Nucleic Acids and MicroRNA

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Questions and Answers

What is the primary role of ATP in biological systems?

It functions solely as a nerve signal transmitter.

It is involved only in the synthesis of proteins.

It acts as a major storage form of energy in cells. (correct)

It serves as a structural component of DNA.

Which nitrogenous base is found only in RNA?

Cytosine

Adenine

Thymine

Uracil (correct)

What significant contribution did Ambros make to the understanding of microRNA?

He cloned multiple genes involved in protein synthesis.

He identified that lin-4 appeared to be a positive regulator.

He showed that lin-4 encoded a tiny RNA that regulates gene expression. (correct)

He discovered that microRNA sequences can directly code for proteins.

What role does ribosomes play in protein synthesis?

They link amino acids together to form proteins. Signup and view all the answers

What did Ruvkun's cloning of the let-7 gene reveal?

MicroRNA regulation is universal among multicellular organisms. Signup and view all the answers

Which process characterizes the accumulation of uric acid in the body?

It can lead to gout. Signup and view all the answers

Which of the following is true about the structure of RNA compared to DNA?

RNA can fold into complex secondary structures. Signup and view all the answers

What is the main function of ATP synthase?

It catalyzes the formation of ATP from ADP and inorganic phosphate. Signup and view all the answers

What is the primary function of ATP synthase in cellular processes?

It rotates to join ADP and Pi using proton movement. Signup and view all the answers

Which of the following energy sources contributes to the body's energy release?

Chemical bonds in nutrients. Signup and view all the answers

How is energy measured in scientific investigations?

In calories, kilocalories, joules, and kilojoules. Signup and view all the answers

Which reaction type releases energy to its surroundings?

Exothermic reactions. Signup and view all the answers

Where is the majority of the body's creatine and phosphocreatine stored?

In skeletal muscle. Signup and view all the answers

What does glycolysis primarily achieve?

Splits one glucose molecule into two pyruvate molecules. Signup and view all the answers

What is the significance of high-energy phosphate in energy storage?

It helps store energy for immediate use in muscle contraction. Signup and view all the answers

Which of the following processes requires energy?

Anabolism. Signup and view all the answers

What is the net gain of ATP molecules per molecule of glucose during glycolysis?

Two ATP molecules Signup and view all the answers

Which molecule is formed concurrently with the generation of ATP in glycolysis?

NADH Signup and view all the answers

In which part of the cell does glycolysis occur?

Cytosol Signup and view all the answers

What is the effect of high ADP concentration on glycolysis activity?

Increases glycolysis activity Signup and view all the answers

What is produced along with pyruvate when glyceraldehyde-3-phosphate is oxidized in glycolysis?

NADH Signup and view all the answers

What happens to NAD+ during glycolysis?

It is consumed Signup and view all the answers

During anaerobic conditions, what does glycolysis primarily generate from glucose?

Lactate and NADH Signup and view all the answers

What is the energy investment phase of glycolysis characterized by?

Consumption of ATP Signup and view all the answers

Which cells are not dependent on insulin for glucose uptake?

Erythrocytes Signup and view all the answers

What is the primary function of GLUT5?

Transport dietary fructose across the brush border membrane Signup and view all the answers

How is the glycemic index (GI) of a food calculated?

By dividing the area under the curve for the test food by the area under the curve for the reference food and multiplying by 100 Signup and view all the answers

What happens to GLUT4 in response to insulin?

It translocates to the plasma membrane from storage vesicles Signup and view all the answers

Which of the following foods has a glycemic index of approximately 71 when white bread is the reference?

White bread Signup and view all the answers

For a food to have a GI greater than 100, what must the reference food be when measuring?

White bread Signup and view all the answers

Which of the following best describes the area-under-the-curve method for GI calculation?

It compares blood glucose elevation over 2 hours post-ingestion Signup and view all the answers

Which glucose transporter is found in the brain and kidneys but does not transport glucose?

GLUT5 Signup and view all the answers

What happens to NADH in the presence of oxygen during glycolysis?

It is oxidized indirectly to produce ATP. Signup and view all the answers

Which end product is formed during anaerobic glycolysis?

Lactate Signup and view all the answers

How many ATP molecules does aerobic glycolysis produce from one glucose molecule?

36 to 38 Signup and view all the answers

What is a key difference between aerobic and anaerobic glycolysis?

Aerobic glycolysis occurs only in eukaryotes. Signup and view all the answers

Which of the following statements is true regarding anaerobic glycolysis?

It involves the conversion of pyruvate to lactate. Signup and view all the answers

What is the effect of lactate accumulation in anaerobic glycolysis?

It reduces the pH of the cell. Signup and view all the answers

What main product is formed at the end of aerobic glycolysis?

Water and carbon dioxide Signup and view all the answers

In which scenario would anaerobic glycolysis be most likely to occur?

During intense exercise when oxygen supply is limited. Signup and view all the answers

Study Notes

Nucleic Acids

DNA and RNA are nucleic acids made up of nucleotides.
Adenine, guanine, and cytosine are found in both DNA and RNA.
Uracil is only found in RNA.
Thymine is only found in DNA.
DNA is double-stranded, with complementary base pairing of adenine with thymine and guanine with cytosine.
RNA is single-stranded but can fold on itself to generate complex secondary structures.
Hyperuricemia is the accumulation of high concentrations of uric acid. This can lead to gout (uric acid crystals depositing in the joints), and kidney stones (uric acid depositing in the kidneys).

MicroRNA

C. elegans is a model organism for understanding how different cell types develop.
lin-4 and lin-14 are genes involved in the development of C. elegans.
lin-4 encodes a microRNA that does not code for a protein and negatively regulates lin-14 gene expression.
lin-4 microRNA sequence is complementary to a sequence in the lin-14 Messenger RNA.
let-7 is another gene encoding microRNA, conserved in evolution.
MicroRNA regulation is universal among multicellular organisms.

Protein Synthesis

Ribosomes link amino acids together to generate proteins.

Biological Energy

ATP is the major storage form of energy in cells.
ATP Synthase is a protein that catalyzes the formation of ATP from ADP and inorganic phosphate.
ATP Synthase is a molecular machine that rotates as protons pass through it, joining ADP and Pi.
Energy is required for physical exertion, anabolism, active transport, and the transfer of genetic information.

Energy Release and Consumption

Energy comes from macronutrients.
Free energy (G) is transferred from one form to another.
Units of energy include calories (cal), kilocalories (kcal), joules (J), and kilojoules (kJ).
1 cal = 4.18 J, or 1 kcal = 4.18 kJ.
Potential energy is released from the bonds of nutrients, called chemical bonds.

Exothermic and Endothermic Reactions

Exothermic reactions release energy.
Endothermic reactions require energy.

The Role of High-Energy Phosphate

Creatine and phosphocreatine are high-energy phosphate molecules that can transfer their phosphate groups to ADP, forming ATP.
Approximately 95% of the body's creatine and phosphocreatine are stored in skeletal muscle.

Glycolysis

Glycolysis is the splitting of one glucose molecule (6 carbons) into two pyruvate molecules (3 carbons).
Glycolysis generates two ATP molecules and two NADH molecules.
NADH production consumes NAD+.
Glycolysis is the major ATP-generating pathway in cells with limited oxygen access.

Glucose Metabolism

Glucose + 6O2 = 6 CO2 + H2O, ΔG = -2840 kJ/mol.
Glucose + 2NAD+ = 2Pyruvate + 2NADH + 2H+, ΔG = -146 kJ/mol.
Glycolysis releases 5.2% of the total free energy that can be released by glucose.

Glycolysis in Different Tissues

Glycolysis occurs in the cytosol, where enzymes involved in glucose processing are found.
Glycolysis is essential for tissues highly reliant on glucose, like the brain.
Under anaerobic conditions, glycolysis generates lactate and ATP.

Stages of Glycolysis

Stage 1 (Energy Requiring): Glucose is phosphorylated, converted to fructose, phosphorylated again, and cleaved into two glyceraldehyde-3-phosphate molecules. Two ATP molecules are invested.
- Phosphorylation traps glucose within the cell.
- The conversion to phosphofructose allows the eventual split of the sugar into two 3-carbon molecules.
- This stage is active when ADP concentration is high and less active when ATP concentration is high.
Stage 2 (Energy Generating): The two glyceraldehyde-3-phosphate molecules are converted to pyruvate, generating four ATP molecules and two NADH molecules. There is a net gain of two ATP molecules per glucose molecule during glycolysis. - The sixth step in glycolysis oxidizes glyceraldehyde-3-phosphate, extracting high-energy electrons. These electrons are picked up by NAD+, producing NADH. - NAD+ regeneration is needed for the continuation of glycolysis. - The conversion of pyruvate to lactate (fermentation) provides NAD+ when oxygen is not available. - In the presence of oxygen, NADH is oxidized, and the high-energy electrons are used to produce ATP through other pathways.

Aerobic and Anaerobic Glycolysis

Aerobic glycolysis: Occurs in oxygen-rich environments, more efficient, produces more ATP, produces pyruvate, and leads to the Citric acid cycle in mitochondria. Ultimately produces 34 ATP molecules, water, and carbon dioxide.
Anaerobic glycolysis: Occurs in oxygen-deficient environments, less efficient, produces lactate, and produces 2 ATP molecules per glucose molecule.

Glucose Transporters

GLUT4 is insulin-dependent and responsible for glucose uptake in muscle and adipose tissue.
GLUT5 is highly specific for fructose and is found in the small intestine, kidney, brain, skeletal muscle, and adipose tissue.

Glycemic Index

The glycemic index (GI) ranks foods based on how quickly they raise blood glucose levels.
The GI of a food is calculated by comparing its glucose response to that of glucose or white bread (reference foods), which are assigned a GI of 100.
The higher the GI, the faster the food raises blood glucose levels.

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Description

Explore the key concepts of nucleic acids, including the structure and functions of DNA and RNA. Delve into the role of microRNA in gene regulation, particularly in the model organism C. elegans. Test your knowledge with this quiz that covers essential molecular biology concepts.