Introduction to Gene Expression and Translation
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Questions and Answers

What is the primary energy source for muscles during anaerobic glycolysis?

  • Fatty acid oxidation
  • Oxidative phosphorylation
  • Glycolysis (correct)
  • Beta-oxidation

Which enzyme is NOT one of the three irreversible regulatory enzymes of the glycolytic pathway?

  • Lactate dehydrogenase (correct)
  • Hexokinase
  • Pyruvate kinase (PK)
  • Phosphofructokinase (PFK-1)

What is a consequence of pyruvate kinase deficiency in mature red blood cells?

  • Increased ATP production
  • Improved oxygen transport
  • Enhanced glycolysis
  • Hemolytic anemia (correct)

How does insulin affect the key enzymes of glycolysis?

<p>Activates them through dephosphorylation (B)</p> Signup and view all the answers

What role does NADH+H+ play in anaerobic glycolysis?

<p>It is reoxidized via lactate formation (C)</p> Signup and view all the answers

What inhibits the activity of enolase in the glycolytic pathway?

<p>Fluoride forming a complex with Mg2+ (D)</p> Signup and view all the answers

Which statement about the glycolytic pathway is true?

<p>It provides intermediates for amino acid synthesis. (C)</p> Signup and view all the answers

What is the net gain of ATP produced through glycolysis?

<p>8 ATP (C)</p> Signup and view all the answers

What are the end products of glycolysis under anaerobic conditions?

<p>Two molecules of lactic acid (A)</p> Signup and view all the answers

In which cellular compartment does glycolysis primarily occur?

<p>Cytoplasm (D)</p> Signup and view all the answers

Which of the following molecules can be derived from the intermediates of glycolysis?

<p>All of the above (D)</p> Signup and view all the answers

What is the main energy currency produced from glycolysis?

<p>ATP (B)</p> Signup and view all the answers

Which regulatory molecule is crucial for the initiation of translation that is also affected by environmental stimuli?

<p>eIF2 (B)</p> Signup and view all the answers

What is the main metabolic consequence of glycolysis occurring in anaerobic conditions?

<p>Net energy production of only 2 ATP molecules (B)</p> Signup and view all the answers

Which enzyme is responsible for the conversion of pyruvate to lactate during anaerobic glycolysis?

<p>Lactate Dehydrogenase (LDH) (C)</p> Signup and view all the answers

What is the effect of an elevated NADH/NAD+ ratio in exercising skeletal muscle?

<p>Enhanced reduction of pyruvate to lactate (C)</p> Signup and view all the answers

In which cycle does lactate produced in muscles ultimately get converted back to glucose?

<p>Cori Cycle (C)</p> Signup and view all the answers

What condition is characterized by elevated lactate concentrations in the plasma?

<p>Lactic acidosis (C)</p> Signup and view all the answers

Which of the following scenarios can lead to lactic acidosis?

<p>Severe hypotension (B)</p> Signup and view all the answers

What is the primary energy yield from anaerobic glycolysis compared to aerobic glycolysis?

<p>2 ATP (A)</p> Signup and view all the answers

What causes cramps in exercising muscle during anaerobic conditions?

<p>Accumulation of lactate and drop in pH (A)</p> Signup and view all the answers

What is the role of the electron transport chain (ETC) during anaerobic respiration?

<p>It does not function effectively (D)</p> Signup and view all the answers

Which vitamin deficiency can severely impact energy production leading to symptoms such as hair loss and thin nails?

<p>Biotin (Vitamin B7) (C)</p> Signup and view all the answers

What is the primary product of glycolysis when oxygen is present?

<p>Pyruvate (B)</p> Signup and view all the answers

What happens to the 2 NADH produced during aerobic glycolysis?

<p>They are shuttled to the inner mitochondrial membranes for oxidation. (A)</p> Signup and view all the answers

Which of the following tissues primarily utilizes anaerobic respiration?

<p>Exercising muscles (C)</p> Signup and view all the answers

What is the net ATP yield from aerobic glycolysis?

<p>8 ATP (B)</p> Signup and view all the answers

Which cells primarily utilize anaerobic respiration regardless of oxygen availability?

<p>Erythrocytes (RBCs) (C)</p> Signup and view all the answers

Under normal conditions, which type of respiration do most cells utilize in the presence of adequate oxygen?

<p>Aerobic respiration (A)</p> Signup and view all the answers

What enzyme converts pyruvate to Acetyl Co-A during aerobic respiration?

<p>Pyruvate dehydrogenase complex (B)</p> Signup and view all the answers

Which statement is true about glycolysis?

