Chapter 7 - Proteins Flashcards
Aside from water, protein is the major part of ____ ____ _____
lean body tissue
Lean body tissue, and therefore protein, makes up what percent of our body weight?
17%
Protein is crucial to…
regulation and maintenance of essential body functions
Protein is composed of…
carbon, hydrogen, oxygen, nitrogen
- sometimes contains mineral sulfur
Each amino acid is composed of a central carbon bonded to what 4 things?
- nitrogen (amino) group
- acid (carboxyl) group
- hydrogen
- side chain (signified by R)
What do side chains determine?
structure, function, and name
If the side chain (R) is hydrogen, what is the amino acid?
Glycine
If the side chain (R) is a methyl group, what is the amino acid?
Alanine
How many amino acids does the body need to function?
20
Nonessential Amino Acids
Amino acids the body can synthesize in sufficient amounts.
- There are 11 nonessential amino acids
Essential Amino Acids
Amino acids that body can’t synthesize in sufficient amounts or at all and must be supplied by the diet.
- There are 9 essential amino acids
What are the 9 essential amino acids?
Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine
Carbon Skeleton
Amino acid without the amino group
Transamination
Transfer of an amino group from an amino acid to a carbon skeleton to form a new amino acid
Deamination
Removal of an amino group from an amino acid
Urea
Nitrogenous waste product of protein metabolism and the major source of nitrogen in the urine.
Complete (High Quality) Protein
Protein with sufficient amounts of the essential amino acids
Incomplete (Low Quality) Protein
Protein with limited amounts of one or more essential amino acids
Pool
Amount of a nutrient found in the body that can be easily mobilized when needed
Limiting Amino Acid
Essential amino acid in the lowest concentration in a food or diet relative to body mass
Complementary Proteins
Two 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, so they provide a high quality protein for the diet.
Examples of Complementary Proteins?
Grains with legumes
Nuts and seeds with legumes
Peptide Bond
A chemical bond formed between amino acids in a protein. Allows for the synthesis of dipeptides, tripeptides, oligopeptides, and polypeptides.
Most proteins are _______, having 50 to 2000 amino acids.
Polypeptides
Gene Expression
Activation of a specific site on DNA, which results in the activation or inhibition of the gene.
What does gene expression determine in terms of proteins?
the synthesis of body proteins; where each amino acid is to be placed in a protein and in what order.
Codon
Specific sequence of 3 nucleotide units within DNA that codes particular amino acids needed for protein synthesis
Amino acids can have up to how many codons?
6
Where does protein synthesis take place?
ribosomes
DNA Transcription
Process of forming messenger RNA (mRNA) from a portion of DNA
What are the nucleotides in mRNA?
A U G C
mRNA Translation
Synthesis of polypeptide chains by the ribosome according to information contained in strands of messenger RNA (mRNA)
What does Transfer RNA do?
Take amino acids to the ribosomes as needed during protein synthesis.
Primary Structure of Protein Organization
Sequential order; strong peptide bonding; determines protein shape
Secondary Structure of Protein Organization
Spiral-like, pleated shape
Tertiary Structure of Protein Organization
3D folding of a protein; determines overall shape and physiological function
Quaternary Structure of Protein Organization
2 or more separate polypetides form a large, new protein
Denaturation
Alteration of a protein’s 3D structure, usually because of treatment by heat, enzymes, acidic or alkaline solutions, or agitation.
- Often destroys protein’s natural biological function
When is denaturation beneficial?
In the stomach when HCl denatures food proteins for digestion; During cooking
Protein Turnover
The constant state of protein breakdown, rebuilding, and repair.
Allows for cell adaptation.
Protein comes from…
Animal and plant sources
Why are plant sources of protein healthier?
No cholesterol, less saturated fat
Protein quality is determined by what two things?
digestibility and amino acid composition compared with a reference protein
Protein Biological Value (BV)
Measures how efficiently absorbed food protein converts into body tissue protein
BV = [nitrogen retained (g) / nitrogen absorbed (g)] x 100
Protein Efficiency Ratio (PER)
Compares the amount of weight gain by a growing lab animal consuming a standardized amount of the protein being studied with the weight gain by an animal consuming a standardized amount of a reference protein
PER = weight gain (g) / protein consumed
What food has a BV of 1.0, the highest BV?
Egg whites
A high BV means a ____ PER and vice versa
high
Chemical Score
Evaluates protein quality.
