Bio Exam 3

catalysts

enzymes that lower activation energy of chemical reactions; they destabilize the current bonds so new ones can form!

T/F: enzymes are used up in a reaction

False!

T/F: Enzymes do not bring energy into a reaction

True! Enzymes simply lower the activation energy required.

What does it mean that enzymes and substrates have a induced fit?

small changes to active site through weak bonds allow substrate to bind

Describe the catalytic cycle

1. Substrates enter the active site

2. They are held in by weak bonds

3. Active site lowers activation energy and increases speed

4. Substrates are converted to products

5. Products get released

Normal binding

occurs when enzymes and substrates fit perfectly without significant changes in shape, allowing efficient catalysis.

competitive binding

a competitive inhibitor binds to the active site and the substrate cannot bind

noncompetitive binding

occurs when an inhibitor binds to an allosteric site on the enzyme, changing its shape and preventing substrate binding, regardless of substrate presence.

feedback loops

like a thermostat; occurs when enough of something is created, it binds to enzyme to inhibit further production

cellular respiration

the process by which cells convert glucose and oxygen into energy, carbon dioxide, and water.

photosynthesis

the process by which plants, algae, and some bacteria convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water.

redox reactions

redox reactions are chemical processes that involve the transfer of electrons between molecules, resulting in changes in oxidation states.

oxidation

loss of electrons (OIL) - glucose is OXIDIZED to CO2 in cellular respiration

reduction

gain of electrons (RIG) - in redox reactions, reduction refers to the process where a molecule gains electrons, often leading to a decrease in oxidation state.

electron carriers

(pickup trucks) transport electrons during redox reactions, playing a crucial role in cellular respiration and photosynthesis. ex. NAD+ (oxidized) and NADH+ (reduced)

explain how electron carriers work

an enzyme binds with an energy molecule and NAD+, 2 e- are transferred to the NAD+ to form NADH and the NADH is released to do work and bind elsewhere

why must energy be released in small steps?

To prevent cellular damage and to effectively harness energy for ATP production, as large bursts of energy can be inefficient and damaging.

substrate level phosphorylation (glycolysis)

An enzyme binds to PEP and ADP, a P is transferred to ADP to form ATP and the PEP becomes pyruvate

where does glycolysis occur?

in the cytoplasm

inputs, outputs, and net gain of glycolysis

Inputs: glucose and 2 ATP

Outputs: 4 ATP, 2 NADH, 2 pyruvate per glucose molecule

Net gain: 2 ATP

pyruvate oxidation

The process occurring in the mitochondrial matrix where pyruvate is converted into acetyl-CoA

fermentation of pyruvate

• used if no oxygen is available

• NADH makes it into lactate by donating a H and becoming NAD+ or it becomes acetaldehyde and releases CO2, the NADH becomes NAD+ and makes ethanol (not in humans!) ex. yeast

oxidation of pyruvate

• used if oxygen is available!

• The conversion of pyruvate into acetyl-CoA, generating NADH and releasing CO2.

• Goes into Krebs cycle

4 stages of cellular respiration

1. glycolysis

2. pyruvate oxidation,

3. Krebs cycle,

4. electron transport chain

Krebs Cycle

• Acetyl CoA binds with oxaloacetate acid to form citrate; NADH and FADH2 are produced, and CO2 is released during a series of reactions that regenerate oxaloacetate to make ATP

• Inputs: Acetyl-CoA

• Outputs: NADH, FADH2, ATP, CO2

• Net gain ATP: 2 ATP per glucose molecule

Electron transport chain

• NADH and FADH2 drop H off to inner membrane

• H want to be less crowdeed so move through ATP synthase gradient

• Generate many ATP

Inputs: NADH, FADH2, O2

Outputs: ATP, H2O

Net gain ATP: Up to 36 ATP per glucose molecule.

How. much ATP do we create in respiration?

36

phosphofruktokinase

Acts as thermostat. If plenty of energy, ATP and citrate bind to inhibit glycolysis. If need more energy, ADP and AMP bind to accelerate glycolysis

catabolism of proteins

Deamination creates ketoglutarate in the Krebs Cycle

catabolism of fats

The breakdown of fats involves lipolysis, where triglycerides are hydrolyzed into glycerol and free fatty acids, which can then be converted into acetyl-CoA for entry into the Krebs Cycle.

cellular respiration equation

C6H12O6 > 6CO2 + 6 H2O + energy

equation for photosynthesis

6CO2 + 6H2O + light energy > C6H12O6 + 6O2

light-dependent reactions

The light-dependent reactions are the first stage of photosynthesis, occurring in the thylakoid membranes of chloroplasts, where sunlight is captured to produce ATP and NADPH while splitting water molecules to release oxygen.

