BIO 105-03

Bio 105 Lecture 5 Notes

A. Degrading and Synthesizing Proteins
1. Amino Acid Sources in Body
2. Amino Acid Uses

B. DNA Directs Synthesis of New Proteins – Process

1. Players: DNA, genes, mRNA, ribosomes
2. Gene Mutations Affect Final Protein

C. Disease of the Day: Phenylketonuria (PKU)
1. Info

* rare genetic disorder (1 in 15k births)

* missing enzyme that breaks down the amino acid phenylalanine

** excess phenylalanine is converted to another compound

** this compound can build up, then released in urine, sweat (“musty” odor)

* left untreated, this condition can cause problems with brain development, leading to progressive mental retardation and seizures

** damage done is irreversible so early detection is crucial

** part of standard genetic testing for newborn babies

* one of the few genetic diseases that can be dontrolled by diet

* treatment

** a diet low in phenylalanine and high in tyrosine

*** at least thru age 18

*** better through life

* looking at drugs that remove excess phenlyalanine; gene therapy to replace missing enzyme

* there is no cure

2. Symptoms

3. Treatment

D. Protein Quality

varies among food sources; quality depends on digestibility and amino acid profile

1. Digestibility – how easily your body can access and break down protein

* animal sources: 90-99% digestible

* plant sources: 70-90% digestible (protected by undigestible cell wall)

2. Amino Acid Profile

* you need all amino acids required in a protein for it to be made

** the amino acids present in a food are the amino acid profile

a. Complete proteins contain all of the essential amino acids along with the nonessential ones

** ex: animal proteins, soy protein (from plant)

b. Incomplete proteins are low in one or more essential amino acids

* the limiting amino acid is the essential amino acid in shortest supply in the incomplete protein

* ex: plant proteins, gelatin (from animals – is missing tryptophan)

c. Complementing incomplete proteins

* plant proteins “upgraded” to complete proteins by:

** consuming mondest amounts of soy or animal protein

** being complemented with other plant proteins which provide enough of the limiting amino acid

** ex:

*** grains have lysine and isoleucine, but little methionine or tryptophan

*** legumes have methionine and tryptophan, but little lysine or isoleucine

E. Nitrogen Balance and Imbalance

1. Nitrogen Balance

* the amount of protein consumed = amount of protein used (nitrogen excreted)

2. Nitrogen Imbalances

a. Positive Nitrogen Balance: more nitrogen is retained for protein synthesis than is excreted

** seen during periods of deveolpment and growth

** ex: infants, children, pregnant women

b. Negative Nitrogen Balance: more nitrogen is excreted than consumed (body proteins broken down)

* seeen when body under large physical stress

* ex: starvation, serious injury, illness

F. Protein in the Diet

* according to Lemon (1995) each day

** sedentary adults need 0.8 g/kg (USRDA)

** strength athletes need ~ 1.4-1.8 g/kg

** endurance athletes need ~1.2-1.4 g/kg

* excess protein does NOT build muscle bulk, strength exercise does

** excess amino acids are stored as fat — NOT made into muscle unless body needs it

1. Athletes

2. Vegetarians

* variety of plant foods — need to make sure to complement incomplete proteins

* protein-rich meat alternatives:

** soy

** dried beans and other legumes

** nuts

** eggs, dairy (lacto-ovo-vegetarians)

3. Too Much Protein in the Diet

* may increase risk of heart disease, kidney stones, calcuium loss from bones

** by products of protein breakdown leads to above

* can displace other nutrient- and fiber-rich foods associated with a reduced risk of chronic diseases

** ex: whole grains, fruits, vegetables

** missing fiber, vitamins, minerals, etc

** often animal protein is associated with high fat as well

4. Too Little Protein in the Diet

* low-protein diets associated with loss of bone mass

* inadequate calories and protein

* more common in children, because they are growing

* factors: poverty, poor food quality, insufficient food, unsanitary living conditions, ignorance, stopping lactation (nursing) too early

a. PEM: Kwashiorkor

* severe deficiency of dietary protein

** edema (swelling), muscle loss, skin rashes, hair changes, water and eletrolyte imbalances

** seen in children weaned to low-protein cereals

b. PEM: Marasmus

* severe deficiency of calories

** starvation

** signs: emaciation, lack of growth, loss of fat stores

* Marasmic Kwashiorkor: worst of both

End of material for Exam 1!
Exam 1 on Thursday
Begin at 8:30 am sharp
50 multiple choice questions – mix of recall and application type questions
All bookbags, purses, books, CELL PHONES ON SILENT OR OFF, etc. will be put in front of classroom
Will only need pen or pencil for scantron at your seat
Sit every other seat; there will be different forms of exam
Extra SI session?

Clicker Questions

The basic building blocks of proteins are:
Peptides
Saccharides
Fatty acids
Amino acids

How many different kinds of amino acids make up proteins?
9
11
20
50

Alteration of the 3-dimensional shape of a protein by heat or acid is called:
Denaturation
Destabilization
Emulsification
Solidification

Which of the following sugar substitutes should PKU patients avoid?
Saccharin
Aspartame
Neotame
Sucralose

Will you add more muscle by eating more protein?
Yes
No

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