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Biochem 24/25 Uea > 5002a Exam > Flashcards

5002a Exam Flashcards

1
Q

Why are metabolic reactions important for cell physiology?

A

Metabolic reactions are essential because they supply cells with energy and molecules needed for growth, repair, and division. They help maintain homeostasis, synthesize key biomolecules, and break down nutrients for energy production.

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2
Q

What is the difference between catabolic and anabolic metabolic pathways?

A

Catabolic pathways: Break down complex molecules into simpler ones, releasing energy (e.g., glycolysis, citric acid cycle).
Anabolic pathways: Build complex molecules from simpler ones, consuming energy (e.g., protein synthesis, DNA replication).

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3
Q

What is the Warburg effect in cancer cells?

A

The Warburg effect refers to the tendency of cancer cells to favor glycolysis over oxidative phosphorylation for energy production, even in the presence of oxygen, resulting in lactate production.

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4
Q

What role does ubiquitination play in protein degradation?

A

Ubiquitination tags proteins for degradation by the proteasome, signaling the proteasome to degrade the protein, thus maintaining cellular protein quality control.

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5
Q

What are Km and Vmax in enzyme kinetics?

A

Km: The Michaelis constant, representing the substrate concentration at which the reaction rate is half of Vmax.
Vmax: The maximum rate of the enzyme-catalyzed reaction when the substrate concentration is saturating.

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6
Q

How does secondary active transport work?

A

Secondary active transport uses the electrochemical gradient of one molecule (often Na+) to drive the transport of another molecule against its concentration gradient, without direct use of ATP.

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7
Q

How does the LacY transporter in E. coli work?

A

The LacY transporter couples the transport of lactose into the cell with the flow of protons (H+) down their electrochemical gradient, using secondary active transport.

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8
Q

What is the key difference between glycolysis and gluconeogenesis?

A

Glycolysis: The breakdown of glucose to produce energy (ATP) and pyruvate.
Gluconeogenesis: The process of synthesizing glucose from non-carbohydrate precursors, typically occurring in the liver during fasting.

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9
Q

What is insulin resistance, and how is it linked to metabolic syndrome?

A

Insulin resistance occurs when cells no longer respond effectively to insulin, leading to higher blood glucose levels. It is a hallmark of metabolic syndrome, which includes obesity, hypertension, and increased risk for type 2 diabetes.

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10
Q

What is the role of leptin in metabolism?

A

Leptin is a hormone produced by adipocytes that regulates energy balance by suppressing appetite and promoting energy expenditure.

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11
Q

Why is ATP hydrolysis essential for cellular processes?

A

ATP hydrolysis releases energy that powers various cellular processes, such as muscle contraction, protein synthesis, and active transport.

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12
Q

What is the role of NAD+/NADH in metabolism?

A

NAD+ is an essential cofactor in redox reactions, acting as an electron carrier, and is reduced to NADH in catabolic reactions.

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13
Q

How are fatty acids metabolized in the body?

A

Fatty acids are broken down in the mitochondria via beta-oxidation to produce acetyl-CoA, which enters the citric acid cycle for ATP generation.

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14
Q

How does the proteasome contribute to protein quality control?

A

The proteasome degrades misfolded, damaged, or unnecessary proteins tagged with ubiquitin, preventing the accumulation of dysfunctional proteins.

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15
Q

What is the role of the pentose phosphate pathway (PPP)?

A

The PPP generates NADPH for anabolic reactions and ribose-5-phosphate for nucleotide biosynthesis, supporting cell growth and division.

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16
Q

What is the main function of the citric acid cycle (Krebs cycle)?

A

The citric acid cycle generates high-energy electron carriers (NADH, FADH2) and ATP by oxidizing acetyl-CoA, producing CO2 as a waste product.

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17
Q

What is oxidative phosphorylation, and where does it occur?

A

Oxidative phosphorylation occurs in the inner mitochondrial membrane, generating a proton gradient that drives ATP synthesis via ATP synthase.

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18
Q

How is glycogen metabolized in the body?

A

Glycogen is broken down into glucose-6-phosphate for energy production and synthesized from glucose in the liver and muscles, regulated by insulin and glucagon.

