Metabolic Fuels -Lecture 1

Vocabulary flashcards covering key concepts from the Metabolic Fuels lecture notes.

ATP

The energy currency of the cell; produced during oxidative metabolism and consumed to power energy-requiring processes.

Dietary components other than xenobiotics can be used to what?

Generate energy or build body components

What will happen to most xenobiotics?

Detoxified or eliminated

What happens to dietary fuels

Digested and then absorbed and transported

Do vitamins, minerals, water and xenobiotics undergo changes in the digestive system before being absorbed and transported?

No

What is the main fate of xenobiotics, vitamins, and minerals that do not have storage pathways?

Detoxification and waste disposal pathways

What happens to fuel not used for biosynthesis, thermogenesis, or energy production?

Will be stored

ATP is what of the cell?

Energy currency

How is ATP made?

Large biomolecules are broken down by oxidative reactions

Each cell must generate its own…

ATP

Metabolism =

Catabolism + anabolism

Energy production via oxidation of …

Carbs, lipids, proteins

Energy utilization …

Biosynthesis, detoxification, muscle contraction, active ion transport, thermogenesis

what is oxidized to CO2 to generate ATP?

Glucose, fatty acids and amino acids

What are used to reduce O2 to H2O, making ATP?

Electrons released from oxidative reactions

Oxidation is …

Loss of electrons

In organic molecules oxidation often means …

Gaining bonds to oxygen or losing bonds to hydrogen

What is the central hub of metabolism?

the tricarboxylic acid cycle (citric acid cycle or Krebs cycle)

When is energy released?

During the movement of electrons through the ETC

Most carbs are digested to form…?

glucose

What are the major dietary carbs?

Starch, sucrose, lactose, fructose, glucose

What are the polysaccharides starch and glycogen composed of?

Glucose monomers linked by O-glycosidic bonds

What are the 2 simpler disaccharides?

Sucrose and lactose

What is an isomer of glucose?

Fructose

What do starch and glycogen differ in?

Number of branch points

Where should most carbs come from in diet?

Whole Foods: veggies, fruit, whole grains - digested slowly and has dietary fibers

What carbs should be limited?

Simple carbs - refined sugars

Carbs should provide ….% of total calories?

45-65%

Complete oxidation of carbs produces how many kcal/g?

4 kcal/g

What is the glycemic index of a food?

Indication of how rapidly blood glucose levels rise after consumption of am amount of food that supplies 50g of carbs

What kinds of carbs have lower glycemic indices?

Complex carbs and simpler carbs eaten with dietary fiber

What is a a kilocalorie?

Amount of energy required to raise the temp of 1L of water by 1oC

What is the majority of dietary fats?

Triglycerides - composed of 3 fatty acid chains attached to a glycerol backbone

What are the three types of fatty acids?

• saturated - no double bonds

• Monounsaturated - MUFAs - only 1 double bond

• Polyunsaturated - PUFAs - multiple double bonds

Animal fats are high in what type of fatty acids?

Saturated Fatty acids

What are oils derived from plants and fish rich in?

MUFA and PUFA

Cholesterol is found in foods containing animal fats but us not a source of what?

Metabolic fuel

Fats should account for what percent of daily calorie intake?

20-35%

Saturated fats should account for what percent or less of calorie intake?

10%

How many kcal/g does complete oxidation of triglycerides produce?

9 kcal/g

What are the 4 essential fatty acids that can’t be made by the body and are used for biosynthesis of some hormones?

• linoleic acid

• A-linoleic acid

• Eicosapentaenoic acid (EPA)

• Docosahexaenoic acid (DHA)

Which 2 of the 4 essential fatty acids come from plants?

• linoleic acid

• A-linoleic acid

Which 3 of the 4 essential fatty acids come from fish and some plants?

• Eicosapentaenoic acid (EPA)

• Docosahexaenoic acid (DHA)

What does consumption of saturated fats increase levels of?

LDL serum cholesterol “bad”

What do trans fats elevate?

LDL and lower “good” HDL serum cholesterol

What are proteins digested to?

Amino acids

how many kcal/g does complete oxidation of amino acids(proteins) produce?

4 kcal/g

How many of the 20 amino acids used in the body are essential?

9 - can’t be synthesized by the body

How many of the 20 amino acids used in the body are conditionally essential?

3

What does the mnemonic PVT TIM HiLL stand for?

P- phenylalanine

V - Valine

T - threonine

T - Tryptophan

I - Isoleucine

M - methionine

H - Histidine

L - leucine

L - lysine

What are the 3 conditionally essential amino acids?

• Cysteine

• Arginine

• Tyrosine

What’s the mnemonic for the conditionally essential amino acids plus the 9 essential amino acids?

PVT TIM HiLL has a CAT that says ARGGGGG

What is special about histidine?

It is efficiently recycled - even though it can’t be made by the body, the dietary requirements are low

What are amino acids obtained by digestion of dietary proteins first used to replace?

