RESPIRATION Flashcards
Why is breathing essential to life?
It helps release energy from food
Do all living organisms breathe?
Yes, but the mechanisms vary
What is the primary source of energy for living organisms?
Food
How do green plants and cyanobacteria obtain energy?
By photosynthesis, trapping light energy
Which parts of green plants carry out photosynthesis?
Only cells containing chloroplasts, mostly in superficial layers
How do non-green parts of plants obtain energy?
Food is translocated from photosynthetic parts for oxidation
What type of nutrition do animals have?
Heterotrophic
What is the source of food for saprophytes like fungi?
Dead and decaying matter
Ultimately, where does all the food respired for life processes come from?
Photosynthesis
What is cellular respiration?
The breakdown of food materials within the cell to release energy and synthesize ATP
Q: Where does photosynthesis occur in eukaryotic cells?
A) Mitochondria
B) Cytoplasm
C) Chloroplasts
D) Nucleus
C) Chloroplasts
Which of the following is usually oxidized to release energy during respiration?
A) Carbohydrates
B) Nucleic acids
C) Minerals
D) Water
A) Carbohydrates
Where does the breakdown of complex molecules to yield energy occur in eukaryotic cells?
A) Chloroplasts
B) Ribosomes
C) Cytoplasm and mitochondria
D) Golgi apparatus
C) Cytoplasm and mitochondria
What is the process of breaking C-C bonds of complex compounds through oxidation within cells called?
A) Photosynthesis
B) Fermentation
C) Respiration
D) Translocation
C) Respiration
What are the compounds that are oxidized during respiration known as?
A) Enzymes
B) Respiratory substrates
C) Photosynthetic pigments
D) Nutrients
B) Respiratory substrates
Besides carbohydrates, which substances can be used as respiratory substrates in some plants under certain conditions?
A) Proteins, fats, and organic acids
B) Vitamins and minerals
C) Water and oxygen
D) Light and chlorophyl
A) Proteins, fats, and organic acids
How is the energy from respiratory substrates released within the cell?
A) In a single, explosive reaction
B) As heat energy only
C) Through slow, step-wise reactions controlled by enzymes
D) By diffusion across cell membranes
C) Through slow, step-wise reactions controlled by enzymes
How is the energy released from respiration stored in the cell?
A) As heat energy
B) As light energy
C) As chemical energy in ATP
D) As glucose
C) As chemical energy in ATP
What is ATP often referred to as?
A) The building block of life
B) The energy currency of the cell
C) The genetic code of the cell
D) The oxygen transporter of the cell
B) The energy currency of the cell
What happens to the carbon skeleton produced during respiration?
A) It is exhaled as carbon dioxide
B) It is stored as fat
C) It is used as precursors for biosynthesis of other molecules in the cell
D) It is converted back into glucose
C) It is used as precursors for biosynthesis of other molecules in the cell
Do plants breathe?
Yes, they require O₂ for respiration and give out CO₂
What structures do plants use for gaseous exchange?
Stomata and lenticels
Why don’t plants need specialized respiratory organs like animals?
Each plant part manages its own gas-exchange needs
How does the rate of gas exchange in plants compare to animals?
Plants respire at rates far lower than animals
Why is oxygen availability not a problem during photosynthesis in plant cells?
Because O₂ is released within the cell during photosynthesis
How do gases diffuse in large, bulky plants?
Over short distances since most living cells are close to the surface
In thick, woody stems, where are the living cells located for gas exchange?
In thin layers inside and beneath the bark
What structures in woody stems allow for gas exchange?
Lenticels
What role do dead cells in the interior of woody stems play?
They provide mechanical support
What facilitates air movement within plant tissues like leaves, stems, and roots?
Loose packing of parenchyma cells creating interconnected air spaces
How does the plant cell ensure that the energy from glucose catabolism is useful?
C) By oxidizing glucose in several small steps to couple energy release with ATP synthesis
What are the products of respiration?
