Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > Lecture 4 - carbs > Flashcards

Lecture 4 - carbs Flashcards

1
Q

what are carbohydrates

A
  • source of energy
    o diet
    o endogenous
    ▪ stored form of energy
  • structural components
    o cell membrane
    o RNA and DNA
    o cell walls of bacteria and plants
  • Glucose
    o Major clinically significant carbohydrate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

4 structural properties may be used to classify carbohydrates:

A
  1. The size of the base carbon chain (number of carbons in the molecule)
  2. Location of the CO group
  3. Number of sugar units
  4. The stereochemistry \
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

C L A S S I F I C A T I O N ( C A R B O N N U M B E R )

A

basic formula where n is the number of carbon

3-triose- glyceraldehyde
dihydroxyacetone
4- tetrose - erythrose
5-pentose - rib or deoxyribose
6-hexose- glucose galactose
7-heptose-sedoheptulose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

A L D O - HEX - O S E F A M I L Y

A
  • ALDO
    – aldehyde group where the carbonyl group is found on the end C so C=O on terminal C
    -carbs from aldehydes are called aldoses
  • HEX
    – 6 carbons
  • OSE
    – carbohydrate
  • 3 naturally occurring forms
    – D-glucose
    – D-galactose
    – D-mannose
  • Chemical formula: C6H12O6
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

THE K E T O - HEX - O S E F A M I L Y

A
  • KETO
    – ketone group where the carbonyl group C=O is found on a C that is in the middle
    -carbs from ketones is called ketoses
  • HEX
    – 6 carbons
  • OSE
    – carbohydrate
  • 1 naturally occurring form
    – D-fructose
  • Chemical formula: C6H12O6
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are isomers

A
  • Isomers
    o compounds with the same molecular formula but different structures
    ▪ identical number of atoms and atomic elements
  • difference in configuration around one specific C atom
    o glucose, fructose, galactose, mannose C6H12O6 (epimer)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is a Stereoisomers

A

o compounds identical in composition and differ only in spatial configuration
* D- and L- configuration
D- -OH on the right
L- -OH on the left
o most sugars in humans are of the D form with OH on the right

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

enantiomers

A

Non-superimposable mirror images are called enantiomers
(optical isomers)
– they have a “chiral” carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is a M O N O S A C C H A R I D E S

A

simple sugar
* a single polyhydroxy aldehyde or ketone unit that cannot be
hydrolyzed to a simpler form
–c=o and -oh groups form a ring structure (with the chiral carbon) through intramolecular hemiacetal or hemiketal linkage

-when an aldehyde and alcohol come together a ring structure is formed through INTRAMOLECULAR HEMIACETAL OR HEMIKETAL LINKAGES

in a HEMIACETAL FORM (alde+alco) - THE HYDROXYL forms a bridge between c1 and c5 and the carbonyl forms alcohol

makes a carboxylic acid OH-C-OR
the anomeric carbon is the c attached to C=O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

carbonyl

A

c=O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

carboxyl

A

COOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

ketone and alcohol reaction - hemiketal

A

It is the =O (carbonyl group) that reacts with the –OH (alcohol or
“hydroxyl” group)

The H+ from the alcohol group moves positions to form a new OH and the remaining O (from the alcohol) forms the “bridge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

fructose

A

❑ Carbonyl group (at C2 - anomeric carbon) and chiral carbon (at C5) form the hemiketal linkage to form the ring structure
❑ Hemiketal linkage: between the carbonyl group (-C=O) and the chiral carbon
❑ Chiral carbon is the highest numbered carbon with 4 different “groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

A and B isomers

A

Two chiral ring forms are possible
o MUTAROTATION alters the equilibrium between the three forms
* spontaneous opening and closing of the hemiacetal or hemiketal structure
* carbon about which this rotation occurs is the anomeric carbon
o  (-OH group down) and  (-OH group up) anomers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

chemical properties of monosacc

A
  • some carbohydrates are reducing substances
    – free aldehyde or ketone group required
  • the anomeric carbon must remain unaltered
  • the ring must be able to open up!