Amino acids lost by protein turnover and for biosynthesis of nitrogen containing molecules

What happens to any remaining amino acids after replacing ones lost by protein turnover?

Used as a fuel source or converted to fatty acids or glycogen for fuel storage

When is someone in nitrogen balance?

When the inputs and outputs to the amino acids pool are equal

How many g/day of protein is usually lost?

400g

When is nitrogen equilibrium achieved?

Intake of nitrogen - in protein - is sufficient enough to replace nitrogen lost in urine, feces, sweat, hair and skin

When does a positive nitrogen balance mean?

Nitrogen excretion is less than nitrogen intake (taking in lots)

What does a negative nitrogen balance mean?

Nitrogen excretion is more than nitrogen intake

Will a pregnant woman be in pos or neg. N balance?

positive - building new tissue

Will a woman who had open heart surgery a day ago have a pos or neg n balance?

Negative - hypercatabolic state - break down protein

What will the N balance of a person whose diet is deficient in phenylalanine be?

Negative

Healthy diets include protein intake of what percent of total calories?

10 - 35%

At a minimum, protein intake should not be less than what g/kg body weight?

0.8 g/kg - minimal amount of protein needed to maintain muscle mass in the average adult

What does chronic high protein intake of >2 g/kg/day result in?

digestive, renal or vascular abnormalities

What should vegans take care to obtain?

Obtain adequate amounts of essential amino acids to avoid going into negative nitrogen balance

What are the components of a good MyPlate?

50% fruits and veggies, 25% grains, 25% protein, a side of dairy

Complete oxidation of ethanol produces how many kcal/g?

7 kcal/g

What does drinking alcohol do other than an empty calorie content?

• inhibit intestinal absorption of some vitamins

• Lead to hepatic steatosis, eventually cirrhosis

• Cause lactic acidosis

When more fuel is consumed than is immediately needed from cellular functions, the excess glucose, amino acids, and fats or ethanol are used to make what?

Gylcogen or triglycerides

glycogen is a polymer of what?

Glucose

Where is glycogen primarily stored?

In muscle tissue and the liver

What is liver glycogen used for?

To maintain constant blood glucose levels between meals

What is muscle glycogen used for?

Supplies energy for muscle contraction during exertion

Why is it not practical to use glycogen as the primary fuel storage form?

• not as energy dense as triglycerides 4 vs 9

• It is polar and associates with water, glycogen binds with about 4 times its weight in water

glycogen creates about how much more than its mass rather than storing it as triglycerides?

10x

Where are triglycerides primarily made and stored?

Made in the liver and stored in adipocytes

About what percent of total stored calories are in the form of triglycerides?

85%

What is 1lb of body fat equal to?

3500 kcal stored energy

What happens to proteins during fasting?

Degraded to release amino acids for fuel

Are excess dietary calories converted to amino acids to. Make proteins for fuel storage?

No

Catabolism

Metabolic pathways that break down molecules to release energy.

Anabolism

Metabolic pathways that build larger molecules from smaller units.

Metabolism

All chemical processes in the body, including both catabolic and anabolic reactions.

Oxidation

Loss of electrons in a chemical reaction; in biology, often involves gain of oxygen or loss of hydrogen.

TCA Cycle (Citric Acid Cycle / Krebs Cycle)

Central hub of metabolism where acetyl-CoA is oxidized to CO2, generating electron carriers for ATP production.

Electron Transport Chain

A series of protein complexes that transfer electrons to generate ATP via oxidative phosphorylation.

Carbohydrates

Macromolecules digested to glucose; include starch, sucrose, lactose, fructose, and glucose; starch/glycogen are glucose polymers.

Glycemic Index (GI)

A measure of how rapidly blood glucose rises after consuming 50 g of carbohydrate; lower for complex carbs and fiber.

Glycogen

Storage form of glucose in liver and muscle; maintained blood glucose and supplied energy; binds water, making it less energy-dense per mass.

Triglycerides

Primary form of dietary fat; three fatty acids attached to glycerol; energy yield ~9 kcal/g.

Saturated Fatty Acids

Fatty acids with no double bonds; common in animal fats; associated with higher LDL cholesterol.

Monounsaturated Fatty Acids (MUFA)

Fatty acids with one double bond; abundant in certain plant oils; generally heart-healthy.

Polyunsaturated Fatty Acids (PUFA)

Fatty acids with two or more double bonds; include essential fatty acids.

Essential Fatty Acids

Fatty acids that cannot be synthesized by humans: linoleic acid, alpha-linolenic acid, EPA, DHA; required for various bodily functions.

Cholesterol

Sterol found in animal fats; not a metabolic fuel.

Dietary Fat Recommendations

Fat should be 20-35% of daily calories; saturated fat ≤10%; trans fats avoided.

Alcohol (Ethanol) as Fuel

Complete oxidation yields ~7 kcal/g; can inhibit vitamin absorption and contribute to liver disease.

Proteins / Amino Acids

Digested into amino acids; complete oxidation yields ~4 kcal/g.