Biology Lesson 9.1 Energy and Life

Lesson 9.1 Energy and Life

• ATP (Adenosine Triphosphate) is a small molecule used by all cells to store and release energy.
• ATP consists of adenine, ribose, and three phosphate groups.
• The phosphate groups are key to ATP's energy storage and release function.
• ADP (Adenosine Diphosphate) has two phosphate groups.
• When energy is available, cells add phosphate groups to ADP to create ATP.
• Cells release energy by breaking the bonds between phosphate groups in ATP.
• ATP is like a fully charged battery, and ADP a partially charged battery.
• Cells use ATP for active transport.
• Cell membranes contain sodium-potassium pumps that move sodium ions out and potassium ions in, using ATP.

Heterotrophs and Autotrophs

• Heterotrophs obtain energy by consuming other living things for food.
• Examples include animals that eat plants or other animals.
• Fungi and some bacteria are also heterotrophs.
• Autotrophs create their own food using energy from sunlight.
• Plants and some bacteria are examples of autotrophs.

Chlorophyll and Chloroplasts

• Photosynthetic organisms use pigments to capture sunlight.
• Chlorophyll is the key pigment in green plants.
• Chloroplasts are the organelles in plant cells where photosynthesis takes place.
• Chloroplasts have two membranes and contain thylakoids.
• Thylakoids are interconnected sacs that form stacks called grana.
• The fluid portion outside the thylakoids is the stroma.

High-Energy Electrons

• Electron carriers are molecules that carry high-energy electrons.
• NADP+ is an important electron carrier.
• It accepts high-energy electrons and hydrogen ions (H+).
• Converting NADP+ to NADPH stores energy.

An Overview of Photosynthesis

• Photosynthesis uses sunlight to convert carbon dioxide and water into sugars and oxygen.
• The overall reaction is represented by the equation 6CO2 + 6H2O → C6H12O6 + 6O2.

Stages of Photosynthesis

• Photosynthesis involves light-dependent and light-independent reactions.
• Light-dependent reactions occur in the thylakoid membranes.
• They require light and use water to produce oxygen, ATP and NADPH.
• Light-independent reactions occur in the stroma.
• They use ATP and NADPH to convert carbon dioxide into sugars (glucose).

Lesson 9.3 - The Process of Photosynthesis (Light-Dependent Reactions)

• Photosystems are clusters of chlorophyll and other proteins in the thylakoid membranes.
• Electron transport chains are a series of electron carrier proteins in the chloroplast.
• Water molecules are split during the light-dependent reactions to release oxygen, hydrogen ions and electrons.
• Electrons move along electron transport chains, releasing energy to pump hydrogen ions into the thylakoid space.
• The buildup of hydrogen ions in the thylakoid space creates a concentration gradient.
• This gradient powers ATP synthase.
• NADP+ accepts the electrons and hydrogen ions to produce NADPH.

Light-Independent Reactions (Calvin Cycle)

• Carbon dioxide is absorbed into the chloroplast.
• A 5-carbon compound combines with carbon dioxide.
• ATP and NADPH provide ATP and energy to make glucose (sugar).
• The cycle regenerates the 5-carbon compound.