question Of Enzyme كتاب الطويل Flashcards
(165 cards)
1
Q
What are enzymes?
A
Specific protein catalysts that accelerate the rate of chemical reactions
Enzymes are essential for various biochemical reactions in living organisms.
2
Q
How does enzyme structure change during reactions?
A
Enzyme structure is not changed by entering the reactions
This means that enzymes can be reused multiple times.
3
Q
Do enzymes affect the equilibrium constant of reactions?
A
No, enzymes do not affect the equilibrium constant of the reactions
They only speed up the rate at which equilibrium is reached.
4
Q
What are the two types of cellular distribution of enzymes?
A
- Intracellular enzymes
- Extracellular enzymes
Intracellular enzymes are produced and act inside the cells, while extracellular enzymes act outside the cells.
5
Q
What are the general properties of enzymes?
A
- They are globular proteins
- They can be denatured
- They are usually specific in action
- They can be simple or conjugated proteins
The specificity of enzymes varies in degree.
6
Q
What happens to enzymes when they are denatured?
A
They lose their biological function due to changes in conformation
Denaturation can be caused by physical or chemical agents.
7
Q
What is the difference between simple proteins and conjugated proteins in enzymes?
A
- Simple proteins: consist solely of amino acids
- Conjugated proteins: consist of a protein part (apoenzyme) and a non-protein part (co-factor)
Holoenzyme refers to the complete enzyme including both parts.
8
Q
What are co-factors in enzymes?
A
Non-protein parts that assist in enzyme activity
Co-factors can be loosely or tightly bound to the enzyme.
9
Q
What are examples of co-enzymes?
A
- NAD+
- FAD
Co-enzymes are a type of co-factor that are organic molecules.
10
Q
Fill in the blank: Some enzymes are secreted as _______ (zymogens) and activated later.
A
zymogens
Zymogens are inactive precursors of enzymes.
11
Q
True or False: Enzymes can act on any substrate.
A
False
Enzymes are usually specific to their substrates.
12
Q
What is the role of a prosthetic group in enzymes?
A
A tightly bound co-factor that is essential for enzyme activity
An example is biotin bound to carboxylases.
13
Q
What are zymogens?
A
Inactive enzymes
Zymogens have their catalytic sites masked by a polypeptide chain.
14
Q
How are zymogens activated?
A
By removal of the polypeptide chain
This process opens the catalytic site for substrate interaction.
15
Q
Name two examples of zymogens.
A
Pepsinogen, Trypsinogen
These are common examples of inactive enzymes that require activation.
16
Q
What is relative specificity in enzymes?
A
One enzyme acts on compounds with the same type of bonds
For example, lipase enzymes act on different triglycerides (TAG).
17
Q
Define group specificity in enzymes.
A
Enzyme acts on a special type of bond at a specific site
Pepsin acts on peptide bonds between aromatic amino acids.
18
Q
What type of bonds does trypsin act on?
A
Peptide bonds between carboxylic group of basic amino acid and amino group of another amino acid
This illustrates trypsin’s group specificity.
19
Q
Explain optical specificity in enzymes.
A
Enzymes act on D or L isomers
For instance, D-amino acid oxidase acts only on D-amino acids.
20
Q
What does absolute specificity mean in enzyme action?
A
One enzyme acts only on one substrate
An example is urease, which acts solely on urea.
21
Q
Fill in the blank: Zymogens are inactive because their catalytic sites are masked by a _______.
A
polypeptide chain
This masking prevents the enzyme from interacting with its substrate.
22
Q
What is the role of the protease-inhibitor complex?
A
Inhibition of protease activity
This complex helps regulate enzyme activity in biological systems.
23
Q
What is the significance of substrate activation?
A
It allows the enzyme to perform its catalytic function
Activation is crucial for metabolic processes.
24
Q
True or False: Enzymes can only act on one specific type of substrate.
A
False
While some enzymes exhibit absolute specificity, others may have relative or group specificity.
25
What is the downstream effect in enzymatic reactions?
