194 Questions
What is the primary function of enzymes in metabolism?
Break down nutrients into precursor metabolites
Which process involves the breakdown of nutrients for energy?
Cellular respiration
Where is energy stored in metabolism?
In the bonds of adenosine triphosphate (ATP)
Which process involves the conversion of light energy into chemical energy?
Photosynthesis
What type of reaction is involved in assembling larger molecules using precursor metabolites and energy?
Anabolic reaction
Which pathway involves the breakdown of lipids?
Lipid catabolism
What is the main function of cellular respiration?
Produce ATP for energy
What are the building blocks for metabolism?
Nutrients
What is formed when two remaining carbons from pyruvic acid join coenzyme A?
Acetyl-CoA
How many molecules of CO2 are produced when two molecules of acetyl-CoA enter the citric acid cycle?
Two
Which cycle is also known as the tricarboxylic acid (TCA) cycle?
Citric Acid Cycle
How many types of enzyme reactions take place in the citric acid cycle?
Six
Where do electron transport chains primarily occur in eukaryotes?
Inner membrane of mitochondria
What process results in the synthesis of ATP during electron transport?
Chemiosmosis
How many molecules of FADH2 are formed for every two molecules of acetyl-CoA that enter the citric acid cycle?
Two
What type of molecules do most organisms get electrons from for the electron transport chain?
(Organic) Molecules
What is the process of breaking down nutrient molecules in a series of steps known as?
Catabolic pathway
Which type of reactions release energy and often produce precursor metabolites for anabolic pathways?
Oxidation-reduction reactions
What happens to a molecule that is an electron acceptor in a redox reaction?
It is reduced
What are the three electron carrier molecules often required in metabolic pathways?
NAD+, NADP+, FAD
What molecule stores energy in the high-energy phosphate bonds of ATP?
Phosphate group
In which type of reaction does a molecule lose an electron and is said to be oxidized?
Dehydrogenation reaction
What is the name of the molecule where free electrons are carried from one site to another?
$\text{NADH}$
When a molecule gains an electron, what is it said to undergo?
$\text{Reduction}$
What is the combination of apoenzyme and its cofactors called?
Holoenzyme
Which molecules functioning as catalysts are called ribozymes?
RNA
What type of ribozymes catalyze the actual protein synthesis reactions of ribosomes?
Ribosomal RNA (rRNA)
What does the induced-fit model describe in enzyme-substrate interactions?
Substrate structure changes after binding
What factors can influence the rate of enzymatic reactions?
Temperature, pH, enzyme concentration, and substrate concentration
How can enzymes be affected by physical and chemical factors such as temperature and pH?
Decreased enzymatic activity
What is the energy required to initiate a chemical reaction known as?
Activation energy
In catabolism, how does an enzyme act on a substrate?
'Enzyme and substrate combine to form a new product'
How many ATP molecules are theoretically yielded from the aerobic respiration of one molecule of glucose?
38
Which pathway yields fewer ATP molecules than the Embden-Meyerhof pathway but generates precursor metabolites not produced in glycolysis?
Entner-Doudoroff pathway
What is the essential function of fermentation?
To regenerate NAD+ for use in glycolysis
Which molecule serves as the final electron acceptor in fermentation when final electron acceptors for complete cellular respiration are unavailable?
NAD+
Which pathway breaks down glucose and produces precursor metabolites and NADPH required for the synthesis of nucleotides, steroids, and fatty acids?
Pentose phosphate pathway
Which bacteria use the Entner-Doudoroff pathway for catabolism of glucose?
Only a few bacteria
What is the function of the citric acid cycle in aerobic respiration?
To generate ATP
In cellular respiration, which molecule serves as the final electron acceptor in redox reactions?
Oxygen
What is the process called when a molecule loses an electron and is said to be oxidized?
Oxidation
Which type of reactions involve the transfer of electrons between molecules?
Redox reactions
What is the series of steps called when nutrient molecules are broken down in metabolism?
Catabolic pathway
Which process concentrates energy from nutrients into high-energy phosphate bonds of ATP?
Phosphorylation
What are the three electron carrier molecules often required in metabolic pathways?
NAD+, NADP+, FAD
Which type of reaction involves the synthesis of macromolecules using ATP energy?
Anabolic reaction
What is the main difference between control of gene expression and control of metabolic expression?
Gene expression controls enzyme production, while metabolic expression controls enzymes already produced.
Which regulatory mechanism involves producing enzymes only in the presence of their substrate?
Producing enzymes only when their substrate is present
How do cells regulate chemical concentrations through channel and transporter proteins?
By regulating the synthesis and degradation of channel and transporter proteins
What is the purpose of catabolizing metabolites to produce lots of energy?
To provide energy for cellular processes
In eukaryotic cells, where are metabolic processes primarily separated?