<p>It can occur in both aerobic and anaerobic conditions. (A)</p> Signup and view all the answers

What is the primary reason for the shift to anaerobic respiration during intense exercise?

<p>Insufficient oxygen supply to meet increased demand (C)</p> Signup and view all the answers

Which of the following best describes the relationship between glycolysis and respiration types?

<p>Glycolysis is the first stage of both aerobic and anaerobic respiration. (C)</p> Signup and view all the answers

What type of reaction is performed by the Pyruvate Dehydrogenase Complex to convert pyruvate to acetyl-CoA?

<p>Oxidative decarboxylation (D)</p> Signup and view all the answers

Which coenzyme is NOT needed for the functioning of the Pyruvate Dehydrogenase Complex?

<p>Selenium (C)</p> Signup and view all the answers

What is an effect of elevated acetyl CoA and NADH+H on the Pyruvate Dehydrogenase Complex?

<p>Allosteric inhibition (A)</p> Signup and view all the answers

What is the primary clinical consequence of Pyruvate Dehydrogenase deficiency?

<p>Lactic acidosis (A)</p> Signup and view all the answers

How many ATP can complete glucose oxidation theoretically produce under aerobic conditions?

<p>38 ATP (B)</p> Signup and view all the answers

Which factor is responsible for the inhibition of the Pyruvate Dehydrogenase Complex by arsenic poisoning?

<p>Inhibition of lipoic acid (D)</p> Signup and view all the answers

Which of the following statements about the Pyruvate Dehydrogenase Complex is true?

<p>It requires five different coenzymes for proper function. (C)</p> Signup and view all the answers

What effect does insulin have on the Pyruvate Dehydrogenase Complex?

<p>Activates the dephosphorylated form (C)</p> Signup and view all the answers

What is the function of pyruvate carboxylase in relation to pyruvate?

<p>Carboxylates pyruvate to oxaloacetate (D)</p> Signup and view all the answers

Which of the following is a symptom of decreased PDH activity in the brain?

<p>Severe respiratory problems (A)</p> Signup and view all the answers

What is the primary outcome of glycolysis occurring under aerobic conditions?

<p>Production of 8 ATP with 2 NADH (D)</p> Signup and view all the answers

Which of the following tissues is least likely to utilize anaerobic respiration under normal conditions?

<p>Liver tissue (A)</p> Signup and view all the answers

Which cellular condition would most likely lead to the predominance of anaerobic glycolysis?

<p>Poor blood perfusion in tissues (A)</p> Signup and view all the answers

What enzyme is responsible for converting pyruvate to Acetyl Co-A under aerobic conditions?

<p>Pyruvate dehydrogenase complex (B)</p> Signup and view all the answers

In exercising muscles, why is there a shift to anaerobic respiration despite the presence of oxygen?

<p>Insufficient oxygen supply to meet energy demands (B)</p> Signup and view all the answers

What is the primary function of glycolysis in red blood cells that lack mitochondria?

<p>To produce ATP regardless of oxygen presence (D)</p> Signup and view all the answers

Which regulatory mechanism is predominantly responsible for the activation of glycolysis during the fed state?

<p>Covalent modification by dephosphorylation (B)</p> Signup and view all the answers

What would be the most immediate consequence of mercury poisoning on glycolysis?

<p>Inhibition of enzymatic reactions (B)</p> Signup and view all the answers

In the absence of oxygen, what is the primary role of NADH+H+ during glycolysis?

<p>To enable the reoxidation of NAD+ via lactate formation (D)</p> Signup and view all the answers

Which substance is primarily responsible for the inhibition of the enzyme enolase in the glycolytic pathway?

<p>Fluoride compounds (A)</p> Signup and view all the answers

What condition is a significant clinical consequence of pyruvate kinase deficiency in red blood cells?

<p>Hemolytic anemia requiring frequent blood transfusions (D)</p> Signup and view all the answers

Which of the following statements accurately describes the role of glycolysis in metabolism?

<p>It serves as a preparatory step for full oxidation of glucose. (B)</p> Signup and view all the answers

What is the primary consequence of biotin deficiency in the context of cellular energy production?

<p>Decreased ATP synthesis (C)</p> Signup and view all the answers

During anaerobic glycolysis in exercising muscle, what happens to the NADH produced?

<p>It is converted to lactate, regenerating NAD+ (D)</p> Signup and view all the answers

Which of the following conditions can lead to lactic acidosis?

<p>Severe hypotension and tissue underperfusion (D)</p> Signup and view all the answers

What is the net ATP production from one molecule of glucose undergoing anaerobic glycolysis?

<p>2 ATP molecules (A)</p> Signup and view all the answers

What role does lactate dehydrogenase play in anaerobic glycolysis?