– Cu2+ or Fe3+ ions can be reduced by reducing sugars
* the resulting oxide is red
* lab application:
o Urinalysis: clinitest tablets with Benedicts reagent /clinitest (Copper 2 Sulphate reduced to copper 1 oxide)
if testing water or egg white the result will be blue or negative but if testing glucose or other sugars the test will be red or post

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are disacc

A

-two monosaccharides joined covalently by a glycosidic bond,
with a formation of h2o
o aldehyde or ketone group of one monosaccharide joins to alcohol or aldehyde or ketone group of another
o Cx(H2O)y

  • physiologically important disaccharides
    maltose = glucose + glucose
    lactose = glucose + galactose
    sucrose = glucose + fructose
17
Q

how does disaccharide act as a reducing sugar

A

-can be a reducing sugar only if there is a free aldehyde or ketone group

  • When the anomeric carbon has a hydroxyl group available to participate, it is considered “reducing”
  • If the anomeric carbon is involved in the linkage, then it cannot be a reducing sugar

so if the anomeric carbon is axial or equatorial alone thats okay but if its joined like \o/ then no

18
Q

what happens when a sugar is reducing

A
  • it reduces another compound and is oxidized i.e the carbonyl group is oxidized to a carboxyl group
  • All monosacccharides are reducing sugars because they are capable of opening up the ring form
  • The reducing end of the disaccharide is the monosaccharide with a free anomeric carbon that is not involved in a glycosidic bond and is capable of converting to the open chain form.
19
Q

how are disaccharides hydrolyzed

A

intestinally by disaccharidases like maltASE, lactase, sucrase

o monosaccharides are absorbed and transported to liver

o the only CHO to be directly used for energy or stored as glycogen is glucose

  • fructose and galactose cannot be used until they are converted to glucose
20
Q

what is starch

A

polysaccharides
o Storage form of carbohydrate in plants

o Composed of two polymers:
* Amylose
▪ linear chain of alpha-1,4-linked glucose units more than a 1000 glucose will make an amylose

  • Amylopectin
    ▪ highly branched chain: with alpha 1-4 and alpha1-6 links
    ▪ up to 1 million glucose units
21
Q

what is Glycogen

A

polysaccharides
o animal storage form of carbohydrate
* liver (hepatocytes)
* muscle
o similar to amylopectin, more highly branched (every 8-12 units)
* enhanced solubility

22
Q

what is Cellulose

A

polysaccharides

structural polysaccharide in plants
o high tensile strength from beta-1,4 linkages look like ////

o humans do not have cellulases
-purest form of cellulose is in
cotton

23
Q

what are two major hormones that help maintain glucose levels between 4.1-5.6 mmol/l

A
  • Insulin:
    ▪ Increases glycogenesis and glycolysis
    ▪ Increases lipogenesis
    ▪ Decreases glycogenolysis
  • Glucagon:
    ▪ Increases glycogenolysis
    ▪ Increases gluconeogenesis

o Regulatory hormones:
* Insulin, Glucagon, Epinephrine, Cortisol, Growth hormone, ACTH
o Disorders of carbohydrate metabolism:
* Hyperglycemia (high blood glucose), Hypoglycemia (low blood glucose)

24
Q

Glycogenesis

A

pathway in glucose metabolism

  • converts glucose to glycogen for storage
  • occurs when blood glucose is high resulting in a lowered blood glucose
  • mainly in liver hepatocytes, influenced by insulin
25
Q

GlycogenoLYSIS

A

pathway in glucose metabolism

breakdown of glycogen to glucose
* occurs when blood glucose is LOW, results in a raised blood glucose

  • mainly in liver, some in muscles, influenced by glucagon and other hormones
26
Q

GlucoNEOgenesis

A

pathway in glucose metabolism
* formation of glucose from non-CHO sources (glycerol, amino acids, lactate)
* occurs when blood glucose is low, results in a raised blood glucose
-it is significant in hypoglycemic states

27
Q

o Glycolysis and Lipogenesis

A

pathways in glucose metabolism

o Glycolysis
* Metabolism of glucose into pyruvate or lactate (energy production)

o Lipogenesis
* Conversion of carbohydrates to fatty acids

28
Q

what monosaccharides are of clinical significance

A

Glucose and galactose

o Hyperglycemia (increased blood glucose) determines a diagnosis of diabetes mellitus (DM)

