pigments?
Primary = chlorophyll a
Accessory = chlorophyll b, carotenoids
Roles of accessory
1. expand usable light spectrum
2. protect chlorophyll from damage
Summarize the net inputs and net outputs of glycolysis starting from one glucose molecule.
1 Glucose --> 2 Pyruvates, 2 net ATP, 2 NADH, 2 H2O
What is a cofactor? What are the two types of cofactors?
Non-protein molecules that bind to enzymes and assist with enzyme function
1. Metallic ions (ex. zinc, iron, copper)
2. Coenzymes (small organic compounds)
How do non-optimal pH levels and chemical agents (salts, solvents) denature enzymes at the molecular level?
pH alters the charges on amino acids, disrupts hydrogen bonds at the active site,
Chemicals unfold proteins
Why does a cell synthesizing organized proteins from simple amino acids NOT violate the 2nd Law of Thermodynamics?
The release of heat, CO₂, and H₂O increases the entropy of the universe more than the decrease in entropy within the cell
How does the double membrane structure of chloroplasts relate to compartmentalization?
Creates distinct separation for proton gradient establishment (keeps reactions separate from other parts of the cell)
In alcohol fermentation, pyruvate is converted into ________.
In lactic acid fermentation, pyruvate is reduced to form ________.
Alcohol fermentation = ethanol
Lactic acid fermentation = lactate