B) Carbon dioxide, water, and energy
What role does oxygen play in respiration?
B) It is used to oxidize glucose
Which of the following organisms can survive without oxygen?
C) Organisms adapted to anaerobic conditions
What are facultative anaerobes?
B) Organisms that prefer oxygen but can survive without it
What are obligate anaerobes?
A) Organisms that require anaerobic conditions to survive
What does the ability of all living organisms to partially oxidize glucose without oxygen suggest?
C) They retain enzymatic machinery for anaerobic respiration
What is the breakdown of glucose to pyruvic acid called?
C) Glycolysis
In what kind of environment did the first cells on Earth likely live?
B) Anaerobic conditions lacking oxygen
Why is glucose oxidation carried out in multiple steps in cells?
B) To allow energy to be captured efficiently for ATP synthesis
What does the term glycolysis mean?
C) Sugar splitting
Who proposed the scheme of glycolysis?
B) Gustav Embden, Otto Meyerhof, and J. Parnas
Glycolysis is also known as:
C) EMP Pathway
In which organisms is glycolysis the only process of respiration?
B) Anaerobic organisms
Where does glycolysis occur in the cell?
C) Cytoplasm
Glycolysis is present in:
C) All living organisms
What is the end product of glycolysis?
B) Pyruvic acid
In plants, from where is glucose for glycolysis derived?
B) From sucrose and storage carbohydrates
Which enzyme converts sucrose into glucose and fructose?
B) Invertase
What happens to glucose and fructose before entering the glycolytic pathway?
B) They are phosphorylated to form glucose-6-phosphate
Which enzyme phosphorylates glucose to form glucose-6-phosphate?
B) Hexokinase
Glucose-6-phosphate is isomerized to form:
B) Fructose-6-phosphate
How many reactions are involved in glycolysis to convert glucose into pyruvate?
C) 10
During glycolysis, energy is captured in the form of:
B) ATP and NADH + H⁺
At which two steps in glycolysis is ATP utilised?
B) Conversion of glucose to glucose-6-phosphate and fructose-6-phosphate to fructose-1,6-bisphosphate
Fructose-1,6-bisphosphate is split into:
C) Dihydroxyacetone phosphate and 3-phosphoglyceraldehyde (PGAL)
NADH + H⁺ is formed during which step of glycolysis?
C) Conversion of PGAL to 1,3-bisphosphoglycerate (BPGA)
The conversion of BPGA to 3-phosphoglyceric acid (PGA) results in:
C) ATP synthesis
Another ATP is synthesised during the conversion of:
B) PEP to pyruvic acid
How many ATP molecules are directly synthesised from one glucose molecule in glycolysis?
B) 4
What is the key product of glycolysis?
C) Pyruvic acid
The metabolic fate of pyruvate depends on:
C) The cellular need and availability of oxygen
Which of the following is NOT a fate of pyruvate?
C) Photosynthesis
Fermentation takes place under anaerobic conditions in:
B) Many prokaryotes and unicellular eukaryotes
Complete oxidation of glucose to CO₂ and H₂O occurs through:
C) Krebs’ Cycle (Aerobic respiration)
Aerobic respiration requires the supply of:
B) Oxygen
In yeast, pyruvic acid is converted to CO₂ and ethanol by the enzymes:
B) Pyruvic acid decarboxylase and alcohol dehydrogenase
In some bacteria, pyruvic acid is converted to:
B) Lactic acid
During intense exercise in animal muscles, pyruvic acid is reduced to lactic acid by which enzyme?
C) Lactate dehydrogenase
What is the reducing agent in both lactic acid and alcohol fermentation?
B) NADH + H⁺
In fermentation, NADH + H⁺ is reoxidised to:
C) NAD⁺
What percentage of the energy in glucose is released during lactic acid and alcohol fermentation?
B) Less than 7%
Why are fermentation processes considered hazardous?
B) They generate acids or alcohols which can be toxic
What is the maximum alcohol concentration yeasts can tolerate before poisoning themselves?
