Carbohydrates Flashcards
Define monomer.
Give examples
Smaller units that join together to form larger molecules
Monosaccharides (glucose, fructose, galactose, ribose)
Amino acids
Nucleotides
Define polymer.
Give examples
Long chain molecules formed when many monomers join together
Polysaccharides
Proteins
DNA/ RNA
condensation + hydrolysis reactions
Condensation = Chemical bond forms between 2 molecules + molecule of water is produced
Hydrolysis = a water molecule is used to break a chemical bond between 2 molecules
EG peptide bonds in proteins
ester bonds between fatty acids and glycerol in lipids
elements found in carbohydrates, lipids, proteins and nucleic acids
Carbohydrates + lipids = C, H, O
Proteins = C, H , O, N, S
Nucleic acids = C, H, O, N, P
Carbohydrates
Also known as saccharides or sugars
Glucose
C6H12O6 - white crystalline solid
Monosaccharide composed of 6 carbons = hexose monosaccharide
2 isomers: alpha and beta
In both, carbon 1 is bonded to a hydrogen atom and an OH group
Polar + soluble (hydrophilic) due to hydrogen bonds between OH group and water - this is important as glucose dissolves in the cytosine of cells do it can be easily transported
Alpha glucose
OH below plane/ring
Beta glucose
OH above plane/ring
Pentode monosaccharide
Monosaccharide composed of 5 carbons
EG Ribose
Present in RNA nucleotides
Deoxyribose present in DNA nucleotides
Other important sugars
Fructose :
Hexose monosaccharide
Occurs naturally in fruit
Galactose:
Hexose monosaccharide
Fructose is sweeter than glucose
Glucose is sweeter than galactose
Monosaccharide + monosaccharide =
Disaccharide + water
Glucose + fructose =
Sucrose + water (cane sugar)
Glucose + galactose =
Lactose + water (found in milk)
Alpha glucose + alpha glucose =
Maltose + water
Condensation reaction
A chemical reaction in which two or more molecules combine to produce water and another larger molecule
EG alpha glucose + alpha glucose = maltose + glucose
- 2 hydrogens + 1 oxygen atom are removed + join to a form a water molecule
- a glycosidic bond forms between carbon 1 and carbon 4 on the glucose molecule
Hydrolysis reaction
A chemical reaction that breaks up a larger molecule into two smaller molecule by adding a molecule of H2O
Glucose is stored as starch by plants, or glycogen by animals and fungi until needed for respiration
- to release glucose for respiration, starch and glycogen undergo hydrolysis reaction
- the reaction is catalysed by enzymes
Enzymes that break down carbohydrates
Carbohydrases
Amylase
Maltase
Starch
Storage polysaccharide of plants
Many alpha glucoses join together to form 2 polysaccharides - known collectively as starch
Chemical energy store
Amylase + amylopectin
Amylose (starch)
Formed by alpha molecules joined 1-4 glycosidic bonds
structure:
- Angle of bond means long chain of glucose twists to form a helix which is further stabilised by hydrogen binding in the molecule
- unbranched structure
Property:
Makes polysaccharides more compact, it is also not soluble
Function
Compactness makes it well suited for energy storage as it takes up little space so more can be stored but it does take longer to release.
Insoluble nature doesn’t affect water potential
Amylopectin (starch)
Alpha glucose molecules joined together by 1-4 glycosidic bonds AND glycosidic bonds for,Ed by condensation reactions between Carbon 1 and 6 on two glucose molecules
Structure:
Branched structure, 1-6 branching points occurs 1 in every 25 glucose subunits
Properties
Branches increase surface area = compact + insoluble
Function
Increases surface area so molecule can be hydrolysed for respiration quickly
Compactness makes it well suited for energy store age as it takes up little space
Insoluble nature doesn’t affect water potential
Glycogen
Storage form in animals (glucose)
Polysaccharide of alpha glucose monomers
1-6 glycosidic bonds = branched structure
More branches than amylopectin
More coiling = more compact = less space
- ideal as animals are mobile
Branching = free ends where glucose molecules can be added or embedded = speeds up process of storing + releasing glucose molecules = increased enzyme activity
Insolubility doesn’t affect water potential
Key properties of amylopectin + glycogen
Insolubility
Branched structure
Compactness = suitable for storage roles
Cellulose
Polysaccharide with linear chain of beta glucose molecules
Cellulose molecules make H-bonds with each other = forms microfibrils = forms macrofibrils = fibres
Fibres are strong = structural support for plants
Insoluble = won’t affect water potential
Held together by C1-4 linkages
Human body doesn’t have the enzymes needed to break the bonds so they pass through our bodies as roughage
