Chapter 10 - Cell respiration Flashcards
What does photosynthesis generate?
Oxygen as well as organic molecules used by the mitochondria of eukaryotes as fuel for cellular respiration
What are the key pathways of respiration?
Glycolysis, pyruvate oxidation and the citric acid cycle, and oxidative phosphorylation.
What is fermentation?
Fermentation is an anaerobic process in which energy can be released from glucose even though oxygen is not available. It is a partial degradation of sugars or other organic fuel that occurs without the use of oxygen
What is aerobic respiration?
Aerobic respiration requires oxygen (O2) in order to create ATP.
What is anaerobic respiration?
Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2)
What is cellular respiration?
Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from oxygen molecules or nutrients into adenosine triphosphate, and then release waste products
What types of respiration does cellular respiration involve?
both aerobic and anaerobic processes.
What is the simple equation for respiration?
Organic compounds + Oxygen > Carbon dioxide + Water + Energy
Is cellular respiration an endergonic or exergonic reaction?
Exergonic
What are oxidation reactions?
The loss of electrons from one substance is called oxidation
What are reduction reactions?
The addition of electrons to another substance is known as reduction
What are oxidation-reduction reactions?
A transfer of one or more electrons (e-) from one reactant to another in a chemical reaction.
What is the reducing agent?
Reducing agent is an element or compound that loses an electron to an electron recipient in a redox chemical reaction
What is the oxidising agent?
an oxidizing agent (oxidant, oxidizer) is a substance that has the ability to oxidize other substances — in other words to accept their electrons
An electron loses potential energy when it what?
it shifts from a less electronegative atom toward a more electronegative one
What is respiration?
In physiology, respiration is the movement of oxygen from the outside environment to the cells within tissues, and the transport of carbon dioxide in the opposite direction.
In respiration, the oxidation of glucose transfers electrons to a lower energy state, which does what? .
It liberates energy that becomes available for ATP synthesis. So, in general, we see fuels with multiple C—H bonds oxidised into products with multiple C—O bonds.
Why is it important that enzymes in your cells lower the barrier of activation energy when you eat glucose?
Because without this to break the C-H bonds, a food substance like glucose would combine almost instantaneously with O
Does cellular respiration oxidise glucose in one step or multiple steps and why?
Multiple steps because if energy is released from a fuel all at once, it cannot be harnessed efficiently for constructive work.
What is the basic thing that happens at each step of glucose oxidation?
At key steps, electrons are stripped from the glucose. As is often the case in oxidation reactions, each electron travels with a proton—thus, as a hydrogen atom.
What is nicotinamide adenine dinucleotide?
In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another.
What is NAD+?
The oxidised form of NADH which can accept electrons and hydrogens
What is NADH?
The reduced form of NAD+ that has accepted electrons or hydrogens
How does NAD+ trap electrons from glucose and the other organic molecules in food?
Enzymes called dehydrogenases remove a pair of hydrogen atoms (2 electrons and 2 protons) from the substrate (glucose), thereby oxidising it. The enzyme delivers the 2 electrons along with 1 proton to its coenzyme, NAD+, forming NADH
Do electrons lose a-lot of their potential energy when they are transferred from glucose to NAD+.?
No! They lose very little
What does each NADH molecule formed during respiration represent?
Stored energy
How do electrons that are extracted from glucose and stored as potential energy in NADH finally reach oxygen?
Instead of occurring in one explosive reaction, respiration uses an electron transport chain to break the fall of electrons to oxygen into several energy-releasing steps
The combination of H2 and O2 is used to as an explosion to boost rockets into space, how come when cellular respiration occurs in our cells there is no explosion?
Instead of occurring in one explosive reaction, respiration uses an electron transport chain to break the fall of electrons to oxygen into several energy-releasing steps.
What is an electron transport chain?
An electron transport chain is a series of complexes that transfer electrons from electron donors to electron acceptors via redox reactions, and couples this electron transfer with the transfer of protons across a membrane. The electron transport chain is built up of peptides, enzymes, and other molecules.
How do electron carriers (NADH) get the electrons to O2 using an electron transport chain (To prevent explosion and loss of energy)?
Electrons removed from glucose are shuttled by NADH to the “top,” higher-energy end of the chain. At the “bottom,” lower-energy end, O2 captures these electrons along with hydrogen nuclei (H+), forming water.
Is the electron transfer from NADH to oxygen an endogonic or exergonic reaction?
Exergonic with a free energy change of -53 cal/mol.
What is the difference between exergonic and exothermic?
an exergonic reaction means that a reaction is spontaneous, an exothermic reaction has nothing to do with spontaneity, but that an energy is released to the surrounding.
In the electron transport chain is each downhill carrier more or less electronegative?
More electronegative, thus capable of oxidising its uphill neighbour.
During cellular respiration what travel route do most electrons take?
The “downhill” route: glucose-NADH-electron transport chain-oxygen
What are the 3 stages for the harvesting of energy from glucose by cellular respiration?
Glycolysis, pyruvate, and oxidative phosphorylation
Where does glycolysis occur?
In the cytosol
What does glycolysis do in cellular respiration?
Begins the degradation process by breaking glucose into two molecules of a compounds called pyruvate. In eukaryotes pyruvate enters the mitochondrion and is oxidised to a compound called acetyl CoA which enters the Citric acid cycle.
What occurs in the citric acid cycle of cellular respiration?
In the mitochondrion, a series of chemical reactions that are used by all aerobic organisms, generate energy through the oxidation of acetate—derived from carbohydrates, fats, and proteins—into carbon dioxide.
What occurs in the third stage of respiration (oxidative phosphorylation)?
The electron transport chain accepts electrons from NADH or FADH2, generated during the first two stages and passes these electrons down the chain. At the end of the chain the electrons are combined with molecular oxygen and hydrogen ions forming water. The energy released at each step of the chain is stores in a form the mitochondrion can use to make ATP from ADP. This mode of ATP synthesis is called oxidative phosphorylation because it is powered by the redox reactions of the electron transport chain.
What part of the mitochondrion is the site of electron transport and other processes like chemiosmosis that together make up oxidative phosphorylation?
The inner membrane
Oxidative phosphorylation accounts for what percentage of the ATP generated by respiration?
90% A smaller amount is formed directly in a few reactions of glycolysis and the citric acid-cycle by a mechanism called “substrate-level phosphorylation”
What is substrate level phosphorylation?
This occurs when an enzyme transfers a phosphate group from a substrate molecule to ADP rather than adding an inorganic phosphate to ADP as in oxidative phosphorylation.
For each molecules of glucose degraded to carbon dioxide and water how many molecules of ATP does the cell make?
32 molecules of ATP each with 7.3 cal/mol of free energy. Having so many molecules of ATP is more practical for the cell to spend on work.
What does the word glycolysis mean?
Sugar splitting
What is split during glycolysis?
Glucose a 6 carbon sugar is split into 2 three carbon sugars. these smaller sugars are then oxidised and their remaining atoms rearranged to form two molecules of pyruvate.
What are the two phases of glycolysis?
The energy investment phase and the energy payoff phase.
During the energy investment phase what happens to ATP?
The cell ‘spends’ ATP, but this investment in repaid with interest during the energy payoff phase.