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Chapters 9 and 10, Importance of Photosynthesis: - Coggle Diagram
Chapters 9 and 10
Chapter 9-Cellular Respiration and Fermentation
Cellular respiration = process that releases energy by breaking down glucose and other food molecules to make ATP. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP + heat)
ATP (adenosine triphosphate) = main energy currency of the cell.
Anabolic pathways = build complex molecules, using energy.
Catabolic pathways = break down complex molecules (like glucose) into simpler ones, releasing energy.
Energy flow
Photosynthesis stores energy in sugars (in plants).
Cellular respiration releases that stored energy (in plants and animals).
→ The two processes form a cycle between the chloroplasts and mitochondria.
Steps for cellular respiration
Glycolysis (in cytoplasm)
Pyruvate oxidation (in mitochondria)
Citric Acid Cycle (Krebs Cycle)
Oxidative phosphorylation (ETC + chemiosmosis)
Important Molecules
Glucose is oxidized → becomes CO₂.
Oxygen is reduced → becomes H₂O.
NAD⁺ = electron carrier; accepts electrons and becomes NADH (reduced form).
NADH carries electrons to the electron transport chain (ETC).
ATP Production
Two ways cells make ATP:
Substrate-level phosphorylation — enzyme directly transfers phosphate to ADP (happens in glycolysis & citric acid cycle)
Oxidative phosphorylation — uses energy from electrons in the ETC to make ATP (most ATP is made here).
OIL-RIG
Cellular respiration involves redox (oxidation-reduction) reactions.
Oxidation = loss of electrons
Reduction = gain of electrons
Sugar Splitting- Glycolysis means “sugar-splitting.”
Occurs in the cytoplasm (does not require oxygen).
Breaks 1 glucose (6C) → 2 pyruvates (3C each).
Produces a net gain of 2 ATP and 2 NADH.
Two Phases
Energy Investment Phase — uses 2 ATP.
Energy Payoff Phase — produces 4 ATP and 2 NADH.
Net Products
2 Pyruvate
2 NADH
2 ATP (net gain)
2 H₂O (byproduct)
The Citric Acid Cycle (Krebs Cycle) and Oxidative Phosphorylation
Step 1: Pyruvate Oxidation
Each pyruvate (3C) from glycolysis moves into the mitochondria.
It’s converted into acetyl CoA (2C) + CO₂ + NADH.
This links glycolysis → citric acid cycle.
Step 2: Citric Acid Cycle (in mitochondrial matrix)
Step 2: Citric Acid Cycle (in mitochondrial matrix)
Acetyl CoA (2C) joins with oxaloacetate (4C) → citrate (6C).
Cycle breaks down citrate → releases 2 CO₂ per turn.
For each glucose (2 turns total):
6 NADH
2 FADH₂
2 ATP
4 CO₂ (waste gas)
Step 3: Oxidative Phosphorylation (ETC + Chemiosmosis)
Electron Transport Chain (ETC):
Series of proteins in the inner mitochondrial membrane.
NADH & FADH₂ donate electrons → passed down the chain.
Oxygen = final electron acceptor, forms H₂O.
Chemiosmosis:
Electrons moving through ETC pump H⁺ ions into intermembrane space → creates proton gradient.
ATP synthase uses the gradient to make ~26–28 ATP.
Total ATP yield per glucose = ~30–32 ATP.
Anaerobic respiration → uses ETC but final electron acceptor is NOT O₂ (ex: sulfate).
Fermentation → no ETC used.
Glycolysis is in both
Glycolysis still makes 2 ATP by substrate-level phosphorylation.
NAD⁺ must be regenerated for glycolysis to contin
Types of Fermentation
Alcohol Fermentation
Pyruvate → ethanol + CO₂
Used by yeast (bread, beer, wine)
Regenerates NAD⁺
Lactic Acid Fermentation
Pyruvate → lactate (no CO₂ released)
Used by muscle cells during exercise & by bacteria (yogurt, cheese)
catabolic pathways are flexible
Not only glucose — cells can break down fats, proteins, and carbs for ATP.
