3.3 Carbohydrates Flashcards
What are carbohydrates?
They are molecules that only contain the elements carbon, hydrogen and oxygen.
What does carbohydrate mean?
Hydrated carbon.
What is the ratio of elements in carbohyrdates?
Cx(H2O)y
What are carbohydrates also known as?
Saccharides or sugars.
What is a monosaccharide?
A single sugar unit
Name examples of monosaccharides
Glucose, fructose and ribose
What happens when 2 monosaccharides link together?
They form a disaccharide
Name examples of disaccharides
Lactose and sucrose.
What happens when more than 2 monosaccharides join together?
They form a polymer called polysaccharide.
Name examples of polysaccharides.
Glycogen, cellulose and starch
What is the chemical formula of Glucose
C6H12O6
What type of monosaccharide is glucose?
Hexose monosaccharide
Describe the molecular structure of glucose
The carbons are numbered clockwise, beginning with the carbon to the right (clockwise) of the oxygen atom within the ring.
What are the two variations of glucose?
Alpha and beta
What is the difference between alpha and beta glucose?
The OH (hydroxyl) group on carbon 1 is in opposite positions.
What are the properties of glucose molecules
They are polar and soluble in water. This is due to the hydrogen bonds that form between the hydroxyl groups and water molecules.
Why is the solubility in water important for glucose molecules?
It means glucose is dissolved in the cytosol of the cell.
What is a condensation reaction?
2 hydrogen atoms and 1 oxygen atom are removed, creating a glycosidic bonds between carbon 1 and carbon 4 (a covalent bond), which is known as a 1,4 glycosidic bond, which creates a disaccharide.
Describe fructose
Naturally occurs in fruits, often in combination with glucose forming the disaccharide sucrose, fructose is sweeter than glucose.
What are pentose monosaccharides?
sugars that contain 5 carbons.
Two pentose sugars are important components of biological molecules - ribpse is the sugar present in RNA nucleotides and deoxyribose is the sugar present in DNA nucleotides.
What is starch?
Alpha glucose molecules can be joined by glycosidic bonds to form two slightly different polysaccharides known collectively as starch.
Glucose made by photosynthesis in plant cells is stored as starch as it is a chemical energy store.
What polysaccharides are in starch?
Amylose and amylopectin
Describe the structure of amylose
Formed by alpha glucose molecules joined together only by 1-4 glycosidic bonds. The angle of the bond means that this long chain of glucose twists to form a helix which is further stabilisied by hydrogen bonding within the molecule. This makes the polyssaccharide more compact, and much less soluble, than the glucose molecules used to make it.
Describe the structure of amylopectin
It is made by 1-4 glycosidic bonds between alpha glucose molecules, but there also some glycosidic bonds formed by condensation reactions between carbon 1 and carbon 6 on two glucose molecules (has a branched structure) and occurs once in every 25 glucose subunits.
What is glycogen?
The functionally equivalent energy storage molecule to starch in animals and fungi
Why is glycogen more compact?
Because it forms more branches
Why is branching advantageous
Many free ends where glucose molecules can be added or removed which speeds up the processes of storing or releasing glucose molecules required by the cell.
What are the key properties of glycogen and amylopectin?
They are insoluble, branched and compact.
What is a hydrolysis reaction?
Breaks a bond between between 2 molecules and involves the use of a water molecule
How is cellulose formed?
It is formed by the condensation of beta glucose, it is unable to coil or form branches.
How are microfibrils made?
Cellulose molecules make hydrogen bonds with each other.
How are macrofibrils made?
By microfibrils joining together
What are the properties of macrofibrils and microfibrils?
Strong and insoluble and are used to make cell wallsDe
Describe cellulose
Important part of our diet is that it is very hard to break down into its monomers and forms the “fibre” or “roughage” necessary for a healthy digestive system
What is a glycosidic bond
Bond formed between two glucose molecules - hydroxyl group of carbon 1 on one molecule and carbon 4 on the other interact in a condensation reaction/removal of water molecule to form an oxygen bridge.