<p>Converts pyruvate to lactate (B)</p> Signup and view all the answers

How does lactate accumulation during intense exercise affect muscle pH?

<p>It lowers the pH, potentially causing cramps (C)</p> Signup and view all the answers

In anaerobic respiration, lactate produced in muscles is transported to which organ for oxidation back to pyruvate?

<p>Liver (D)</p> Signup and view all the answers

Elevated concentrations of lactate in the plasma can occur due to conditions like:

<p>Hypotension or shock (D)</p> Signup and view all the answers

What is the significance of the Cori cycle in human metabolism?

<p>It facilitates the conversion of lactate to glucose (C)</p> Signup and view all the answers

What can cause increased levels of NADH during glycolysis in muscle cells under anaerobic conditions?

<p>Increased glucose influx without sufficient oxygen (A)</p> Signup and view all the answers

Flashcards

Glycolysis's role in RBCs

Glycolysis is the sole energy source for red blood cells (RBCs) because they lack mitochondria.

Anaerobic glycolysis

The main energy source for muscles during strenuous activity, it functions in the absence of oxygen.

NADH+H+ reoxidation

Under anaerobic conditions, NADH+H+ is reoxidized via lactate formation, enabling glycolysis to continue without oxygen.

Pyruvate kinase deficiency

A condition that leads to a decrease in ATP production in red blood cells, resulting in hemolytic anemia.

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Glycolytic pathway's precursor function

Glycolysis is a preliminary step in complete oxidation and provides building blocks for amino acids and fats.

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Regulatory enzymes of glycolysis

Hexokinase, phosphofructokinase (PFK-1), and pyruvate kinase are the key regulatory enzymes of the glycolytic pathway.

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Hormonal regulation of glycolysis

Insulin activates glycolysis (by dephosphorylation), while glucagon inhibits it (by phosphorylation).

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Glycolysis inhibitors

Mercury inhibits glyceraldehyde-3-P dehydrogenase, and fluoride interferes with enolase activity.

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Biotin deficiency effect on cells

Biotin deficiency, even mild, impacts cellular energy production, leading to symptoms like hair loss, thin nails, and conjunctivitis.

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Anaerobic glycolysis ATP production

In anaerobic conditions, glycolysis produces only 2 ATP molecules, and pyruvate is converted to lactate, not Acetyl CoA.

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Lactate formation in muscles

During intense exercise, high NADH production outpaces the electron transport chain, resulting in lactate build-up.

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Lactic acid accumulation effect

Lactate accumulation during intense exercise lowers intracellular pH and can lead to muscle cramps.

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Cori cycle

Lactate produced in muscles and RBCs travels to the liver, where it's converted back to pyruvate and then glucose, to be reused.

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Lactic acidosis cause

Lactic acidosis is a condition caused by a deficiency in tissue perfusion, like severe hypotension, heart attacks, or hemorrhage, affecting ATP production.

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Lactic acidosis effect

Lactic acidosis involves high lactate levels in the blood and is associated with decreased oxidative phosphorylation and ATP synthesis.

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Reversible reaction in CAC

A specific irreversible reaction is essential to maintain the intermediate balance of the Citric Acid Cycle.

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NADH use in anaerobic respiration

In anaerobic respiration, NADH produced during glycolysis is used up by lactate dehydrogenase, preventing further energy generation from the electron transport chain.

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Pyruvate to Lactate Conversion

Pyruvate is converted to lactate by the action of Lactate Dehydrogenase (LDH) enzyme in a reversible reaction in anaerobic conditions, as it is important to maintain energy production.

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Aerobic Respiration

Metabolic process that uses oxygen to produce energy.

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Anaerobic Respiration

Metabolic process that doesn't use oxygen to produce energy.

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Pyruvate Dehydrogenase Complex

Enzyme complex that converts pyruvate to Acetyl CoA.

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Glycolysis

Metabolic pathway that breaks down glucose into pyruvate.

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Mitochondria

Cellular organelles where aerobic respiration occurs.

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Exercising Muscles

Muscles use anaerobic respiration during high activity levels when oxygen supply is insufficient.

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Red Blood Cells (RBCs)

Cells lacking mitochondria that always use anaerobic respiration.

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NADH+H+

Electron carrier molecule important in cellular respiration..

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Acetyl CoA

Intermediate molecule connecting glycolysis to the Krebs cycle.

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RNA Editing

A process that modifies RNA sequences after transcription, often leading to changes in protein structure or function. In the case of apolipoprotein B, RNA editing creates a premature stop codon, resulting in a shorter protein (B-48) in intestinal cells.