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19
Q

What role does acetyl-CoA play in metabolism?

A

Acetyl-CoA enters the citric acid cycle for energy production and serves as a precursor for fatty acid synthesis and cholesterol biosynthesis.

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20
Q

How are fatty acids synthesized in the body?

A

Fatty acid synthesis occurs in the cytoplasm, involving the enzyme fatty acid synthase and using NADPH as a reducing agent.

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21
Q

What is the process of protein synthesis?

A

Protein synthesis involves transcription (DNA to mRNA) in the nucleus, and translation (mRNA to protein) in the cytoplasm.

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22
Q

How do insulin and glucagon regulate blood glucose levels?

A

Insulin lowers blood glucose by promoting glucose uptake and glycogen synthesis. Glucagon raises blood glucose by promoting glycogen breakdown and gluconeogenesis.

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23
Q

What is the role of phosphorylation in metabolic pathways?

A

Phosphorylation regulates enzymes by adding a phosphate group, activating or inactivating enzymes involved in metabolic pathways.

24
Q

How does NAD+/NADH function in redox reactions?

A

NAD+ accepts electrons and becomes reduced to NADH in catabolic reactions, which donates electrons to the electron transport chain.

25
Q

What is the role of hexokinase in glycolysis?

A

Hexokinase catalyzes the conversion of glucose to glucose-6-phosphate, trapping glucose inside the cell.

26
Q

What role does GTP play in cellular metabolism?

A

GTP functions similarly to ATP, providing energy for protein synthesis and the citric acid cycle.

27
Q

How does calcium regulate muscle contraction?

A

Calcium ions released from the sarcoplasmic reticulum bind to troponin, allowing myosin to bind to actin and initiate muscle contraction.

28
Q

What is the role of B vitamins in metabolism?

A

B vitamins act as coenzymes in metabolic pathways, supporting energy production and various enzymatic reactions.

29
Q

What are the liver’s key roles in metabolism?

A

The liver maintains blood glucose levels, stores and releases glucose, detoxifies substances, synthesizes proteins, and produces bile.

30
Q

How does vitamin D regulate calcium homeostasis?

A

Vitamin D promotes calcium absorption in the intestines and reabsorption in the kidneys, ensuring sufficient calcium levels.

31
Q

What is allosteric regulation of enzymes?

A

Allosteric regulation involves the binding of molecules to sites other than the active site, causing a conformational change that alters enzyme activity.

32
Q

How are redox reactions important in metabolism?

A

Redox reactions involve the transfer of electrons, essential for energy production in metabolism.

33
Q

How do glucose transporters (GLUT) function in the body?

A

GLUT transporters facilitate the passive transport of glucose into cells, with different types found in various tissues.

34
Q

How are ketone bodies used for energy production?

A

Ketone bodies are produced in the liver from fatty acids during fasting and are used by tissues for energy when glucose is scarce.

35
Q

How do hormones regulate metabolism?

A

Hormones like insulin and glucagon regulate glucose homeostasis, fat storage, and protein synthesis by activating signaling pathways.

36
Q

What is the significance of mitochondrial DNA?

A

Mitochondrial DNA encodes essential proteins involved in oxidative phosphorylation and is inherited maternally.

37
Q

How is glycolysis regulated in the cell?

A

Glycolysis is regulated at key enzymes by allosteric effectors, allowing the cell to control energy production efficiently.

38
Q

What is lipolysis and how is it regulated?

A

Lipolysis is the breakdown of triglycerides into glycerol and fatty acids, regulated by hormones like epinephrine and glucagon.

39
Q

How does fatty acid beta-oxidation generate energy?

A

Beta-oxidation breaks down fatty acids into acetyl-CoA units, producing NADH and FADH2 for ATP production.

40
Q

What is the urea cycle, and why is it important?

A

The urea cycle detoxifies ammonia by converting it into urea, which is excreted in urine, essential for removing excess nitrogen.

41
Q

What is the difference between competitive and non-competitive enzyme inhibition?

A

Competitive inhibition occurs when an inhibitor binds to the enzyme’s active site, while non-competitive inhibition occurs when the inhibitor binds elsewhere.

42
Q

What is the urea cycle, and why is it important?

