Ch. 22 - Nutrition and Energy for Life

Macronutrients

Substances that are needed by the body in large amounts

• Include carbohydrates, lipids, and proteins

Micronutrients

Substances that are needed by the body only in small amounts

• Classified as either vitamins or minerals

• Some are utilized in enzymes

Other Essential Nutrients

• Water

  • Constitutes 45%–75% of the human body mass

• Fiber -

  • Prevents or relieves constipation by absorbing water and softening the stool for easier elimination

Nutrition Labeling and Education Act of 1990

brought changes to the regulations that define what is required on a food label

• includes creation of daily values (DVs)

Daily Values (DVs)

Reference values developed by the FDA specifically for use on food labels

includes:

• Reference Daily Intakes (RDIs): Standards for protein, vitamins, and minerals used on food labels

• Daily Reference Values (DRVs): Standards for nutrients and food components such as fat and fiber that are important for health

FDA

The Food and Drug Administration

• they finalized the Nutrition Facts label for packaged foods, which lets consumers make better informed food choices

• Uses 2000 Calories as a standard for energy intake when calculating DRVs

• Reviews and revises the guidelines every 5 years

1 nutritional Calorie is equivalent to…

1 kcal of energy

USDA

U.S. Department of Agriculture

• issued the MyPlate food guide to replace the MyPyramid posters with new recommendations

Carbohydrates

Main dietary source of energy

• Provide useful materials for the synthesis of cell and tissue components

• Considered to be fattening

  • Excess calories are bc of high-calorie foods eaten with the carbs

  • Ex) Bread is eaten with butter, a high-energy lipid

Simple vs. Complex Carbs

Simple:

• includes monosaccharides and disaccharides, aka sugars

Complex:

• Include the polysaccharide starch, composed of amylose and amylopectin

• Cellulose has a non-nutritive role as fiber bc it cannot be digested by humans

Lipids

About 95% of lipids in the body and in foods are triglycerides

• Provides more than twice the energy of a carbohydrate

• Contain some fat-soluble vitamins and help carry them through the body

• Include essential fatty acids, which must come from diet

• Improves the texture of foods and absorbs and retains flavors

• Prolongs satiety as they are digested more slowly than other foods

Lipids in Diet

research shows a correlation between the consumption of too much fat and the wrong type of fat and obesity and cardiovascular disease

• Moderate amount of fat is needed in a diet

• Many people consume more fat than required

• monounsaturated fats are better fats for your health

Proteins

Proteins are the only macronutrients with an established RDI (Reference Daily Intake)

• Used in the body to aid in:

  • Production of new tissue as the body grows

  • Maintenance and repair of cells

  • Production of enzymes, hormones, and other important N-containing compounds of the body

  • Supplies energy (4 calories/gram)

• Broken down to individual amino acids that are absorbed into the body's amino acid pool

What makes something a complete protein?

if they contain all the essential amino acids in the proportions needed by the body

How does the RDI for protein for pregnant women differ from the average adult

Average protein intake for adult is 50g

• it is higher for pregnant and nursing mothers

The Essential Amino Acids:

• 9 of them

• have to get these from our diet because our body doesn’t make enough of them

• not every amino acid is essential

Vitamins

Organic compounds that cannot be produced by the body in the amounts needed for good health

2 Types:

• Water soluble

• Fat soluble

Water-Soluble Vitamins

• Highly polar in nature

• Function as coenzymes, minus vitamin C

• Excess is excreted through the kidneys

• go through body faster than fat soluble vitamins

• includes Vitamin C, B₁, B_2, B₆, B_12, and niacin, folic acid, pantothenic acid, and biotin

Fat-Soluble Vitamins

• Have nonpolar molecular structures

• Function like hormones

• Excess accumulation in body tissues can lead to toxic effects

• stay in body longer than water-soluble vitamins

• Includes Vitamin A, D, E, and K

Minerals

Metals or nonmetals used in the body in the form of ions or compounds

• includes major minerals and trace minerals

Major Minerals

Found in the body in quantities greater than 5g

• Examples

  • Calcium and Phosphorus - Primary inorganic structural components of bones and teeth

  • Na, K, Cl, and Mg - Ions distributed throughout the body’s fluids

  • Sulfur

Trace Minerals

Found in the body in quantities less than 5g

• Components of vitamins, enzymes, hormones, or specialized proteins

• Examples : Fe, Mn, Cu, and I

What is the ultimate source of energy used in all biological processes?