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MicroRNA (miRNA)

Small non-coding RNA molecules that regulate gene expression by binding to target messenger RNAs (mRNAs), leading to either degradation or blocking of translation of the target mRNA.

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eIF2 Phosphorylation

The phosphorylation of eukaryotic initiation factor 2 (eIF2) inhibits its activity, thereby slowing down protein synthesis. This is a key mechanism for regulating translation in response to stress.

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Protease Inhibitors

Drugs that block the activity of proteases, enzymes responsible for breaking down proteins. They are used in treating viral infections like HIV and Hepatitis C by inhibiting the processing of viral proteins.

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Pyruvate's fate after glycolysis

After glycolysis, pyruvate is transported into mitochondria via a special transporter where it is converted into Acetyl CoA.

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Pyruvate Dehydrogenase Complex (PDH)

PDH is a complex of 3 enzymes that catalyzes the irreversible conversion of pyruvate to Acetyl CoA, a key step in cellular respiration.

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What does PDH require to function?

PDH requires 5 coenzymes: thiamine pyrophosphate (TPP), lipoic acid, Coenzyme A, flavin adenine dinucleotide (FAD), and nicotinamide adenine dinucleotide (NAD).

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How does acetyl CoA affect PDH?

Elevated levels of acetyl CoA inhibit PDH allosterically, slowing down pyruvate's conversion to Acetyl CoA.

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How does NADH+H+ affect PDH?

High levels of NADH+H+ also allosterically inhibit PDH, as a way to regulate the flow of pyruvate into the citric acid cycle.

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How does insulin affect PDH?

Insulin activates PDH by promoting its dephosphorylation, increasing pyruvate conversion to Acetyl CoA.

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What is the effect of mercury on PDH?

Mercury inhibits the activity of PDH, interfering with the conversion of pyruvate to Acetyl CoA.

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How does arsenic affect PDH?

Arsenic poisoning inhibits PDH by interfering with the action of lipoic acid, a vital coenzyme for its function.

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What is pyruvate dehydrogenase deficiency?

Pyruvate dehydrogenase deficiency is a rare, serious condition where the PDH enzyme complex is impaired, leading to insufficient energy production.

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What are the clinical implications of PDH deficiency?

PDH deficiency can cause severe health problems like lactic acidosis, neurological issues, and even death. Often, it's caused by nutritional deficiencies.

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Glycolysis: The Energy Provider

Glycolysis is the breakdown of glucose into pyruvate, generating ATP (energy) for the cell. It occurs in the cytoplasm and doesn't require oxygen.

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Red Blood Cells and Glycolysis

Red blood cells (RBCs) rely solely on glycolysis for energy because they lack mitochondria, the powerhouse of the cell.

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Anaerobic Glycolysis: Muscles' Backup Plan

Anaerobic glycolysis fuels muscles during strenuous exercise when oxygen is limited. It produces less ATP but allows the muscles to keep working.

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Pyruvate Kinase Deficiency: A Blood Problem

A deficiency in the enzyme pyruvate kinase disrupts ATP production in RBCs, leading to hemolytic anemia. Less energy means fragile RBCs.

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Regulating Glycolysis: The Key Players

Three enzymes – hexokinase, phosphofructokinase (PFK-1), and pyruvate kinase – control the speed of glycolysis.

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Hormonal Control of Glycolysis

Insulin, released during feeding, activates glycolysis, while glucagon, released during fasting, inhibits it.

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Inhibitors of Glycolysis: Blocking Energy Production

Mercury and fluoride disrupt key enzymes in glycolysis, leading to energy production failure and potentially cell death.

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Aerobic vs Anaerobic Respiration

Aerobic respiration uses oxygen to produce energy, while anaerobic respiration does not. Anaerobic respiration occurs when oxygen supply is limited, like during intense exercise or in cells lacking mitochondria.

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What is glycolysis?

Glycolysis is the first stage of cellular respiration, breaking down glucose into pyruvate. It occurs in both aerobic and anaerobic conditions.

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Pyruvate's fate in aerobic respiration

In aerobic conditions, pyruvate is transported into mitochondria where it is converted into Acetyl CoA by the Pyruvate Dehydrogenase Complex (PDH). Acetyl CoA then enters the citric acid cycle to generate more energy.

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Where does anaerobic respiration happen?

Anaerobic respiration occurs in cells lacking mitochondria, like red blood cells, and in tissues experiencing oxygen deprivation, like muscles during intense exercise.

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What happens to NADH in aerobic respiration?

In aerobic conditions, NADH produced during glycolysis is transported to the mitochondria where it is oxidized, generating ATP. This is a crucial step for maximizing energy production.

