BioChem Lab Flashcards

1
Q

enzymes

A

-most are protein in nature
-proteins that act as catalyst in biochemical reactions
-most efficient catalyst

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2
Q

sucrose

A

-table sugar
-disaccharide composed of an alpha-d-glucose + beta d-fructose molecule linked together by alpha-1,4-glycosydic bond

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3
Q

invert sugar

A

when the bond is cleaved in a hydrolysis reaction, an equimolar mixture of glucose and fructose are generated

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4
Q

invertase

A

beta-fructofuranosidase
mainly used in the food (confectionary) industry
commercial invertase is biosynthesized by yeast strains of saccharomyces cerevisiae or saccharomyces carlsbergensis

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5
Q

reducing sugars

A

capable of acting reducing agents because it has a free aldehyde group or a ketone group

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6
Q

reducing sugars

A

Glucose
Fructose
Lactose
Maltose
Galactose

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7
Q

non reducing sugars

A

sucrose

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8
Q

DNS

A

-3,5-dinitrosalicylic acid or 2-hydroxy-3,5-dinitrobenzioc acid
-an aromatic compound that reacts with -reducing sugars and other reducing -molecules to form 3-amino-5-nitrosalicylic acid
-strongly absorbs light at 540nm

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9
Q

DNS colorimetric method

A

-detects the presence of free carbonyl group (C=O) of reducing sugars
-it involves the oxidation of the aldehyde functional group in glucose and ketones functional groups in fructose

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10
Q

Effects of pH

A

optimum pH- the most favorable pH values- the point where the enzymes is most effective

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11
Q

enzymes optimum pH

A

enzymes optimum pH
lipase (pancreas) 8.0
lipase (stomach) 4.0- 5.0
lipase (castor oil) 4.7

amylase (pancreas) 6.7- 7.0
amylase (malt) 4.6- 5.2

pepsin 1.5- 1.6
trypsin 7.8- 8.7

urease 7.0
catalase 7.0

invertase 4.5
maltase 6.1- 6.8

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12
Q

effects of temperature

A

-the reaction rate increases with temperature to a maximum level then abruptly decline with further increase of temperature
-most of the enzymes rapidly become denatured at temperature above 40degC
-storage of enzymes at 5degC or below is generally the most suitable

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13
Q

catalysts

A

-a substance that can be added to a reaction to increase the reaction rate without getting consumed in the process
-it typically speed up a reaction by reducing the activation energy or changing the reaction mechanism

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14
Q

A- simple enzyme

A

active site
substrate
enzyme

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15
Q

B- holoenzyme

A

made up of protein groups (apoenzyme) and non protein component (cofactor)

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15
Q

Co-factors

A

organic (co-enzymes)
non-organic (activators)
prosthetic group

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16
Q

organic co-enzymes

A

vitamins
B2: FAD FADH2 (flavine adenine dinucleotide)
B3: NAD NADH (nicotinamide adenine dinucleotide)
B5: CoA (acetyl co-enzyme)

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17
Q

non-organic activators

A

metals:
K+
Ca+2
Mn+2
Co+2
-the main or product of the active structural conformation of the enzyme
-promote the formation of enzyme-substrate complex
-acting as e-donors or acceptors cause distortions in the substrate or the enzyme

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17
Q

prosthetic groups

A

cofactor that is bound so tightly to the apoenzyme and is difficult to remove without damaging the enzyme

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17
Q

C- allosteric sites

A

binding can increase (allosteric activation) or decrease (allosteric inhibition) the affinity to the substrate

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17
Q

properties and characteristics of enzymes

A

-catalyze biological and reactions
-can speed up reaction to go a million or billion faster
-rate of reaction is dependent to enzyme reaction
-the max velocity of an enzyme reaction is proportional to its concentration
-enzymes are substrate specific
-enzymes are very sensitive to pH and temperature

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18
Q

theories of bonding

A

1- lock and key- exact (rigid) specific bonding
2- induced fit- flexible bonding

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18
Q

enzymes classifications

A

1- oxidoreductase
2- transferase
3- hydrolase
4- lyase
5- isomerase
6- ligase

19
Q

oxidoreductase

A

catalyze redox reactions
-oxidase/dehydrogenase
-reductase/hydrogenase
-enzymes with NAD or NADH and FAD or FADH cofactor

20
Q

transferase

A

catalyzes the transport of 1 functional group from 1 molecule to another
- aminotransferase
-transcarboxylase
-enzymes that ends with kinase
all phase II enzymes

21
Q

hydrolase

A

catalyzes hydrolytic reactions or the breaking of bonds involving introduction of water
- protease
- lipase
- acetylcholinesterase
- esterase
- amylase
-phosphatase
- sucrase
- maltase
- lactase
- peptidase
- pepsin
- trypsin
- chymotrypsin

22
Q

lyase

A

catalyzes non-hydrolytic cleavage- removal or form a double bond or breaking a double bond by an interaction of a functional group
- anhydrase = removes H2O
- carboxylase= adds COOH, CO2
- decarboxylase = removes CO2
- deaminase = removes NH2

23
Q

isomerase

A

catalyzes intramolecular rearrangement of atoms
- enzymes with suffixes: isomerase, mutase, epimerase
- phophoglucoseisomerase
- phosphoglucomutase
- glucose 4 epimerase

24
Q

ligase

A

catalyzes reaction that join 2 molecules forming covalent linkage using an energy released from hydrolyzing pyrophosphate bond (C-C, C-N)
- enzymes with suffixes: synthase, synthethase
- nitric oxide synthase
- glutamine synthethase

25
Q

enzyme kinetics / activity
factors

A
  • affinity
  • degrees of speed
  • limited (saturable)
  • temperature
  • pH
26
Q

enzyme inhibition
binding

A

Agonist- binds = activity
Antagonist- binds = no activity

27
Q

types of enzyme inhibition
competitive

A

Vmax= same
Km= increased
surmountable by 1 concentration

28
Q

types of enzyme inhibition
non-competitive

A

Vmax= decreased
Km= same
unsurmountable irreversible

29
Q

types of enzyme inhibition
uncompetitive

A

Vmax= decreased
Km= decreased
similar to noncompetitive except it only affects the enzyme-substrate complex

30
Q

Michaelis menten plot

A

V= Vmax x Substrate/Km + Substrate

Km- reflection of affinity
S- substrate concentration
Vmax- max of rate of reaction
Vi or V0- initial rate of reaction

31
Q

enzyme in clinical diagnosis
1- lipase

A

an enzyme catalyzing the hydrolysis of fats
-secreted by pancreas and liver
-plasma lipase level may be low in liver disease, vitamin A deficiency, some malignancies, DM

32
Q

enzyme in clinical diagnosis
2- alpha-amylase

A

enzyme concerned with the breakdown of dietary starch and glycogen to maltose
-present in pancreatic juices and saliva as well as in liver, fallopian tubes and muscles
-excreted in the urine
-plasma amylase level may be low in liver disease
-plasma amylase level may increase in high intestinal obstruction, mumps, acute pancreatitis and diabetes

33
Q

enzyme in clinical diagnosis
3- trypsin

A

secreted by the pancreas
-elevated levels of trypsin may occur during acute pancreatic disease

34
Q

enzyme in clinical diagnosis
4- alkaline phosphatases (ALP)

A

groups of enzymes, which hydrolyzes phosphate esters at an alkaline pH
-found in bone, liver, kidney, intestinal wall, lactating mammary glands and palcenta
-level of these enzymes may be increased in rickets and osteomalacia, hyperthyroidism, paget’s disease of the bone, obstructive jaundice, and metabolic carcinoma
-serum alkaline phosphatase levels may increase in CHF result of injury to the liver

35
Q

enzyme in clinical diagnosis
5- acid phosphatase (ACP)