The consequences of enzyme activity on subsequent biochemical processes
## Footnote
This includes changes in metabolic pathways due to enzyme function.
26
What is activation energy?
The amount of energy required to raise 1 mole of substance to the transition state.
## Footnote
Activation energy is crucial for chemical reactions as it determines the rate at which reactions proceed.
27
How do enzymes affect activation energy?
Enzymes decrease the energy of activation.
## Footnote
This allows reactions to occur more readily and at lower temperatures than would otherwise be possible.
28
What is the transition state in a chemical reaction?
The state where there is a high probability that a chemical bond will be made or broken to form the product.
## Footnote
The transition state is a temporary, unstable condition that occurs during the conversion of reactants to products.
29
What is an enzyme-substrate complex?
A temporary combination formed between the enzyme and its substrate during enzyme action.
## Footnote
This complex is essential for catalyzing the biochemical reaction.
30
What occurs at the active site of an enzyme?
The binding of the substrate occurs, leading to the formation of the enzyme-substrate complex.
## Footnote
The active site is specifically shaped to fit the substrate, facilitating the reaction.
31
What is the lock and key theory of enzyme action?
The theory that the active site of the enzyme is complementary in conformation to the substrate.
## Footnote
This model suggests that enzymes and substrates fit together like a key in a lock.
32
What is the induced fit theory of enzyme action?
The theory that the enzyme changes shape upon binding the substrate, making the enzyme-substrate complex complementary.
## Footnote
This model illustrates that the enzyme is flexible and can adapt to fit the substrate.
33
Fill in the blank: The energy required to reach the transition state in a chemical reaction is known as _______.
[activation energy]
34
True or False: Enzymes are consumed in the reactions they catalyze.
False
## Footnote
Enzymes are not consumed and can be used repeatedly.
35
List the two theories proposed to explain the specificity of enzyme action.
* Lock and key theory
* Induced fit theory
36
What are oxidoreductases?
Enzymes that catalyze oxidation-reduction reactions
## Footnote
These enzymes facilitate the transfer of electrons between molecules.
37
What do transferases do?
Catalyze the transfer of functional groups other than hydrogen
## Footnote
This includes groups such as methyl, acyl, or glycosyl.
38
What is the function of oxidases?
Catalyze the removal of hydrogen from substrates using oxygen
## Footnote
They can form either water or hydrogen peroxide as a product.
39
What types of products do oxidases form?
Water (H2O) and hydrogen peroxide (H2O2)
## Footnote
These products depend on the specific oxidase and its reaction conditions.
40
What is catalase and where is it present?
An enzyme that breaks down hydrogen peroxide, present in all cells, especially liver, kidney, and erythrocytes
## Footnote
Catalase helps protect cells from oxidative damage.
41
What is the role of peroxidases?
Utilize hydrogen peroxide as a substrate
## Footnote
They are found in red blood cells, milk, and leukocytes.
42
What do dehydrogenases do?
Remove hydrogen from substrates
## Footnote
They depend on nicotinamide coenzymes (NAD, NADP) and riboflavin coenzymes (FAD, FMN).
43
What is the difference between dioxygenases and monooxygenases?
Dioxygenases incorporate two oxygen atoms into substrates; monooxygenases incorporate one oxygen atom
## Footnote
Monooxygenases are also known as hydroxylases or mixed function oxidases.
44
What do transglycosylases catalyze?
Transfer of an activated glycosyl (sugar) residue
## Footnote
This usually involves activation by UDP glucose.
45
What do transphosphorylases do?
Catalyze the transfer of a phosphoryl group
## Footnote
Examples include kinases and phosphoglucomutases.
46
What is the function of transacylases?
Catalyze the transfer of an acyl group
## Footnote
They require coenzyme A (CoA) as a carrier for the acyl group.
47
Fill in the blank: Enzymes that incorporate oxygen into substrates are called _______.
Oxygenases
## Footnote
Oxygenases are involved in various metabolic processes, including drug metabolism.