How: Carbohydrates → enter as glucose → glycolysis.
Proteins → broken into amino acids → enter as pyruvate, acetyl CoA, or citric acid cycle intermediates.
Must remove amino group (NH₃) first = deamination.
Fats → broken into glycerol + fatty acids.
Glycerol → glycolysis intermediate.
Fatty acids → acetyl CoA via beta oxidation.
Fats produce 2× more ATP per gram than carbs.
Anabolic (Biosynthetic) Pathways
Cells also use parts of glycolysis & citric acid cycle to build molecules.
Examples:
Some amino acids made from citric acid intermediates.
Regulation of Cellular Respiration
Controlled by feedback inhibition:
When ATP is high, respiration slows down.
When ATP is low / AMP is high, respiration speeds up.
Chapter 10-Photosynthesis
Photosynthesis: Conversion of sunlight into chemical energy stored in sugars. 6CO2+6H2O+light→C6H12O6+6O2
Autotrophs ("self-feeders") – Make their own food using CO₂ and inorganic materials.
Photoautotrophs use sunlight for energy (plants, algae, cyanobacteria).
Heterotrophs ("other-feeders") – Cannot make their own food; they depend on autotrophs for energy and organic molecules.
Include animals, fungi, and most bacteria.
Decomposers: Fungi and prokaryotes that get energy by breaking down dead organisms.
Chloroplast structure
Stomata – Tiny pores that allow CO₂ in and O₂ out.
Mesophyll – Leaf cells that contain most of the chloroplasts.
Thylakoids – Flattened sacs inside chloroplasts; site of light reactions.
Grana – Stacks of thylakoids.
Stroma – Fluid around thylakoids; site of the Calvin cycle.
The light reactions occur in the thylakoid membranes.
Purpose: Convert solar energy → ATP and NADPH (chemical energy).
Main steps
Light is absorbed by chlorophyll pigments.
Water (H₂O) is split, releasing O₂.
Electrons move through an electron transport chain.
Energy from the electrons helps produce ATP (via chemiosmosis).
Electrons and hydrogen reduce NADP⁺ → NADPH.
Products: ATP, NADPH, and O₂.
Pigments
Chlorophyll a – Main pigment that drives photosynthesis.
Chlorophyll b and carotenoids – Accessory pigments that help absorb additional light wavelengths.
Three Phases of the Calvin Cycle: Calvin cycle occurs in the stroma of the chloroplast.
Uses ATP and NADPH (from light reactions) to fix CO₂ and ma
Carbon Fixation:
CO₂ is attached to a 5-carbon molecule (RuBP) using the enzyme rubisco.
Reduction:
ATP and NADPH convert the carbon compound into G3P (a 3-carbon sugar).
Regeneration of RuBP:
Some G3P leaves to form glucose; the rest regenerates RuBP to continue the cycle.
Output:
For every 3 CO₂, the cycle produces 1 G3P (which can make glucose).
Types of Plants:
C₃ Plants – Most common type.
Use the Calvin cycle directly.
Problem: In hot weather, they lose water as stomata close, and photorespiration occurs (a wasteful process where O₂ replaces CO₂).
C₄ Plants – Adapted to reduce photorespiration.
Use a 4-carbon compound to store CO₂ before entering the Calvin cycle.
Examples: Corn, sugarcane.
CAM Plants – Open stomata at night to take in CO₂ and store it for daytime use.
Examples: Cacti, pineapples, succulents.
How Plants Use Sugar:
Energy: Sugar is used for cellular respiration to make ATP.
Transport: Converted to sucrose and transported to non-photosynthetic cells.
Storage: Stored as starch in roots, seeds, and fruits.
Structure: Used to make cellulose, which builds cell walls.
Importance of Photosynthesis:
Produces oxygen for living organisms.
Supplies food and energy for the biosphere.
Forms the basis of fossil fuels (ancient stored sunlight).
Globally produces billions of tons of carbohydrates each year.
Importance of Photosynthesis: