Topic 1: Carbohydrates Flashcards
Name the four main dietary risk factors for CVD
- High CARBOHYDRATES (especially sugars) may cause obesity - depending on the ENERGY BALANCE
- High saturated fat (lipid)
- High cholesterol (lipid)
- High salt
Name the THREE elements that all carbohydrates are made from.
- Carbon
- Hydrogen
- Oxygen
NOTE: The word ‘carbohydrate’ means hydrated carbon (carbon with water added)
Define condensation reaction (3 points)
- Joining of monomers or smaller molecules to make a larger molecule
- Water is removed, so produced
- A bond is formed
Define hydrolysis reaction (3 points)
- {Splitting/ breaking down} of polymers or large molecule into smaller {molecules / monomers }
- Water is added
- A bond is broken
Define Hexose sugar (1 point)
- Six carbon sugar
Define Monosaccharide (1 point)
Give its formula (1 point)
- Single sugar unit - no glycosidic bond
1. Formula CnH2nOn (n is a number)
Define disaccharide (1 point)
- {Two/double} sugar units joined together by a glycosidic bond in a condensation reaction
Key Summary: Differences between a monosaccharide and a disaccharide (or named ones)
(3 points)
- A monosaccharide is a single sugar unit, a disaccharide is a double sugar unit
- A disaccharide contains {A / ONE} glycosidic BOND, a monosaccharide has NO glycosidic bond
- A monosaccharide has the formula CnH2nOn (n is a number)
Note: The question could give names – so you need to learn the 3 monosaccharides and 3 disaccharides e.g. explain the difference between glucose and maltose
List the monosaccharides (3 monosaccharides)
- Glucose
- Fructose
- Galactose
List the Disaccharides (3 disaccharides)
- Maltose
- Sucrose
- Lactose
List the Polysaccharides (5 polysaccharides)
- Starch
- Amylose
- Amylopectin
- Glycogen
- Cellulose
Glucose: List properties (3 points), biological function (3 points)
Properties: Sweet, soluble, Crystalline
Biological function:
(1) IMMEDIATE ENERGY SOURCE FOR RESPIRATION.
(2) Can be joined to form starch or glycogen for energy storage
(3) cellulose for cell walls
Fructose: List properties (3 points), biological function (2 points)
Properties: Sweet, soluble, crystalline
Biological function:
(1) IN FRUIT - ATTRACTS ANIMALS FOR SEED DISPERSAL
(2) Component of sucrose (plant transport sugar)
Galactose: List properties (3), biological function (1)
Properties: Sweet, soluble, crystalline
Biological function:
1. Component of lactose (found in milk)
Key Summary: Explain how the structure of a monosaccharide (eg. glucose) makes it suitable for its role
(1 point to state role) + (3 points for how it is suitable for its role)
- ROLE IS IMMEDIATE ENERGY SOURCE FOR RESPIRATION
- SMALL – DOES NOT NEED TO BE HYDROLYSED, so can be quickly and easily absorbed into blood and diffuse into cells
- SOLUBLE – IS A POLAR MOLECULE WITH HYDROPHILIC OH GROUPS ON THE OUTSIDE – these can form hydrogen bonds with water making it SOLUBLE so quickly absorbed into the blood + transported dissolved in blood
- Carried to tissues eg. muscle - quickly absorbed into cells (to be immediately used for respiration to release energy)
In the human body, monosaccharides join to form …
________- energy store in liver and muscles
In plants, monosaccharides join to form …
________- for plant cell walls
________- energy store in plant cells and roots
________-for transport in phloem
________- energy in seeds
Glycogen Cellulose Starch Sucrose Maltose
Key Summary: {Explain how {disaccharides/polysaccharides} (or named disaccharide/ polysaccharide) are formed / how monosaccharides join}
(5 steps)
- {Disaccharides/polysaccharides} are made from MONOSACCHARIDES (2 for disaccharide or many for polysaccharide + give names e.g. if sucrose, then glucose and fructose, if starch then glucose)
- CONDENSATION REACTIONS CATALYSED BY ENZYMES
- GLYCOSIDIC BOND(S) FORM (state type e.g. in sucrose 1,4 glycosidic bond, in glycogen and starch 1,4 and 1,6 glycosidic bonds) BETWEEN monosaccharides
- One WATER RELEASED for each glycosidic bond formed
- {Disaccharide/polysaccharide} forms (name if applicable)
Glycosidic bonds can be split through hydrolysis reactions.