48
What are enzymes that act by adding water to split a certain bond called?
Hydrolases
## Footnote
Hydrolases cleave bonds by hydrolysis
49
Which enzymes act on glycosidic linkages causing their separation?
Glycosidases
## Footnote
Glycosidases perform moos-hydrolysis
50
What type of enzymes attack the ester linkage between acidic and alcoholic groups?
Esterases
## Footnote
Esterases cleave ester bonds
51
Which enzymes split the peptide linkage (CO-NH) of proteins?
Peptidases
## Footnote
Peptidases are crucial for protein digestion
52
What are the enzymes called that catalyze the addition or removal of groups without hydrolysis, oxidation, or reduction?
Lyases
## Footnote
Lyases facilitate non-hydrolytic reactions
53
What enzymes catalyze the interconversion of two isomers using energy from ATP?
Isomerases
## Footnote
Isomerases rearrange molecular structures
54
Fill in the blank: Transmethylases are also known as _______.
methyltransferases
## Footnote
Methyltransferases transfer methyl groups
55
Which vitamin is a coenzyme for the transfer of one-carbon groups?
Vitamin B6
## Footnote
Vitamin B6 is essential for amino acid metabolism
56
What is the primary methyl donor in transmethylation reactions?
S-adenosyl-methionine
## Footnote
SAM is a key methyl group donor
57
What are the products of lipase acting on triglycerides?
Glycerol and 3 fatty acids
## Footnote
Lipase is vital for fat digestion
58
What type of peptidases act on internal bonds in the polypeptide chain?
Endo-peptidases
## Footnote
Endo-peptidases break peptide bonds within proteins
59
What are the two types of exo-peptidases?
* Carboxypeptidase
* Aminopeptidase
## Footnote
Exo-peptidases cleave from the ends of peptide chains
60
Fill in the blank: Dehydratases catalyze the removal or addition of ______ from the substrate.
water
## Footnote
Dehydratases are important for various metabolic processes
61
What do decarboxylases catalyze?
Splitting of CO2
## Footnote
Decarboxylases are involved in amino acid metabolism
62
What is the role of aldose-ketose isomerases?
They interconvert aldoses and ketoses
## Footnote
These enzymes are crucial in carbohydrate metabolism
63
What is the function of carboxylase enzymes?
They catalyze the addition of CO2
## Footnote
Carboxylases are important for biosynthetic processes
64
What are vitamin coenzymes derived from thiamine (vitamin B1)?
Thiamine pyrophosphate (TPP)
## Footnote
TPP is crucial for carbohydrate metabolism.
65
Which coenzyme is derived from riboflavin (vitamin B2)?
Flavin adenine dinucleotide (FAD) and Flavin mononucleotide (FMN)
## Footnote
FAD and FMN are involved in redox reactions.
66
What is the coenzyme derivative of nicotinate (niacin)?
Nicotinamide adenine dinucleotide (NAD)
## Footnote
NAD is essential for metabolic processes.
67
Fill in the blank: The coenzyme derived from pyridoxine, pyridoxal, and pyridoxamine (vitamin B6) is _______.
Pyridoxal phosphate (PLP)
## Footnote
PLP is vital for amino acid metabolism.
68
Which coenzyme is associated with pantothenic acid?
Coenzyme A (CoA)
## Footnote
CoA plays a key role in fatty acid metabolism.
69
What group does biotin carry in its activated form?
Carboxyl group
## Footnote
Biotin is important for carboxylation reactions.
70
What is the role of tetrahydrofolate (THFA)?
One carbon unit transfer
## Footnote
THFA is crucial for nucleotide synthesis.
71
Which vitamin functions as a hydrogen carrier among coenzymes?
Vitamin C (L-ascorbic acid)
## Footnote
Vitamin C also acts as an antioxidant.
72
True or False: NAD+ is a coenzyme for the transfer of hydrogen.
True
## Footnote
NAD+ is essential in oxidative reactions.
73
List some nucleotide coenzymes.
