3.3 carbohydrates

what elements does carbohydrates contain?

carbon, hydrogen and oxygen

What does carbohydrate mean?

‘hydrated carbon’ (carbon and water)

What is the general formula of carbohydrates?

Cx(H20)y

what are carbohydrates also known as?

saccharides or sugars

what is a single sugar unit called?

monosaccharide

what are examples of monosaccharides?

glucose, fructose and ribose

what is it called when two monosaccharides link together?

disaccharide

what are examples of disaccharides?

Lactose and sucrose

What is it called when two or more monosaccharides are linked together?

polysaccharides

what are examples of polysaccharides?

Glycogen, cellulose and starch

What is glucose?

basic building blocks, or monomers of some biologically important large carbohydrates

what is the chemical formula for glucose?

C6H12O6

How many carbons does glucose have?

6

what type of unit is glucose?

monosaccharide

what is the 6 carbon glucose called?

hexose monosaccharide

how are carbons numbered?

numbered clockwise

What is the difference between alpha glucose and beta glucose?

In alpha OH group on carbon 1 is at the bottom where as on Beta glucose the OH group is at the top

Are glucose molecules polar?

yes

Are glucose molecules soluble in water?

yes

Why is glucose soluble in water?

Due to the hydrogen bonds that form between the OH (hydroxyl) group and water molecules

why is solubility in water important with glucose?

it means glucose is dissolved in the cytosol of the cell (fluid present in the cell and is a part of the cytoplasm)

what happens when two alpha glucose molecules are side by side?

two hydroxyl groups react and new bonds are formed which produces new molecules

What is a 1,4 glycosidic bond?

where carbon 1 and carbon 4 join together with an oxygen atom

what is a glycosidic bond?

a covalent bond formed between two glucose molecules

what is a condensation reaction?

when a water molecule is formed as one of the products of the reaction when combine molecules

what is a disaccharide?

a molecule made up of two monosaccharides

What do the two glucose molecules form?

maltose

where does fructose occur from?

in fruit, often in combination with glucose forming the disaccharide sucrose (cane sugar or sugar)

what does galactose and glucose form?

lactose

what does fructose and glucose form?

sucrose

what is a hexose monosaccharide

simple sugar that contains 6 caron atoms and 1 sugar unit

what does glucose and glucose form?

maltose

where is lactose found?

in milk and milk products

what is fructose sweeter than?

glucose

what is glucose sweeter than?

galactose

what are pentose monosaccharides?

sugars that contain 5 carbon atoms

what does two pentose monosaccharides form?

ribose

what is ribose?

the sugar which is present in RNA nucleotides

what is deoxyribose?

sugar present in DNA nucleotides

How is starch formed?

many alpha glucose molecules joined by glycosidic bonds to form two slightly different polysaccharides

what type of store is glucose?

chemical energy store

How is glucose made?

by photosynthesis in plant cells and is stored as starch

What are the different polysaccharides in starch called?

amylose and amylopectin

how is amylose formed?

by alpha glucose molecules joined together only by 1,4 glycosidic bonds

how does the amylose make a helix shape?

the angle of the bond means that it is able to twist and form a helix which is further stabilised by hydrogen bonding within the molecule

Features of the amylose polysaccharide due to the helix shape?

more compact and much less soluble

What is a 1-6 glycosidic bond?

when carbon 1 and carbon 6 bond

how is amylopectin made?

by 1,4 glycosidic bonds between alpha glucose molecules but there are also some 1,6 glycosidic bonds formed by condensation reactions between carbon 1 and carbon 6 on two molecules

what structure does amylopectin have?

branched structure with the 1,6 branching points which occur approximately once in every 25 glucose subunits

what type of reaction are 1,6 glycosidic bonds?

condensation reaction

Where is amylose and amylopectin found?

starch

where is starch found?

plants

where is glycogen found?

in animals (and fungi)

what is the functionally equivalent energy storage molecule to starch in animals?

glycogen

What is glycogen’s structure?

more branches than amylopectin which means its more compact and less space is needed for it to be stored

Why is the compact structure of glycogen important?

Animals are mobile so coiling or branching makes it compact and ideal for storage

Why is branching beneficial?

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

How is glucose stored in plants?

starch

how is glucose stored in animals and fungi?

glycogen

What is respiration?

the process in which biochemical energy in these stored nutrients is converted into a usable energy source for the cell

What reaction occurs when releasing glucose for respiration?

hydrolysis reactions

What does hydrolysis reaction require?

addition of water molecules

What is hydrolysis reactions catalysed by?

enzymes

What is the reverse of the condensation reaction?

hydrolysis reaction

Why are beta glucose unable to join together like alpha glucose?

the hydroxyl groups on carbon 1 and carbon 4 of the two glucose molecules are too far from each other to react

how can beta glucose molecules join together to form a polymer?

if alternate beta glucose molecules are turned upside down

What is the structure of a beta glucose polysaccharide?

it is unable to coil or form branches so it creates a straight chain molecule

What is formed by the straight chain of beta glucose?

cellulose

where is cellulose found?

plants

What does cellulose molecules make hydrogen bonds with?

with each other forming microfibrils

What is it called when microfibrils join together?

macrofibrils

what is it called when macrofibrils combine?

fibres

What are fibres?

strong and insoluble and are used to make cell walls

Why is cellulose an important part of our diet?

it is very hard to break down into its monomers and forms the ‘fibre’ necessary for a healthy digestive system

where is cellulose found?

in the cell wall of all plants