2.3 - Biological Molecules Flashcards
State the general formula of a carbohydrate
Cₓ(H₂O)ᵧ
State the three main groups of carbohydrates
- Monosaccharides
- Disaccharides
- Polysaccharides
What is a monosaccharide?
A simple sugar with the general formula (CH₂O)ₙ where ₙ can be 3-7.
They are examples of monomers.
e.g. glucose, fructose, ribose
What are disaccharides?
‘Double sugars’ formed from two monosaccharides.
e.g. lactose, sucrose
What are polysaccharides?
Large molecules formed from many monosaccharides.
e.g. glycogen, cellulose, starch
How many carbons are contained in one molecule of pentose?
5 carbons.
How do ribose and deoxyribose differ?
Ribose has one H atom and one -OH group on Carbon-2, whereas deoxyribose has 2 H atoms and no -OH group on Carbon-2.
What type of sugar is glucose?
It is a hexose sugar.
What is the difference between alpha and beta glucose?
On alpha glucose the -OH group is BELOW Carbon-1.
On beta glucose the -OH group is ABOVE Carbon-1.
What reaction occurs when two monosaccharides join to form a disaccharide?
Condensation reaction.
What reaction is used to break apart polysaccharides and disaccharides?
Hydrolysis reaction.
How is maltose formed?
Two glucose molecules joined by an Alpha 1-4 Glycosidic bond.
How is sucrose formed?
One glucose molecule and a fructose molecule joined by an Alpha 1-4 glycosidic bond.
How is lactose formed?
Glucose and galactose joined by a Beta 1-4 glycosidic bond.
What is the major polysaccharide in animals?
Glycogen.
What is the major polysaccharides in plants?
Cellulose and starch.
What is starch made from?
Amylose and amylopectin polysaccharides.
- 30% amylose (1-4 bonds)
- 70% amylopectin (1-4 and 1-6 bonds)
How is starch stored in plants?
Stored as intracellular grains in plastids.
What is cellulose made from?
Long chains of beta glucose molecules joined by beta 1-4 glycosidic bonds.
How is cellulose structured?
Long glucose chains form rope-like microfibrils forming a network.
What is glycogen made from?
Many alpha 1-6 glycosidic bonds producing a branched network.
How is glycogen stored?
Small granules in the muscles an liver.
How does the metabolic properties of glycogen differ from starch?
Glycogen is less dense and more soluble than starch - meaning it can be broken down more rapidly.
What elements are proteins made from?
CHONS
What functions do proteins provide?
- Structure (connective tissue, skeletal fibre, hair, etc.)
- Body regulation (enzymes and hormones)
- Immunity (antibodies)
- Energy
Outline the basic structure of an amino acid
- Amine group
- R-Group
- Carboxyl Group
What kind of bond joins two amino acids together?
Peptide bond.
What is a polypeptide?
10 or more amino acids in a chain.
What is a protein?
One or more polypeptide chains folded into a highly specific 3D shape.
What does primary structure of a protein involve?
Simple long chains with no intermolecular bonds/interactions.
What does secondary structure of a protein involve?
Hydrogen bonds from causing the molecule to either fold or coil.
Forms either an alpha helix or beta pleating sheet.
What does tertiary structure of a protein involve?
- Hydrophilic/hydrophobic interactions
- Hydrogen bonds
- Ionic bonds
- Disulphide bridges
What does quaternary structure of a protein involve?
Same as tertiary but with two or more separate polypeptide chains interlinked.
e.g. haemoglobin (4 chains), insulin (12 chains).
How do proteins become denatured?
Changes in temperature, pH or salt concentration can break the bonds which maintain the protein’s specific shape.
What happens when proteins become denatured?
- Bonds which maintain protein’s specific shape are
broken. - Fibrous proteins lose their structural strength.
- Globular proteins become insoluble and inactive.
Outline the properties of a globular protein.
- Soluble
- Metabolically active
- Mostly alpha helix
- Forms globules (enzymes, hormones etc.)
Outline the properties of a fibrous protein.
- Insoluble
- Structural
- Mostly beta pleating sheet
- Forms fibres (collagen, keratin etc.)
Outline the structure and properties of haemoglobin.
- Globular
- 4 polypeptide subunits (2 alpha, 2 beta)
- Most of structure is alpha helix
- Each haem group (prosthetic group) contains Fe²⁺
which is responsible for the colour. - Each molecule binds to 4 O₂ molecules.
Outline the structure and properties of collagen.
- Fibrous
- Very strong
- 3 polypeptide chains wound around each other
- Each of the chains are coils held together by H bonds.
- Each collagen molecule forms strong covalent bonds
with other collagen molecules - Form collagen fibrils. Many collagen fibrils make a
collagen fibre.
Why is collagen so strong?
- Glycine is small allowing close packing between
molecules. - Collagen chains form a tight coil - they lie close to
each other. - Many H bonds between R-Groups hold chains
together very closely. - Strong covalent bonds with adjacent molecules
- Staggered ends to parallel fibres prevent lines of
weakness.
Which elements do lipids contain?
CHO
What is the most common form of lipid?
Triglyceride.
How many water molecules are formed in the formation of a triglyceride?
3
Why are some lipids liquids (oils) at room temperature?
They have unsaturated fatty acid chains. Double bonds cause kinks in the chains meaning there are fewer intermolecular forces between chains.
Where in the cell do lipids play a major role?
The plasma membranes.
Outline the functions of lipids.
- Energy and metabolic water source
- Buoyancy aid
- Heat insulation
- Waterproofing on hair/feathers
- Electrical insulation
- Protection of internal organs
Outline the structure and function of cholesterol.
- Small narrow molecule
- 4 Carbon ring-based structure.
- Regulates the fluidity of a membrane