* ATP
* UDP-glucose
* Other nucleotide derivatives
## Footnote
Nucleotide coenzymes are involved in energy transfer.
74
What is S-adenosyl methionine (SAM) classified as?
Nucleoside coenzyme
## Footnote
SAM is a major methyl donor in biological methylation.
75
Which coenzyme is known as a peptide coenzyme?
Glutathione (GSH)
## Footnote
GSH is crucial for detoxification and antioxidant defense.
76
What are the coenzymes for group transfer other than hydrogen?
* ATP
* GTP
* CTP
* Thiamin pyrophosphate (TPP)
* Coenzyme A (CoA)
* Folic acid
* Pyridoxal phosphate (B6)
* Biotin
## Footnote
These coenzymes are involved in various metabolic pathways.
77
What is the relationship between enzyme concentration and reaction velocity?
The initial velocity of a reaction is directly proportional to the amount of the enzyme present, provided that all other conditions remain constant.
## Footnote
This means that increasing enzyme concentration will increase the rate of reaction, assuming substrate concentration and other factors are unchanged.
78
What happens to reaction velocity when substrate concentration increases?
The initial velocity of a reaction is directly proportional to the amount of substrate present until it reaches a maximum point known as maximum velocity (Vmax).
## Footnote
Beyond Vmax, further increases in substrate concentration do not affect the reaction velocity due to enzyme saturation.
79
Define maximum velocity (Vmax).
It is the maximum point in the substrate velocity curve where any further increase in the amount of substrate causes no increase in the velocity of the reaction due to enzyme saturation.
## Footnote
At Vmax, the enzyme is fully saturated with substrate.
80
What is the Michaelis constant (Km)?
It is the substrate concentration that produces half maximum velocity.
## Footnote
Km is a key parameter in enzyme kinetics that indicates the affinity of an enzyme for its substrate.
81
True or False: A smaller Km value indicates a higher affinity of the enzyme for the substrate.
True.
## Footnote
A small Km reflects that a low concentration of substrate is needed to half saturate the enzyme.
82
What does a large (high) Km value indicate about an enzyme's affinity for its substrate?
It reflects a low affinity of the enzyme for the substrate, meaning a high concentration of substrate is needed to half saturate the enzyme.
## Footnote
This indicates that the enzyme is less effective at lower substrate concentrations.
83
Fill in the blank: Km is a constant characteristic of an enzyme and a particular _______.
substrate.
## Footnote
Km is unique to each enzyme-substrate pair and is used to compare enzyme efficiencies.
84
What is the order of reaction when increasing substrate concentration does not affect reaction rate?
Zero order.
## Footnote
In zero-order kinetics, the reaction rate remains constant regardless of substrate concentration.
85
In first-order kinetics, what affects the reaction rate?
Enzyme concentration and substrate concentration.
## Footnote
In first-order reactions, the rate is directly proportional to the concentration of one reactant.
86
What is the effect of doubling enzyme concentration on the reaction rate?
It doubles the rate of reaction.
## Footnote
This relationship holds true under conditions where substrate concentration is not limiting.
87
What is the optimal temperature for enzymatic activity in the human body?
37 °C
## Footnote
This is the temperature of the cells.
88
What happens to enzyme activity at zero temperature?
The enzyme is inactive.
89
What occurs to reaction velocity as temperature increases until a maximum is reached?
Reaction velocity increases.
90
What happens to reaction velocity if the temperature exceeds the maximum?
It decreases.
91
At what temperature do most enzymes become denatured and permanently inactive?
55°C - 60°C.
92
What is the optimal pH for enzyme activity?
The pH at which the enzyme acts maximally.
93
What happens to the ionic state of enzymes and substrates when pH is above or below the optimal level?
It changes, decreasing the rate of reaction.
94
What is the optimal pH for salivary amylase?
6.8.
95
What is the optimal pH for pepsin?
2.
96
What is the optimal pH for trypsin?
8.
97
What is the optimal pH for alkaline phosphatase?
8.4.
