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biochem of saliva Flashcards

1
Q

what is saliva?

A

saliva is a clear liquid secreted by the salivary glands in the mouth

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2
Q

what is the function?

A

tasting and moistening of food

bolus formation

speech and swallowing facilitation

buffering ( it contains protein and phosphate buffers and bicarbonate )

digestion : amylase , lipase

Anti microbial ;lysozymes , peroxidase , histatins

inhibition of calcium deposition

protection of tooth decay

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3
Q

what is the composition of saliva?

A

water - 98%

electrolytes : high K

high HCO3

mucous : mucin ( glycoproteins )

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4
Q

what are the characteristics of saliva?

A

ph 6-8 –> optimum for amylase ( requires 5.6 - 7)

hypotonic

1-1.5 liter/day ( it gets recycled thats why dont feel the whole liter )

low Na and low CL ( cuz they get reabsorbed )

high K and high HCO3 ( cuz they get deposited )

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5
Q

describe the production of saliva?

A

initial saliva secretion is isotonic from the plasma

then the secretion moves down the ducts where the cells lining the ducts will modify the composition of secretion by reabsorbing Na and CL and secrete HCO3 and K to lesser extent than NaCL reabsorption

these ducts are impermeable to water so water stays within the lumen of the duct reducing the concentration of solute in the saliva

the final product is hypotonic because duct cells are impermeable to water

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6
Q

what does the tonicity of saliva depend on?

A

the time it takes the secretion to pass through the duct – ionic composition of the saliva change as the flow rate changes

at highest flow rates –> final saliva will be isotonic because the cells have less time to modify saliva

at high flow rates —> final saliva will be isotnic because cells have less time to modify saliva

at lowest flow rates —-> final saliva is mostly hypotonic because ductal cells have more time to modify saliva ( ions gets reabsorbed )

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7
Q

what regulates the ducts channels?

A

aldosterone

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8
Q

what is the enzyme content of saliva?

A

alpha amylase –> breaks starches into sugar

lingual lipase —> fat digestion

salivary peroxidase–> protects against harmful bacteria

lysozyme—> breaks down bacterial cell wall to fight infection

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9
Q

what is the protein content of the saliva?

A

statherins –> prevent tooth mineral loss or prevent precipitation of calcium phosphate in saliva

proline rich proteins ( PRPs) –> protect enamel and aid in digestion

histatins —> fight fungi and bacteria

cystatins —> inhibit harmful enzymes and protect tissues

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10
Q

what is the antibody content of saliva?

A

igA

immune function of the mucous membrane

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11
Q

what are examples of monosaccharides and how are they broken down?

A

glucose

fructose

Galactose

No need to breakdown , absorbed directly

Least complex one

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12
Q

what are examples of disaccharides and how they are absorbed?

A

maltose

surcose

lactose

2 monosacchardies linked

linked by glycosidic bonds and require specific enzymes to breakdown like maltase and sucrase and lactase

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13
Q

what are examples polysaccharides and how they are broken down?

A

starch

glycogen

cellulose

multiple monosaccharides connected together by glycosidic bonds

alpha bonds that are found in starch and glycogen are broken down by amylase

But Beta bonds that are found in cellulose cannot be broken down by human

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14
Q

how are glycosidic bonds formed?

A

condensation reaction between hydroxyl residue on carbon 1 and carbon 4 on two monosaccharides

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15
Q

what are the components of starch?

A

amylose

Amylopectin

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16
Q

what is the difference between them?

A

amylose –> linear and no branches

amylopectin —-> has branches at 1,6

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17
Q

whats starch broken into when digested by alpha amylase?

A

dextrin

maltoriose

maltose

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18
Q

what happens to alpha amylase when it reaches the stomach?

A

due to the acidic environment of the stomach the enzyme is broken down and is deactivated

but in small intestine it comes back in the form of pancreatic amylase and continue breaking down the starch

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19
Q

what type of enzymes is salivary amylase?

A

calcium metalloenzyme ( contains a metal ion )

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20
Q

what is the function of salivary amylase?

A

breaks alpha 1-4 glycosidic bonds of starch into maltose , maltotriose and dextrin

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21
Q

is salivary amylase endoglycosidase or exoglycosidase ?

