Unlocking the Secrets of Metabolism

Metabolism

• Metabolism is “the sum of all the chemical reactions that occur

within living organisms”.

• Metabolic reactions are controlled by enzymes.

Metabolism

Metabolism Vocabulary

Intracellular vs Extracellular

Linear vs cyclical

Anabolic vs catabolic

Multiple Choice

What is metabolism?

• The breakdown of molecules into smaller units

• The sum of all the chemical reactions that occur within living organisms

• The process of photosynthesis

• The formation of molecules from smaller units

Metabolic reactions can be:

Intracellular

The metabolic reactions occur within a cell,
such as:

•Protein synthesis occurring in the nucleus (transcription
and RNA processing) and cytoplasm (translation and
protein folding)

•Cellular respiration occurring in the cytoplasm (glycolysis)
and mitochondria (Krebs cycle and ETC)

Extracellular

The metabolic reactions occur outside a cell,
such as:

•Cells of the pancreas secreting enzymes that chemically
digest food in the alimentary canal.

Multiple Choice

Where do intracellular metabolic reactions occur?

• Within a cell

• Outside a cell

• In the bloodstream

• In the nervous system

Metabolic Pathways

• A series of ‘steps’ from a starter molecule or precursor

toward a final end product.

• Each step is catalyzed by a different enzyme.

Enzyme B

Enzyme A

Intermediate

chemical

Precursor
chemical

End product

When an enzyme is
written on a reaction
arrow, it means the
enzyme catalyzes the
reaction shown

To catalyze means

to “speed up” a

reaction

Multiple Choice

What regulates metabolic reactions in living organisms?

• Fatty acids

• Enzymes

• ATP

• Amino acids

Multiple Choice

What is the role of an enzyme in a metabolic pathway?

• To transport molecules within the cell

• To store energy in the form of ATP

• To speed up a reaction

• To regulate blood glucose levels

Metabolic Pathways

can be either linear or cyclical

Linear pathway

Cyclical pathway

LINEAR PATHWAY

• The digestion of starch is

an example of a LINEAR
metabolic pathway.

CYCLICAL PATHWAY

Some metabolic pathways operate in a cyclic way. The scientists who elucidated two

of the important biological cycles have had their names attached to the pathways by

the scientific community.

Calvin cycle of photosynthesis

Kreb’s cycle of respiration

Only the names of the reactants and products are shown. In this case, the names of the enzymes doing the reaction are NOT written.

Multiple Choice

What are the two types of metabolic pathways?

• Linear and cyclical

• Linear and branched

• Cyclical and branched

• Cyclical and circular

Example:

ANABOLIC

CATABOLIC

Glycogenesis: the formation of glycogen, the primary
carbohydrate stored in the liver and muscle cells of
animals, from glucose. Glycogenesis takes place when
blood glucose levels are sufficiently high to allow excess
glucose to be stored in liver and muscle cells.

Glycogenolysis: the breakdown of glycogen, the primary
carbohydrate stored in the liver and muscle cells of
animals, into glucose. Glycogenolysis takes place in liver
and muscle cells when blood glucose levels are low.

Metabolic Pathways

ANABOLIC

CATABOLIC

Multiple Choice

What is the process of glycogenesis?

• The breakdown of glycogen into glucose

• The breakdown of starch into glucose

• The formation of glycogen from glucose

• The breakdown of glucose into glycogen

Multiple Choice

What is the difference between anabolic and catabolic pathways?

• Anabolic pathways are linear, while catabolic are cyclical

• Anabolic pathways require energy, while catabolic pathways release energy

• Anabolic pathways occur outside the cell, while catabolic pathways occur inside the cell

• Anabolic pathways break down molecules, while catabolic pathways construct molecules