Where does O2 come from in photosynthesis?

Oxygen (O2) is released during the light-dependent reactions of photosynthesis when water molecules are split, a process known as photolysis.

how does a light-dependent reaction work?

• Sunlight absorbed by photosystem II, water molecules are broken down into O2. ATP and NADPH are produced and used in the Calvin Cycle

• Inputs: Sunlight, water, ADP, NADP+

• Outputs: ATP, NADPH, O2

Where is visible light on the electromagnetic spectrum?

In between UV and infrared light; 380-750 nm

red-orange light

longer wavelength and lower energy

blue-purple light

shorter wavelength and higher energy

What type of light is used in photosynthesis?

Light that is absorbed by chlorophyll, primarily red and blue wavelengths; green is reflected

Engelmann’s experiment

demonstrated that different wavelengths of light affect the rate of photosynthesis in green algae, using aerobic bacteria to determine oxygen production. This experiment showed that red and blue light promote higher rates of photosynthesis compared to green light.

chlorophyll a

a photosynthetic pigment that absorbs light primarily in the blue and red wavelengths, playing a crucial role in converting light energy into chemical energy.

chlorophyll b

a photosynthetic pigment that complements chlorophyll a by absorbing light in the blue and orange-red wavelengths, helping to broaden the spectrum of light that plants can use for photosynthesis.

carotenoids

a class of pigments that absorb light in the blue and green wavelengths, playing an accessory role in photosynthesis by transferring energy to chlorophyll and providing photoprotection.

porphyrin ring

a cyclic structure that consists of four pyrrole rings interconnected by methine bridges, which is the core component of chlorophyll and other biological pigments, facilitating light absorption. Magnesium in the middle

van Helmont experiment

An early scientific experiment conducted by Jan Baptista van Helmont to determine plant growth origins, showing that the increase in mass of a willow tree was primarily due to water absorption, not soil.

Z-diagram

Light hits chloroplasts in PSII, energy travels up to special P680, which excites electrons and sends to reaction center, leads to ETC where it interacts with plastoquinone, cytochrome complex, and plastocyanin, losing energy as it goes. It then goes to P700 in PSI, where it goes down another ETC, interacting with ferredoxin and NADP+ reductase

Outputs: NADPH, and ATP for Calvin Cycle

Difference between P680 and P700

P680 gets its energy from the sun, P700 gets its energy from P680

light independent reactions

Also known as the Calvin Cycle, these reactions occur in the stroma of chloroplasts, using ATP and NADPH produced in the light-dependent reactions to convert carbon dioxide into glucose.

Steps of calvin cycle

carbon fixation, reduction, and regeneration of ribulose bisphosphate (RuBP).

carbon fixation

The first step in the Calvin cycle, where carbon dioxide is incorporated into an organic molecule - RuBP + CO2 > PGA

• catalyzed by rubisco

• occurs in stroma

Inputs: CO2 and RuBP

Outputs: PGA

reduction in the Calvin Cycle

PGA is reduced to G3P by NADPH and ATP

Inputs: NADPH and ATP

Outputs: G3P and ADP

how is RuBP regenerated in the calvin cycle

RuBP is regenerated from G3P through a series of reactions involving ATP, allowing the cycle to continue.

Inputs: G3P and ATP

Outputs: RuBP and ADP

T/F: Glucose is a direct output of the Calvin Cycle.

False; 12 G3P are made and two leave the cycle to form glucose, while the other 10 go to the regeneration of RuBP

photorespiration

happens in plants in dry/hot conditions. Plants release to much water and O2, but by closing “doors” to conserve water, O2 builds up and reacts with rubisco, reducing the efficiency of photosynthesis and leading to the production of toxic byproducts.

T/F: in photorespiration, CO2 and O2 compete for the rubisco active site.

True; during photorespiration, high levels of O2 and low levels of CO2 promote competitive inhibition of rubisco, reducing the efficiency of carbon fixation.