Membrane-bound organelles
Which mechanism involves modifying enzyme function through binding at sites other than the active site?
Allosteric regulation of enzyme function
How is the availability of cofactors regulated in metabolic pathways?
By controlling the synthesis and degradation of cofactors
Why is feedback inhibition an important regulatory mechanism in cells?
To prevent the accumulation of excess metabolites
Which stage of glycolysis involves the splitting of glucose into two molecules of pyruvic acid?
Lysis
During glycolysis, how many molecules of ATP are invested and how many are produced?
2 invested, 4 produced
Which molecule is produced by substrate-level phosphorylation during glycolysis?
ATP
What is the main difference between oxidative phosphorylation and photophosphorylation?
The energy source used
Where can pyruvate from glycolysis be directed depending on the availability of final electron acceptors?
Both a and b
What is the first stage of cellular respiration that involves the synthesis of acetyl-CoA?
Synthesis of acetyl-CoA
Which category of enzymes is responsible for rearranging atoms in a molecule?
Isomerases
How many stages does cellular respiration involve?
3
What is the role of apoenzymes in enzyme structure?
Require cofactors for activity
Which type of cofactor includes ions like iron, magnesium, zinc, or copper?
Inorganic cofactors
What characterizes substrate-level phosphorylation?
Phosphate transfer from organic nutrient to ADP
What is the primary criterion for naming enzymes?
The chemicals they act on
Which type of enzymes are composed of both apoenzymes and nonprotein cofactors?
Complete enzymes
In which type of reaction do ligases or polymerases enzymes play a crucial role?
Joining molecules together
What is the primary function of the citric acid (Krebs) cycle in aerobic respiration?
Break down acetyl-CoA to produce CO2 and energy carriers
What is the main function of the electron transport chain in cellular respiration?
Pump protons (H+) across the membrane
Which process involves the synthesis of ATP through the movement of protons across a membrane?
Substrate-level phosphorylation
What is the primary role of acetyl-CoA in cellular respiration?
Transfer energy and electrons to coenzymes
Which statement best describes the energy production during the citric acid cycle?
Production of energy carriers like NADH and FADH2
Which type of enzyme reaction is NOT directly involved in the citric acid cycle?
Anabolic
What characterizes the electron transport chain in terms of energy production?
Utilization of chemiosmosis to form ATP
What is the key role of coenzyme A in cellular respiration?
Facilitate the production of acetyl-CoA from pyruvic acid
What are the precursor metabolites derived from glycolysis and the citric acid cycle used for in nucleotide biosynthesis?
Forming the pyrimidine and purine bases
How do catabolic and anabolic pathways interact based on the text?
Catabolic pathways produce energy for anabolic reactions
In what way can amphibolic reactions be described based on the provided information?
They can be either anabolic or catabolic as needed
Which amino acids are involved in the synthesis of purines and pyrimidines according to the text?
Glutamine and Aspartic Acid
What is the role of ribose 5-phosphate in nucleotide biosynthesis?
Serving as a precursor for ribose and deoxyribose
How does energy released in catabolic reactions contribute to anabolic reactions?
By driving the synthesis of complex molecules from simpler ones
What is the source of phosphate groups required for nucleotide biosynthesis according to the text?
ATP
What is the main function of folic acid in nucleotide biosynthesis?
Aids in the production of purines and pyrimidines
What is the term for the amount of energy required to initiate a chemical reaction?
Activation energy
What is the net gain of ATP molecules during glycolysis?
2
What is the role of ribozymes in eukaryotic cells?
Catalyze protein synthesis reactions
Which stage of glycolysis involves the splitting of glucose into two molecules of pyruvic acid?
Energy-conserving
Which model describes the phenomenon where the active site of an enzyme changes shape upon substrate binding?
Induced-fit model
What is the primary function of citric acid (Krebs) cycle in cellular respiration?
Production of ATP
In enzyme-substrate specificity, what determines the compatibility between the enzyme's active site and the substrate?
Complementary shapes
Which factors can influence the rate of enzymatic reactions?
Temperature, pH, enzyme and substrate concentration, and presence of inhibitors
During glycolysis, what is the total number of ATP molecules involved in energy conservation steps?
8
What process may occur if enzymes are denatured by extreme pH or temperature changes?
Permanent change
Where can pyruvate be directed depending on the availability of final electron acceptors?
Fermentation reactions
'Apoenzyme' combined with organic cofactors forms:
'Holoenzyme'
What is the first stage of cellular respiration that involves the synthesis of acetyl-CoA?
Synthesis of acetyl-CoA
'Ribosomal ribozymes' primarily catalyze:
'Protein synthesis reactions'
Which metabolic pathway leads to the production of acetyl-coenzyme A from pyruvic acid?
Glycolysis
What is the total number of NADH molecules produced during glycolysis?
