Carbohydrates Flashcards
What is one calorie?
- one calorie is the quantity of heat energy required to raise the temperature of 1cm³ of water by 1°C
What is a kilocalorie?
- 1 kc = 1000 calories
- food labels normally display units of 1000 calories, called kilocalories
How many joules are in one calorie?
4.18 Joules = 1 calorie
What is a kilojoule?
1 kJ = 1000 Joules
What is a condensation reaction?
- A condensation reaction is a chemical reaction in which two molecules join together forming a larger molecule and release a smaller molecule such as water in the process.
- it is an anabolic reaction
What is hydrolysis?
- hydrolysis is a chemical reaction that breaks a chemical bond between two molecules by adding water
- is the opposite of a condensation reaction
- (is basically the addition of water to break a chemical bond)
What is a glycosidic link?
- the glycosidic link (or bond) is the bond that forms between two sugar units when they are joined through a condensation reaction
What are monosaccharides, disaccharides and polysaccharides?
- a monosaccharide is one single sugar unit
- a disaccharide is the molecule that is formed when two monosaccharides are joined together through a condensation reaction
- a polysaccharide is a long chain of saccharides bonded together by glycosidic links
What is the general formula for carbohydrates?
the general formula for carbohydrates is Cx(H2O)n
What does carbohydrate mean?
What are the atoms that make up a carbohydrate?
- the term carbohydrate means ‘hydrated carbon’ and hydration means adding water
- carbohydrate are made up of carbon, hydrogen and oxygen atoms
What are sugars with six carbons called? What are sugars with 3 carbons called?
- sugars with 6 carbons are called hexose sugars
- sugars with 3 carbons are called triose sugars
What are three common monosaccharides and where are they found? (need to know the structures of all of these)
- glucose = is found in blood and used by all cells for respiration
- galactose = occurs in our diet and is found in milk (it is part of the disaccharide lactose)
- fructose = occurs naturally in fruit, honey and some vegetables. (Its sweetness attracts animals which helps with seed dispersal)
What are three common disaccharides and what are the monosaccharides that make them?
- sucrose = glucose + fructose
- maltose = glucose + glucose
- lactose = galactose + glucose
What does sucrose contain? What is it linked by?
- sucrose contains a molecule of glucose and a molecule of fructose linked by a 1,2 glycosidic bond
What does maltose contain? What is it linked by?
- maltose contains two molecules of glucose linked by a 1,4 glycosidic bond
What does lactose contain? What is it linked by?
- lactose contains a molecule of glucose and a molecule of galactose linked by a 1,4 glycosidic bond
What are some features of mono/disaccharides?
- sweet
- crystalline
- small (can diffuse out of cell)
- soluble
What are some features of polysaccharides?
- non-sweet
- non-crystalline
- large (cannot diffuse out of cell)
- insoluble (no osmotic effect on the cell)
What are some examples of polysaccharides?
- starch
- glycogen
- cellulose
- amylose
- amylopectin
What do starch and glycogen act as?
- starch and glycogen act as an energy storage molecule within cells
What is starch? What is it made up of?
- starch is the storage carbohydrate found in plants
- its made up of a mixture of two molecules: amylose and amylopectin
What is amylose?
- amylose is composed of a straight chain of between 200 and 5000 glucose molecules with 1,4 glycosidic bonds between adjacent glucose molecules
- the position of the bonds causes the chain to coil in a spiral shape
What is amylopectin?
- amylopectin is also a polymer of glucose but it has side branches
- a 1,6 glycosidic link holds each side branch onto the main chain
What is used instead of starch as an energy store?
- glycogen is used by bacteria, fungi and animals instead of starch as an energy store
What is glycogen? Where is it stored?
- glycogen is another polymer composed of glucose molecules
- its numerous side branches mean that it can be rapidly hydrolysed, giving easy access to stored energy
- In humans glycogen is stored in the liver and muscles
What are the two forms that glucose comes in? How are they different?
- glucose comes in two forms: alpha (a) and beta (B)
- Alpha glucose has the H above carbon 1 and the Oh group below (Alpha = (H) Above)
- beta glucose has the H below carbon 1 and the OH group above (Beta = (H) Below)
What is the main function of monosaccharides?
- the main function of monosaccharides is to store energy within their bonds
- when the bonds are broken during respiration energy is released
How is the structure of monosaccharides related to their function?
- it is soluble so can be transported easily
- it has many covalent bonds which store energy
What bond forms between disaccharides/ polysaccharides?
- disaccharides and polysaccharides form a strong covalent bond called the glycosidic bond
How do 1,4 glycosidic bonds form? How do 1,6 glycosidic bonds form?
- If the OH groups are located on carbon 1 of one monosaccharide and carbon 4 of the other a 1,4 glycosidic bond forms
- if the OH groups are located on carbon 1 of one monosaccharide and carbon 6 of the other, a 1,6 glycosidic bond forms
What reaction forms a glycosidic bond? As a result, what reaction breaks a glycosidic bond?
- the glycosidic bonds are formed by condensation reactions
- the glycosidic bond is broken when water is added in a hydrolysis reaction
What is the function of disaccharides?
- the function of disaccharides is to provide the body with a quick-release source of energy
- they are easily broken down by enzymes in the digestive system into their respective monosaccharides and then absorbed into the bloodstream
Are disaccharides soluble? Why?
- disaccharides are easily soluble in water due to the presence of a large number of hydroxyl groups
- these hydroxyl groups form hydrogen bonds with the water molecules when dissolved in aqueous solutions
What increases the rate at which polysaccharides can be broken down?
- polysaccharides may be branched or unbranched
- being branched increases rate at which polysaccharides can be broken down
What happens if polysaccharides are straight or coiled?
- being straight makes the molecules suitable for constructing cellular structures e.g. cellulose
- being coiled makes a molecule more compact and suitable for storage e.g. amylose in starch
What are useful storage polysaccharides and why?
- starch and glycogen are useful as storage polysaccharides:
- they are compact = large quantities can be store
- they are insoluble = they will have no osmotic effect
