Proteins (Chapter 6)

Polypeptides

10 or more amino acids

AMDR

10% to 35% of total kcal

Dipeptides

2 amino acids

Tripeptides

3 amino acids

Oligopeptides

4 to 9 amino acids

Denaturation

Alteration of a protein's three-dimensional structure, usually because of treatment by heat, enzymes, acid or alkaline solutions, or agitation.

Gluten

Protein found in wheat, rye and barley

Protein isolate

Protein powder that has been processed more than a protein concentrate to remove lower protein portions and collect pure protein fractions

Epigenetics

The study of heritable changes in gene function that are independent of DNA sequence. Example: malnutrition during pregnancy may modify gene expression in the fetus and affect long term body weight regulation in the offspring

Lower- Quality (incomplete) Proteins

dietary proteins that are low in or lack one or more essential amino acids -Limiting amino acids -All or none principle of protein synthesis -complementary proteins

High-Quality (complete) Proteins

dietary proteins that contain ample amounts of all 9 essential amino acids

What digestion steps take place in the stomach and small intestine?

Upper muscle in stomach relaxes to let food enter, and lower muscle mixes food with digestive juice

Kwashiorkor

marginal amount of calories and insufficient protein

Marasmus

starvation and insufficient protein and calories

Limiting Amino Acids

the essential amino acid in lowest concentration in a food or diet relative to body needs

Protein Synthesis

the formation of proteins by using information contained in DNA and carried by mRNA

Fate of Absorbed Amino Acids

~ Protein synthesis ~ Metabolized for fuel/energy (to some degree) ~ Stored as fat (in excess) - Can be converted to glucose if needed

positive protein balance

a state in which protein intake exceeds related protein losses, as is needed during times of growth

Protein Equilibrium

a state in which protein intake is equal to related protein losses; the person is said to be in protein balance

Gruel

a thin mixture of grains or legumes in milk or water (porridge)

Carbon Skeleton

amino-acid structure that remains after the amino group (-NH2) has been removed

Where and how does protein digestion begin?

begins in the mouth and continues in the stomach and small intestine

Complementary Proteins

-2 plant food protein sources that make up for each other's inadequate supply of specific essential amino acids -together they yield a sufficient amount of all 9 and so provide high quality (complete) protein for the diet Example: rice and beans or peanut butter on whole grain bread

Proteins are Made of Amino Acids

-20 different amino acids make up all proteins —9 essential amino acids —11 nonessential amino acids -composed of C, H, O, & N

Trends of Vegetarianism

-5% of U.S adults are self proclaimed vegetarians -12% of college students consider themselves vegetarian

Nonessential Amino Acid Examples

-Alanine -Arginine -Asparagine -Aspartic Acid -Cysteine -Glutamine -Glycine -Proline -Serine -Tyrosine

Essential Amino Acids

-Cannot be synthesized by humans in sufficient amounts or at all, must be included in the diet -9 essential amino acids aka Indispensable Amino Acids

Protein Digestion in the Small Intestine

-Cholecystokinin (CCK) signals pancreas to release enzymes -Enzymes break polypeptides into smaller peptides and amino acids —from the pancreas (e.g., trypsin) —from the intestinal cells — enzymes that digest tri- and di-peptides

Vegan Diets

-Complementary proteins -Nutrient deficiency concerns

Protein-calorie malnutrition (PCM)

-Consequences -stunted growth -increased risk of infection -Special cases of PCM -marasmus -kwashiorkor -a condition resulting from regularly consuming insufficient amounts of calories and proteins. The deficiency eventually results in body wasting, primarily of lean tissue, and an increases susceptibility to infections. Aka protein energy malnutrition (PEM)

Characteristics of Kwashiorkor

-Edema -mild to moderate weight loss -maintenance of some muscle and subcutaneous fat -growth impairment (60% to 80% of normal weight for age) -rapid onset -fatty liver

Protein digestion in the Stomach

-HCI denatures food proteins and kills pathogens -pepsin -Gastrin —thinking of an chewing food cause release into stomach —stimulates the release of acid and pepsin

Essential Amino Acid Examples

-Histidine -Isoleucine -Leucine -Lysine -Methionine -Phenylalanine -Threonine -Tryptophan -Valine

Health Benefits of Plant Proteins

-Low in saturated fat -No trans fat -High in fiber -High in antioxidants — vitamin A — vitamin E — vitamin C — Carotenoids -High in magnesium -Reduced risk of chronic diseases —cardiovascular disease —hypertension —cancer —type 2 diabetes —obesity

Nutrient Dense (plant sources of protein)

-Magnesium -Fiber -Folate -Vitamin E -Iron -Zinc -Calcium

Protein Organization

-Order of amino acids in a protein determines its ultimate shape -Protein's final shape determines its function in the body