A

it is endoglycosidase ( breaks down from the middle )

exoglycosidase will remove the sugar units from the end of sugar chains , one at a time

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22
Q

what happens to the starch digested by lingual amylase ?

A

when starch is digested in the mouth it produces a small amount of glucose that oral streptococci use this glucose to produce lactic acid

the lactic acid can erode the tooth enamel leading to dental caries

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23
Q

what secretes lingual lipase?

A

von ebners glans of the tongue

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24
Q

what is the function of lingual lipase?

A

involved in the first phase of fat digestion

important for digestion of milk fat in newborns

similar to pancreatic lipase - digests lipids

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25
what is the special unique ability of lingual lipase?
it can catalyze reactions without bile and salts works at wide PH ranges
26
lingual lipase converts what to what?
triglycerides into monoacylglycerols and free fatty acids
27
how does lingual lipase breakdown fat ( Triglyceride )?
in 2 steps : 1- hydrolyze the first fatty acid 2 - hydrolyze the third fatty acid producing 2 monoacylglycerol and 2 fatty acid molecules
28
which bonds in the triglyceride are broken by lingual lipase?
ester bonds
29
what is the function of salivary peroxidase system?
prevent toxic accumulation of hydrogen peroxide H2O2 inactivates many carcinogenic and mutagenic compounds
30
what is the function peroxidase enzyme?
oxidation of salivary thiocyanate ion by hydrogen peroxide into hypothiocyanite ( OSCN ) potent antibacterial substances
31
what is lysozyme?
lysozyme is a 14 kDa protein present in many mucosal secretions ( tears , saliva , mucus )
32
what is the function of lysozymes?
damage bacterial cell wall and destroy the bacterial peptidoglycan component of the bacterial cell wall antimicrobial enzyme ---> damages the bacterial wall
33
how does lysozymes destroy the cell wall?
catalyzes the hydrolysis of 1-4 beta linkages in the bacterial peptidoglycan ( component of cell wall )
34
what is the difference between lysozymes and lysosomes ?
lysosomes are cellular organelles in the animal cells that degrade and recycle cellular waste using hydrolytic enzyme such as proteases, lipases and nucleases which function best in acidic environment
35
what is mucin?
glycoprotein ( protein + carbohydrates chain ) Carbohydrates chains are linked via glycosidic bonds same thing with the protein and carbohydrate bond
36
what secretes mucin?
mainly from sublingual salivary glands
37
what is the function of mucin?
tissue coating
38
how does mucin block the bacterial action?
making bacterial aggregations
39
where are the glycoprotein found?
plasma membrane present in extra cellular matrix
40
what is glycosylation ?
process of attaching oligosaccharides to protein
41
what amino acids allow the attachment of proteins to oligosaccharides?
asparagine threonine serine
42
what type of bond is formed by asparagine ?
N glycosidic bonds
43
what type of bond is formed by threonine?
O glycosidic bond
44
what type of bond is formed by serine?
O glycosidic bond
45
what is the result of glycosylation ?
covalent bond either N glycosidic bond or O glycosidic bond
46
mucins are rich in which type of animo acids?
mucins are heavily glycosylated protein rich in serine and threonine ( O glycosidic bonds )
47
mucins are major component of what?
mucous membrane
48
what type of tissue produces mucin?
epithelial tissue
49
where do they go after being produced?
most of them are secreted in extra cellular matrix some remain attached to the plasma membrane
50
what is the function of mucin?
lubrications Trap pathogens
51
describe protein synthesis?
begins with transcription where DNA is converted to mRNA mRna undergoes post transcriptional modifications ( capping polyadenylation, splicing ) Translation occurs in cytoplasm on ribosomes which are 2 types of free ribosomes , synthesizing proteins for the cytoplasm , nucleus and mitochondria, other type is rough ER bound ribose which produces secretory membrane and lysosomal proteins translation involves initiation , elongation and termination resulting in polypeptide chain -- peptides are synthesized from N terminus to the C terminus then post translation modifications proteins made by free ribose stay in cytoplasm and go other organelle protein made by ER are transported to golgi or ER or secretory pathways
