, Metabolism, Nutrition, and Energetics
● body builds energy reserves when nutrients are abundant and mobilizes them
when nutrient supply is short supply.
● The nervous and endocrine systems control the storage and mobilization of E
reserves.
Chemicall Reactions
25-1 Metabolism = all catabolic + anabolic reactions + energetics =all chemical
and physical changes in the body
● Energetics = the ow and transformation of energy one form to another
● Cells are chemical factories that break down organic molecules to obtain
energy. E used to make ATP from ADP and Pi .
● Reactions within mitochondria provide most of the energy a typical cell needs.
● mitochondria ATP provides energy to both anabolism and cell functions
● cells must have a reliable supply of oxygen and nutrients (water, vitamins,
mineral ions, and organic substrates).
● Substrates are the substances acted on by an enzyme.
Metabolism
● catabolism (catabolic reactions) - converts large molecules into smaller ones
● anabolism (anabolic reactions). converts small molecules into larger ones.
● Energy-rich macromolecules; fats CHO protein
● The pathways making up these reactions extract energy from nutrients,
transfer and use energy, and build and store excesses for later use.
● Nutrients, the components in food, such as water, vitamins, mineral ions,
CHO, fats, and proteins, a
● All the available nutrient molecules distributed in the blood form a nutrient pool
Euriction
e
ic turnover
Turn
glucose
into fat
Growth/cell division Triglycerides
special process
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, Catabolism
1. In the cytosol. Fats are broken down into fatty acids and glycerol; CHO -x->
digest
-
glucose; and proteins -x-> amino acids.
Stomach
small intest ● fat catabolism involves lipolysis (fat breakdown),
mouth
● CHO catabolism involves glycogenolysis (breakdown of glycogen into glucose)
and glycolysis (breakdown of glucose into pyruvate).
● Lungs absorb O2, digestive absorbs nutrients. cardiovascular system delivers
for cell absorption/feeding to make ATP
Anabolism
● uphill” process - involves the formation of new chemical bonds.
● require more amino acids
● Cells synthesize new organic components for 4 basic reasons:
● 1) Carry Out Structural Maintenance or Repairs. most structures in the cell are
temporary. continuously replace membranes, organelles, enzymes, and
structural proteins. metabolic turnover
● 2) To Support Growth. Cells preparing to divide increase in size and
synthesize extra proteins and organelles.mitosis vs meiosis.
● 3) To Produce Secretions. Secretory cells must synthesize and transport
secretions to the interstitial uid
● 4) To Store Nutrient Reserves.
● a period of emergency - extreme activity, inadequate nutrients in the
bloodstream
● In lipogenesis (fat formation), triglycerides are the most abundant storage
form. adipose tissue
● In glycogenesis (glycogen formation), CHO are stored as glycogen, a
#Issursenes branched chain of glucose molecules. If glucose is unavailable, it may be
Liver synthesized through the process of gluconeogenesis.
adipose ● Muscle cells and liver cells store glucose in the form of glycogen, but
muscle
-
adipocytes and liver cells store triglycerides.
Neural ● Proteins are the most abundant organic components in the body.
other Liver is a local point of metabolic regulation and control
↓
No reserves
small
reserves Neural
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, ● when energy is available, cells synthesize additional proteins.
● When glucose and fat are low the body will break down protein as a fuel
source.
● Mitochondria creates cell E so cell can make ATP. Mitochondria is feed by
cell’s nutrient pool
● Mitochondria is a picky eater: They accept only speci c organic molecules
● For this reason, chemical reactions in the cytosol take whichever organic
nutrients are available and break them down into smaller fragments that the
mitochondria can process. The mitochondria then break the fragments down
further, generating CO2, H2O, and ATP.
● ATP made by oxidative phosphorylation. involves the oxidation of high-energy
carrier molecules from the citric acid cycle and the phosphorylation of ADP to
form ATP.
Energetics
● energy and nutrient requirements of each tissue is different due to its make-up
and function (activity level)
● requirements vary from moment to moment (resting versus exercising), hour to
hour (sleep versus awake), and year to year (growing child versus adult).
● Understanding energy requirements is one aspect of energetics, the study of
the ow of energy and its transformation.
Oxidation and Reduction - chemical reactions. redox reaction
● transfers of oxygen, H, electrons, or electrons
● Oxidation - gain oxygen, loss of H/electrons => decrease in potential energy
Oxidized ● Reduction - loss oxygen, gain of H/ electrons => increase in potential energy
● the electron donor is oxidized and the electron recipient is reduced.
● the reduced atom gains energy at the expense of the oxidized atom
● the reduced atom does not gain all the energy released by the oxidized
molecule. Some E is lost as heat. The remaining E may be used to do physical
or chemical
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