Chapter 7 Proteins

What elements make up a protein?

Carbon, hydrogen, oxygen, and nitrogen

What are the building blocks (monomers) of proteins?

Amino acids

What are the parts of an amino acid?

Central carbon, hydrogen, amino group (NH₂), carboxyl group (COOH), and an R-group (side chain)

What makes each amino acid unique?

Its R-group (side chain)

How many amino acids are there total?

20

How many amino acids are essential?

9 (must get from diet)

How many are nonessential?

11 (body can make them)

What are “conditionally essential” amino acids?

Nonessential AAs that become essential during stress, illness, or infancy

What is a peptide bond?

The bond between two amino acids formed via a condensation reaction

What is a polypeptide?

A chain of 10+ amino acids

List the 4 levels of protein structure.

1. Primary – sequence of amino acids; 2. Secondary – coils & sheets from H-bonding; 3. Tertiary – 3D folding; 4. Quaternary – 2+ polypeptides

What is protein denaturation?

Loss of structure/function from heat, acid, salt, agitation

Where does protein digestion begin?

Stomach

What hormone triggers protein digestion?

Gastrin – stimulates HCl & pepsinogen

What does HCl do in protein digestion?

Denatures protein and activates pepsin

What does pepsin do?

Breaks large proteins into polypeptides & amino acids

What enzyme is released in the small intestine?

Proteases from the pancreas: Trypsin, chymotrypsin, carboxypeptidase

What enzymes are in the brush border?

Aminopeptidase, Dipeptidase, Tripeptidase

What is the final end-product of digestion?

Free amino acids

How are amino acids absorbed?

Active transport into enterocytes, then into bloodstream → liver

What is protein turnover?

Ongoing breakdown & resynthesis of body proteins

What are the steps of protein synthesis?

1. Transcription – DNA → mRNA; 2. Translation – mRNA → protein

What happens if the DNA sequence is wrong?

Protein may be abnormal (ex: sickle cell hemoglobin)

What is deamination?

Removal of the amino group (NH₂) forming ammonia (NH₃)

What happens to ammonia in the body?

Converted to urea, filtered by kidneys, excreted in urine

What is transamination?

Transfer of amino group to make a new nonessential amino acid

What is gluconeogenesis?

Making glucose from amino acids

Name 5 functions of proteins.

1. Structural – collagen, muscles; 2. Enzymes; 3. Hormones; 4. Transport; 5. Immune – antibodies

What does protein do for fluid balance?

Prevents edema by pulling fluid into blood vessels

How does protein affect pH balance?

Acts as a buffer to prevent acidosis or alkalosis

What is protein sparing?

Using carbs & fats for energy, saving protein for body functions

What is the RDA for protein?

0.8 g/kg body weight (for healthy adults)

What is nitrogen balance?

Positive – building tissue; Negative – breaking down tissue; Zero – equal intake & excretion

What makes a high-quality protein?

Contains all 9 essential AAs, highly digestible

What are complementary proteins?

Two plant proteins that together provide all essential amino acids (ex: rice + beans)

What is kwashiorkor?

Protein deficiency → edema, brittle hair, skin issues

What is marasmus?

Overall starvation → severe weight loss & wasting

What is marasmic-kwashiorkor?

Combo of both – edema plus severe muscle/fat loss

What conditions may result from too much protein?

Kidney strain, kidney stones, osteoporosis, heart disease

What causes food allergies?

Immune system reacts to proteins as foreign invaders

What is anaphylaxis?

Life-threatening allergic reaction → drop in blood pressure, difficulty breathing

What is celiac disease?

Autoimmune reaction to gluten → damages intestinal villi

What is PKU (Phenylketonuria)?

Genetic disorder → can’t convert phenylalanine to tyrosine, leads to brain damage if untreated

The health professional who will consider genetically driven dietary recommendations when helping people with their personalized nutrition plan is the ….

registered dietitian nutrionist

Every cell contians protein.

True

A food intolerance may occur after the consumption of nonprotein substances, such as:

Lactose, MSG, and short chain fermentable carbs

Where are dipeptides and tripeptides broken into amino acids?

Microvilli

Making dietary choices based on nutritional genomics, height, weight and health assessment is the concept of….

Personalized nutrition

Intolerance to wheat products, resulting in IBS-like symptoms is defined as….

non-celiac glutern sensitivity

There are….nonessential amino acids

11

What happens to peptides once they enter the absorptive cells?

They are broken down into amino acids.

After proteins are digested, most of the resulting amino acids are….

transported into absorptive cells

To determine a person's RDA for protein, multiply his or her weight in kilograms by….grams

0.8

A high-protein diet is defined as a protein intake of….of calories

20-35%

Following the digestion of proteins, most amino acids are first transported into….

Absorptive cells