carbohydrates Flashcards
what are carbohydrates
Carbohydrates
a. Carbon: hydrogen: oxygen (1:2:1)
b. Provide rapid supply of energy for cellular reactions (muscle and liver glycogen)
c. Important part of molecules (DNA sugar-phosphate backbone)
d. Form markers on cell surface which aid cell recognition (blood group markers)
how does the Plants produce energy via carbohydrate?
Plants produce energy via carbohydrate
a. Produce carbohydrates via photosynthesis
b. UV light locked in C-H bond
c. Breaking bond release energy
d. Organisms unlock, use, and transport the energy within complex carbohydrate polymers
Classification of carbohydrates
a. Monosaccharide – general formula (CH2O) n
b. Disaccharide – dimer of monosaccharides
c. Oligosaccharide – polymer of 3-20 monosaccharides
d. Polysaccharide – polymer of mono- or disaccharides
names of number of carbons: from 3-10
a. Three carbons – triose
b. Four carbons – tetrose
c. Five carbons – pentose
d. Six carbons – hexose
e. Seven carbons – heptose
f. Eight carbons – octose
g. Nine carbons – nonose
h. Ten carbons – decose
how to name a suger molecule
Count carbons from top
See if it either has a aldehyde or ketone
If so add:
Prefix- aldo Or keto
aldotriose (glyceraldehyde), aldopentose (ribose), aldohexose (mannose), ketohexose (fructose)
Then add number of carbon name
monosaccharides facts
a. Hydroxyl group position differs between different sugars(glucose, galactose and mannose)
b. Can exist in ‘deoxy’ forms (hydroxyl replaced with H), ( 3-deoxy-glucose,2-deoxy-ribose)
what is a stereoisomer ?
a. Same chemical and same order and types of bonds
b. Different spatial arrangement, biological function
c. D-isomers and L-isomers
d. Non-overlapping mirror images
e. Chiral carbon required for stereoisomerism
Naming stereoisomers:
a. Plane polarised light rotates to the right
- dextrorotatory
- given + symbol or d designation
b. Plane polarised light rotates to the left
- laevorotatory
- given – symbol or l designation
Configurational
a. D and L designation given
b. Related to structure of D/L-glyceraldehyde
c. D/L designation does not predict optical properties
what are examples of isomeric sugars
a. D-glyceraldehyde – the simplest sugar (a triose)
b. D-glucose – important dietary sugar
c. D-galactose – part of milk sugar
d. D-fructose – a very sweet simple sugar(l) – multiple chiral carbons -
e. D-ribose/D-deoxyribose – part of RNA/DNA, respectively
• All D-enantiomers, but not all dextrorotatory (d)
why is D-fructose D designation
• However, structural configuration is the same as D-glyceraldehyde at the penultimate carbon, thus its D designation
Exist as open-chain or ring (cyclic) structures joined by covalent bonds
cyclization ?
D-glucose- open chain
forms closed chain
can form:
alpha-D-Glucopyranose(36%)
beta-D-Glucopyranose(64%)(other OH and H on right side have swaped)
cylization II
cyclization of glucose in solution.
Glucose
- The primary energy source for life
- Seven energy-rich C-H bonds
- Bonds broken down during cellular respiration
- Released energy stored in ATP for future use
Fructose
- Seven energy-rich C-H bonds
- Important source of energy, along with glucose and galactose
- Sweet monosaccharide found in fruits, honey, berries and melons
- Forms a five ring furan-based structure (furanose) despite being a hexose sugar
Disaccharides
- Two monosaccharides linked together
- Formed by dehydration synthesis (condensation reaction) with the loss of H2O
- Reaction aided by biological catalysts (enzymes)
- Molecules joined at –OH groups by glycosidic links
- Multiple configurations possible
- Primary function is as a nutritional source of monosaccharides
the structure of maltose and where is it found:
- Two glucose molecules joined at carbons 1 and 4 via an alpha 1,4 glycosidic link (bond)
- Present in germinating seeds and grain (originating from breakdown of seed starch by amylase) and metabolism of maltose by yeast yields ethanol and CO2
the structure of lactose and where is it found:
- Glucose and galactose molecules joined at carbons 1 and 4 via a beta 1,4 glycosidic link (bond)
- Produced by lactating mammals as energy source for young
the structure of sucrose and where is it found:
- Glucose and fructose molecules joined at carbons 1 and 2 via an alpha 1,2 glycosidic link (bond)
- Found in plants/sap, especially sugar cane and sugar beet
- Very sweet tasting and plentiful in the western diet
Disaccharide Hydrolysis
- The glycosidic links in disaccharides can be broken down during digestion into constituent monosaccharides
- This reaction requires H2O and specific enzymes
- Monosaccharides are more easily absorbed through the gut lining
state the three enzyme responsible for the hydrolysis of the following substances and the products formed.