52
where does glycosylation take place?
in ER and golgi ( addition of sugar chains )
53
describe the process of glycoprotein synthesis?
starts in rough ER 1- translation - ribosomes on the rough ER make polypeptide chain based on mRNA instructions 2- Sugar chain assembly - sugar chain ( oligosaccharide ) is built on DOLICHOL PHOSPHATE , lipid in the ER membrane 3- Glycosylation : sugar chain is transferred to an Asparagine residue for N linked glycosylation 4- trimming in the ER - the enzymes trim parts of the sugar chain as protein folds 5- modification in Golgi : sugar are trimmed further and new sugar are added to create either complex or high mannose glycoproteins 6- targeting to lysosomes -- some glycoproteins are marked with MANNOSE 6 PHOSPHATE in the golgi directing them to lysosomes
54
wheres dolichol found?
primarily found in endoplasmic reticulum
55
what is the function of dolichol?
its a hydrocarbon that plays crucial role in glycosylation where sugars are attaached to proteins or lipids to form glycoprotein / glycolipids it act as a carrier for the sugar chain and transport it to the protein
56
what are complex glycoproteins?
proteins that have carbohydrate chains attached to them, these carbonhydrates may contain animo sugars ( glucosamine / galactosamine ) which contain NH2 instead of OH
57
what enzymes responsible for adding the mannose derivates to the glycoprotein to direct them to lysosomes?
phosphotransferase ( N-acetylglucosamine 1 phosphate transferase GLcNAc phosphotransferase )
58
what happens when you have deficiency in GlcNAc phosphotransferase ?
I-cell disease results in improper targeting of gylcoproteins to the lysosomes causing build of undigested material in cells and affecting various body function
59
describe lysosomes ?
spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules lysosomes are involved in various cell processes
60
what is lysosomal storage disease ? ( LSD)?
inborn errors of metabolism characterized by excess accumulation of substrates in various organs cell due to defective functioning of lysosomes leading to dysfunction of the organ and contribute to great morbidity and mortality
61
what is I-cell disease ( inclusion cell disease , mucolipidosis 2 ) lysosomal storage disease ?
the lysosomal enzymes are glycosylated proteins synthesized in the ER and modified at golgi apparatus in order to direct them to the lysosomes they need to have a mannose derivate which is added by phosphotransferase in deficiency of phosphotransferase the hydrolytic enzymes fail to be directed to the lysosome ---> lysosomes are deficient --- accumulation of products ---> formation of inclusion cell ( I cell )
62
what are the symptoms of I cell disease?
high plasma levels of lysosomal enzymes ( Secreted and not stored ) skeletal abnormalities restricted joint movement psychomotor retardation early death coarse facial features no treatment
63
what is fabry's disease?
most common lysosomal storage disease X linked Deficiency of alpha galactosidase
64
what is the function of alpha galactosidase ?
responsible for hydrolysis of terminal alpha D- galactose residues in D galactosides including galactose , oligosaccharides, galactomannas . glycoprotein and galactolipids
65
what results in the deficiency of alpha galactosidase ?
accumulation of glycosphingolipids particularly ceramide trixoside in the brain, heart , kidney symptoms -- neropathic pain and renal failure
66
what is xerostomia?
dry motuh due to salivary gland hypofunction people suffering from dry mouth have white saliva that is stringy or foamy in consistency
67
what are the causes of dry mouth?
malnutrition Dehydration psychological radiation therapy some medications : anti- depressants, anti hypertensives , anti emetics, diabetes treatments
68
what are the systemic causes of dry mouth?
Sjogre syndrome ( autoimmune disease attaacking exocrine lands ) diabetes end stage renal disease Cystic fibrosis
69
how are the saliva used as a diagnostic tool?
alteration in human genetics by extracting DNA/RNA for molecular diagnostics biomarkers for cancer, metabolic disorders, alzheimers and periodontal disease hormones - adrenal gland hormones like cortisol
70
what are the benefits of using saliva as diagnostic tool?
non invasiveness low cost Rapid tests

BIOCHEM Y2S2 (8 decks)

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