Carbohydrates Flashcards
what are macromolecules
large molecules composed of thousands of covalently connected atoms (carb, protein, nucleic acids)
what are polymers
long molecule consisting of many similar building blocks (monomers) linked by covalent bonds
which of the four classes of life’s organic
molecules contain polymers
carbohydrates
proteins
nucleic acids
what are carbohydrates
includes sugars and their polymers (ex: starch and cellulose)
* the names of sugars typically end in–ose
what are the functions of carbs
- short term energy (sugar)
- intermediate term energy storage (starch from plants and glycogen from animals)
- structural components in cells (cellulose in plants and chitin in fungi)
what is the ratio of carbohydrates
carbon, hydrogen and oxygen in a 1:2:1 ratio (approx.)
what are examples of monosaccharides (3)
- glucose (used in polyemer synthesis)
- fructose (component of table sugar)
- galactose (component of milk sugar)
where is ribose used
used in RNA nucleotides
where is deeoxyribose used
used in DNA nucleotides
what are examples of disaccharides (3)
- sucrose = glu+fru (table sugar, in plants)
- lactose = glu+gal (milk sugar)
- maltose = glu+glu (brewing sugar)
what are examples of polysaccharides (5)
- starch (storage in plants)
- glycogen (sorage in animals)
- cellulose (structural in plants)
- chitin (structural in animals and fungi)
- peptidoglycan (structural in bacteria)
what is the difference between aldoses and ketoses
the location of the carbonyl group (C=O)
what carb is made with aldose
glucose
what carb is made with ketose
fructose
what is the ration of monosaccharides
have molecular formulas that are some multiple of [CH2O]n (1:2:1 ratio)
– where n is a subscipt and a # from 3 to 7
what are the most common sugars
- trioses (3 carbon; smallest sugars)
- pentoses (5 carbon; in DNA)
- hexoses (6 carbon; common sugars)
what are three common monosaccharides that are all hexoses
glucose, galactose, fructose
– all C6H12O6 therefore are structural isomers from one another
what is the most common monosaccharide
glucose: forms a ring structure which is the most common form of living organisms
how can the ring structure of glucose exist
can exist as two isomers, α-glucose and β-glucose. the two isomeric forms differ in the orientation of the OH group at C1
what is the orientation in α-glucose
the OH group at C1 is on the opposite side of CH2OH
what is the orientation in β-glucose
the OH group at C1 is on the same side as CH2OH
what is the end product of photosynthesis in plants
glucose
what happens during cellular respiration
cells oxidize glucose molecules converting the stored energy to a form that can be readily used for cell work
why do mechanisms evolve
mechanisms evolve to maintain the concentration of glucose at constant levels in the blood, which is regulated by the hormones insulin and glucagon produced by the pancreas and transported through the body via blood vessels
what is insulin
insulin can bind to receptors on surface of fat, muscle and liver cells and promote the transport of
glucose inside cells
what is the purpose of insulin
- it’s made in the pancreas, released into the blood stream and then bind to receptors
- a lot of glucose triggers the release of insulin to decrease blood glucose
how does insulin decrease blood glucose levels
- stimulating uptake of glucose in muscle
- preventing breakdown of glycogen to glucose in the liver
- stimulates adipose cells to store glucose as fat
how does glucagon increase blood glucose levels
– stimulating conversion of glycogen to glucose in the liver
– breakdown of proteins into amino acids in muscle cells
– breakdown of fats in adipose tissue and release of fatty acids
what are the symptoms of diabetes
- excess urination
- dehydration
- low energy
- excessive hunger
what is the best-known endocrine disorder
diabetes mellitus
what is type 1 diabetes
caused by a deficiency of insulin
what is type 2 diabetes
a decreased response to insulin in target tissues
– cosuming too much glucose and the insulin receptors are decensatized so glucose stays in bloodstream
how are sugars found in food
it’s often found as part of a disaccharide or starch and rarely found in its monosaccharide form
how is fructose found
fructose is more commonly found in foods as it’s the primary sugar in foods such as fruits, vegetables, and honey
how are disccharides formed
when a dehydration reaction joins two monosaccharides by a covalent bond that is called a glycosidic linkage
what do the cells lining the small intestine do
digestion of disaccharides and other carbs is mediated by enzymes synthesized by cells lining the small intestine
what is lactose intolerance
