4-5 biology

autotrophs

“self feeders,” make energy-rich molecules (plants, some bacteria).

photosynthesis equation:

Energy (light) + 6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

photosynthesis reaction type

Anabolic (builds molecules) & Endergonic (requires energy)

energy source for photosynthesis

Light energy (photons) from the sun.

light reaction location

thylakoid membranes.

Calvin Cycle

st

light reaction function

capture sunlight, make ATP & NADPH, release O₂

Calvin cycle function

use ATP & NADPH to build glucose

shorter wave length energy

more energy (blue/violet)

longer wavelength energy

less energy (red)

why plants are green?

Chlorophyll reflects green light & absorbs red/blue (green is rejected so that’s what we see)

photosystem structures

Pigment molecules (chlorophylls, carotenoids), reaction center, electron acceptors.

how photosystems trap light

Pigments absorb light → transfer energy to reaction center → excite electrons.

source of excited electrons

PSII → water splitting.
PSI → electrons from PSII.

oxygen generation:

Water is split (photolysis) → O₂ released as waste.

proton gradient

Electrons moving down ETC pump H⁺ into thylakoid lumen.

ATP from H⁺ Gradient

H⁺ flows back through ATP synthase → chemiosmosis makes ATP.

light reaction input

light, H₂O, NADP⁺, ADP + Pi

light reaction output

O₂, NADPH, ATP

light reaction connection to Calvin cycle

Products of light reactions (ATP & NADPH) = reactants for Calvin Cycle.

Calvin cycle input:

CO₂, ATP, NADPH

Calvin cycle output

G3P, ADP +Pi, NADP⁺

carbon fixation

CO₂ attached to RuBP (5C) → forms 3C molecules (G3P).

carbon fixation enzyme

Rubisco

why are 6 turns needed?

Each turn fixes 1 C → 6 CO₂ needed for 1 glucose (6C).

photosynthesis function

stores energy in glucose.

heterotrophs

“other feeders,” must eat other organisms (animals, fungi, humans).

respiration function

releases energy from glucose.

Why does the human body need to eat?

To get energy for survival, making molecules (like proteins & nucleic acids), and running life processes

What is metabolism?

The sum of all chemical reactions in a cell

What is the function of chemical bonds?

They store energy and release it when broken

Why is ATP good for storing & releasing energy?

It has high-energy phosphate bonds that are easy to break

What happens in catabolic reactions?

Molecules are broken down, releasing energy

What happens in anabolic reactions?

Molecules are built, requiring energy

What happens in exergonic reactions?

Release energy (products have less energy than reactants)

What happens in endergonic reactions?

Require energy (products have more energy than reactants)

How are catabolic, anabolic, exergonic, and endergonic reactions related?

Catabolic = exergonic (release energy). Anabolic = endergonic (require energy)

 How are ATP & ADP related?

ATP has 3 phosphates (more energy). When a phosphate is removed → ADP (less energy)

What happens in redox reactions?

Electrons are transferred: oxidation = lose e⁻, reduction = gain e⁻

What is the equation for cellular respiration?

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~36 ATP

Where does glycolysis occur?

Cytoplasm

Where does pyruvate oxidation occur?

Mitochondrial matrix (1)

Where does the Citric Acid Cycle occur?

Mitochondrial matrix (2)

Where does the Electron Transport Chain occur?

Inner mitochondrial membrane

What is substrate-level phosphorylation?

Direct transfer of a phosphate to ADP to make ATP

What is chemiosmosis?

ATP synthase uses proton gradient energy to build ATP

How many carbons are in glucose?

6

How many carbons are in pyruvate?

3

What are the inputs & outputs of glycolysis?

In: glucose, 2 ATP, 2 NAD+ → Out: 2 pyruvate, 2 NADH, 2 net ATP

What are the inputs & outputs of pyruvate oxidation?

In: 2 pyruvate → Out: 2 acetyl-CoA, 2 CO₂, 2 NADH

What are the inputs & outputs of the Citric Acid Cycle?

In: 2 acetyl-CoA, 6 NAD+, 2 FAD → Out: 4 CO₂, 2 ATP, 6 NADH, 2 FADH₂

What are the inputs & outputs of the Electron Transport Chain?

 In: NADH, FADH₂, O₂ → Out: H₂O, ~32 ATP

What is the function of electron carriers?

NADH and FADH₂ carry high-energy electrons to the ETC

How do electrons build a proton gradient?

ETC proteins pump protons into the intermembrane space as electrons pass through

How does proton movement build ATP?

 Protons flow back through ATP synthase, powering ATP production

What is oxygen’s role in cellular respiration?

Final electron acceptor, forming water

What is the purpose of fermentation?

To regenerate NAD+ so glycolysis can keep making ATP without oxygen

How does alcohol fermentation work?

Yeast converts pyruvate → ethanol + CO₂, regenerating NAD+

How does lactic acid fermentation work?

Pyruvate → lactic acid (in animals, bacteria, fungi), regenerating NAD+

What is feedback inhibition in respiration?

Extra ATP shuts down enzymes (like phosphofructokinase) to stop overproduction