1A - Biological Molecules Flashcards
What type of molecule are carbohydrates?
Polymers
What are polymers?
Large complex molecules made up of long chains of repeating monomers joined together.
What are monomers?
Small, basic molecular units.
Give some examples of monomers.
- Monosaccharides
- Amino acids
- Nucleotides
What elements do all carbohydrates contain?
- Carbon
- Hydrogen
- Oxygen
What are monomers in carbohydrates called?
Monosaccharides
What are some examples of monosaccharides?
- Glucose
- Fructose
- Galactose
What are some examples of disaccharides?
- Maltose
- Sucrose
- Lactose
What type opf sugar is glucose?
Hexose - it contains 6 carbon atoms.
What are the types of glucose?
Alpha (α) and Beta (β)
What can alpha and beta glucose be referred to as?
Isomers
What are isomers?
Molecules with the same molecular formula as each other but with the atoms arranged differently.
Give an example of isomers.
Alpha and beta glucose are isomers.
Remember to practice drawing out the structure of alpha and beta glucose.
Pg 2 of revision guide.
Describe the difference between an alpha and beta glucose molecule.
- Alpha glucose -> The end hydrogens both point upwards
- Beta glucose -> Left hydrogen points up, right one points down
What is a condensation reaction?
When two molecules join together with the formation of a new chemical bond, and a water molecule is released.
What type of reaction is two monosaccharides joining together?
Condensation
What type of bond is formed between two monosaccharides when two monosaccharides join in a carbohydrate?
Glycosidic
What is formed when two monosaccharides join?
Disaccharide
What monosacchaides join to form maltose?
Glucose + Glucose
What monosacchaides join to form sucrose?
Glucose + Fructose
What monosacchaides join to form lactose?
Glucose + Galactose
What monosacchaides join to form maltose, sucrose and lactose?
Maltose = Glucose + Glucose Sucrose = Glucose + Fructose Lactose = Glucose + Galactose
What type of glucose is found in maltose?
Alpha
What is found in the middle of a glycosidic molecule?
An oxygen atom
Remember to practise drawing a glycosidic bond.
Pg 2 of revision guide.
What type of reaction is used to break down a polymer?
Hydrolysis reaction
What type of reaction is used to break down and form polymers?
Breaking down -> Hydrolysis
Forming -> Condensation
What is a hydrolysis reaction?
When a chemical bond is broken by a water molecule.
Remember to practise drawing hydrolysis reactions.
Pg 3 of revision guide.
What does the term sugar refer to?
Monosaccharides and disaccharides
What is the difference between sugars and carbohydrates?
- Sugars -> Monosaccharides and disaccharides
- Carbohydrates -> Polysaccharides
What is the test for sugars called?
Benedict’s test
What are the two types of sugar?
Reducing and non-reducing
What are the reducing sugars?
- All monosaccharides
- Some disaccharides (e.g. maltose and lactose)
What are the non-reducing sugars?
- Most disaccharides (e.g. sucrose)
Give some examples of reducing disaccharides.
Maltose and lactose
Give some examples of non-reducing disaccharides.
Sucrose
Describe the test for reducing sugars.
- Add Benedict’s reagent (blue) to a sample
- Heat in a water bath that’s been brought to boil
- If the test is positive -> Orange precipitate
- If the test is not positive -> Stays blue
Describe how the colour of the precipitate in the test for reducing sugars changes with concentration of the sugar.
Blue -> Green -> Yellow -> Orange -> Brick red
Instead of looking at colour change, what is a more accurate way of measuring the sugar concentration?
Filtering the solution and weighing the copper oxide precipitate.
Describe the test for non-reducing sugars.
- Add dilute hydrochloride acid to the sample.
- Heat in a water bath that’s been brought to boil
- Neutralise with sodium hydrogencarbonate.
- Carry out normal Benedict’s test for reducing sugars.
- If test is positive -> Orange precipitate -> Non-reducing sugar present
- If test is not positive -> Stays blue -> No sugars present at all
Why are two separate tests needed for reducing and non-reducing sugars?
A non-reducing sugar will not react with Benedict’s reagent, but it can be hydrolysed into reducing sugars which will react with Benedict’s reagent.
How are polysaccharides formed?
When two or more monosaccharides are joined by condensation reactions.
How do plants use starch to store glucose?
- Excess glucose is stored as starch
* When a plant needs glucose, it breaks down the starch into glucose
What are the two types of starch?
- Amylose
* Amylopectin
What are amylose and amylopectin?
Polysaccharides of alpha glucose.
What is amylose?
- Type of starch
- Long, unbranched chains of alpha glucose
- Coiled structure
Describe the structure of amylose and relate it to its function.
- Long, unbranched chains of alpha glucose.
* Angles of glycosidic bonds give it a coiled structure -> This makes it compact and good for storage.
What type of glucose is starch made up of?
Alpha
What is amylopectin?
- Type of starch
* Long, branched chain of alpha glucose
Describe the structure of amylopectin and relate it to its function.
- Long, branched chains of alpha glucose
- Its side branches allow enzymes that break down the molecule to get to the glycosidic bonds easily -> Energy can be released quickly.
What is the difference between amylose and amylopectin?
- Amylose -> Unbranched, spiral
* Amylopectin -> Branched
How does the structure of starch relate to its function?
- Made of alpha glucose -> Store of glucose for energy
- Insoluble -> Many glycosidic bonds
- Spiral shape (amylose) -> Compact
- Branched (amylopectin) -> More SA for enzymes to release glucose
- Doesn’t affect osmotic potential -> Water doesn’t enter cells by osmosis, which would cause them to swell
What is the test for starch?
- Add iodine dissolved in potassium iodide solution to sample
- If starch present -> Turns blue-black
- If no starch present -> Remains browny-orange
What is the function of glycogen?
Excess glucose is stored as glycogen in animal cells.
What type of glucose is starch made up of?
Alpha glucose
Describe the structure of glycogen.
Highly-branched, long chains of glucose.
How does the structure of glycogen relate to its function?
- Made of alpha glucose -> Store of glucose for energy
- Insoluble -> Many glycosidic bonds
- Highly branched -> More SA for enzymes to release glucose
- Compact -> Efficient storage
- Doesn’t affect osmotic potential -> Water doesn’t enter cells by osmosis, which would cause them to swell
What is the function of cellulose?
Structure in plants -> It is found in cell walls.
What type of glucose is cellulose made up of?
Beta glucose
Describe the structure of cellulose.
- Long unbranched chains of beta glucose.
* Chains are linked together by hydrogen bonds -> This forms microfibrils
How does the structure of cellulose relate to its function?
- Insoluble -> Many glycosidic bonds
- Doesn’t affect osmotic potential -> Water doesn’t enter cells by osmosis, which would cause them to swell
- Hydrogen bonds -> Cumulative strength
- Microfibrils -> Cumulative strength
What are the types of lipids?
- Triglycerides
* Phospholipids
Are fatty acids hydrophilic or hydrophobic?
Hydrophobic
What is a triglyceride made of?
- 1 glycerol molecule
- 3 fatty acid molecules
(See pg 6 of revision guide)
Describe the structure of a fatty acid.
- Carbon
- O and OH attached to the carbon
- R group hydrocarbon chain attached to the carbon
(See pg 6 of revision guide)
What makes various fatty acids different?
The length of the hydrocarbon tail.