  • Diabetes mellitus
    ▪ Glucose is underutilized
    ▪ Insulin secretion is impaired or there is tissue insensitivity to its action (or both)
    ▪ Type 1
    ▪ Type 2
    ▪ Gestational diabetes mellitus
29
Q

what is type 1 diabetes

A

-diagnosed in childhood
* ABOSULTE insulin deficiency - autoimmune destruction of the insulin-secreting beta cells of the pancreas

30
Q

what is type 2 diabetes

A

appears in adulthood (most common)
* insulin deficiency (insulin is present, but the target tissues are not sensitive enough)

  • glucotoxicity - beta cells of the pancreas increasingly unresponsive to glucose
  • environmental factors
31
Q

what is gestational diabetes

A

insulin resistance during pregnancy
* maternal hyperglycemia associated with increased neonatal morbidity and mortality

32
Q

Consequences of untreated prolonged hyperglycemia or DIABETES

A

Retinopathy
o Renal dysfunction
oPeripheral circulatory problems
o Myocardial infarction
oStroke

Lab findings in hyperglycemia
o↑ glucose in (serum and urine)
o↑ osmolality in (serum and urine)
o ketonemia and ketonuria in (serum and urine)
o↓ pH (blood and urine)- acidosis
o↑ urine-specific gravity
o electrolyte imbalance
o↓ insulin

33
Q

what is HYPOglycemia and why is it clinically significant

A

from a monosaccharide - Glucose (decreased blood glucose)
* not as common
* defective glucose counter-regulation by glucagon, epinephrine

  • unawareness in half of long-standing
    Type 1 diabetics
    o no neurogenic warning symptoms
    o decreased epinephrine response
34
Q

consequences of untreated hypoglycemia

A

-severe CNS dysfunction : headache, confusion, dizziness, seizures, loss of
consciousness, death

  • Lab findings in hypoglycemia
    o ↓↓ blood glucose levels
    o ↑ insulin

glucose in infants is lower than in adults
hypogly in infants is transient - prematurity, maternal diabetes, GMD, maternal toxemia

less transient if there are inborn metabolism errors

35
Q

hypoglycemia in infants is called :

A

galactosemia
o congenital enzyme deficiency
o cannot convert galactose to glucose
o “failure to thrive”
o screen at birth
o easy to treat

o Lab findings
* hypoglycemia
* hyperbilirubinemia
* ↑ galactose

causes brain damage, cataracts, jaundice, enlarged liver, kidney damage,

if a galactosemic baby is given milk the unmetabolized milk sugars will build up and damage the liver, eyes, kidneys and brain

36
Q

hypoglycemia in adults causes

A

Decreased glucose production or increased glucose utilization

o drugs - most prevalent cause
o ethanol - inhibits gluconeogenesis
o hepatic disease
o pancreatic tumours
o septicemia
o defective glucose counter regulation

37
Q

what are some disaccharide deficiencies of clinical significance

A

-can lead to forms of glycogen storage disease ie Lactase deficiency
-deficiencies of individual disaccharidases

38
Q

what is Lactase deficiency:

A
  • inability to digest lactose (milk sugar)
  • occurs after weaning
  • unabsorbed lactose is fermented by intestinal bacteria leading to cramps, bloating, gas formation, diarrhea
  • premature infants are more prone to lactose intolerance: the enzyme levels do not increase significantly until the third trimester of pregnancy

o Diagnosis would be lactose intolerance
* lactose tolerance test
* breath hydrogen
* stool acidity
* reducing substances

o Treatment
* avoid lactose-containing foods
* lactase tablets

39
Q

Polysaccharides deficiency clinical significance

A

Glycogen storage disease -deficiency of an enzyme involved in glycogen metabolism - glycogenolysis
* inherited defects will present in childhood
* affects liver and skeletal muscle
o LIVER forms are marked by hepatomegaly and hypoglycemia
o MUSCLE forms have mild symptoms that manifest after strenuous exercise
* no specific treatment or cure
o liver transplant

Chemistry (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions