Unit 10 assignment 2
What is a metabolic pathway?
● A metabolic pathway is a series of chemical reactions that take place in a cell to carry
out specific biological processes. Cellular respiration is an example of a metabolic
pathway. It involves the breakdown of glucose molecules to produce ATP. The stages
of cellular respiration include glycolysis, link reaction, Krebs cycle, and oxidative
phosphorylation.
Stages of respiration
Glycolysis
Importance
● The importance of glycolysis is it’s the first stage in cellular respiration and it doesn't
need oxygen which makes it the main source of ATP during anaerobic conditions. It
also provides a source of energy for many cellular processes and it is the initial stage
for both aerobic and anaerobic respiration.
Process of glycolysis
● Glycolysis is the initial step of respiration, and it
happens in the cytoplasm. The six-carbon
glucose molecule splits into two smaller,
three-carbon molecules known as pyruvate
during the glycolysis process. Since it doesn't
require oxygen to function, this step is anaerobic
and a component of both aerobic and anaerobic
respiration pathways. Glucose is phosphorylated
using the phosphate groups from two ATP
molecules. ADP and inorganic phosphate are the
byproducts of ATP hydrolysis. As a result, an
unstable molecule known as triose phosphate
(TP) is created, which divides into two molecules
with three carbons each. The hydrogen in TP
needs to be eliminated in order to convert it to
pyruvate. When the hydrogen is transferred to
the coenzyme NAD, reduced NAD (NADH) is
produced. When the hydrogen is taken out of TP,
it oxidises. The last stage of aerobic respiration,
oxidative phosphorylation, uses the link reaction,
decreased NAD, while pyruvate enters the
mitochondria for the subsequent phase of
respiration. Triose phosphate was converted to
pyruvate by producing four molecules of ATP.
Since two ATP molecules are needed for the first stage of glucose phosphorylation,
glycolysis produces a net gain of two ATP molecules.
, Link reaction
Importance
● The importance of the link reaction is it joins glycolysis and the krebs cycle by
converting pyruvate into acetyl-CoA. It also produces NADH which is an essential
electron carrier for oxidative phosphorylation. Without the link reaction, cells wouldn’t
be able to produce the energy needed for processes like DNA synthesis or muscle
contraction.
Process of link reaction
● Pyruvate is converted to acetyl coenzyme A (acetyl CoA) in the mitochondrial matrix
through a mechanism called the link
reaction. Reduced NAD and acetyl
CoA are produced as a result of this
cycle, but no ATP energy is produced.
Acetyl CoA is utilised in the Krebs
cycle, the next stage of aerobic
respiration, whereas decreased NAD
is used in oxidative phosphorylation.
When pyruvate loses one of its carbon
atoms during the link reaction, carbon
dioxide is produced. Now pyruvate is
converted into acetate (a 2-carbon
molecule) and hydrogen is eliminated
during this conversion, the coenzyme
NAD absorbs this hydrogen to
produce reduced NAD. The coenzyme A and acetate join together to form acetyl
CoA. Because of the link reaction's ability to convert one glucose molecule into twice
as much pyruvate, every glucose molecule travels through it twice. This means that
for every glucose molecule, 2 molecules of acetyl CoA, twice as much NADH and
twice as much carbon dioxide is created.
Krebs cycle
Importance
● The krebs cycle is an important process as it is needed for energy production,
biosynthesis and metabolic regulation. The krebs cycle is where high energy
electrons are produced which the electron transport chain needs in order for ATP
synthesis. The krebs cycle is important for the survival of cells and their function as it
supports cellular function by ATP synthesis, metabolic control and carbon
metabolism.
Process of krebs cycle
● The krebs cycle happens in the mitochondrial matrix. The reduced NAD and reduced
FAD that are produced by the Krebs cycle, also known as the citric acid cycle, are
two molecules that are necessary for oxidative phosphorylation. Acetyl CoA from the
link reaction reacts with oxaloacetate, a four-carbon molecule. After being partly
removed, the enzyme Acetyl CoA is reintroduced into the link process for additional
use. Six carbons are added to the molecule to form citric acid. When carbon and
hydrogen are taken out of citrate, reduced NAD and carbon dioxide are created. The
citrate yields a five-carbon molecule. The original 4-carbon molecule, oxaloacetate, is