98
What can extreme pH levels lead to?
Denaturation of the enzyme.
99
How does co-enzyme concentration affect enzymatic activity?
It has the same effect as substrate concentration.
100
What effect do red and blue lights have on enzyme activity?
They increase enzyme activity.
101
What physical agents inhibit enzyme activity?
Heating, shaking, stirring, ultraviolet rays, and infrared rays.
102
Why must time be considered in enzyme kinetics?
To measure its effect against other factors.
103
What happens to enzyme activity with increased product concentration?
It decreases.
104
What are the possible reasons for decreased enzyme activity due to increased product concentration? (List at least two)
* Change in the pH of the medium
* Product competition with the substrate for the catalytic site
105
What is one way a product may interact with an allosteric enzyme?
It may bind to the enzyme at the allosteric site.
106
What do enzyme activators do?
Increase the rate of enzyme catalyzed reactions
## Footnote
The velocity of the reaction depends on activator concentration.
107
What is a zymogen?
Inactive form of an enzyme that is converted to active form
## Footnote
Example: Pepsinogen is converted to pepsin.
108
Which vitamin acts as a reducing agent to activate some enzymes?
Vitamin C
## Footnote
It is necessary for the activation of enzymes containing SH groups.
109
What are metal activated enzymes?
Enzymes that require minerals for activation
## Footnote
Example: Amylases require non-metal ions like Mg²⁺.
110
What are allosteric activators?
Modifiers that bind to enzymes and induce conformational changes
## Footnote
Example: AMP is an allosteric activator of phosphofructokinase.
111
Which of the following is NOT true regarding enzymes? (Select one)
d- Enzymes are very small molecules, much smaller than their substrates.
112
Which statement about enzymes is true?
Enzymes lower activation energy
## Footnote
They alter the equilibrium of the reaction and accelerate chemical reactions.
113
What are pro-enzymes?
Enzymes synthesized in inactive form
## Footnote
Also known as zymogens.
114
Identify an enzyme that is NOT an oxidoreductase.
d- Aldolase
## Footnote
Glutathione peroxidase, dioxygenase, and catalase are oxidoreductases.
115
Provide an example of a lyase enzyme.
b- Fumarase
## Footnote
Other options include glutamine synthetase and cholinesterase.
116
Which enzyme belongs to the ligase class?
a- Glycogen synthase
## Footnote
Other options include porphobilinogen deaminase and histidine decarboxylase.
117
What are coenzymes?
Dialyzable, non-protein molecules
## Footnote
They are not colloidal protein molecules or structural analogues of enzymes.
118
What are enzyme inhibitors?
Substances that can diminish the velocity of enzymatic reactions.
## Footnote
Enzyme inhibitors can be classified as reversible or irreversible.
119
What are reversible inhibitors?
Inhibitors that bind to enzymes through non-covalent bonds and can dissociate.
## Footnote
Recovery of enzyme activity occurs when the inhibitor is removed.
120
What are the two main types of reversible inhibitors?
Competitive inhibitors and non-competitive inhibitors.
## Footnote
Each type affects enzyme activity differently.
121
What characterizes competitive inhibitors?
They compete with substrate for the active site of the enzyme.
## Footnote
Examples include malonate and succinate.
122
What happens to Vmax and Km when a competitive inhibitor is present?
Vmax is unchanged; Km is increased.
## Footnote
More substrate cannot reverse the inhibition.
123
What characterizes non-competitive inhibitors?
They bind to different sites on the enzyme and do not alter the catalytic site.
## Footnote
Both substrate and inhibitor can bind simultaneously.
124
What effect do non-competitive inhibitors have on Vmax and Km?
Vmax is decreased; Km remains unchanged.
## Footnote
This type of inhibition affects the maximum reaction rate.
125
What are irreversible inhibitors?
Inhibitors that permanently deactivate an enzyme.
## Footnote
They include denaturation agents and antienzymes.
126
Name two examples of irreversible inhibitors.
Cyanide and carbon monoxide.