C) 13%
Alcoholic beverages with more than 13% alcohol content are obtained through:
C) Distillation processes
Complete oxidation of glucose for maximal ATP synthesis occurs in:
D) Mitochondria
Which process leads to complete oxidation of organic substances in the presence of oxygen?
D) Aerobic respiration
Aerobic respiration results in the release of:
A) CO₂, water, and a large amount of energy
Where does the final step of aerobic respiration occur?
B) Mitochondrial matrix
In aerobic respiration, pyruvate is oxidised to release CO₂ and hydrogen atoms. These hydrogen atoms are passed to:
C) Oxygen
What happens to pyruvate in the mitochondrial matrix?
B) It undergoes oxidative decarboxylation
The oxidative decarboxylation of pyruvate requires the participation of which coenzymes?
A) NAD+ and Coenzyme A
What is the main product of the oxidative decarboxylation of pyruvate?
A) Acetyl CoA
How many molecules of NADH are produced from the metabolism of two molecules of pyruvic acid?
B) Two
What cycle does acetyl CoA enter after its formation?
B) Krebs’ cycle
The Krebs’ cycle is also known as the:
B) Citric acid cycle
Who is the scientist after whom the Krebs’ cycle is named?
B) Hans Krebs
The TCA cycle starts with the condensation of acetyl group with which molecule?
C) Oxaloacetic acid (OAA)
Which enzyme catalyzes the formation of citric acid in the TCA cycle?
B) Citrate synthase
What is released during the condensation of the acetyl group with oxaloacetic acid in the TCA cycle?
B) CoA
What is the product formed after the isomerisation of citrate in the TCA cycle?
B) Isocitrate
In the TCA cycle, the conversion of succinyl-CoA to succinic acid produces:
C) GTP
During the TCA cycle, the reduction of NAD+ leads to the formation of:
A) NADH
What is required for the TCA cycle to continue its oxidation of acetyl CoA?
A) Regeneration of NAD+ and FAD+
How many molecules of NADH + H+ are produced per cycle of the TCA cycle?
B) Three
What is the main product of the TCA cycle that is utilized in further stages of cellular respiration?
C) NADH and FADH2
Q: The electron transport system (ETS) is located in which part of the mitochondria?
A) Outer mitochondrial membrane
B) Mitochondrial matrix
C) Inner mitochondrial membrane
D) Cytoplasm
C) Inner mitochondrial membrane
Which complex oxidizes electrons from NADH in the electron transport system?
A) Complex II
B) Cytochrome c oxidase
C) NADH dehydrogenase (Complex I)
D) Cytochrome bc1 complex
C) NADH dehydrogenase (Complex I)
What is the role of ubiquinone (Coenzyme Q) in the electron transport system?
A) Transfer of electrons from NADH to cytochrome c
B) Oxidation of NADH
C) Transfer of electrons from NADH and FADH2 to cytochrome c
D) Reduction of oxygen to water
Answer: C) Transfer of electrons from NADH and FADH2 to cytochrome c
Which complex is responsible for transferring electrons to cytochrome c in the electron transport system?
A) Complex I
B) Complex III
C) Complex IV
D) Complex II
Answer: B) Complex III
What is the role of cytochrome c in the electron transport system?
A) It acts as a mobile carrier for electrons between complex III and complex IV
B) It oxidizes FADH2
C) It reduces oxygen to form water
D) It synthesizes ATP
Answer: A) It acts as a mobile carrier for electrons between complex III and complex IV
What does Complex IV in the electron transport system contain?
A) Cytochrome b and b3
B) Cytochrome a and a3, and two copper centers
C) Ubiquinone
D) ATP synthase
Answer: B) Cytochrome a and a3, and two copper centers
Which complex in the electron transport chain is responsible for ATP synthesis?
A) Complex I
B) Complex III
C) Complex IV
D) Complex V (ATP synthase)
Answer: D) Complex V (ATP synthase)
How many ATP molecules are generated from the oxidation of one molecule of NADH?