4
What is the process called when the flow of ions down an electrochemical gradient across a membrane is used to synthesize ATP?
Chemiosmosis
Which molecule functions as the final electron acceptor in redox reactions during aerobic respiration?
Oxygen
What is the primary function of flavoproteins in the electron transport system?
Carrying electrons
What is the electrochemical gradient of protons with potential energy known as?
Proton Motive Force
In anaerobic respiration, what molecules are commonly used as final electron acceptors?
Carbonate
Which enzyme synthesizes ATP in both oxidative phosphorylation and photophosphorylation?
ATP Synthase
What is the key aspect of chemiosmosis regarding the synthesis of ATP?
Flow of Protons
What is the role of metal-containing proteins in the electron transport system?
Transporting Electrons
What is a key characteristic of gluconeogenesis?
Involves seven reactions that are the reverse of glycolysis reactions
How are triglycerides (fats) synthesized?
From glycerol and three molecules of fatty acids
What is the process involved in synthesizing waxes like mycolic acid?
Long synthesis pathways requiring lots of energy
How are essential amino acids obtained?
By obtaining them from the diet
What is the main characteristic of steroids synthesis?
Involves complex pathways of polymerizations and isomerizations
What is the primary difference between gluconeogenesis and lipid biosynthesis?
Gluconeogenesis consists of reverse glycolysis reactions, while lipid biosynthesis does not
What is the process by which some amino acids are synthesized using the amine group from ammonia?
Transamination
What is the source of most essential amino acids for organisms?
Obtained in the diet
What is the net gain of NADH molecules during glycolysis?
Two
Which stage of glycolysis involves energy investment through ATP consumption?
Energy-investment
During cellular respiration, what is the first stage after glycolysis?
Synthesis of acetyl-CoA
How many steps are involved in the lysis phase of glycolysis?
Two
What determines whether pyruvate is directed to the citric acid cycle or fermentation reactions?
Availability of final electron acceptors
Which metabolic pathway follows glycolysis if pyruvate is directed to fermentation?
Anaerobic respiration
What is the total net gain of ATP molecules from one molecule of glucose undergoing glycolysis?
$4$
In which phase of glycolysis does substrate-level phosphorylation occur?
Energy-conserving
Which type of reactions involve the transfer of electrons?
Redox reactions
What is the primary function of flavin adenine dinucleotide (FAD) in metabolic pathways?
Electron carrier
During which process is energy from nutrient bonds concentrated in the high-energy phosphate bonds of ATP?
Phosphorylation
What happens to a molecule when it is said to be reduced in a redox reaction?
Gains an electron
What role do ribozymes play in cells?
Are enzymes that catalyze RNA splicing
What is the characteristic of exergonic reactions?
Release energy
Which enzyme is involved in adding inorganic phosphate to molecules during phosphorylation?
Kinase
What do free electrons carry from one site to another in metabolic pathways?
Hydrogen atoms
What is the main difference between aerobic respiration and anaerobic respiration with respect to electron acceptors?
Aerobes use oxygen as the final electron acceptor, while anaerobes use inorganic molecules like sulfate.
What is the function of chemiosmosis in the context of the electron transport chain?
To create a proton gradient that generates ATP synthesis through the flow of protons down their electrochemical gradient.
Which of the following molecules is NOT a carrier molecule in the electron transport system?
ATP synthases
What is the primary role of metal-containing proteins in the electron transport system?
To serve as intermediate carriers of electrons.
What is the purpose of a proton motive force created during chemiosmosis?
To synthesize ATP through ATP synthases.
How many molecules of ATP are synthesized during chemiosmosis from the oxidation of 10 molecules of NADH and two molecules of FADH2?
34 molecules
What type of gradient is utilized by chemiosmosis to synthesize ATP?
Proton gradient
Which pathway for the catabolism of glucose yields fewer ATP molecules than the Embden-Meyerhof pathway but generates precursor metabolites not produced in glycolysis?
Entner-Doudoroff pathway
What is the essential function of fermentation in cellular respiration?
Regeneration of NAD+ for use in glycolysis
Which pathway breaks down glucose during a process that produces precursor metabolites and NADPH required for the synthesis of nucleotides, steroids, and fatty acids?
Pentose phosphate pathway
What is the net theoretical yield of ATP molecules from the aerobic respiration of one molecule of glucose via glycolysis, the citric acid cycle, and the electron transport chain?
38 ATP
What is the final electron acceptor in fermentation when complete cellular respiration electron acceptors are unavailable?
An organic molecule within the cell
Which process involves the partial oxidation of sugar using an organic molecule as the final electron acceptor?
Fermentation
Which pathway is primarily used by only a few bacteria, utilizes different enzymes than glycolysis, and yields precursor metabolites and NADPH?
