BIOL 2020 Lecture Notes - Lecture 9: Thioester, Coenzyme A, Decarboxylation

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24 Jan 2018

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Types of chemical reactions that occur in metabolism: (1) redox reactions. An enzyme that does the redox reactions has a dehydrogenase. A great deal of the energy acquired in cells comes from the oxidation of high energy electrons into reduced forms. The most reduced carbon is ch4 and the most oxidized carbon is co2. The major acceptor of electrons during oxidation of metabolites is nad+, oxidizing agent. The major donor of electrons during reduction of metabolites is nadph, reducing agent (2) group transfer reaction. One of the most common and important groups transferred during metabolism is the phosphoryl group po3, using from atp (3) hydrolysis reactions. Adding water across a covalent bond is called hydrolysis of atp is highly exergonic. All chemical reactions occur to minimize gibbs free energy g, for all spontaneous reaction, g must be negative. Energy is absorbed, endergonic: s is positive.

Related Questions

Q1:

Enzymes are essential for the conversion of organic molecules in biochemical pathways. Which of the following statements is incorrect?

Enzymes reduce the activation energy of chemical reactions.

Enzymes are catalysts and appear unchanged at the end of the reaction.

Enzymes change the equilibrium of a reaction.

Enzymes form a complex with the substrate.

Enzymes facilitate both the conversion of substrates into products and of products into substrates.

Q2:

NADH and NADPH are important energy carriers in biochemical pathways. Which of the following statements about these compounds is incorrect?

NADP+ is reduced by two electrons (involving 2 protons) from photosystem I to form NADPH + H+.

NADH is produced both during glycolysis and in the TCA cycle.

NADH feeds electrons into the respiratory chain of mitcohondria, which are ultimately used to form water.

In the absence of oxygen NADH produced during glycolysis is reoxidised by formation of lactate from pyruvate or by formation of ethanol from acetaldehyde (fermentation).

The majority of NADH produced during oxidation of glucose (in the presence of oxygen) is generated during glycolysis.

Q3:

The respiratory chain converts the reducing power of NADH into the production of ATP. Which of the following statements is incorrect?

Electrons are passed through the respiratory chain in a way to optimise the production of heat.

The complexes of the respiratory chain use the energy of redox reactions to pump protons across the inner mitochondrial membrane.

The ATP synthase uses the protonmotive force to synthesize ATP.

The principle of energy conversion by respiratory chain and ATP synthase is called âchemiosmosisâ.

The electrons from NADH are passed along the respiratory chain in a number of redox reactions mostly involving complexes

raspberrytortoise897

Question 1

Which of the following statements regarding photosynthesis and cellular respiration is true?

	A.	Photosynthesis occurs in mitochondria, and cellular respiration occurs in chloroplasts.
	B.	Photosynthesis occurs in chloroplasts, and cellular respiration occurs in mitochondria.
	C.	Photosynthesis occurs in mitochondria and in chloroplasts.

Question 2

How do cells capture the energy released by cellular respiration?

	A.	They produce glucose
	B.	The energy is coupled to oxygen
	C.	They produce ATP

Question 3

During redox reactions

	A.	the loss of electrons from one molecule is called reduction
	B.	electrons are lost from one substance and added to another substance
	C.	protons from one molecule replace the electrons lost from another molecule

Question 4

Oxidation is the ________, and reduction is the ________.

	A.	gain of oxygen; loss of oxygen
	B.	loss of electrons; gain of electrons
	C.	gain of protons; loss of protons

Question 5

During cellular respiration, NADH

	A.	delivers its electron load to the first electron carrier molecule.
	B.	is chemically converted into ATP
	C.	is the final electron acceptor

Question 6

A drug is tested in the laboratory and is found to create holes in both mitochondrial membranes. Scientists suspect that the drug will be harmful to human cells because it will inhibit

	A.	the citric acid cycle only.
	B.	glycolysis only
	C.	the citric acid cycle and oxidative phosphorylation

Question 7

Which of the following metabolic pathways is common in aerobic and anaerobic metabolism?

	A.	glycolysis
	B.	the citric acid cycle
	C.	electron transport chain

Question 8

Which of the following is a result of glycolysis?

	A.	production of CO2
	B.	a net loss of two ATPs per glucose molecule
	C.	conversion of glucose to two three-carbon compounds

Which of the following is common to both aerobic and anaerobicmicrobes?

	Fermentation
	An electron transport chain
	Pyruvate oxidation
	Glycolysis
	All of the above

The primary purpose of catabolism is

	generation of ADP.
	generation of ATP.
	oxidation of NADH to NAD⁺.
	degradation of organic molecules.
	biosynthesis.

What is a fate of pyruvate during alcoholic fermentation byyeast?

	It is reduced to lactic acid.
	It is oxidized to form glucose and carbon dioxide
	It is cleaved to form acetylaldehyde and carbon dioxide.
	It is catabolized in glycolysis.
	It is oxidized to form lactic acid and carbon dioxide.

Electrons needed to reduce an oxidized electron acceptor areprovided by

	a) externally provided compounds such asH<sub>2</sub>, lactate or formate.
	b) an intermediate electron carrier such as NADH.
	c) 0<sub>2</sub>.
	d) Both a and b
	e) All of the above

How are aerobic respiration and anaerobic respirationsimilar?

	Both use oxygen as a terminal electron carrier.
	These are other names for glycolysis.
	Both utilize inorganic molecules as terminal electronacceptors.
	Neither receives electrons from glycolysis.
	Anaerobic respiration does not exist in microbes.

The conversion of phosphoenolpyruvic acid (PEP) topyruvate

	a) releases CO<sub>2</sub>.
	b) involves the conversion of ADP and ATP.
	c) involves substrate-level phosphorylation.
	d) Both a and b
	e) Both b and c

Which of the following is the best definition offermentation?

	The reduction of glucose to pyruvic acid
	The complete catabolism of glucose to CO₂ andH₂O
	The oxidation of a carbohydrate with organic molecules servingas electron donors and acceptors
	The production of ATP from glucose
	The production of ethanol from glucose

A reaction that yields energy has a

	positive ?G_o?.
	negative ?G_o?.
	positive ?E_o?.
	negative ?E_o?.
	negative ?H_o?.

Oxidation and reduction reactions are always coupledbecause

	a) electrons generally accompany protons.
	b) protons generally accompany protons.
	c) electrons cannot exist free in solution.
	d) Both a and b
	e) All of the above

10.

Which of the following is true of aerobic respiration?

	It involves the reduction of oxygen.
	It involves the oxidation of oxygen.
	It involves the reduction of lactic acid.
	It involves the oxidation of lactic acid.
	It does not generate ATP.

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BIOL 2020 Lecture Notes - Lecture 9: Thioester, Coenzyme A, Decarboxylation

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