A) 2
B) 3
C) 4
D) 1
Answer: B) 3
The oxidation of one molecule of FADH2 results in the production of how many ATP molecules?
A) 1
B) 2
C) 3
D) 4
Answer: B) 2
What is the role of oxygen in the electron transport chain?
A) It donates electrons at the start of the chain
B) It acts as the final hydrogen acceptor
C) It synthesizes ATP directly
D) It converts NADH to NAD+
Answer: B) It acts as the final hydrogen acceptor
What is the term for ATP synthesis powered by the energy from oxidation-reduction reactions?
A) Photophosphorylation
B) Substrate-level phosphorylation
C) Oxidative phosphorylation
D) Chemiosmosis
Answer: C) Oxidative phosphorylation
In ATP synthase, which component forms the channel for proton movement across the membrane?
A) F1 component
B) F0 component
C) Cytochrome c
D) Complex IV
Answer: B) F0 component
How many protons (H+) need to pass through the F0 component of ATP synthase to produce one ATP?
A) 2
B) 3
C) 4
D) 5
Answer: C) 4
The F1 headpiece of ATP synthase is responsible for:
A) Forming the proton gradient
B) Transferring electrons to oxygen
C) Synthesizing ATP from ADP and inorganic phosphate
D) Pumping protons into the intermembrane space
Answer: C) Synthesizing ATP from ADP and inorganic phosphate
What is the theoretical net gain of ATP molecules during the aerobic respiration of one glucose molecule?
A) 36
B) 38
C) 40
D) 32
Answer: B) 38
Which of the following is NOT an assumption made when calculating the respiratory balance sheet?
A) All intermediates are used only in respiration
B) Glycolysis, TCA cycle, and ETS occur sequentially without overlap
C) Alternative substrates like fatty acids are included in the calculation
D) NADH from glycolysis undergoes oxidative phosphorylation in the mitochondria
Answer: C) Alternative substrates like fatty acids are included in the calculation
How many ATP molecules are gained from fermentation of one glucose molecule?
A) 4
B) 6
C) 2
D) 38
Answer: C) 2
Which process results in the complete breakdown of glucose to CO2 and H2O?
A) Fermentation
B) Anaerobic respiration
C) Aerobic respiration
D) Glycolysis
Answer: C) Aerobic respiration
In fermentation, NADH is oxidised to NAD+:
A) Rapidly
B) Slowly
C) Only in the presence of oxygen
D) Without any energy release
Answer: B) Slowly
Why are the assumptions used in the respiratory balance sheet not entirely valid in living systems?
A) Enzymes don’t function properly in cells
B) Pathways operate simultaneously, and intermediates are used for other processes
C) Glucose is never fully oxidized in living organisms
D) ATP is not produced in real biological systems
Answer: B) Pathways operate simultaneously, and intermediates are used for other processes
Which of the following is TRUE regarding ATP production in aerobic vs. anaerobic respiration?
A) Fermentation produces more ATP than aerobic respiration
B) Aerobic respiration produces fewer ATP but more NADH
C) Aerobic respiration produces significantly more ATP than fermentation
D) Both produce the same number of ATP
Answer: C) Aerobic respiration produces significantly more ATP than fermentation
Which statement best describes the efficiency of energy extraction in aerobic respiration?
A) It extracts less than 7% of the energy in glucose
B) It uses light energy to drive ATP synthesis
C) It completely oxidizes glucose, yielding maximum ATP
D) It operates without oxygen at all stages
Answer: C) It completely oxidizes glucose, yielding maximum ATP
Why is the respiratory pathway considered amphibolic rather than purely catabolic?
A) It only synthesizes ATP
B) It involves both breakdown (catabolism) and synthesis (anabolism) of biomolecules
C) It is only responsible for the degradation of glucose
D) It does not contribute to anabolic processes
Answer: B) It involves both breakdown (catabolism) and synthesis (anabolism) of biomolecules
Which of the following must fats be converted into before entering the respiratory pathway?