Branched-Chain Amino Acids

-R-group has a branched structure -examples in human diet —Leucine —Isoleucine —Valine -can be used by muscles for energy needs -whey protein (from milk) is a rich source of BCAAs

Protein Requirements

-RDA -AMDR -Most of us eat more than the RDA for protein -Excess protein cannot be stored as protein —the amino acids are used for immediate or future energy

Nutrient Deficiency Concerns of Vegan Diets

-Vitamin B12 -Iron -Zinc -Calcium -Omega-3 Fatty Acids

Denaturation of Proteins

-alteration of a protein's 3 dimensional structure; loses biological activity —heat —enzymes —acid/alkaline solutions —agitation -cooking -digestion

Producing Vital Body Structures

-amino acid pool within cells can be used to form body proteins -structural components: Muscles & Bones -blood proteins -transport proteins -enzymes -hormones -immune proteins

Why Choose a Vegetarian Lifestyle?

-appropriately planned vegetarian diets can meet nutritional needs throughout life cycle -trends -common reasons

Contributing to Acid-Base Balance

-blood pH must be maintained within a narrow range (slightly alkaline) -proteins in cell membranes pump ions into and out of cells to maintain blood pH -amino acids act as buffers - compounds resist changes in pH in a solution

Protein Turnover

-breakdown and synthesis -cell responds to change -amino acids can be rejected -during any day, an adult breaks down and synthesizes about 250-300 grams of protein

Functions of Proteins

-building blocks of body components -fluid balance -acid/base balance -building blocks of hormones and enzymes -immune function -forming glucose -energy yielding (non preferred source) -contributing to satiety

Common Reasons for Vegetarianism

-ethics -religion -economics -health

RDA

-for sedentary adults: 0.8g/kg -athletes may require up to 1.7g/kg

Overview of Protein

-form important structures in body, make up key part of blood, help regulate body functions, can fuel body cells -body made up of thousands of proteins -contains: Nitrogen, Carbon, Hydrogen & Oxygen -North Americans generally consume more than they need to maintain health -functions —regulates and maintains body functions —provides essential form of nitrogen (in the form of amino acids)

Positive Protein Balance

-growth -pregnancy -recovery stage after illness, injury -athletic training

Protein Quality of Foods

-high quality (complete) proteins -lower quality (incomplete) proteins -animal & plant proteins can differ greatly in proportions of essential and nonessential amino acids —plant proteins in grains are often low in 1 or more of the 9 essential amino acids (incomplete) —animal protein generally contains all 9 essential amino acids (complete)

Food Protein Allergies

-immune system mistakes food protein for harmful invader -8 most common food allergens (account for 90% of blood related allergies) —soy —peanuts —tree nuts —wheat —milk —eggs —fish —shellfish -reactions range from mild intolerance to fatal allergic reactions -introducing allergenic foods early in life may prevent allergies

Negative Protein Balance

-inadequate protein intake (e.g., fasting, intestinal tract diseases) -inadequate calorie intake -fevers, burns, infections -increased protein loss (e.g., kidney disease)

Gluten Sensitivity & Celiac Disease

-incomplete gluten breakdown in small intestine leaves small peptides and amino acids -in people with a genetic predisposition for celiac disease, exposure to gluten leads to inflammatory response that damages the small intestine

Contributing to Immune Function

-key components of cells within immune system (e.g., antibodies) -malnutrition — immune dysfunction

Potentially Harmful Aspects of a High Protein Diet

-low intake of fiber, some vitamins, and phytochemicals -high intake of fat? -excessive intake of processed red meat is linked with colon cancer -increased burden on the kidney -may increase calcium loss in the urine -increase urine production — increase risk for dehydration

Plant Sources of Protein

-nutrient dense -source of phytochemicals -examples: legumes, beans, peas, nuts, and seeds

Using amino acid supplements is not considered safe

-overwhelms absorptive mechanisms in small intestine -excess amino acids may cause toxicity (e.g., methionine, cysteine, and histidine)

Peptide Bonds

-proteins linked together peptide bonds -bonds form between amino group of one amino acid and acid (carboxyl) group of another —dipeptides —tripeptides —oligopeptides —polypeptides -most proteins are polypeptides, 50 to 2000 groups

Contributing to Satiety

-provide feeling of satiety after a meal -higher protein diets are appropriate if nutritionally sound, being moderate in fat and having enough fiber

Characteristics of Marasmus

-severe weight loss -wasting of muscle and body fat (skin and bones appearance) -severe growth impairment (less than 60% of normal weight for age) -develops gradually

