Unit 4 Exam: Diet & Nutrition

Nutrients

Promote normal growth and development.

Major nutrients (macronutrients)

Carbohydrates, proteins, lipids

Micronutrients

Vitamins and minerals

MyPlate guidelines (USDA)

½ of plate = fruits & vegetables

Other half = grains & proteins

How many essential nutrients are there? Why do we need them in our diet?

Essential nutrients = 40-50

Must be in the diet for healthy physiology b/c body doesn’t make enough

Carbohydrates include….

sugars from monosaccharides, disaccharides, and polysaccharides

Glucose

Used by cells to get energy (i.e., make ATP). Neurons + Red blood cells rely on it.

• type of carb

Insoluble polysaccharides

Such as: cellulose, provide fiber for intestinal health and defecation.

Soluble fibers…

are found in some foods.

Most abundant dietary lipids are…

triglycerides (neutral fats)

Saturated fats

“With hydrogen”

Found in meat and diary

Unsaturated fats

Found in olive oil and seeds

Essential fats include:

Linoleic and linolenic acids

Found in most vegetable oils

Cholesterol

Found in egg yolks, milk, meat, and liver secretions

What are lipids use for in the body?

• Cell membrane stability

• Myelin in the nervous system

• Absorption of fat-soluble vitamins

• Energy storage and a source in some conditions

• Chemical messengers (prostaglandins)

• Adipose tissue for cushioning and insulation

Complete proteins

Proteins that have all essential amino acids.

Protein sources

Dairy, meat, fish, soybeans

Incomplete proteins

Lack one or more of the 8 essential amino acids

Amino acids from dietary proteins may be used to:

• Synthesize new proteins (needs all 20 amino acids)

• Be broken down to make energy

Nitrogen balance is …

critical determinant of how amino acids are used

Positive nitrogen balance

Tissues build proteins under these conditions:

• all needed amino acids are present

• sufficient caloric intake from carbs/fats

• favorable hormone levels

  • low levels = stress hormones

  • high levels = growth hormones

Negative nitrogen balance

Not much protein is built (protein mass can be lost)

• person is stressed or malnourished

Vitamins (micronutrients)…

mostly serve as coenzymes to assist in catalysis.

Fat-soluble vitamins

A, D, E, and K

• Vitamin A in rhodopsin of rod photoreceptors for night vision

Water-soluble vitamins

B-complex and C

• Folic acid (B9) = important for DNA replication in fetal development b/c lack of it leads to birth defects

• B12 = important for blood cell production

Minerals (like Calcium—Ca++)

• Adds strength to bones and teeth

• Messenger to influence protein functions

  • Ca++ binds to calmodulin in smooth muscle

• Excitability

  • Ca++ entry depolarizes heart cells for E-C coupling in a heart beat

Metabolic processes are either…

Anabolic (building big molecules)

or

Catabolic (breaking down big molecules into smaller parts)

Cellular respiration

Food molecules are broken down and their energy is used to make ATP.

3 stages of processing energy-containing nutrients:

1. GI system digests + absorbs nutrients

2. Convert small nutrient molecules into a form that can produce energy

3. Aerobic production of energy in mitochondria

Oxidation-reduction (redox) reactions

Involves transfer of electrons from one molecule to another

When a molecule loses electrons, ….

it is oxidized (often occurs with loss of H or gain of O).

• redox reaction

When a molecule gains electrons, …..

it is reduced (often occurs with gain of H or loss of O).

• redox reaction

In the body, redox reactions are….

catalyzed by enzymes with the help of coenzymes that act as electron carriers.

Coenzymes such as ______ and ______ accept high-energy electrons (often along with H) from nutrient molecules during their breakdown.

1. NAD⁺

2. FAD

Where do reduced coenzymes (NADH, FADH₂) deliver electrons? Why are they delivered here?

Deliver to = Electron transport chain

They are delivered here b/c this is where the energy released is used to produced ATP.

Substrate-level Phosphorylation

An ATP synthesis mechanism

1. A phosphate group is directly transferred from a high-energy intermediate molecule to ADP to form ATP.

2. This process is enzyme-catalyzed and does not require oxygen or the electron transport chain.

3. Occurs during pathways like glycolysis and the citric acid cycle.

Oxidative Phosphorylation

An ATP synthesis mechanism

1. Electrons carried by NADH and FADH₂ pass through the electron transport chain in the inner mitochondrial membrane.

2. The membrane released is used to pump protons (H⁺) across the membrane, creating an electrochemical gradient.

3. As H⁺ flows back through ATP synthase, this gradient powers the synthesis of ATP from ADP and Pi.

4. Oxygen serves as the final electron acceptor, allowing the process to continue.

Carbohydrate Metabolism

Glucose + Oxygen react to make Carbon Dioxide, Water, and Energy (that will make ATP)

• Similar to Cellular Respiration Equation

Glucose entry

Usually facilitated diffusion (mostly when insulin calls for placement of glucose transporters into cell membranes).

• Step 1 of carb metabolism

Glycolysis

“Sugar splitting” in the cytosol (no O2 needed)

• Step 2 of carb metabolism

Phases of Glycolysis:

1. Investment of 2 ATP to add phosphate groups to glucose

2. Sugar cleavage: split glucose into two 3-C fragments

3. 3-C fragments are oxidized into pyruvic acid;

   • Since 4 ATP are made and 2 were invested, it results in a net gain of 2 ATP:

   • Also, NAD+ reduced to NADH

Pyruvic acid pathway

Dependent on Oxygen availability

No O2: pyruvate ferments to lactic acid

With adequate O2: pyruvate and NADH enter mitochondria to start aerobic respiration

• Step 3 of carb metabolism

Aerobic pathways begin

• Pyruvic acid enters mitochondrion through active transport

• Converted to Acetyl CoA (removes 1 Carbon and adds CoA)

• Krebs Cycle (Citric Acid Cycle)

  • Step 4 of carb metabolism

Krebs Cycle (Citric Acid Cycle)

1. Occurs in mitochondrial matrix

2. Acetyl CoA + Oxaloacetic acid → citric acid which is then oxidized

3. The cycle is a multistep process yielding:

   1. 2 ATP

   2. Some NADH

   3. FADH2

   4. CO2

   5. H+

Electron Transport Chain

• Requires O2 to take electrons from reduced coenzymes (making H2O)

• Generates H2O and pushes H+ out of the matrix to build a very high concentration

• As H+ flows back into matrix, it drives oxidative phosphorylation (makes ATP) via ATP synthase (H+ passage turns ATP synthase on)

  • Step 5 of carb metabolism