## Footnote
They inhibit cytochrome oxidase.
127
What is the effect of a competitive inhibitor on the enzyme-substrate complex?
The complex is inactive.
## Footnote
Both substrate and inhibitor cannot bind simultaneously.
128
Fill in the blank: The inhibitor can bind either free enzyme or the _______.
enzyme-substrate complex.
129
What factors determine the binding of substrate and inhibitor to the enzyme?
* Concentration of substrate
* Concentration of inhibitor
* Affinity of both inhibitor and substrate to the active site
## Footnote
These factors influence the rate of reaction.
130
True or False: The inhibitor in non-competitive inhibition alters the catalytic site.
False.
## Footnote
Non-competitive inhibitors do not alter the catalytic site.
131
What is the effect of irreversible inhibitors on enzyme activity?
They permanently decrease enzyme activity.
## Footnote
Examples include inhibitors of sulfhydryl groups.
132
What is allosteric regulation of enzyme activity?
It is a mechanism where effectors bind non-covalently at a site other than the active site of allosteric enzymes, which generally catalyze irreversible steps in metabolic pathways.
## Footnote
The term 'allosteric' means 'other site'.
133
What are effectors in the context of enzyme activity?
Molecules that can stimulate or inhibit catalytic reactions by binding to allosteric sites.
## Footnote
Positive effectors stimulate the reaction, while negative effectors inhibit it.
134
What is feedback inhibition?
It is when the end product of a series of reactions directly inhibits the first enzyme of that series.
## Footnote
This regulatory mechanism helps control metabolic pathways.
135
In feedback inhibition, what happens when the product is present?
It inhibits enzyme 1 in the metabolic pathway.
## Footnote
This prevents the overproduction of the end product.
136
What is feedback regulation?
It refers to the end product of a series of reactions affecting the gene(s) coding for the enzyme, preventing its synthesis instead of inhibiting the enzyme directly.
## Footnote
This mechanism helps regulate enzyme levels rather than activity.
137
What is covalent modification in enzyme regulation?
It is the regulation of enzymes through the addition or removal of phosphate groups, commonly via phosphorylation and dephosphorylation.
## Footnote
This type of modification can significantly alter enzyme activity.
138
What role do protein kinases play in enzyme regulation?
They catalyze phosphorylation reactions, adding phosphate groups to enzymes using ATP as a phosphate donor.
## Footnote
This process can activate or deactivate enzymes.
139
How are phosphate groups removed from phosphorylated enzymes?
By the action of phosphoprotein phosphatase.
## Footnote
This process is essential for reversing the effects of phosphorylation.
140
Fill in the blank: The process of adding a phosphate group to an enzyme is called _______.
[phosphorylation]
141
Fill in the blank: The process of removing a phosphate group from an enzyme is called _______.
[dephosphorylation]
142
What is the significance of glycogen synthase and glycogen phosphorylase in enzyme regulation?
They are involved in the regulation of glycogen synthesis and degradation through phosphorylation and dephosphorylation mechanisms.
## Footnote
Protein kinases and phosphatases regulate these enzymes to control glucose storage and release.
143
What are isoenzymes?
Different molecular forms of the enzyme that activate the same reaction, use the same coenzyme and substrate, but differ in chemical protein structure
## Footnote
Isoenzymes lead to different immunological reactions, Km, Vmax, and physical properties.
144
List three key characteristics of isoenzymes.
* Different immunological reactions
* Different Km and Vmax
* Different physical properties
## Footnote
These characteristics arise from their distinct chemical structures.
145
Provide an example of an isoenzyme and its significance.
Lactate dehydrogenase (LD)
## Footnote
LD is a tetramer with different proportions of H and M chains, and its isoenzymes are important for diagnosing diseases like myocardial infarction.
146
What does an increase in Serum LD1 indicate?
Heart diseases such as myocardial infarction
## Footnote
Different isoenzymes can indicate various conditions based on their levels in serum.
147
What are the five isoenzymes of lactate dehydrogenase?
