Photosynthesis and the Calvin Cycle

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Questions and Answers

What is produced during the light-dependent reactions of photosynthesis?

Oxygen (correct)

Starch

Glucose

Carbon dioxide

Where do the light-dependent reactions of photosynthesis occur in plant cells?

Cytoplasm

Chloroplast outer membrane

Thylakoid membranes (correct)

Stroma

What role do photosystems play in the light reaction of photosynthesis?

Gather light energy (correct)

Fix carbon

Store oxygen

Convert glucose to ATP

What are some of the risk factors associated with thiamine deficiency?

Alcohol dependence Signup and view all the answers

Which food source is the richest in riboflavin?

Yeast Signup and view all the answers

Which of the following molecules are utilized during the dark reactions of photosynthesis?

NADPH and ATP Signup and view all the answers

What is the initial substrate in the shikimic acid pathway that reacts with erythrose-4-phosphate?

Phosphoenolpyruvate Signup and view all the answers

What is the main purpose of the Calvin cycle in photosynthesis?

To produce glucose Signup and view all the answers

How does riboflavin change when exposed to light?

It converts to lumichrome or lumiavin Signup and view all the answers

Which enzyme catalyzes the conversion of shikimate to shikimate 3-phosphate?

Shikimate kinase Signup and view all the answers

Which of these best describes the light-independent reaction?

It is dependent on ATP and NADPH from light reactions Signup and view all the answers

What is one of the primary functions of riboflavin in the body?

Releases energy from carbohydrates Signup and view all the answers

Which aromatic amino acid is synthesized directly from the chorismate produced in the shikimic acid pathway?

Tryptophan Signup and view all the answers

During which stage of the Calvin cycle does carbon dioxide get fixed?

Carbon fixation stage Signup and view all the answers

Which vitamin is riboflavin also known as?

Vitamin B2 Signup and view all the answers

Which of the following stresses can trigger the expression of aromatic compounds produced through the shikimic acid pathway?

Excessive light Signup and view all the answers

What role does riboflavin play in vision?

Aids in the formation of retinal pigments Signup and view all the answers

What is the final product formed before the synthesis of aromatic amino acids in the shikimic acid pathway?

Chorismate Signup and view all the answers

What is the general chemical equation for the light reaction of photosynthesis?

2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP Signup and view all the answers

What enhances the absorption of free riboflavin in the intestines?

Active transport systems Signup and view all the answers

What type of compounds are primarily produced via the shikimic acid pathway?

Phenolic compounds Signup and view all the answers

Which of the following statements about riboflavin stability is correct?

It is stable during cooking in the presence of light Signup and view all the answers

Which carbon unit is associated with the synthesis of aromatic amino acids through the shikimic acid pathway?

C6-C3 from phenylalanine or tyrosine Signup and view all the answers

Which of the following organisms utilizes the shikimic acid pathway for biomass production?

Bacteria, archaea, fungi, algae, and some protozoans Signup and view all the answers

What vitamin is referred to as niacin?

Vitamin B3 Signup and view all the answers

What condition is caused by deficiency of niacin?

Pellagra Signup and view all the answers

Which of the following is NOT a form of vitamin B3?

Pyridoxine Signup and view all the answers

What is one of the primary functions of niacin?

Neutralizes free radicals Signup and view all the answers

Which statement about niacinamide is true?

It has an activity similar to niacin. Signup and view all the answers

What is the chemical classification of niacin?

Pyridine derivative Signup and view all the answers

Which of the following symptoms is NOT associated with deficiency in niacin?

Nausea Signup and view all the answers

Niacinamide can be used for which of the following purposes?

For dietary and therapeutic purposes Signup and view all the answers

What is another name for vitamin B5?

Pantothenic acid Signup and view all the answers

Which of the following is NOT a function of vitamin B5?

Regulates blood pressure Signup and view all the answers

Which food sources are rich in pantothenic acid?

Animal organs and cereal grains Signup and view all the answers

What symptoms can arise from a deficiency in vitamin B5?

Fatigue and sleep disturbances Signup and view all the answers

Which of the following compounds is formed when pantothenic acid is hydrolyzed?

B-alanine and pantoic acid Signup and view all the answers

Which vitamin is related to pyridoxol, pyridoxal, and pyridoxamine?

