Energy and Respiration Flashcards
What is glycolysis and where does it happen?
Glycolysis is the splitting, or lysis, of glucose into two molecules of pyruvate, taking place in the cytoplasm of a cell.
What is the net ATP gain during glycolysis?
The net gain is two ATP molecules per glucose molecule. Four ATP molecules are produced, but two are used in the initial steps.
What is the first step of glycolysis called, and what happens during it?
The first step is phosphorylation, where phosphate groups are transferred from ATP to glucose, raising its energy level to make it more reactive. Two ATP molecules are used for each molecule of glucose. The donation of the first phosphate group produces glucose phosphate whose atoms are rearranged to form fructose phosphate. The second ATP molecule donates another phosphate group forming fructose 1,6-bisphosphate. Fructose 1,6-bisphosphate then breaks down to produce two molecules of triose phosphate.
How many ATP molecules are used in the phosphorylation step?
Two ATP molecules are used.
What happens to triose phosphate during glycolysis?
Triose phosphate is oxidized, and hydrogen is transferred to NAD, forming reduced NAD.
How many molecules of reduced NAD are produced per glucose molecule during glycolysis?
Two molecules of reduced NAD are produced.
What is substrate-linked phosphorylation, and when does it occur in glycolysis?
Substrate-linked phosphorylation is the direct transfer of a phosphate group from an intermediate substrate to ADP to form ATP, using energy provided directly from another chemical reaction. It occurs during the conversion of triose phosphate to pyruvate. In this case from a phosphorylated molecule to an ADP molecule.
What happens to the pyruvate produced at the end of glycolysis if oxygen is available?
Pyruvate moves into the mitochondrial matrix via active transport, where it undergoes further processing.
Explain the structure of an ATP molecule.
ATP is a phosphorylated nucleotide. An ATP molecule is made up of the base adenine, ribose sugar, and three phosphate groups.
State the uses of energy in living organisms.
- Substances must be moved across membranes against their concentration gradient by active transport.
- Movement requires energy. This can be inside a cell, such as transporting a protein from where it is made on a ribosome to the Golgi apparatus, or it can involve whole cells, tissues, or organs, such as contracting a muscle.
- Synthesizing large molecules from smaller ones, such as replicating DNA molecules or synthesizing proteins, always requires energy. This type of reaction is said to be anabolic.
Why is ATP the perfect energy providing molecule?
- The hydrolysis of a molecule of ATP can be done quickly and easily in whichever part of the cell the energy is required.
- The hydrolysis of one molecule of ADP releases a useful quantity of energy, enough to fuel an energy-requiring process in a cell, but not so much that it will be wasted.
- ATP is a relatively stable molecule in the range of pH that normally occurs in cells, it does not break down unless a catalyst such as the enzyme ATPase is present.
What is a substrate-linked reaction?
It is the transfer of phosphate from a substrate molecule directly to ADP to produce ATP using energy provided directly by another chemical reaction.
What is chemiosmosis?
It is the synthesis of ATP using energy released by the movement of hydrogen ions down their concentration gradient across a membrane in a mitochondrion or chloroplast.
Where does the link reaction take place?
The link reaction takes place in the mitochondrial matrix.
Describe the link reaction.
When pyruvate arrives in the matrix of mitochondrion, enzymes remove carbon dioxide and hydrogen from it. The removal of carbon dioxide is called decarboxylation. The removal of hydrogen is dehydrogenation. The remainder of the molecule combines with coenzyme A to produce acetyl coenzyme A. This process is known as the link reaction.
What is coenzyme A and what is its function?
Coenzyme A is a complex molecule composed of a nucleotide combined with a vitamin. A coenzyme is a molecule that is needed by an enzyme to catalyze a reaction, though it does not take part in the reaction itself. In this case, coenzyme A carries and supplies acetyl groups, which are needed for the conversion of oxaloacetate to citrate.
What are the inputs and outputs of the link reaction?
The hydrogen removed from pyruvate in the link reaction is transferred to NAD producing more reduced NAD. So the inputs are pyruvate, coenzyme A, and NAD, and the outputs are acetyl coenzyme A, carbon dioxide, and reduced NAD.
Where does the Krebs cycle take place?
In the mitochondria matrix.