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Biotin Deficiency Impact

Biotin (vitamin B7) deficiency, even mild, disrupts cellular energy production, causing symptoms like hair loss, brittle nails, eye inflammation, and neurological problems.

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Anaerobic Glycolysis ATP

In the absence of oxygen, glycolysis produces only 2 ATP molecules per glucose molecule, with pyruvate converted to lactate instead of Acetyl CoA.

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Lactate Accumulation Effect

Excess lactate in muscles lowers the internal pH and can cause cramps, as your body struggles to cope with this acidic environment.

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Study Notes

Introduction to Gene Expression and Translation

  • Gene expression is the translation of nucleotide sequences in mRNA into amino acid sequences in proteins.
  • Translation is the process of protein synthesis, involving mRNA, tRNA, ribosomes, and enzymes.

Requirements of Translation

  • mRNA carries the genetic information.
  • tRNA is an adapter molecule, recognizing amino acids and corresponding codons.
  • Ribosomes coordinate interactions between mRNA, tRNA, enzymes, and protein factors.

Genetic Code

  • The genetic code is the relationship between nucleotide sequences in DNA or mRNA and amino acids in a polypeptide chain.
  • Each amino acid can be specified by more than one codon.
  • There is one start codon (AUG - Methionine).
  • There are three stop codons (UAA, UAG, UGA).
  • The genetic information is read from 5' to 3'.

Characteristics of the Genetic Code

  • Degenerate: Multiple codons can code for the same amino acid (except tryptophan and methionine).
  • Unambiguous: Each codon specifies only one amino acid.
  • Non-overlapping: The code is read from a fixed point.
  • Commaless: The code is read continuously without punctuation.
  • Universal: The same code words are used in all organisms.

Stages of Protein Biosynthesis

  • Initiation: Formation of the initiation complex involving tRNA, rRNA, mRNA, and initiation factors.
  • Elongation: Repeated cycles of aminoacyl-tRNA binding to the A site, peptide bond formation, and translocation.
  • Termination: Stop codons signal the release of the polypeptide chain and dissociation of the ribosome.

Post-translational Modifications

  • Modifications of proteins after synthesis (folding, proteolysis, modifications of individual amino acids, glycosylation and acylation).

Clinical Implications of Translation

  • Bacterial protein synthesis inhibitors: Some antibiotics target bacterial translation to kill bacteria.
  • Toxins acting on eukaryotic translation: Some toxins inhibit eukaryotic translation, leading to cell death.

Genetic Variations and Mutations

  • Mutations are permanent changes in DNA sequences.
  • Types: point mutations (single base substitutions, that can be transitions or transversions), frameshift mutations (insertion or deletion of nucleotides), trinucleotide repeat expansion.
  • Consequences:
    • Silent mutation: No change in the amino acid that is coded for.
    • Missense mutation: A change in one amino acid.
    • Non-sense mutation: Creates a stop codon, resulting in a shortened protein.
  • Clinical implications:
    • Hereditary hemochromatosis (HH).

Regulation of Gene Expression

  • Gene regulation controls the amount of protein produced from (transcription and translation) from gene.
  • Constitutive genes are expressed continuously.
  • Regulated genes are expressed in response to specific signals.
  • Regulation can occur at several stages, including DNA levels, transcription, mRNA stability, and translation level.
  • Methods:
    • Chromatin remodeling
    • Transcription factors
    • Post-transcriptional modification
    • Epigenetics
  • Clinical implications: Drug action at gene levels (e.g cancer therapy).

Cytosolic Respiration

  • Glycolysis is the first step of respiration, a pathway that does not require oxygen that results in a net gain of ATP or pyruvate.
  • Different pathways exist depending on the availability of oxygen (aerobic vs. anaerobic).
  • Key enzymes in glycolysis: hexokinase, phosphofructokinase, and pyruvate kinase.

Mitochondrial Electron Transport System

  • The electron transport chain (ETC) is a series of protein complexes in the inner mitochondrial membrane.
  • The ETC oxidizes NADH and FADH2, creating a proton gradient used by ATP synthase to produce ATP.
  • Inhibitors of ETC and oxidative phosphorylation: Many agents inhibit oxidative phosphorylation, leading to serious health consequences.
  • Diseases related to mitochondrial problems and clinical implications.

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Gene Expression 2: RNA Translation and Genetic Code PDF

Description

This quiz explores the fundamental concepts of gene expression and the translation process. Understand the roles of mRNA, tRNA, ribosomes, and the genetic code in protein synthesis. Test your knowledge on the characteristics and requirements of translation.

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