A

catalyzes hydrolysis of various phosphate esters at acidic pH
-found in the prostate, liver, red cells, platelets, and bone
-may increase in metastatic prostatic carcinoma

36
Q

enzyme in clinical diagnosis
6- transaminases

A

a- aspartate transaminases (AST) or glutamate oxaloacetate transaminase (GOT)
-catalyzes the transfer of amino group of alanine to alpha-ketoglutarate, forming glutamate and pyruvate
-present in high concentration in liver and to a lesser extent in skeletal muscle, kidney and heart
-serum levels of glutamate serum pyruvate (SGPT) and serum glutamate oxaloacetate transaminase (SGOT) are useful in the diagnosis of liver parenchymal damage and myocardial damage respectively
-in liver damage, both enzymes are increased, but SGPT increases more
-in myocardial infarction SGOT is increased with little or no increase in SGPT

37
Q

enzyme in clinical diagnosis
7- Lactate dehydrogenase

A

catalyzes the reversible interconversion of lactate and pyruvate
-widely distributed with high concentration in the hear, skeletal muscle, liver, kidney, brain and erythrocytes
-increased in plasma in MI, acute leukemias, generalized carcinomatosis, and in acute hepatitis
-estimation of its isoenzymes is more useful in clinical diagnosis to differentiate hepatic disease and MI

38
Q

enzyme in clinical diagnosis
8- creatinine kinase or creatinine phosphokinase (CPK)

A

found in the heart muscle, brain, skeletal muscle
-measurement of the serum creatinine phosphokinase activity is of value in the diagnosis of disorders affecting skeletal and cardiac muscle
-the level of CPK in plasma is highly increased in MI

39
Q

DNA

A

deoxyribonucleic acid
supplies the genetic information

40
Q

nucleic acids

A

informational molecules made up of polymers of nucleotides linked together by phosphodiester bonds

41
Q

nucleotides

A

building blocks of nucleic acids, composed of nitrogen containing heterocyclic base, phosphate, pentose sugar (sugar moiety)

42
Q

nucleoside

A

heterocyclic base + pentose sugar (sugar moiety)

43
Q

2 types of nucleic acids in cells

A

DNA and RNA

44
Q

DNA

A

sugar: 2 deoxyribose
double stranded
purine bases: guanine, adenine
pyrimidine bases: cytosine, thymine

45
Q

RNA

A

sugar: ribose
single stranded
purine bases: guanine, adenine
pyrimidine bases: cytosine, uracil

46
Q

CTAB METHOD

A

cetyl-trimethylammonium bromide
-a cationic detergent facilitates the separation of polysaccharides during purification such as polyvinylpyrrolidone can aid in removing polyphenols
-widely used when purifying DNA from plant tissues
-polysaccharides and DNAa have different solubilities (depending on the concentration of sodium chloride)
-higher salt concentrations - polysaccharides are insoluble
-lower concentrations - DNA is soluble`

47
Q

preparation of CTAB buffer

A

temp. 60degC

48
Q

DNA isolation from the onion

A

onion is used: it has low starch content, which allows the DNA to be seen clearly

ice-cold ethanol used: DNA is not soluble in ice cold ethanol- when it is added to the mixture, all components of the mixture will stay in the solution- DNA will precipitate

49
Q

test for deoxyribose (dische test)

A

the reaction between dische reagent and 2-deoxyribose - blue color
- the intensity of the blue color is proportional to the concentration of DNA
-dische reagent does not react with the ribose in RNA and does not form blue colored comples

50
Q

test for phosphates

A

determined the presence of a phosphate ions
-hydrolysis of pyrophosphates to phosphates
-formation of bright yellow precipitate

51
Q

test for purines: murexide test

A

ammonium purpurate or ammonium salts of purpuric acid
-test for presence of uric acids: yellow residue
-test for xanthine: red residue

52
Q

test for pyrimidines: wheeler johnson test

A

test for pyrimidine bases cytosine and uracil
-produce green coloration- treated with bromine water
-purple liquid- addition of barium hydroxide