Biomolecules — Carbohydrates Flashcards
Physical properties of glucose
Sweet,
soluble,
Crystalline structure
alpha-glucose vs beta-glucose
Alpha:
- On carbon-1, H atom is above the plain
- OH group is below the plain
Beta:
- On carbon-1, H atom is below the plain
- OH group is above the plain
Formation of Maltose
- 2 alpha-glucose molecules join tgt via a alpha-1, 4 glycosidic bond.
- 1 H20 molecule join is produced
- Reaction: condensation
Why is hydrolysis?
- breaking a disaccharide into its monomers with 1 molecule of H20
Starch properties + Function
- mixture of amylose and amylopectin
PROPERTIES:
-
Folds into compact shape
- To pack as many glucose residues in a fixed volume
- forms starch granules in plant tissue / storage organs
-
Folds into compact shape
-
Large and Insoluble in water
- Exert no osmotic effect on cells when stored in large amts
- Won’t diffuse out of cell -
Easily hydrolysed
- can be converted into glucose easily for release of energy in the form of ATP adenosine triphosphate
What mixture does starch consist of?
Amylose and amylopectin
Amylose Structure in Starch
- made of a-glucose residues
- Joint ONLY via a-1, 4-glycosidic bonds
- unbranched chain polymer
- coils into compact helical structures
- to pack more glucose residues
- (—OH) group on carbon-2 projects into the middle of the helix
- H bonds formed between OH of adjacent glucose
Amylopectin structure in starch
- made of a-glucose residues
- joint via a-1, 4-glycosidic bonds
- AND a-1, 6-glycosidic bonds
- Branched chain polymer
- Branches every 12-30 residues
- Average branch length is 24-30 residues
(Twice as many glucose residues as amylose) - coils into helical compact structure stabilised by H bonds
- OH on each carbon-2 projects into the middle of the helix
- H bonds are formed between OH groups of adjacent glucose residues
Sim & Diff of Amylose and Amylopectin
SIMILARITIES
- Both made of a-glucose linked by glycosidic bonds
_ - Both coil into a compact helical structure stabilised by H bonds
_ - Both unreactive and chemically stable as OH groups of anomeric Carbons are bonded in glycosidic bonds
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DIFFERENCES
- Amylose:
- a-1, 4-glycosidic bonds ONLY
Amylopectin:
- a-1, 4-glycosidic bonds AND a-1, 6-glycosidic bonds
———
2.
Amylose:
- **Unbranched chain straight chain
Amylopectin:
- highly Branched in straight chain
- Branches every 12-30 residues
- Average branch length is 12-30 residues
How is Starch/ Glycogen Adapted to its Function as a Storage Molecule?
4 pts
- Large & insoluble due to H bonding btwn OH groups
STRUC:
- In amylose and amylopectin, OH group projected to centre of coiled helix
- and they form glycosidic bonds with other OH groups of adjacent glucose.
- So can’t form H bonds w/ H2O
FUNCTION:
- Doesn’t exert osmotic effect on the cell when stored in large amts
- Can’t diffuse in/out of cells
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2. Highly branched due to a-1, 6-glycosidic bonds in amylopectin/glycogen
- Very compact
- Stores more glucose monomers per unit volume
- Branching of amylopectin gives many free ends available for hydrolysis when needed
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3. Glucose monomers joined by a-1, 4-glycosidic bonds
- Starch easily hydrolysis by amylase into monosaccharides for use as respiratory substrates
- Glycogen easily hydrolysed into monosaccharides for use as respiratory substrates
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4. Carbon-1 involved into glycosidic bond
- Unreactive & chem stable
- doesn’t interfere with/ chem reactions
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5. Has Many glucose monomers
- Large store of energy
Glycogen Strcuture
Doesn’t have amylopectin or amylose
- But similar Struc to amylopectin
- More branching than amylopectin
- Branches every 8-12 glucose residues
- More compact than amylopectin
- a-glucose residues
- joined by a-1, 4-glycosidic bonds
- AND a-1, 6-glycosidic bonds
- Branched chain polymer
- Coils into compact helical shape stabilised by H bonds
Cellulose structure
- made of b-glucose residues
- joint via b-1, 4 glycosidic bonds
. - Alternate glucose residues are rotated 180 degrees
- allows for intra-chain H bonds between OH group and O atom of adjacent glucose residues.
- this prevents coiling
- keeps cellulose molecule straight
. - Chains run parallel to one another
- There is also Inter-chain H bonds
- between OH groups of neighbouring chains
- Forms rigid cross-links between chains
XX(covalent cross-links for collagen)
. - Cellulose chains associate in groups called microfibrils
- Microfibrils form larger bundles called macrofibrils
. - Many macrofibrils are interwoven & embedded in gel-like matrix
- to form cell wall
- so it has high tensile strength
Properties of Cellulose in Cell Wall that support its function
-
_ Large & insoluble due to bonding_
FUNCTION
- OH groups involve in glycosidic & intrachain and interchain H bonds
- Cannot form H bonds with water
- Good structural material
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2. Long, Unbranched, straight chains w/ extensive H bonds (rigid cross links)
- Allows many cellulose chains to form microfibrils
- Many microfibrils can form macrofibrils
- Gives cellulose high tensile strength & struc support
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3. Cellulose fibres load on diff orientations in various layers of cell wall
- Able to **withstand forces from all directions
- High tensile strength & stability
Where is Starch stored?
Starch accumulates to form starch grains in chloroplasts of plant cells
Where is Glycogen stored?
Glycogen accumulates to form glycogen granules in liver and muscle cells