lactose intolerance is the result of a drop in lactase production often following childhood
how does lactose intolerance work
lactose intolerance creates an osmotic pull drawing water from surrounding tissue into the intestine (causing diarrhea)
– also bacteria digest the disaccharides, producing gas (bloating and cramps)
what is an oligosaccharide
a term often used for relatively small sugar polymers that consist of 2 to 6 monosaccharide units
where are oligosaccharides found
They are most often found attached to glycoproteins and some glycolipids (collectively called glycoconjugates)
– cell to cell communication
in what foods are oligosaccharides found in
present in beans and other legumes and the human stomach and small intestine do not produce an enzyme capable of breaking them down, so these are finally digested by the bacteria in your large intestine => causes gas
what do glycoproteins do
glycoproteins are involved] in cell-to-cell adherence, identification and protection
what are polysaccharides made of
consists of a few hundred to a few thousand monosaccharides linked together by dehydration synthesis
why do polysaccharides vary in their properties
- are composed of different isomers
- units may be arranged differently
what are the two types of polysaccharides
- those that are easily broken down to their subunits are used for energy storage (starch, glycogen)
- those having a particular 3-D arrangement are suited as structural polysaccharides (cellulose, chitin)
where can we see α -linkages
α -linkages are characteristic of sugars and starches that can be metabolized and used as an
energy source by higher organisms
where can we see β-linkages
occur in structural molecules such as cellulose that
cannot be digested by most eukaryotes (not digestible by the mammalian body)
what is glycogen
a branched polysaccharide formed by α-1-4 and α-1-6 glycosidic linkages
– it has a much higherdegree of branching than starch which helps with its solubility
how can glycogen be broken down
into a readily useable form of glucose:
- glucose-6-phosphate
which is ideal for powering short-term metabolism
how is glycogen used in muscle cells
in muscle cells, glycogen is stored and broken down for use by the muscle cell only.
how is glycogen used in the liver
liver cells store glycogen and can break it down to then release it in the blood for use by the body’s cells
what is starch
the main storage molecule for plants
where can starch be found
Found in high concentrations in tubers (enlarged root or stem for storage) and seeds.
what is amylase and where is it made
an enzyme, or special protein, that helps you digest carbohydrates, which is made in the pancreas and salivary glands
how is cellulose formed
formed by a series of β-glucose molecules (β-1-4 linkages).
** the chain is unbranched
what is special about β-glucoses linkages
linkage of β-glucoses allows for extensive hydrogen bonds between cellulose molecules, which promotes the aggregation of the molecules into cellulose fibers
where is cellulose located
in the cell wall of plants
why can’t animals and humans break down cellulose
humans and most animals lack the cellulase enzyme to break the β1-4 link
how do cattle break down cellulose
- cellulose is broken down inside the bacterial cell walls
- bacteria take in cellulose and release the nutrients into gut
how do termites break down cellulose
- bacteria release cellulase into the intestinal lumen
(intestinal space) - cellulose from ingested wood is broken down
what is dietary fibre
cellulose is part of a group of carbs referred to as dietary fiber, which humans need for proper digestion but we lack the enzymes necessary to break these down into monosaccharide units
how does fiber work
fiber adds bulk and absorbs water making feces larger and softer
- reduces pressure for defecation (hemorrhoids, diverticulosis)
- some fibers lower cholesterol (colon cancer and heart disease)
- fiber slows rate of carb absorption (diabetes and obesity)
what is chitin
- unbranched polysaccharide
-the protective exoskeleton of arthropods (insects, arachnids, and crustaceans) - also found in smaller amounts in the cell walls of yeasts, and other fungi
what can chitin be used to make
used to make strong and flexible surgical thread which decomposes as the incision heals
what is peptidoglycan
peptidoglycan is the polysaccharide in bacterial cell walls which identifies gram-positive & gram-negative bacteria
why is gram a valuable tool in medicine
to quickly check if a patient’s infection is caused by a Gram + or Gram – bacterium, and the proper antibiotic will be selected to treat the infection
how does penicilin work
interferes with peptidoglycan synthesis by
inactivating transpeptidases, so it kills gram-positive bacteria