Calculated by dividing the amount of each essential amino acid in a gram of food being tested by the “ideal” amount for that amino acid in a gram of the reference protein.
- Scores range from 0 to 1.0
Protein Digestibility Corrected Amino Acid Score (PDCAAS)
Measure of protein quality.
chemical score x digestibility
highest score is 1.0
Its recommended that __ to ___% of your total calorie intake be proteins
10 to 35%
Negative protein balance leads to..
loss of proteins in skeletal muscles, blood, heart, liver, and other organs
Positive protein balance is desired when…
you need to build or repair tissues during periods of growth or recovery
How do you calculate an estimate of protein intake?
nitrogen (g) x 6.25 = protein (g)
RDA of protein for most adults
0.8g/kg body weight
What is the role of the stomach in protein digestion and absorption?
pepsin enzyme and HCl partially digest protein
What is the role of the pancreas in protein digestion and absorption?
further protein digestion by enzymes released by the pancreas into the small intestine
What is the role of the small intestine in protein digestion and absorption?
final digestion of protein to amino acids occurs here
What is the role of the liver in protein digestion and absorption?
amino acids are absorbed into the portal vein and transported to the liver, where they can enter the general blood stream
What is the role of the large intestine in protein digestion and absorption?
little dietary protein is present in feces
When is protein used for energy?
When you don’t eat enough carbs or fat
Which three proteins provide major structural support for cells and tissues?
collagen, actin, myosin
What two blood proteins help maintain fluid balance between the blood and surrounding tissue space?
albumin and globulin
Capillary Beds
Blood vessels one cell thick that create a junction between arterial and venous circulation. Gas and nutrient exchange occurs here between blood cells and the blood.
Edema
Build up of excess fluid in extracellular spaces
Proteins have a ____ charge
negative
Buffers
Compounds that help maintain acid-base balance within a narrow range (protein is a buffer)
Amino acids are required from the synthesis of what three things?
hormones, enzymes, neurotransmitters
Anergy
Lack of an immune response to foreign compounds entering the body
Vitamin A is carried by what protein?
retinol-binding protein
Iron is carried by what and stored by what?
Transferrin, ferritin
Copper is carried by what protein?
Cerulosplasmin
Innate (Nonspecific) Immunity
Immune response present at birth that provides the first barrier of protection against invading antigens; includes: –physical barriers that prevent access to the inside of the body
- chemical secretions that destroy antigens
- physiological barriers that prevent the growth of antigens
- phagocytic cells that engulf and destroy antigens
Acquired (Specific) Immunity or Adaptive Immunity
Immune response that develops over a lifetime; initiated by the recognition of specific antigen and release of antibodies and other specialized immune cells that destroy the antigen.
Gluconeogenesis
Using proteins/amino acids to make new glucose
Protein yields how much energy?
4 kcal/g
Protein-Energy Malnutrition (PEM) or Protein-Calorie Malnutrition
Condition resulting from insufficient amounts of energy and protein, which eventually results in body wasting and an increased susceptibility to infection and disease.
Marasmus
Condition that results from a severe deficit of energy and protein, which causes extreme loss of fat stores, muscle mass, and body weight.
Kwashiorkor
Condition occurring primarily in young children who have an existing disease and consume a marginal amount of energy and severely insufficient protein. Results in edema, poor growth, weakness, and increased susceptibility to further infection and disease.
How can you preserve kidney health?
Eat a lower protein diet and consume adequate amounts of fluids
Diets high in what kind of meat are linked with a higher risk of certain cancers?
red meat
What are the most toxic amino acids? (top three)
methionine, cysteine, and histidine
Allergen
Components, typically (food) proteins, that induce a hypersensitive response, with excess production of certain immune system antibodies. Subsequent exposure to the same protein leads to allergic symptoms.
Immunoglobulins
Proteins (AKA antibodies) that are responsible for identifying and neutralizing antigens as well as pathogens that bind specifically to antigens
90% of all food allergies are to what 8 foods?
- peanuts
- tree nuts
- milk products
- soy
- wheat
- eggs
- fish
- shellfish
__ to __% of children have food allergies
6 to 7%
__ to __% of adults have food allergies
1 to 2%
___% of Americans are vegetarians and ___ to ___% of Americans say they eat at least 4 meatless meals each week.
2.5; 20-25%
What are nutritional concerns for vegetarians?
riboflavin, vitamin D and B-12, calcium, zinc, iron
