Carbohydrates Flashcards
Carbohydrate functions
[SISTER acronym]
Substrate for respiration (glucose is essential for cardiac tissues)
•Intermediate in respiration (glyceraldehydes)
•Structural (cellulose in plants, chitin in fungi, peptidoglycan/murein in bacteria)
•Transport (sucrose is transported in the phloem of a plant)
•Energy stores (starch, glycogen)
•Recognition of molecules outside a cell (attached to proteins or lipids on cell surface membrane)
Starch is formed when […] monomers join together
Alpha glucose
What is starch made up of
Amylose & amylopectin
How are glucose molecules bonded in amylose
Using 1-4 glycosidic bonds
What shape does amylose form
A helix shape
-> this stabilises the structure as it allows H bonds to form throughout
—> therefore making the molecule more compact + less soluble
what bonds is amylopectin made of
1-4 glycosidic between a-glucose molecules but also 1-6 glycosidic bonds (every 25 glucose subunits)
What structure does amylopectin have
A branching one
What is cellulose
The main structural constituent of plant cell walls
Cellulose has strong [………] which keeps the plant cell walls strong, which is important as plants don’t have a skeleton
Microfibrils
Unlike glycogen and starch, cellulose is made up of […]
Beta glucose
Every molecule in cellulose is rotated by […]
180°
What bonds do cellulose have
- 1-4 glycosidic bonds that form between adjacent beta glucose molecules
- bonds between the rotated beta glucose molecules on the same cellulose chain and between the rotated B glucose on cellulose chains that lie alongside each other
What is glycogen
The main storage polysaccharide in animals & fungi
Why is glycogen so compact
Due to it forming more branches (than amylopectin)
Why is it important that glycogen is a branched polysaccharide
It being branded makes it easier to remove glucose molecules when they are needed
-> hydrolysis can happen quicker when urgent need for glucose
What bonds does glycogen have
1-4 and 1-6 (every ~10 subunits) glycosidic bonds
Basic structure + functions of glycogen
STRUCTURE:
shorter chains than starch and is more highly branched
FUNCTIONS:
carbohydrate storage in animals, structurally suited for because:
- insoluble so does not tend to draw water into cells by osmosis
- insoluble so does not diffuse out of cells
compact so a lot can be stored in a small space - more highly branched than starch so has more ends that can be acted on simultaneously by enzymes so is therefore more rapidly broken down to form glucose monomers, which are used in respiration - important because animals have a higher metabolic rate and therefore respiratory rate than plants because they are more active.
Basic structure + functions starch
STRUCTURE:
made up of chains of alpha-glucose linked by glycosidic bonds formed by condensation reactions.
chains may be branched or unbranched - unbranched chain wound into a tight coil that makes the molecule very compact
FUNCTION:
main role is energy storage for plants, structurally suited for because:
- insoluble and so doesnt affect water potential, so water isnt drawn into cells by osmosis
- large and insoluble so does not diffuse out of cells
- compact so a lot of it can stored in a small space
- when hydrolysed it forms alpha-glucose, which is easily transported and readily used in respiration
- branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly
Basic structure + functions of cellulose
STRUCTURE:
made of monomers of beta-glucose rather than alpha glucose, unlike starch and glycogen.
unlike a coiled chain in starch, cellulose has straight unbranched chains that run parallel to one another, allowing hydrogen bonds to form cross-links between adjacent chains. this strengthens the molecule and makes it a suitable structural material.
FUNCTIONS:
provides rigidity to the plant cell and prevents the wall from bursting as water enters it by osmosis.
structurally suited to its function because:
- made up of beta-glucose and so form long, unbranched chains
- chains run parallel to each other and are crosslinked by hydrogen bonds that add collective strength
- molecules grouped to form microfibrils which are grouped to form fibres that provide more strength
