March 8, 2015 --> 75-90 Flashcards Preview

BOARD: Biochemistry (Dental Decks) > March 8, 2015 --> 75-90 > Flashcards

Flashcards in March 8, 2015 --> 75-90 Deck (65):

The regulation of metabolic processes is achieved through what 2 mechanisms

1. Allosteric regulation
2. Covalent Modification


The synthesis of glycogen from glucose is carried out by what enzyme?

glycogen synthase


Glycogen synthase is responsible for making what type of linkages in glycogen?

alpha-1,4 linkages


To initiate glycogen synthesis, G-6-P is converted to what? By what enzyme?

To Glucose-1-Phosphate by Phosphoglucomutase


After Glucose-1-Phosphate is made from G-6-P, what happens next in the process of making glycogen?

Glucose-1-Phosphate is converted to UDP-glucose by the action of UDP-glucose pyrophosphorylase


T or F, Glycogen synthase occurs in both phosphorylated and dephosphorylated forms



What is the active form of Glycogen synthase, is it phosphorylated or dephosphorylated and what activates it?

Glycogen synthase A is active form
- Dephosphorylated in active form
- Activated by Insulin (dephosphorylated)


What is the inactive form of Glycogen synthase, is it phosphorylated or dephosphorylated and what inactivates it?

Glycogen synthase B is inactive form
- Phosphorylated
- Inactivated by Epinephrine (in muscle and liver) and Glucagon (in liver)


Which enzyme breaks down glycogen?

Glycogen phosphorylase


Is the active form of glycogen phosphorylase phosphorylated or dephosphorylated?

-Phosphorylated (happens in liver cells) --> Active form A
***Activated by glucagon and epinephrine

-Dephosphorylated form is inactive form B
***Inactivated by insulin


Where are the enzymes glycogen synthase and phosphorylase phosphorylated at?

Specific Serine residues


What are the 4 types of enzyme inhibition?

1. Competitive inhibition
2. Noncompetitive inhibition
3. Uncompetitive inhibition
4. Mixed inhibition


Describe competitive inhibition:

Competitive inhibitor resembles the substrate and binds to the ACTIVE SITE of the enzyme. The substrate is then prevented from binding to the same active site.


What is the hallmark of competitive inhibition:

The inhibition can be overcome by increasing the substrate concentration


Describe noncompetitive inhibition:

The inhibitor and substrate can bind simultaneously to an enzyme molecule. This means that their binding sites DO NOT OVERLAP.


T or F, Noncompetitive inhibition can be overcome by increasing the substrate concentration

False, Cannot be overcome
- This is because the inhibitor and substrate do not compete for the same site. Increasing substrate will do nothing.


Which type of enzyme inhibition by definition is an allosteric inhibitor?

Noncompetitive inhibition


Describe Uncompetitive inhibition:

Like noncompetitive, the inhibitor and substrate bind at different sites which do not overlap. However, an uncompetitive inhibitor will bind ONLY to an enzyme that has a substrate already attached (ES complex)


Describe Mixed inhibition:

The inhibitor binds to a site other than the active site, but has a different affinity for the lone enzyme versus the enzyme-substrate complex (ES)


T or F, the noncompetitive inhibitor binds to a free enzyme only

False, can bind to either a free enzyme or the ES complex.

*** Uncompetitive inhibitor is like a noncompetitive inhibitor but can only bind when a substrate is attached


Describe Vmax and Km changes for a noncompetitive inhibition

Vmax is decreased
Km is unchanged


Describe Vmax and Km changes for competitive inhibition

Vmax remains the same
Km is increased


The rate at which an enzyme works is influenced by what factors?

1. Concentration of substrate molecules
2. Temperature (increased temperature = increased activity)
3. Presence of inhibitors
4. pH


The presence of what in the small intestine stimulates the release of CCK?

Amino acids (from protein digestion)


CCK causes the release of what?

The release of pancreatic zymogens (trypsinogen, chymotrypsinogen, proelastase, etc.)
And the contraction of the gallbladder to deliver bile to the duodenum.


Trypsinogen is activated by what?

Trypsin or enteropeptidase


Trypsin converts what 4 enzymes to their active forms?

1. Trypinsogen
2. Chymotrypsinogen
3. Proelastase
4. Procarboxypeptidase


T or F, Trypsin can act as an activator for ALL zymogens of pancreatic proteases



- Where is secreted from
- What is it activated to
- What activates it

1. Secreted by chief cells of the stomach
2. Activated to pepsin
3. Activated by the low pH in the stomach or other activated pepsin molecules


You might find alkaline phosphatase in the serum for what reason?

Bone and liver enzymes are most abundant in normal serum. Alkaline phosphatase will be found in serum levels that rise in bone conditions with increased osteoblastic activity.
*Will be found in liver levels in patients with biliary obstruction


Plasma cholinesterase will be found at what levels in what diseases?

It is decreased in severe liver diseases, including viral hepatitis and liver cirrhosis.
- Most important in the diagnosis of organophosphate poisoning.
- Responsible for metabolism of ester anesthetics used in dentistry


Alanine transaminase and Aspartate transaminase are most abundant where? What levels are they found at during what diseases?

Most abundant in Liver
- They are not secreted into the blood and therefore any elevation of their plasma levels is due to leakage from damaged cells.
- The transaminase levels are used for diagnosis of liver diseases


Gamma-Glutamyl transferase (GGT) is most abundant where? It is found during what disease?

Most abundant in liver and kidney but present in most tissues.
- Is used as a sensitive indicator of biliary obstruction


Acid phosphatase (ACP) and Prostate-specific antigen (PSA) are used in what diagnosis?

They are tumor markers. Used for diagnosis and follow-up of patients with prostatic cancer


Creatine kinase is found in what diagnosis? What other enzymes may be found here?