the sun

What does the enormous energy output from the sun come from?

the fusion of hydrogen atoms into helium atoms

Role of the sun in plants:

A portion of the liberated energy reaches the Earth’s surface and is absorbed by chlorophyll pigments in the plants

• Big part of photosynthesis

• Energy stored in plants is obtained by all animals directly or indirectly

Photosynthesis

Photosynthesis converts CO 2 and H2O into glucose, and then into starch, triglycerides, and other storage forms of energy

Cellular Respiration

plants and animals combine energy-rich compounds with oxygen from the air to produce CO 2 and H 2O and release energy

• Portion of energy released is ATP

• Remainder of the energy is released as heat

Energy Flow Chart

1. Nuclear fusion from the sun

2. Photosynthesis

3. Cellular Respiration

4. Production of ATP and heat

5. ATP either synthesizes biomolecules, muscle contraction, or active transport

Carbon Cycle

Some of Earth’s carbon compounds are repeatedly recycled by living organisms

Metabolism

sum of all reactions involved in maintaining a living cell

• Categories

  • Catabolism

  • Anabolism

Catabolism

All reactions that lead to the breakdown of

biomolecules

• releases energy

Anabolism

All reactions involved in the creation of

biomolecules

• requires energy

Metabolic Pathway

Sequence of reactions used to produce one product or accomplish one process

• Ex) - Citric acid cycle and ETC

Catabolism of Food - Stage 1

Large molecules are digested into smaller ones via hydrolysis

Catabolism of Food - Stage 2

Small molecules are broken down into simpler units, primarily the two-carbon acetyl portion of acetyl coenzyme A (acetyl CoA)

Catabolism of Food - Stage 3

Common catabolic pathway

• Reactions of the CAC plus the ETC and oxidative phosphorylation

• Purpose is to convert chemical energy in foods to ATP molecules

Structure of ATP

• Adenosine portion has adenine bonded to a ribose

• Triphosphate portion is bonded to the ribose

• ATP molecule has a charge of –4

• ATP is complexed with Mg 2+ in a 1:1 ratio

• Net charge of complex is –2

• Triphosphate end is essential in the transfer of biochemical energy

• Is used quickly once it is formed

Hydrolysis of ATP in water:

• Results in the transfer of a phosphate group from ATP to water

• Products are adenosine diphosphate (ADP) and an inorganic phosphate, Pi

• reaction releases free energy (ΔG), which is used in cellular processes that require input of energy

• ATP is a high-energy compound

  • generates a great amount of free energy during hydrolysis

ΔG

has a positive value when energy is absorbed and a negative value when energy is released

• Represented by ∆G° when measured under standard conditions

• Represented by ∆G°′ when measured at body conditions

The ATP-ADP Cycle

Plays a central role in linking energy production with energy utilization

Mitochondria

organelles where reactions of the common catabolic pathway occur

• Known as cellular power stations

• Contain both inner and outer membranes

• Folds of the inner membrane are called cristae

• Gel-filled space that surrounds the cristae is called the matrix

Coenzyme A (CoA)

Central compound in metabolism and is a part of acetyl CoA

• Derived from the B vitamin pantothenic acid (B5)

• Contains:

  • Phosphate derivative of ADP

  • b-mercaptoethylamine

  • sulfhydryl group (—SH)

• transfers acyl groups

  • Acyl groups are linked to CoA by the sulfur atom in a thioester bond

Thioester bond

Nicotinamide Adenine Dinucleotide (NAD+ )

Derivative of ADP and the vitamin nicotinamide

• Reactive site is located in the nicotinamide portion

• Acts as an electron acceptor

  • accepts 2 electrons and 1 proton during oxidation of a substrate, which forms NADH

How NAD+ accepts electrons:

NAD+ Reaction

Flavin Adenine Dinucleotide (FAD)

Derived from ADP and the vitamin riboflavin

• Reactive site is located within the riboflavin ring system

• Substrates of enzymes that use FAD as the coenzyme give up two electrons

  • FAD accepts both the H atoms Involved in the reactions in which a —CH2—CH2— portion of the substrate is oxidized to a double bond

FAD Reactions