Unit 3: Cell energy

Slogan: Energy Efficiency

Critical Info

Thermodynamics

First law: Energy can be transferred and transformed, but energy CANNOT be created nor destroyed

Second law: Every energy transfer of transformation increases entropy (disorder) of the universe

Free Energy

Exergonic reactions (-ΔG): Release energy

  • “Export your ex cause of his negative energy“

Endergonic reactions (ΔG): Store energy

  • “Enter the store with a positive attitude”

Energy coupling: using an exergonic process to drive an endergonic one

Heterotrophs: need to find food/energy to consume

Enzymes

Acid-base catalysis: when covalent bonds in substrate may be destabilized when H ion transfer occurs between the active site of the enzyme and the substrate

Covalent Catalysis: when R groups interact and temporarily bond with the substrate

Metal ion Catalysis: when metal ion electrons are gained or lost without detaching from protein

Cofactors: chemicals which assist enzymic action

  • nonprotein enzyme helpers such as minerals (Zn, Fe, Cu)

Coenzymes: Organic cofactors

  • Vitamins

Regulation of enzyme activity ↴

Competitive: binds to the active site

  • competes for the bond with the enzyme against the substrate

Non-competitive: Binds to another part of the enzyme

  • alters the shape of the active site via another location

Cooperativity: A form of allosteric regulation which can amplify enzyme activity

Feedback inhibition: occurs when the end product of a metabolic pathway shuts down pathway by binding to the allosteric of an enzyme

  • this prevents wasting chemical resources, increase efficiency of the cell

Photosynthesis

Equation:

6CO2 + 6H2O + Light energy → C6H12O6 + 6O2

Chloroplasts are the site of photosynthesis

  • Light dependent reaction occur in the Thylakoids

  • Light-Independent reaction occur in the Stroma

Chemiosmosis: the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient

  • Osmosis for ions

  • Found in both Cellular Respiration and Photosynthesis

LEO (Loss of Electrons is Oxidation) the lion says GER (Gaining Electrons is Reduction)

Phosphorylation: the process of adding a phosphate group to a molecule

Light Reaction

Linear Electron Flow

  1. A photon hits a light-harvesting complex of PS II

  2. An excited electron is transferred to the primary electron acceptor

  3. H2O is split by enzymes

  • H+ is released into thylakoid space

  • O2 is released as a byproduct

  1. Each electron falls down an electron transport chain

  • this forms a proton gradient across the thylakoid membrane

  1. Potential energy is stored in the proton gradient drives production of ATP by Chemiosmosis

  2. In PS I, transferred light energy excites P700, which loses an electron to the primary electron acceptor

  3. Each electron falls down another electron transport chain

  4. NADP+ reductase catalyzes the transfer of electrons to NADP+, reducing it to NADPH

  • The electrons of NADPH are ready for the Calvin cycle

  • This process removes an H+ ion from the stroma

Cyclic Electron Flow

Same as linear flow except the electrons in photosystem I cycle back from Fd to the PS I reaction center (cytochrome complex) via a plastocyanin molecule

never go past Fd

Produces ATP but NOT NADPH

  • due to the fact that the electrons never make it to the NADP+ reductase

  • No oxygen is needed during this process

Calvin Cycle

Key points:

Creates:

  • 1 G3P

  • 9APD

  • 6 NADP+

  • 6 +pi

Carbon fixation evolution

TBF

C3 plants

C4 plants

CAM plants

Cellular Respiration

3 steps:

Glycolysis

“Sugar Splitting“

Glycolysis occurs in the cytosol outside the mitochondria

Oxidizes glucose into 2 Pyruvates

The process has net gains of:

  • 2 ATP

  • 2 NADH

  • 2H2O

Note that glycolysis does NOT require O2 as it is a theorized ancient process

Glycolysis also must first invest 2 ATP before it has a payoff of 4 ATP resulting in the net of 2 ATP

Pyruvate Oxidation + Citric acid cycle (Krebs)

Pyruvate is converted to Acetyl CoA to be used for the Citric Acid cycle (Krebs)

There is a Net gain of:

  • 2 ATP

  • 6NADH

  • 2FADH

Oxidative Phosphorylation (ETC and chemiosmosis)

This part uses an ETC.

PRODUCES RHE BULK OF ATP (26-28)

same concept with ETC and H+ ions.

  • the electrons move H+ ions against the gradient, the ATP synthase then allows H+ ions to diffuse back, creating ATP

Kahoot Questions

(Will be plugged into the notes)

What BEST describes the type of metabolic pathway of photosynthesis?

  • Endergonic (catabolic)

What BEST describes the type of metabolic pathway of Cellular respiration?

  • Exergonic (anabolic)

In respiration, O2 is the final electron (e-) acceptor in the ETX. Where for these e- come from?

  • NADH & FADH2

In respiration, which would be evidence of cellular respiration NOT occurring?

  • An increase in lactic acid concentration

Both Krebs cycle and glycolysis make a net gain of 2 ATP

Which of the following is considered substrate level phosphorylation?

  • Both Krebs and Glycolysis

Which of the following is involved in Oxidative Phosphorylation?

  • Electron Transport chain

On hot, dry days, what do C3 plants do?

  • Partially close their stomata

How can you measure the rate of photosynthesis? Measuring the production of O2

The “extra“ pigments in plants are called an accessory

Plants imbed pigments in what structures to be used in photosynthesis?

  • Thylakoid membranes

Essential Questions

How do enzymes affect the rate of biological reactions?

What environmental factors can influence the rate of reaction by impacting the structure and function of enzymes?

How do environmental conditions impact enzyme function?

What processes are shared (conserved) throughout both photosynthesis and cellular respiration?

How do membranes in the chloroplast and mitochondria contribute to their function?

How do electron transport chains create hydrogen gradients?

How do hydrogen gradients create ATP?