DNA Errors may Cause Disease

-sickle cell anemia -cancer

Protein Absorption

-small peptides and individual amino acids are taken up by active transport into absorptive cells that line that small intestine -absorbed peptides are further broken down to amino acids -amino acids (water soluble) are transported via the hepatic portal vein to the liver -fate of absorbed amino acids

Amino Acid Supplements

-sometimes used by athletes and dieters -the right amount of protein will aid athletic performance -using amino acid supplements is not considered safe

Forming Hormones and Enzymes

-thyroid hormones are made from tyrosine -insulin hormone composed of 51 amino acids -most enzymes are proteins

Increasing Plant Proteins

-try the veggie burger -sprinkle seeds, nuts on salad -peanut butter on whole wheat bread -choose beans with taco seasoning instead of beef or chicken for taco filler

Providing Energy

-typically, carbohydrates and fats are metabolized for fuel, but in some circumstances, proteins can yield energy — prolonged exercise — calorie restriction -amino group from amino acid is removed, and the remaining carbon skeleton is metabolized for energy needs -increase in urea production -protein is a costly source of calories

Food Planning for Vegetarians

-vegan -fruitarian -lactovegetarian -lactoovovegetarian -concerns for infants and children

Forming Glucose

-when blood glucose is low and glycogen stores are depleted, the liver can synthesize glucose from amino acids —red blood cells —nerves and brain cells -starvation — muscle wasting and edema

Epignome

A network of chemical compounds surrounding DNA that modify the genome without altering the DNA sequences and have a role in determining which genes are active (expressed) or inactive (silenced) in a particular cell

Trypsin

A protein digesting enzyme secreted by the pancreas to act in the small intestine

negative protein balance

A state in which protein intake is less than related protein losses, as is often seen during acute illness.

Conditionally Essential Amino Acids

Amino acids made from essential amino acids if insufficient amounts are eaten -nonessential amino acids that cannot be made In adequate amounts to support the body's increased requirements during conditions of rapid growth, disease, or metabolic stress, and therefore become essential (i.e., must be obtained from food)

nonessential amino acids

Amino acids that can be synthesized by a healthy body in sufficient amounts; there are 11 nonessential amino acids. These are also called Dispensable Amino Acids.

Digestion (denaturation of proteins)

Breaks down protein to make amino acids available

Buffer

Compounds that causes solution to resist changes in acid base conditions

Extracellular Space

The space outside cells; contains 1/3 of body fluid

Fruitarian

Eats fruits, nuts, honey and vegetable oils

Vegan

Eats only plant foods

lactovovegetarian

Eats plant products, dairy and eggs

lactovegetarian

Eats plants and dairy products

Limiting Amino Acid

Essential amino acid in lowest concentration in food or diet relative to body needs

Proteins in Foods

Grains: bread, breakfast cereals, rice, & noodles (2-3 grams per serving) Vegetables: carrots, corn, & broccoli (2 -3 grams per serving) Fruits: apples, oranges, & bananas ( < 1 gram per serving) Dairy: milk, yogurt, & cheese (8-10 grams per serving) Protein: meat, eggs, fish, dry beans, & nuts (7 grams per serving)

Protein Equilibrium

Healthy adult meeting nutrient needs, notably protein and calorie needs

Gastirn

Hormone produced by stomach cells

Sickle Cell Anemia

Illness that results from malformation of red blood cells because of an incorrect structure in part of its hemoglobin protein chains

Capillary Bed

Network of one cell thick vessels that create a junction between arterial and venous circulation. It is hear that gas and nutrient exchange occurs between body cells and the blood.

Satiety

No further desire to eat; a feeling of satisfaction

Translation

The process of adding amino acids one at a time to a growing polypeptide chain, according to the instructions on the mRNA

Pollovegetarian

Referring to a dietary pattern that is primarily plant based but also includes chicken, turkey, and other poultry

Ovovegetarain

Referring to a dietary pattern that is primarily plant based but also includes egg products

Pescovegetarian (pescatarian)

Referring to a dietary pattern that is primarily plant based but also includes fish and other aquatic animal protein

Preterm

Referring to an infant born before 37 weeks of gestation; also referred to a premature

Pepsin

Stomach enzyme that breaks polypeptides into shorter chains of amino acids

nutritional genomics

Study of interactions between nutrition and genetics; includes nutrigenetics and nutrigenomics.

Pool

The amount of a nutrient stored within the body that can be mobilized when needed

Edema

The buildup of excess fluid in the extracellular spaces of tissues

Protein turnover

The process by which cells breakdown old proteins, and re-synthesize new proteins. In this way, the cell will have the proteins it needs to function at that time.

Transcription

The process by which the code or gene for a protein on a DNA sequence is copied and into a single stranded mRNA molecule that is ready to leave the nucleus