A

The urea cycle detoxifies ammonia by converting it into urea, which is excreted in urine. This cycle occurs in the liver and is essential for removing excess nitrogen from the body after protein breakdown.

43
Q

What is the difference between competitive and non-competitive enzyme inhibition?

A

Competitive inhibition occurs when an inhibitor binds to the enzyme’s active site, competing with the substrate. Non-competitive inhibition occurs when the inhibitor binds to a site other than the active site, changing the enzyme’s conformation and reducing its activity.

44
Q

What is enzyme cooperativity?

A

Enzyme cooperativity refers to the phenomenon where the binding of a substrate to one subunit of an enzyme affects the activity of other subunits. This is commonly observed in enzymes with multiple subunits, like hemoglobin.

45
Q

What are the key enzymes involved in DNA replication?

A

Key enzymes in DNA replication include:
* DNA helicase (unwinds the DNA)
* DNA polymerase (synthesizes the new strand)
* Primase (lays down RNA primers)
* Ligase (joins Okazaki fragments on the lagging strand).

46
Q

What role do telomeres play in aging?

A

Telomeres are repetitive DNA sequences at the ends of chromosomes that protect DNA from degradation. As cells divide, telomeres shorten, leading to cellular aging and senescence. Telomerase can extend telomeres in certain cells, like stem cells and cancer cells.

47
Q

What are transcription factors, and what role do they play in gene expression?

A

Transcription factors are proteins that bind to specific DNA sequences near genes and regulate the transcription of those genes. They can activate or repress gene expression, influencing cellular functions and responses to signals.

48
Q

Why is protein folding essential for cellular function?

A

Protein folding is essential because the three-dimensional shape of a protein determines its function. Misfolded proteins can lose their function and lead to diseases like Alzheimer’s and cystic fibrosis.

49
Q

What is the role of chaperones in protein folding?

A

Chaperones are specialized proteins that assist in the folding of other proteins. They help prevent misfolding and aggregation, ensuring that proteins reach their correct, functional structure.

50
Q

What is metabolic flux analysis, and how is it used?

A

Metabolic flux analysis is a method to measure the rate at which metabolites flow through metabolic pathways. It helps identify rate-limiting steps and metabolic changes under different conditions, such as during disease or drug treatment.

51
Q

How is the structure of a lipid bilayer important for membrane function?

A

The lipid bilayer forms the fundamental structure of cell membranes. It consists of phospholipids with hydrophobic tails and hydrophilic heads, which create a semi-permeable membrane. This structure is crucial for maintaining cellular integrity and regulating substance movement in and out of cells.

52
Q

What are signal transduction pathways, and why are they important?

A

Signal transduction pathways are processes by which cells respond to external signals (e.g., hormones, growth factors) through a series of molecular events. These pathways involve receptors, second messengers, and kinases, and are crucial for regulating cellular activities like growth, metabolism, and differentiation.

53
Q

What is the role of cAMP in cellular signaling?

A

cAMP (cyclic adenosine monophosphate) acts as a secondary messenger in many signaling pathways. It is produced by adenylate cyclase in response to signals from G protein-coupled receptors (GPCRs) and activates protein kinase A (PKA), which regulates various cellular processes.

54
Q

What is the role of NADP+/NADPH in metabolism?

A

NADP+ is the oxidized form, and NADPH is the reduced form. NADPH is primarily involved in anabolic reactions like fatty acid and cholesterol synthesis, acting as a reducing agent by donating electrons.

55
Q

How do glycogen synthase and glycogen phosphorylase regulate glycogen metabolism?

A

Glycogen synthase catalyzes the synthesis of glycogen from glucose, while glycogen phosphorylase breaks down glycogen into glucose-1-phosphate. Both enzymes are regulated by phosphorylation, with glycogen synthase being activated by insulin and glycogen phosphorylase by glucagon.

56
Q

What is oxygen debt, and how does lactate production relate to it?

A

Oxygen debt occurs when muscles operate anaerobically, producing lactate as a byproduct of glycolysis. When oxygen is insufficient for oxidative phosphorylation, pyruvate is converted to lactate, leading to temporary muscle fatigue.

Biochem 24/25 Uea (1 decks)

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