Unit 3: Cellular Energetics

Enzyme structure

EU: The highly complex organization of living systems requires constant input of energy and the exchange of macromolecules

• Describe the properties of enzymes

The structure of enzymes include: ACTIVE SITE that specifically interacts with a substrate molecule

For a reaction the to occur the SHAPE and CHARGE of the substrate must be compatible with the active site

• Enzymes make and break things and make reactions in the cell happen faster

Enzyme Catalysis

EU: The highly complex organization of living systems requires constant input of energy in the exchange of macromolecules

• Explain how enzymes affect the rate of biological reactions

The structure and function of enzymes contribute to the regulation of biological processes

• Enzymes are biological catalysts that facilitate chemical reactions in cells by lowering the activation energy

Catalysts- lowers activation energy and helps things process faster (starts a process)

Activation energy- the minimum amount of energy needed to start a chemical reaction

The push needed to get a ball offer the hill, once it’s over the reaction can happen

Environmental Impacts on Enzyme Function

EU: The highly complex organization of living systems requires constant input of energy and the exchange of macromolecules

• Explain how changes to the structure of an enzyme may affect its function

• Explain how the cellular environment affects enzyme activity

Change to the molecular structure of a component in enzymatic system may result in a change of a function or efficiency of the system-

• DENATURE - The enzyme’s shape changes so it no longer works properly. (Heat, extreme pH levels, or chemicals cause this)

Environmental pH can alter the efficiency of enzyme activity,

• pH affects enzyme shape

• Substrate amount affects speed - more substrate means it goes faster (concentration)

• Heat increases collisions - make molecules move faster, which causes enzymes and substrates to collide more often, increasing the reaction rate

• Inhibitors reduce enzyme activity - Inhibitors slow or stop enzymes

Cellular Energy

EU: The highly complex organization of living systems requires constant input of energy and the exchange of macromolecules

• Describe the role of energy in living organisms. All living systems require constant input of energy.

Life requires a highly ordered system

• Cells must take in more energy than they lose in order to maintain organization and carry out life processes.

• Cells use energy from one process to power another process that needs energy

• If a cell can’t keep its organization or energy flow, it will die

Photosynthesis

EU: The highly complex organization of living systems requires constant input of energy in the exchange of macromolecules

• Describe the photosynthetic process that allow organisms to capture and store energy

• Explain how cells capture energy from light and transfer it to biological molecules for storage and use

What photosynthesis does

• Captures energy from sunlight

• Stores energy in sugars (glucose)

Origins of photosynthesis

• First evolved in prokaryotes (cyanobacteria)

• Cyanobacteria produced oxygen, leading to Earth’s oxygen-rich atmosphere

• Eukaryotic photosynthesis evolved from prokaryotic pathways

Light-dependent reactions (thylakoid membrane)

• Use light energy

• Produce:

  • ATP

  • NADPH

• ATP & NADPH provide energy for making sugars later

How light energy is captured

• Chlorophyll absorbs light

• Light excites electrons in:

  • Photosystem II

  • Photosystem I

• These photosystems are in the thylakoid membrane

Electron Transport Chain (ETC) in photosynthesis

• Excited electrons move through an ETC

• Energy released is used to:

  • Pump H⁺ (protons) across the membrane

• This creates a proton gradient

Making ATP (chemiosmosis)

• Protons flow back through ATP synthase

• ATP is made from ADP + phosphate

Calvin Cycle (stroma)

• Uses ATP + NADPH

• Converts CO₂ → carbohydrates (glucose)

Cellular Respiration

• Describe the process that allow organism sees energy stored in biological micro molecules

Purpose of cellular respiration

• Breaks down biological macromolecules (like glucose)

• Produces ATP

• Occurs in almost all organisms

• Includes:

  • Respiration

  • Fermentation

Cellular respiration overview

• Series of enzyme-catalyzed reactions

• Energy from glucose is captured gradually

Electron Transport Chain in respiration

• Occurs in:

  • Mitochondria (eukaryotes)

  • Plasma membrane (prokaryotes)

• NADH and FADH₂ donate electrons to the ETC

• Electrons move through carriers → release energy

Terminal electron acceptors

• Cellular respiration: oxygen (O₂)

• Photosynthesis: NADP⁺

• Aerobic prokaryotes: oxygen

• Anaerobic prokaryotes: other molecules (not oxygen)

Proton gradient & ATP production

• Electron movement pumps H⁺ across a membrane

• Creates a proton gradient

• Protons flow through ATP synthase

• This makes ATP

How Cells Make ATP (Big Picture)

• Energy is made using electron transport chains (ETCs) in:

  • Mitochondria (cellular respiration)

  • Chloroplasts (photosynthesis)

  • Plasma membrane (prokaryotes)

• ETCs create a proton (H⁺) gradient across a membrane.

⚙ Chemiosmosis & ATP Synthase

• Protons move from high → low concentration

• They flow through ATP synthase

• This makes ATP from ADP + phosphate

• Name depends on the process:

  • Oxidative phosphorylation → cellular respiration

  • Photophosphorylation → photosynthesis

🔥 Heat & Respiration

• If electron transport is uncoupled from ATP production:

  • Energy is released as heat

  • Used by endotherms to regulate body temperature

🍞 How Cells Get Energy from Glucose

1. Glycolysis (cytosol)

• Glucose → pyruvate

• Produces:

  • ATP

  • NADH

2. Pyruvate Oxidation & Krebs Cycle (mitochondria)

• Pyruvate enters mitochondria

• CO₂ released

• Produces:

  • ATP

  • NADH

  • FADH₂

3. Electron Transport Chain (inner mitochondrial membrane)

• NADH & FADH₂ deliver electrons

• Electrons move through ETC

• Creates H⁺ gradient

4. ATP Production

• H⁺ flows through ATP synthase

• ATP is made

🧪 Fermentation (No Oxygen)

• Allows glycolysis to continue

• Produces:

  • Lactic acid or alcohol

  • No ETC or Krebs cycle used

⚡ ATP Use

• ATP → ADP releases energy

• Energy powers cellular work (movement, transport, synthesis)

Fitness

EU: naturally occurring diversity among in between components within biological systems, affects interactions with the environment

• Explain the connection between variation and the number and types of molecules within cells to the ability of the organism to survive and/or reproduce indifferent environments

• Biological systems naturally have diversity.

• This diversity affects how organisms interact with their environment.

Key idea:

• Variation at the molecular level (different types and amounts of molecules in cells) helps organisms:

  • Respond to different environmental conditions

  • Survive

  • Reproduce

In simple terms:

• The more molecular variety an organism has, the better its chances of survival in changing environments.