In the human body, this happens in _________.
digestion
Key Summary: Explain how {disaccharides/polysaccharides} (or named disaccharide/polysaccharide) are {broken down/digested}
(4 steps)
- HYDROLYSIS REACTIONS CATALYSED BY ENZYMES
- GLYCOSIDIC bond(s) (state names e.g. in sucrose 1,4 glycosidic bond, in glycogen 1,4 and 1,6 glycosidic bonds) BETWEEN monosaccharides BREAK
- One WATER MOLECULE IS {USED / NEEDED} for every glycosidic bond that breaks
- MONOSACCHARIDES ARE RELEASED (2 or many/give names e.g. if sucrose, then glucose and fructose, if starch then glucose)
Maltose: What monosaccharides is it made of? Biological function? (1 function)
Made of: Glucose + glucose
Function: Found in germinating seeds(the enzyme amylase breaks down starch into maltose, then maltase releases glucose) for energy for growth
Sucrose: What monosaccharides is it made of? Biological function? (1 function)
Made of: glucose + fructose
Function: transport sugar in phloem (found in plants)
Lactose: What monosaccharides is it made of? Biological function? (1 function)
Made of: Glucose + galactose
Function: Sugar in milk - releases glucose for energy
Key Summary: What is the role of a disaccharide? (1 point) & How does their structure help them carry out this role? (3 points)
- Role of a disaccharide = can be hydrolysed (broken down) to provide monosaccharides for energy
How does their structure help them to carry out this role?
- Relatively small
- Have OH groups on surface which can hydrogen bond with water, so are soluble
- Need to be hydrolysed (happens more quickly than for polysaccharides), to release monosaccharides that can quickly be absorbed into the bloodstream, then carried to tissues eg. muscle, where they are absorbed into cells and used for respiration
Define polysaccharide (1 point)
- Many sugar units (monomers) joined together by glycosidic bonds formed in condensation reactions
Glucose has two isomers; α glucose and ß glucose
the position of the hydroxyl groups is different in each
Alpha glucose makes ______ and _______
Beta glucose makes _______
starch glycogen
cellulose
Key Summary: Describe the structure of starch (3 points)
- made of alpha glucose molecules, joined by glycosidic bonds to make the polysaccharides amylose and amylopectin
- amylose is an unbranched chain, coiled into a helix, with alpha 1-4 glycosidic bonds between glucose molecules in the chain
- amylopectin is branched with alpha 1-4 glycosidic bonds in the chains and alpha 1-6 glycosidic bonds where a branch joins a straight chain
Key Summary: Describe the structure of glycogen (4 points)
- made of alpha glucose molecules joined by condensation reactions
- joined by alpha 1,4 glycosidic bonds in main chains and alpha 1,6 glycosidic bonds at a branch point
- branched
- more compact than starch
Key Summary: Explain why {starch/glycogen} is a good energy storage molecule (5 points)
- POLYSACCHARIDES are polymers made of MANY GLUCOSE monomers – glucose released can be used for respiration
- LARGE - so can store large amounts of {energy/glucose} and cannot pass out of cells
- INSOLUBLE – has no osmotic effect in cells and cannot diffuse out of cells
- COMPACT due to {spiral/branched} structure - more {starch/glycogen} and therefore glucose and energy can be stored in a smaller space
- BRANCHED SO CAN BE RAPIDLY HYDROLYSED to release glucose for respiration when energy is required - as enzymes can work on all branch endings at same time
Describe the structure of cellulose
3 points
- Composed of beta glucose
- {Unbranched/straight} chain
- only 1,4 glycosidic bonds
What is the function of starch?
1 point
- Energy storage in PLANTS (due to large, compact, insoluble, branched)
What is the function of glycogen?
1 point
- Energy storage in ANIMALS (due to large, compact, insoluble, branched)
What is the function of cellulose?
1 point
- Strengthens the cell wall in plants
