Enzymes in Biochemistry

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Questions and Answers

What is the primary role of chlorophyll A in photosynthesis?

To regulate the wavelength of light absorbed

To energize electrons and transfer them to the primary electron acceptor (correct)

To absorb water molecules

To produce oxygen through oxidation

At which wavelengths do Photosystem I (P700) and Photosystem II (P680) primarily absorb light?

P700 at 750 nm and P680 at 670 nm

P700 at 700 nm and P680 at 680 nm (correct)

P700 at 680 nm and P680 at 600 nm

P700 at 600 nm and P680 at 700 nm

What is produced as a byproduct of water oxidation during photosynthesis?

ATP

NADPH

Oxygen (correct)

Carbon dioxide

Which process primarily drives the synthesis of NADPH and ATP in photosynthesis?

Flow of electrons through photosystems Signup and view all the answers

What happens to the energized electron after it reaches the primary electron acceptor?

It is transferred to the electron transport chain Signup and view all the answers

What is the purpose of RuBP in photosynthesis?

To regenerate ribulose bisphosphate for the Calvin Cycle Signup and view all the answers

What are the main inputs required for the Calvin Cycle to function?

ATP and NADPH Signup and view all the answers

During photosynthesis, what is produced from the breakdown of water?

Oxygen and hydrogen ions Signup and view all the answers

What is a product of the Calvin Cycle?

Glucose Signup and view all the answers

What compound is formed when 6 CO2 molecules are fixed in the Calvin Cycle?

12 G3P Signup and view all the answers

What is the primary goal of the Calvin Cycle in photosynthesis?

To fix carbon into glucose Signup and view all the answers

Which organelle is responsible for photosynthesis?

Chloroplast Signup and view all the answers

What role do pigments play in photosynthesis?

They absorb visible light Signup and view all the answers

Which of the following components is generated during the light reactions of photosynthesis?

ATP and NADPH Signup and view all the answers

What happens to electrons in chlorophyll when light is absorbed?

They are excited to a higher energy shell Signup and view all the answers

How is ATP produced during the light reaction of photosynthesis?

By using hydrogen ion gradient Signup and view all the answers

What is the significance of the stroma in chloroplasts?

It is where the Calvin Cycle takes place Signup and view all the answers

What is the function of ATP Synthase in photosynthesis?

To produce ATP from ADP Signup and view all the answers

What role do enzymes play in chemical reactions?

They accelerate reactions by lowering the energy of activation. Signup and view all the answers

Which statement accurately describes the transition state?

It is a temporary state where bonds are ready to break. Signup and view all the answers

Which characteristic of enzymes is true?

They are specific to certain substrates. Signup and view all the answers

How do enzymes affect the activation energy of reactions?

They decrease the activation energy needed. Signup and view all the answers

What type of energy relationship is observed in exothermic reactions?

Reactants have more energy than products. Signup and view all the answers

Which of the following statements is false about enzymes?

They can modify the reactants. Signup and view all the answers

What is the primary composition of most enzymes?

Proteins Signup and view all the answers

What is the main benefit derived from using enzymes in reactions?

They allow reactions to proceed with minimal energy expenditure. Signup and view all the answers

What is the primary function of photosynthesis in plants?

To convert solar energy into chemical energy Signup and view all the answers

Which of the following organisms are classified as photoautotrophs?

Plants and multicellular algae Signup and view all the answers

Where in the plant does most photosynthesis occur?

In the leaves Signup and view all the answers

What is the purpose of stomata in plant leaves?

To allow gas exchange Signup and view all the answers

What role do chloroplasts play in plant cells?

They synthesize sugar through photosynthesis Signup and view all the answers

What is the main chemical equation for photosynthesis?

CO2 + H2O + light energy → C6H12O6 + O2 Signup and view all the answers

What is the purpose of veins in plant leaves?

To export sugars and transport water Signup and view all the answers

What theory explains the multiple membranes found in chloroplasts?

Endosymbiotic Theory Signup and view all the answers

What is the primary byproduct of photosynthesis?

Oxygen Signup and view all the answers

Which process is direct reverse of photosynthesis?

Respiration Signup and view all the answers

Study Notes

Enzymes

Biological catalysts that speed up chemical reactions
Enzymes assist in metabolic pathways
Help make reactions start, requiring less energy
Enzymes are proteins that speed up chemical reactions, making them more likely to happen
They don't make reactions happen that wouldn't have happened otherwise
Enzymes make reactions cheaper to run
Enzymes push reactants up the hill until they reach an energy state high enough for the bonds to break - this is referred to as the transition state
Transition state is the point at which the reaction goes from needing energy to put into the reaction to releasing energy
Energy of activation is the energy needed to reach the transition state
Reactants energy is greater than products energy= Exothermic
Products energy is greater than reactants energy= Endothermic
Enzymes speed up a reaction by lowering the energy of activation
Want to get the benefit with minimal effort

Characteristics of Enzymes

They don't create reactions
Not altered or used up by the reaction, they are recycled
Substrate specific (specific to reaction type)
Function is based on 3-dimensional shape
Mostly proteins

Photosynthesis

Life is powered by solar energy
Photosynthesis converts solar energy into chemical energy
Autotrophs are the producers of the biosphere
Photoautotrophs are photosynthetic organisms including plants, multicellular algae, unicellular protists, cyanobacteria, and purple sulfur bacteria
Heterotrophs are the consumers of the biosphere and typically depend on photoautotrophs for food and oxygen

Plant Leaf Morphology

Some plant structures have evolved to absorb sunlight
Leaves are the main area for photosynthesis
Leaves have about half a million chloroplasts per square millimeter
Chloroplasts are found mainly in the mesophyll
Mesophyll cells are densely packed with chloroplasts (about 30-40 per cell)
Leaves have a high surface area to act as photosynthetic arrays
They are wide and thin to absorb sunlight to power photosynthesis
Leaves are organs composed of tissues (layers of cells) like the mesophyll
CO2 and O2 enter and exit through stomata and the open/close state is controllable by the plant
H2O enters through the roots, reaches the leaves through a network of veins and veins export sugar to roots and other non-photosynthetic parts of the plant
Plants have both chloroplasts for photosynthesis and mitochondria for cellular respiration
Chloroplasts have multiple membranes because they were once free-living organisms (bacteria) that was engulfed by another organism (eating)
This deposited another membrane, referred to as the endosymbiotic theory

Chloroplast Structure

Thylakoid is a cookie-shaped sack in a stacked structure called granum (contains a lumen)
This is where photosynthesis takes place
Stroma is the space around the thylakoids
Chemical equation for photosynthesis is 6CO2 + 12H2O + light -> C6H12O6 + 6O2 + 6H2O
The reaction is the reverse of cellular respiration
It's an endergonic redox process
H2O is oxidized to O2 and CO2 is reduced to glucose
The goal is to make sugar for food or structure
Water is oxidized to oxygen, and CO2 is reduced to sugar

Photosynthesis Stages

Two stages of photosynthesis: the light reaction and the Calvin Cycle (light-independent reaction)
Light reaction converts light energy into ATP and NADPH (reducing power) which is sent to the Calvin Cycle
Thylakoid membranes transport the energy from light-dependent reactions to the Calvin Cycle
Calvin Cycle uses ATP and NADPH to fix carbon
The goal of the Calvin Cycle is to create glucose from CO2
This takes place in the stroma

Light Energy

Light is electromagnetic energy or radiation
Electromagnetic spectrum ranges from 380 to 750 nm (visible light spectrum)
Light travels in rhythmic waves but consists of discrete particles called photons
Photons have a fixed quantity of energy
Pigments absorb visible light

ATP Production During Photosynthesis

ATP is made through the same process as cellular respiration
Hydrogen ion gradient
Dropping ions through ATP Synthase, spins it to produce ATP
Stoma/Stomata are openings that allow CO2 and O2 in and out

Light Absorption

Light energy causes electrons to become excited
The electrons move to a higher energy shell, which makes them unstable
They fall back to a stable ground state, releasing heat and a photon (fluorescence)
Pigments are organized into photosystems in the thylakoid membrane
Light harvesting complexes are proteins with suspended chlorophyll molecules that can absorb photons of light energy
This energy is handed off until it gets to paired chlorophyll a molecules, which energizes an electron that jumps up to the primary electron acceptor found in the reaction-center complex
The primary electron acceptor prevents the energized electron from falling back down

Photosystems

Two photosystems: Photosystem I (P700) and Photosystem II (P680)
P700 absorbs wavelengths of 700nm (far-red)
P680 absorbs wavelengths of 680nm (also red part of the spectrum)
Light drives the synthesis of NADPH and ATP
The key to energy transformation is the flow of electrons through photosystems
There are two types of electron flow: non-cyclic and cyclic electron flow
Non-cyclic electron flow is the primary type
Water is oxidized, which provides electrons
This is why oxygen is produced during photosynthesis

Electron Transport Chain

Electrons move to an electron transport chain between the photosystems
This provides energy to regenerate ATP
ATP is regenerated by sticking electrons onto NADP+
This requires H+
H+ is needed for RuBP regeneration (ribulose bisphosphate)

Calvin Cycle

The input for the Calvin Cycle is 6 CO2
There are 6 RuBP (ribulose bisphosphate) molecules.
These bind to the CO2 and result in 12 molecules of 1,3-BPG (bisphosphoglycerate)
12 NADPH donate electrons to reduce 12 BPG to 12 G3P (glyceraldehyde 3-phosphate)
12 NADP are produced during this reaction
12 G3P are converted to 10 G3P and 2 G3P
These 2 G3P molecules are used to create glucose
The remaining 10 G3P molecules are recycled back into 6 RuBP molecules

Breaking Down Photosynthesis Stages

6 CO2 + 12 H2O + light -> sugar + 6 O2 + 6 H2O
H2O is the source of electrons
This is extracted from the stripping off of electrons and H
CO2 is the source of carbon fixed into organic molecules
Water is oxidized to oxygen
Light-dependent reactions produce ATP and NADPH
The Calvin Cycle produces sugar
Light-dependent reactions require water and produce oxygen
The Calvin Cycle requires CO2 and produces sugar

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Description

This quiz covers the essential roles and characteristics of enzymes as biological catalysts. Learn how enzymes speed up chemical reactions by lowering the activation energy and understand the concepts of exothermic and endothermic reactions. Test your knowledge on metabolic pathways and the enzyme functionality.