Vitamin B6 Signup and view all the answers

Which statement about vitamin B5 is FALSE?

It is a pyridine derivative. Signup and view all the answers

Which of the following does vitamin B5 help synthesize?

Lipids and neurotransmitters Signup and view all the answers

Study Notes

Photosynthesis

Photosynthesis is a two-stage process: light-dependent reaction and light-independent reaction.
The light-dependent reaction occurs in the thylakoid membranes of chloroplasts.
Photosystems I and II are involved in light-dependent reactions.
ATP and NADPH are generated in light-dependent reactions.
Water is used and oxygen is produced in the light-dependent reactions.
The light-dependent reaction equation is: 2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP
The light-independent reaction is also known as the carbon-fixing reaction.
The light-independent reaction occurs in the stroma of the chloroplast.
Carbon dioxide is captured from the atmosphere through stomata.
The Calvin cycle converts 6 molecules of carbon dioxide into one glucose molecule.
The light-independent reaction equation: 3CO2 + 6 NADPH + 5H2O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi

The Calvin Cycle

Consists of carbon fixation, reduction, and regeneration of the starting molecule.
Carbon fixation involves capturing carbon dioxide.
Reduction involves using NADPH and ATP to convert carbon dioxide into sugar.
Regeneration involves regenerating the molecule used to capture carbon dioxide.
C1, C2, C5, and C6-C3 units are formed during carbon fixation based on the number of carbon atoms.

Shikimate Pathway

Biosynthesis of phenolic compounds, alkaloids, and other secondary metabolites is catalyzed by the shikimate pathway.
This pathway occurs in chloroplast plant cells and is triggered by environmental stresses.
The pathway starts with phosphoenol pyruvate and erythrose-4-phosphate.
Chorismate, a substrate for the three aromatic amino acids, is the final product.
The shikimate pathway is also known as the chorismate pathway.

Vitamin B2 (Riboflavin)

Riboflavin, a yellow, heat-stable substance, is slightly soluble in water.
It is sensitive to light and degrades into lumichrome or lumiflavin.
Yeast is the richest source of riboflavin.
Dairy products, eggs, legumes, and meats are good dietary sources.
Riboflavin is stable during cooking in the absence of light.
Riboflavin 5'-phosphate (FMN) and flavin adenine dinucleotide (FAD) are the forms found in foods.
Active transport in the intestinal mucosa absorbs free riboflavin.

Uses of Vitamin B2

Coenzyme in oxidation-reduction reactions for energy release from carbohydrates, fats, and proteins.
Stimulates growth and reproduction.
Plays a role in vision.
Converts vitamin B6, folic acid, and niacin into their active coenzyme forms.
Acts as an antioxidant by neutralizing free radicals.
Deficiency causes stomatitis and dermatitis.

Vitamin B3 (Niacin)

Niacin, also known as nicotinic acid or vitamin B3, is a pyridine derivative that prevents pellagra.
Niacinamide (nicotinamide) also has anti-pellagra activity and is used for dietary and therapeutic purposes.

Vitamin B5 (Pantothenic Acid)

Pantothenic acid, also known as vitamin B5, is a component of the B vitamin complex.
It was historically known as the "chick antidermatitis factor."
Animal organs (heart, kidney, liver) and cereal grains are good sources of pantothenic acid.

Uses of Vitamin B5

Helps convert food into energy.
Involved in the synthesis of lipids, neurotransmitters, steroid hormones, and hemoglobin.
Contributes to tissue and cell maintenance and repair, particularly of skin and hair.
Aids in healing wounds and lesions.
Normalizes blood lipid profiles.
Deficiency causes fatigue and sleep disturbances.

Vitamin B6

Vitamin B6 encompasses three closely related substances: pyridoxol, pyridoxal, and pyridoxamine.
They share similar physiological activity and are naturally occurring, highly substituted pyridine derivatives.
Pyridoxine is the term commonly used for pyridoxol in pharmacy and medicine.

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Description

This quiz explores the processes of photosynthesis, focusing on the light-dependent and light-independent reactions. It covers key components such as ATP, NADPH, and the Calvin cycle, providing insight into how plants convert light energy into chemical energy. Test your knowledge on these critical biological processes.