* LD1 (HHHH)
* LD2 (HHHM)
* LD3 (HHMM)
* LD4 (HMMM)
* LD5 (MMMM)
## Footnote
Each isoenzyme has diagnostic importance for different diseases.
148
What is the role of creatine kinase (CK) isoenzymes?
* CK-BB: in brain
* CK-MB: in skeletal muscle
* CK-MM: in myocardium
## Footnote
These isoenzymes are used to assess muscle damage and other conditions.
149
What are functional plasma enzymes?
Enzymes present normally in blood for physiological functions
## Footnote
They are synthesized in the liver, present in higher concentrations in blood than tissues, and have substrates in circulation.
150
What characterizes non-functional plasma enzymes?
* Present in low concentration in blood
* Perform no physiological function
* Levels increase in tissue damage
## Footnote
These enzymes increase due to tissue turnover and damage.
151
Fill in the blank: The measurement of enzymes in serum can be used in the diagnosis of certain _______.
[diseases]
152
True or False: Non-functional plasma enzymes are synthesized in the liver.
False
## Footnote
Non-functional plasma enzymes are present in low concentrations and do not perform physiological functions.
153
What is alkaline phosphatase associated with?
Increases in obstructive jaundice, hyperparathyroidism, rickets, and metastatic carcinoma to bone
## Footnote
Alkaline phosphatase is an enzyme that can indicate various medical conditions when elevated.
154
What does an increase in aspartate aminotransferase (AST) indicate?
Increases in heart disease
## Footnote
AST is an enzyme that can indicate damage to heart tissue.
155
What does an increase in alanine aminotransferase (ALT) indicate?
Increases in liver diseases
## Footnote
ALT is an enzyme primarily found in the liver and is a marker for liver health.
156
Define tumor markers.
Macromolecules mostly proteins whose appearance or changes in concentration in blood or other body fluids is indicative of the presence, extent, or progress of a malignant tumor
## Footnote
Tumor markers may include tumor antigens, hormones, or enzymes.
157
What can cause alterations of serum enzymes in malignancy?
1. Production of increased amounts of enzymes by tumor cells
2. Release of intracellular enzymes due to cell damage
## Footnote
These changes can help in diagnosing and monitoring cancer.
158
Which enzyme is used as a tumor marker that increases in bone metastasis?
Alkaline phosphatase (ALP)
## Footnote
ALP is frequently measured in patients suspected of having bone involvement in cancer.
159
What is the role of creatine kinase (CK) in cancer diagnosis?
The isoenzyme fraction of the brain (CKBB) diagnoses breast tumors, prostatic carcinoma, colonic cancer, and transitional cell carcinoma of bladder
## Footnote
CK is important for identifying certain types of tumors.
160
What does an increase in lactic dehydrogenase (LDH) indicate?
Generally increased in malignancy
## Footnote
LDH is a marker that can indicate tissue damage and is often elevated in various cancers.
161
Fill in the blank: Decreased level of glucose-6-phosphate dehydrogenase is seen in _______.
Favism
## Footnote
Favism is a condition related to the consumption of fava beans leading to hemolytic anemia.
162
What are some enzymes used in the treatment of diseases?
1. Fibrinolysins (e.g., streptokinase) for infarctions
2. Digestive enzymes for maldigestion
3. a-chymotrypsin for intraocular hemorrhage
## Footnote
These enzymes have therapeutic applications in various medical conditions.
163
Which of the following causes a conformational change to the active site of an enzyme?
b- Allosteric inhibitor
## Footnote
Allosteric inhibitors bind to sites other than the active site, causing changes in enzyme shape and function.
164
In feedback inhibition, the inhibitor is _______.
An end product of the enzyme action
## Footnote
Feedback inhibition is a regulatory mechanism where the end product of a pathway inhibits an earlier step.
165
What does the Km value of an enzyme represent?
The substrate concentration at half maximal velocity
## Footnote
Km is an important parameter in enzyme kinetics indicating the affinity of the enzyme for its substrate.