Is the first heart enzyme to appear in the blood after a heart attack.
Followed by aspartate transaminase (AST) and lactate dehydrogenase (LDH)


Levels of lipase and amylase are elevated in what disease?
- What is their main use in diagnosis?

Acute pancreatitis
- Their main use is the differential diagnosis in patients who present with severe abdominal pain of sudden onset.


A cofactor binds with what to form the active enzyme? What is the name of the active enzyme?

Cofactor binds with apoenzymes.
- Apoenzymes are functionally inactive. When bound with cofactor, they form active enzyme called holoenzyme.


Thiamine pyrophosphate is required as a cofactor for what enzyme? What is the action of that enzyme?

Pyruvate dehydrogenase
- catalyzes the oxidative decarboxylation of pyruvate, to form acetyl-CoA, which then enters into the Krebs cycle


Thiamine pyrophosphate is a coenzyme for transketolase in what pathway?

Pentose phosphate pathway, an alternate pathway for glucose oxidation


Flavin adenine dinucleotide (FAD) is derived from what?
- What is its function?

Derived from Riboflavin (Vitamin B2)
- Functions in certain oxidation/reduction reactions in the body


Nicotinamide adenine dinucleotide (NAD) is derived from what?
- What is its function?

Derived from Nicotinic acid (Niacin/Vitamin B3)
- Utilized alternately with NADH as an oxidizing or reducing agent in various metabolic processes


Coenzyme A is derived from what?
- What is its function?

Derived from Pantothenic acid (Vitamin B5)
- Functions as an acyl group carrier and is necessary for fatty acid synthesis and oxidation, pyruvate oxidation and other acetylation reactions


Pyridoxal Phosphate (PLP) is derived from what?
- What is its function?

Derived from Pyridoxine (Vitamin B6)
- Is essential for many enzymatic reactions, almost all of which are associated with amino acid metabolism


Tetrahydrofolate is derived from what?
- What is its function?

Derived from Folic acid (Vitamin B9)
- Participates in the transfer of various carbon fragments from one molecule to another - for instance, involved in the synthesis of methionine and thymine


Lipoate is derived from what?
- What is its function

Not required in diet
- Cofactor for the pyruvate dehydrogenase complex, which breaks down pyruvate to form acetyl-CoA


Coenzyme B12 is derived from what?
- What is its function?

Vitamin B12
- Is an essential cofactor for several enzymes


Growth hormone is also called what and is secreted by what part of the pituitary?

Also called somatotrophin hormone or Somatotropin
- Synthesized and secreted by cells called somatotropes in the ANTERIOR pituitary and is part of the hypothalamus-pituitary-liver axis.


T or F, GH stimulates body growth, secretion of IGF-1 and lipolysis; It however inhibits the actions of insulin on carbohydrate and lipid metabolism



What is the major target of GH

The liver, where it causes the liver to form several small proteins called somatomedin that have the effect of increasing all aspects of bone growth. Therefore, the somatomedin are also called insulin-like growth factors (IGFs).
- Most important is Somatomedin C (IGF-1). Its concentration in plasma closely follows rate of GH secretion


Excessive GH can lead to what two things?

Gigantism and Acromegaly


A few factors that stimulate GH secretion?

Decreased blood glucose
Decreased blood free fatty acids
Starvation or fasting
Trauma, stres, excitement
Growth hormone-releasing hormone


A few factors that inhibit GH secretion?

Increased blood glucose
Increased blood free fatty acids
Growth hormone inhibitory hormone


What cells express the androgen receptors and the FSH receptors?

Only Sertoli cells.
So these hormones regulate spermatogenesis indirectly through their actions on Sertoli cells.


What hormones are from the posterior pituitary

Antidiuretic hormone (Vasopressin)


What hormones are from the anterior pituitary

Follicle-Stimulating Hormone
Luteinizing hormone
Adrenocorticotropic hormone
Thyroid-stimulating hormone

Melanocyte-stimulating hormone
Growth hormone


cAMP is synthesized from ATP by what hormone?

Adenylate cyclase


cAMP is degraded by a group of enzymes that are collectively known as what?



The most important target of cAMP is?

Protein kinase A


Which hormones use Adenylyl Cyclase-cAMP as the second messenger system: (11)

1. Adrenocorticotropic hormone
2. Angiotensin II (epithelial cells)
3. Calcitonin
4. Catecholamines (beta receptors)
5. FSH
6. Glucagon
7. LH
8. Parathyroid hormone
9. Thyroid-stimulating hormone
10. Secretin
11. Somtostatin


Which hormones use Inositol triphosphate (IP3) and DAG and or calcium-calmodulin as the second messenger system (7)

1. Angiotensin II (vascular smooth muscle)
2. Catecholamines (alpha receptors)
3. Gonadotropin-releasing hormone
4. Growth hormone-releasing hormone
5. Oxytocin
6. Thyroid-releasing hormone
7. Vasopressin


TSH controls the rate of secretion of what two hormones from the thyroid gland?

Thyroxine (T4)
Triiodothyronine (T3)


The hormones of what part of the pituitary are synthesized in neuroendocrine cells located within the supraoptic and paraventricular nuclei of the hypothalamus?

Posterior pituitary


ADH is formed in what nucleus of the hypothalamus? Oxytocin?

ADH: Supraoptic nuclei
Oxytocin: Paraventricular nuclei


Does insulin respond to increased blood free fatty acids?

Yes, Insulin is responsible for maintaining the upper limit of blood GLUCOSE AND FREE FATTY ACID levels.


5 things that decrease insulin secretion

1. Decreased blood glucose
2. Fasting
3. Somatostatin
4. Alpha-adrenergic activity
5. Leptin