carbohydrates Flashcards
what type of carb is glucose?
hexose monosacchride
what are some useful properties of glucose?
soluble
allows glucose to dissolve in cytoplasm
polar
bonds with water to be transported around the body
what takes place in a condensation reaction?
2 glucose molecules
their hydroxyl groups interacts
causes bonds to break and new bonds reformed to produce a new molecule
water is produced
where is fructose found in
what are its properties compared to other sugars
what does it produce when combined with glucose?
fruit
sweetest compared to glucose , then galactose
sucrose
what does galactose + glucose form?
lactose
how is starch formed?
what are the uses of starch?
formed from amylose and amylopectin
chemical energy store (in plants)
glucose produced in photosynthesis stored as starch
how is amylose formed?
alpha-glucose molecules joined by 1-4 glycosidic bonds
how is a polysaccharide able to be compact?
angle of bonds means chain of glucose twists/coils
how is amylopectin formed?
formed from 1-4 glycosidic bonds between alpha-glucose
branches off in glycosidic bonds formed by condensation reactions between carbon 1 & carbon 6 on 2 glucose molecules
gives amylopectin a branched structure
what is the energy storage molecule for animals?
what are some of its properties that are useful?
glycogen
forms branches
lots of end points for quick release of glucose for aerobic respiration
compact
what are the properties important in amylopectin and amylose?
insoluble
branched
compact
C + H + O
carbohydrate
or lipid
C + H + O + N (+S)
protein
C + H + O + N + P
nucleic acids
describe the difference between an alpha and beta glucose
hydroxyl group on carbon 1 is in a different position
in alpha-glucose it is below the plane
in beta-glucose it is above the plane
describe the formation of a 1,4 glycosidic bond
bond formed between two glucose molecules
hydroxyl group on carbon 1 on one molecule and carbon 4 on the other molecule
interacts in a condensation reaction
removal of water molecule forms an ‘oxygen’ bridge
how is the structure of cellulose related to its function?
straight chain molecule
many hydrogen bonds between individual chains and staggered ends
grants strength to fibres
why does the polymerisation of beta glucose lead to cellulose instead of starch?
in beta glucose the hydroxyl group at carbon 1 is above the ring
alternate glucose molecules must rotate upside down
so the hydroxyl groups on carbon 1 and carbon 4 (on the alt molecule) are close enough to react
condensation reaction
forming a glycosidic bond
rotation of alternative molecules forms a straight chain molecule – cellulose
describe a hydrolysis reaction?
reverse of condensation reaction
needed for glucose, starch or glycogen to be released
requires additional water molecules and is catalysed by enzymes
how are fibres produced from cellulose molecules?
cellulose molecules make hydrogen bonds with each other forming microfibrils
microfibrils form together to form macrofibrils
macrofibrils form together to form fibres
what is the relation between cellulose and the digestive system?
cellulose is hard to break down into its monomers because it is a straight chain molecule
forms the roughage needed for a healthy digestive system
fibres are insoluble, strong and used to make cell walls
what’s another name for a simple sugar?
monosaccharide
what’s glucose used for?
production of ATP in respiration
(plants and animals)
what’s the test procedure for the presence of reducing sugars (monosaccharides)?
add benedict’s reagent
heat (60-80 degrees)
turns green – red (depending on amt of sugar)
what’s the test procedure for the benedict’s reagent on non-reducing sugars?
hydrolysis on molecules
add HCl (breaks glyosidic bonds) and neutralise
add benedict’s reagent
what kind of bond is a glyosidic bond?
covalent
what’s the general formula for carbohydrates?
(CH2O)n
what are some uses of carbohydrates?
respiration to produce ATP
energy storage
structural role
(cellulose in plants)
describe the structure of chitin
made of glucosamine units (glucose + amino acids) and is linked by beta 1,4 glycosidic bonds
amine groups causes more hydrogen bonding between the chains (more than cellulose)
resilient and tough
describe the test for starch?
add 2-3 drops of iodine
positive result - blue/black ppt forms
outline a biochemical test which you could use to distinguish between a solution of glucose and a solution of sucrose
add benedict’s reagent to each solution
heat to 60-80 degrees celsius
results:
glucose solution gives red solution
sucrose solution does not change colour
how is starch digested
starch => maltose
(salivary & pancreatic) amylase
alpha amylase - breaks 1-4 links (randomly)
beta amylase - breaks alternate 1-4 links
maltose => glucose
maltase
how is glycogen digested
beta cells in islets of langerhans secrete glucagon which activates enzymes for glycogenolysis
how is cellulose digested
cellulase
how does insolubility make for good storage molecules
osmotically inactive
doesn’t affect water potential gradient
where is glycogen stored
mainly in the liver and muscles
explain the structure of cellulose and what do these join to form
inverted arrangement of successive glucose molecules means thousands of hydrogen bonds form
cellulose molecules tightly cross-linked to form microfibrils
microfibrils form macro fibrils which then form fibres
fibres run across each other, interwoven and held together by a matrix of other substances
gives cellulose a mechanically strong structure
state two ways in which the molecular structure of cholesterol is similar to the molecular structure of glucose
both contain carbon and hydrogen atoms
have a hydroxyl group
explain why mammals store glycogen instead of glucose
insoluble
so has no effect on water potential
metabolically inactive
compact
so can store large amounts of energy
state three structural similarities between lactose and maltose
two 5C rings (hexose)
1-4 glycosidic bonds
two CH2OH groups
does lactose contain beta glucose or alpha glucose
beta
how does the structure of galactose allow it to be used as a respiratory substrate
bonds contain energy which can be broken down
soluble so can be moved within cell
has OH groups so is water-soluble
how is cellulose suitable for its function as a basis of plant cell walls
insoluble in water
unreactive
high tensile strength
flexible
forms hydrogen bonds with neighbouring chains (stability)
state the similarities and differences between the structures of glycogen and chitin
similarities:
polymers
have 6 carbons
have 1-4 glycosidic bonds
differences:
chitin contains nitrogen
chitin has beta glycosidic bonds
(therefore) no branching in chitin
Explain how the structure of glycogen differs from that of amylopectin to make it better suited as an
energy store in animals
glycogen (compared to amylopectin)
more branched
branching gives more free ends where glucose can be added or removed
(so) speeds up glucose release/hydrolysis
more coiled
(so is) more compact / less space needed (for storage)