Entner-Doudoroff pathway
Which metabolic pathway reduces pyruvic acid to lactic acid or ethanol to regenerate NAD+ for glycolysis?
Fermentation
How are fats catabolized in the presence of lipases?
Glycerol is converted to DHAP and then to pyruvic acid.
Where do prokaryotes carry out protein catabolism?
Outside their cell walls
What is the role of chlorophyll in photosynthesis?
To capture light energy for carbohydrate synthesis
Where are chlorophyll molecules held within photosystems?
In the thylakoids
What characterizes eukaryotic thylakoids compared to prokaryotic thylakoids?
Eukaryotic thylakoids are infoldings of chloroplast inner membranes.
In photosynthesis, what is the role of bacteriochlorophylls?
They help absorb light energy for carbohydrate synthesis.
What metabolic process involves the breakdown of proteins for energy production?
Proteolysis
Where do eukaryotes typically find their thylakoids during photosynthesis?
Infoldings of the inner membranes of chloroplasts
What are the components that nucleotides are composed of?
A 5-carbon sugar, a phosphate group, and a pyrimidine or purine base
Where do ribose and deoxyribose, components of nucleotides, come from?
From glycolysis and the citric acid cycle
Which amino acids are involved in the production of purines and pyrimidines?
Glutamine and aspartic acid
What is the primary outcome of catabolic pathways interacting with anabolic pathways?
Energy for anabolic reactions
What term is used to describe reactions that can be both anabolic or catabolic depending on the cellular needs?
Amphibolic reactions
Where do phosphate groups for nucleotide synthesis come from?
ATP
What is the main function of the Entner-Doudoroff pathway compared to the Embden-Meyerhof pathway?
Generates precursor metabolites not produced in glycolysis
What is the role of folic acid in nucleotide biosynthesis?
Provides the carbon source for purines and pyrimidines
What is the primary purpose of fermentation in cellular respiration?
To regenerate NAD+ for use in glycolysis
How do catabolic pathways contribute to anabolic pathways in terms of precursor metabolites?
Supply precursor metabolites for use as substrates in anabolic reactions
Which metabolic pathway is characterized by breaking down glucose and producing precursor metabolites necessary for synthesizing nucleotides, steroids, and fatty acids?
Pentose phosphate pathway
What is a key outcome of the citric acid cycle in terms of ATP production?
Produces 2 ATP molecules
Which process characterizes fermentation in terms of the final electron acceptor?
Uses an organic molecule within the cell as the final electron acceptor
What is the essential role of the electron transport chain in aerobic respiration?
Produces ATP molecules
What is a significant difference between lactic acid and ethanol fermentation processes?
Different final electron acceptors used
What is the term for RNA molecules functioning as catalysts?
Ribozymes
Which model describes how the active site of an enzyme may change shape after substrate binding?
Induced-fit model
What is the term for the amount of energy required to initiate a chemical reaction?
Activation energy
Which factor can influence the rate of enzymatic reactions along with temperature and substrate concentration?
pH
In which type of reaction does an enzyme separate from the two new products after breaking the bonds within the substrate?
Catabolic reaction
What is the term for the molecule onto which substrates fit in enzymes?
Active site
What can denature enzymes by changing their shape and thus their ability to bond?
Physical and chemical factors
What are organic cofactors also called?
Coenzymes
What type of phosphorylation describes the transfer of phosphate from a phosphorylated organic nutrient to ADP to form ATP?
Substrate-level phosphorylation
How are enzymes classified based on their mode of action?
By their substrate specificity
What is the primary function of ligases or polymerases enzymes?
Joining molecules together
What are inorganic cofactors in enzyme structure derived from?
Ions
Which type of enzymes rearrange atoms in a molecule to create isomers?
Isomerases
What is the category of enzymes that split molecules without using water?
Lyases
What is the primary function of transferases among the different types of enzymes described?
Transferring functional groups
What is the role of NADP+ and FAD in enzyme structure?
Cofactors made from vitamins
In noncyclic photophosphorylation, where do oxygenic organisms obtain electrons from?
Water
What is the primary role of ATP and NADPH in the light-independent reactions of photosynthesis?
To drive carbon fixation
What is the name of the pathway that involves the synthesis of glucose by carbon fixation?
Calvin-Benson cycle
Amphibolic reactions are metabolic reactions that can proceed towards:
Catabolism
What is the source of electrons in noncyclic photophosphorylation for anoxygenic organisms?
H2S
What is formed by the reduction of NADPH in the light-independent reactions of photosynthesis?
$G3P$
Which compound is combined with CO2 in the Calvin-Benson cycle?
$RuBP$
What drives the synthesis of glucose in photosynthesis?
$ATP$ and $NADPH$
Test your knowledge on enzymes, coenzymes, holoenzymes, ribozymes, and activation energy in biological reactions.
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