- Maltase
- Catalyses the hydrolysis of maltose to glucose & glucose
- Lactase
- Catalyses the hydrolysis of lactose to glucose & galactose
- Sucrase
- Catalyses the hydrolysis of sucrose to glucose & fructose
why does Organisms must sometimes convert soluble sugars into an insoluble form?
- For storage in the cell
- For building structures
- For taking part in cellular processes
how are oligo and polysaccharides?
- Monosaccharides are joined together by dehydration synthesis (condensation reactions) into small polymers:
- Oligosaccharides (3-20 monosaccharides)
- Or into long polymers:
- Polysaccharides (long chains or branched structures)
what are glycoproteins ?
Glycoproteins are proteins that contain oligosaccharide chains (glycans) attached covalently to their protein structure. They are glycosylated proteins.
what is Glycolipids ?
Glycolipids are lipids that contain oligosaccharide chains attached covalently to their lipid structure. They are glycosylated lipids
what are the two types of links that can be formed of oligosaccharide to glycoprotein.
- Oligosaccharide attachment can be:
- N-linked to amide N of asparagine residue of the protein (polypeptide) backbone
- O-linked to hydroxyl O of serine and threonine residues of the protein (polypeptide) backbone
whats the function of glycosylated proteins
- Glycosylated membrane proteins play an important role in immune recognition
- Secreted glycoproteins make up mucin and the glycocalyx
what are Glycosaminoglycans (GAGs)
• Long unbranched repeating disaccharide units
what does GAGs contain?
• Consist of amino sugars and uronic acids
glucose to glucuronic acid
what are GAGs properties ?
- Hydrophilic (-ve charge) and readily form gels
- High viscosity and low compressibility
- Good lubricants and add structural integrity
what are proteoglycans?
• When GAGs are attached to proteins via N or O links, they are known as proteoglycans (these are heavily glycosylated glycoproteins)
what are mucopolysaccharides
• When GAGs are not attached to proteins, they are known as mucopolysaccharides
give the names of two GAGs
- Chondroitin
* Hyaluronic acid
describe the bonds formed in chondroitin and hyaluronic acid.
- Chondroitin
- N-acetyl D-galactosamine (GalNAc) and D-glucuronic acid joined by beta 1,3 glycosidic links
- Hyaluronic acid
- N-acetyl D-glucosamine (GlcNAc) and D-glucuronic acid joined by beta 1,3 glycosidic links
describe if the following molecules are sulphated and or attached to a protein.
Chondroitin
Hyaluronic acid
Chondroitin: Sulphated and attached to proteins via O link
Hyaluronic acid:Not sulphated and not attached to proteins (mucopolysaccharide)
give uses Chondroitin and Hyaluronic acid
chondroitin: Forms proteoglycans in cartilage, heart valves and bone
Hyaluronic acide : • Acts as lubricant and shock absorber in synovial fluid and vitreous humour of eye
what are glycolipid functions ?
- Recognition signals
- Attachment factors
- Membrane stabilisers
what are glycolipids associated with ?
- Glycolipids are lipids with attached saccharide carbohydrate chains
- Usually associated with phospholipids on the outer surface of the cell membrane
what is Sphingolipids ?
- Sphingolipids are a subtype of glycolipid
- They contain sphingosine, a fatty acid and a charged head group
- Sphingosine is an 18 carbon amino alcohol
R determines the type of sphingolipid . Name 3 types of sphingolipid
H = Ceramide (signalling molecule) Phosphocholine = Sphingomyelin (found in membranes) Carbohydrate = Glycosphingolipid
what do Glycosphingolipids include ?
cerebrosides and gangliosides
what are Cerebrosides and where are they found ?
Cerebrosides contain glucose or galactose and are found in muscles and nerves
what are Gangliosides and where are they found ?
Gangliosides are complex, containing oligosaccharides and are found in plasma membranes