A) Amino acids and glycerol
B) Glucose and pyruvate
C) Glycerol and fatty acids
D) Acetyl CoA and glucose
Answer: C) Glycerol and fatty acids
Glycerol enters the respiratory pathway after being converted into:
A) Acetyl CoA
B) Pyruvate
C) Phosphoglyceraldehyde (PGAL)
D) Oxaloacetic acid
Answer: C) Phosphoglyceraldehyde (PGAL)
Fatty acids are degraded into which molecule before entering the Krebs cycle?
A) Pyruvate
B) Oxaloacetate
C) Acetyl CoA
D) Succinyl CoA
Answer: C) Acetyl CoA
During protein respiration, amino acids enter the respiratory pathway after which process?
A) Oxidation
B) Deamination
C) Glycolysis
D) Decarboxylation
Answer: B) Deamination
Which of the following intermediates is withdrawn from the respiratory pathway for fatty acid synthesis?
A) Pyruvate
B) Acetyl CoA
C) Succinic acid
D) NADH
Answer: B) Acetyl CoA
Which of the following correctly matches the process with its definition?
A) Catabolism - synthesis of biomolecules
B) Anabolism - breakdown of molecules
C) Catabolism - breakdown of molecules to release energy
D) Anabolism - release of energy from glucose
Answer: C) Catabolism - breakdown of molecules to release energy
Which of the following best describes how proteins enter the respiratory pathway?
A) After conversion into glucose
B) After being degraded into nucleotides
C) After deamination, entering as pyruvate, acetyl CoA, or Krebs cycle intermediates
D) After being converted into fatty acids
Answer: C) After deamination, entering as pyruvate, acetyl CoA, or Krebs cycle intermediates
What is the respiratory quotient (RQ)?
A) The ratio of ATP produced to glucose consumed
B) The ratio of CO2 evolved to O2 consumed during respiration
C) The ratio of O2 consumed to CO2 evolved during respiration
D) The ratio of NADH produced to FADH2 produced
Answer: B) The ratio of CO2 evolved to O2 consumed during respiration
What is the RQ value when carbohydrates are completely oxidized during aerobic respiration?
A) 0.7
B) 0.9
C) 1.0
D) 1.5
Answer: C) 1.0
Which of the following respiratory substrates will have an RQ less than 1?
A) Glucose
B) Proteins
C) Fats
D) Both B and C
Answer: D) Both B and C
The RQ of tripalmitin (a fatty acid) when used as a respiratory substrate is:
A) 0.7
B) 1.0
C) 0.9
D) 1.2
Answer: A) 0.7
When proteins are used as respiratory substrates, the RQ is approximately:
A) 1.0
B) 0.9
C) 0.7
D) 1.2
Answer: B) 0.9
If the RQ of a respiratory substrate is greater than 1, it suggests the substrate is likely:
A) A carbohydrate
B) A fat
C) A protein
D) An organic acid
Answer: D) An organic acid
Which of the following is true about the RQ value during aerobic respiration of glucose?
A) More CO2 is evolved than O2 consumed
B) Less CO2 is evolved than O2 consumed
C) Equal amounts of CO2 and O2 are exchanged
D) No CO2 is evolved
Answer: C) Equal amounts of CO2 and O2 are exchanged
Why do fats have an RQ less than 1 during respiration?
A) Fats produce more CO2 than O2 consumed
B) Fats consume more O2 than CO2 produced
C) Fats do not produce CO2 during respiration
D) Fats are converted into carbohydrates before respiration
Answer: B) Fats consume more O2 than CO2 produced
In living organisms, why is the RQ value usually not exactly 1, 0.9, or 0.7?
A) Only proteins are used as substrates
B) Respiration always involves multiple substrates simultaneously
C) Respiration does not produce CO2
D) Fats are never respired
Answer: B) Respiration always involves multiple substrates simultaneously
