Week 1: Amino Acids + Proteins

Question 1

How many amino acids (aa) are there in humans?

Answer 1

20

Question 2

What is an essential amino acid?

Answer 2

You must eat it

Question 3

What is the net charge of an aa?

Answer 3

Neutral

Question 4

What is a peptide bond?

Answer 4

Amino group of one aa bonds with the carboxyl group of another aa

Question 5

What is a zwitterion?

Answer 5

Have positive and negative charges but net neutral, like aa

Question 6

What properties does the secondary protein structure add?

Answer 6

Strength + flexibility

Question 7

What properties does the tertiary protein structure add?

Answer 7

Shape + function

Question 8

Describe protein digestion

Answer 8

1. Swallow food, which travels down esophagus to stomach
2. Stomach pepsin + HCl breaks protein down into peptides
3. Intestinal enzymes (trypsin, chymotrypsin, elastase, sodium bicarbonate) digest peptides into aa
4. Amino acids from intestine get reabsorbed into bloodstream to get recycled

Question 9

What is an aminoacidopathy?

Answer 9

Inherited enzyme defect that inhibits the metabolism of certain aa

Question 10

List aminoacidopathies

Answer 10

• Maple syrup urine disease (MSUD)
• Phenylketonuria (PKU)
• Tyrosinemia
• Alkaptonuria
• Isovaleric acidemia
• Homocystinuria
• Citrullinemia
• Argininosuccinic aciduria
• Cystinuria

Question 11

Blood samples should be drawn after at least what time frame of fasting?

Answer 11

6-8 hr fast

Question 12

How are samples collected for aa analysis?

Answer 12

Heparin tube. Plasma removed promptly from cells. Leave buffy coat alone

Question 13

Deproteination must occur within _____ of sample collection

Answer 13

30 min

Question 14

If analysis cannot be performed immediately, how do you store aa sample?

Answer 14

Freeze -20°C to -40°C

Question 15

Properties of proteins

Answer 15

• 6k to 1 million Da
• Small is less than 20k Da
• Variable solubility
• Electrical charge
• Adsorption
• Specific binding to antibodies

Question 16

What makes proteins more easy to dissolve?

Answer 16

More positive charge

Question 17

Carbs and lipids lack which element?

Answer 17

Nitrogen

Question 18

Contrast globular and fibrous proteins

Answer 18

Globular: symmetric, soluble in saline, (albumin, globulins, histones, protamines)
Fibrous: asymmetric, water insoluble, (collagens, elastins, keratins)

Question 19

List conjugated proteins

Answer 19

• Nucleoproteins (DNA + RNA)
• Mucoproteins (carbs > 40% wt)
• Glycoproteins (carbs 10-40% wt)
• Lipoproteins (cholesterol, triglyc, phospholipids)
• Metalloproteins (heme)
• Enzymes (aminotransferase, phosphatase)
• Hormones
• Ig

Question 20

What is total protein made of?

Answer 20

Total protein = albumin + globulins

• 54% albumin
• 46% globulin

Question 21

Total protein reference range

Answer 21

6.5-8.3 g/dL

Question 22

Albumin reference range

Answer 22

3.5-5.5 g/dL

Question 23

Factors that affect protein concentration

Answer 23

• Nutritional status
• Physiologic changes
• Synthesis rate
• Extracellular distribution
• Clearance rate

Question 24

Most common cause of hyperproteinemia?

Answer 24

Dehydration

Also increased protein production

Question 25

A/G reference range?

Answer 25

1.1:1.8

Question 26

List all the globulins

Answer 26

- alpha-1 antitrypsin - alpha-2 macroglobulin - haptoglobin - ceruloplasmin - transferrin - fibrinogen - CRP - Myoglobin

Question 27

Categorize each globulin as positive or negative APP

Answer 27

**Positive APP**: alpha-1 antitrypsin, alpha-2 macroglobulin, haptoglobin, ceruloplasmin, CRP **Negative APP**: transferrin

Question 28

Cause of hypoproteinemia?

Answer 28

- Negative nitrogen balance - Accelerated protein degradation - Reduced synthesis/intake - Excessive loss

Question 29

List methods of protein analysis

Answer 29

- Total nitrogen - Total protein (serum) - Salt fractionation - Albumin - Total globulins - Electrophoresis

Question 30

In which conditions is urine protein (microprotein) elevated?

Answer 30

- Kidney failure - Nephrotic syndrome - Glomerulonephritis

Question 31

CSF protein reference range?

Answer 31

15-60 mg/dL

Question 32

CSF produced and reabsorbed by?

Answer 32

Produced by choroid plexus cells and reabsorbed through arachnoid

Question 33

CSF protein composition?

Answer 33

95% plasma protein, 5% synthesized protein

Question 34

Most common test on CSF?

Answer 34

Protein + glucose

Question 35

Describe lab findings in Wilson's disease pts

Answer 35

- Reduced ceruloplasmin levels - Increased serum and urinary copper concentrations - Cu deposited in liver, brain, cornea...etc

Question 36

HS-CRP can help evaluate risk of what?

Answer 36

Heart disease

Question 37

Function of myoglobin? Toxicity? Where is it found?

Answer 37

- Functions to store oxygen intracellularly - Nephrotoxin that can lead to renal failure - Mainly striated skeletal and cardiac tissue