Energy Metabolism Flashcards
Define anabolic reactions, and give an example
Anabolic reactions: build compounds, uses energy (glucose + glucose → glycogen)
Define catabolic reactions and give an example
Catabolic reactions: breakdown compounds, releases energy (protein → amino acids)
Define ATP, and describe its 3 major functions in the body.
Adenosine triphosphate: a chemical that is body’s main source of energy. Mechanical work (muscular contraction) Chemical work (biosynthesis) Transport work (osmosis)
Mechanical Work
heart beat, breathing, movement
Chemical work
create new enzymes, protein synthesis, etc
Active transport
move items across cell membrane and throughout the body
Besides ATP, list the other 2 compounds produced in cells after food is completely metabolized.
CO2 and H20
Identify where energy metabolism occurs in the cell.
mitochondria
Identify the 3 major metabolic pathways through which the macronutrients are converted into energy.
glycolysis, TCA cycle, electron transport chain
Breakdown of carbohydrates
glucose → pyruvate via glycolysis; pyruvate → acetyl CoA → TCA cycle → ETC
Breakdown of fat
glycerol → pyruvate; fatty acids → acetyl CoA
Breakdown of protein
AAs → pyruvate (glucogenic); → acetyl CoA (ketogenic); or straight to TCA cycle
Glycolysis
6 carbon glucose becomes two 3 carbon pyruvate molecules (reversible reaction)
TCA Cycle
loss of CO2 from pyruvate and it becomes Acetyl CoA (irreversible reaction). The TCA cycle is a series of chemical reactions that cells use to convert the carbons of an acetyl group to CO2 while harvesting energy to produce ATP
ETC
Electron Transport Chain: the passage of electrons along a series of electron carriers. As electrons are passed from carrier to the next, small amounts of energy are released
Sources of glucose
carbohydrate food sources, body glycogen stores, and endogenous biosynthesis (some amino acids, glycerol → gluconeogenesis)
HSL
Hormone Sensitive Lipase: TG in adipose cells catabolized to glycerol plus free fatty acids with hormone-sensitive lipase (HSL). HSL activity increased by glucagon, growth hormone, epinephrine (decreased by insulin)
When does fatty acid oxidation work best?
When carbohydrates are available
Ketosis
Condition that results from the incomplete oxidation of fatty acids
When does ketosis occur
when low CHO intake or insufficient insulin. Acetyl CoA accumulates because fatty acids cannot enter TCA cycle (no glucose for oxaloacetate). Acetyl CoA → ketones
Outline the metabolic consequences of consuming an excessive amount of any macronutrient (in excess of the body’s energy/calorie needs).
Body stores little glycogen and lots of fat. No need for TCA cycle, so acetyl CoA accumulates from excess fatty acids, AAs and glucose. Acetyl CoA converted into triglycerides.
Lipogenesis
glucose and AAs become fatty acids
Symptoms of ketosis
Nausea, Fatigue, Constipation, Low blood pressure, Elevated uric acid, Stale foul taste in mouth, Fetal harm and still birth
Describe the fate of each macronutrient during short-term and prolonged fasting (starvation).
0-6 hours: Body uses glycogen and fat stores for energy (glycogenolysis: liver glycogen converted to glucose)
3-5 days: Body breaks down proteins to AAs for glucose (gluconeogenesis)
Starvation: Glucose still needed for some brain cells (from protein), shift to ketosis
Metabolism Regulation
Enzymes: availability, phosphorylation status, their presence and rate of activity are critica to chemical reactions in the body
Hormones: glucagon, insulin, epinephrine; low level of insulin promote gluconeogenesis, protein breakdown and lipolysis
Blood glucose concentration
ATP concentration: high ATP concentrations decrease energy-yielding reactions and vice versa
Liver
