Chapter 2 - Biological Molecules Flashcards
How many bonds can a carbon atom form?
4 bonds
How many bonds can a nitrogen atom form?
3 bonds
How many bonds can an oxygen atom form?
2 bonds
How many bonds can a hydrogen atom form?
1 bond
What is an electrolyte?
Ions in a solutions, these often have important roles in living organisms
What atoms is water formed from?
2 Hydrogen and 1 Oxygen
How does surface tension affect water?
It causes it to behave like a plastic sheet
It is caused by intermolecular attraction
It isn’t affected by molecules around them so it pulls more strongly
Means it can become a habitat for other lovings things.
What causes surface tension of water?
Hydrogen bonds
Which occurs between hydrogen atoms to oxygen atoms of other molecules
e.g another water molecule
Why is it important that water is colourless?
It means that it is transparent to light as a result, sunlight can reach cells in a plant to allow photosynthesis to occur
What is cohesion?
Cohesion is strong attraction to eachother making water a sticky liquid, which causes surface tension.
What does it mean by water is polar?
It has regions of positivity and negativity
Describe the specific heat capacity of water.
It is the energy required to raise 1kg of water by 1 °C
It is important that it is high so body temperature doesn’t raise too quickly otherwise homeostasis can’t function properly and enzymes would denature
Describe the latent heat of water.
It is relatively large meaning evaporation of water provides a cooling effect with little water loss
Describe the density of water.
The density of water decreases as it freezes.
This is because it expands as it freezes by forming a rigid structure with more space in between them compared to as a liquid.
This is why ice floats on water.
How is water a solvent?
Water is polar, as a result it forms electrostatic interactions with other charged particles (hydrophilic)
As a result many metabolic reactions are able to occur
What is a carbohydrate?
Consists of carbon, hydrogen and oxygen and are long chains of sugar units called saccharides.
It is an important energy source for plants and animals.
What is the ratio of carbon, hydrogen and oxygen atoms in a carbohydrates?
C : 2H : O
What are the three main types of carbohydrates?
Monosaccharides, Disaccharides and Polysaccharides
What is a monosaccharide?
It is a single sugar unit
What is a disaccharide?
It is a two sugar units bonded by a glycosidic bond
What is a polysaccharide?
Three or more sugar units bonded together in a chain by glycosidic bonds and are joined together by condensation reactions
How do saccharides bond together?
By condensation reactions
What are the 6 properties of water?
- It is a metabolite in many metabolic reactions
- It is the solvent where metabolic reactions occur
- Relatively high heat capacity
- Relatively large latent heat of vaporisation
- Strong cohesion between water molecules
- Ice is less dense than water
What is a monomer?
A monomer is a small unit that makes up larger molecules
What is a polymer?
Large molecules made of a large chain of monomers
How are polymer bonds broken?
Hydrolysis using a water molecule
What elements are carbohydrates made from?
Carbon, Hydrogen and Oxygen
What elements are lipids made from?
Carbon, Hydrogen and Oxygen
What elements are proteins made from?
Carbon, Hydrogen, Oxygen, Nitrogen and Sulfur
What elements are nucleic acids made from?
Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorus
Which saccharides form maltose?
Glucose and glucose
What saccharides make sucrose?
Glucose and fructose
What saccharides make lactose?
Glucose and galactose
What is starch?
Polysaccharide
Made up of alpha glucose molecules
Non-soluble
What are the two types of starch?
Amylose and amylopectin
What is amylose?
Starch
No branches and forms a coil
Straight chain
1-4 glycosidic bonds
What is amylopectin?
Starch
Forms a coil and has branches at regular intervals (around every 23 subunits)
Branches allow it to be stored
1-4 and 1-6 (branches) glycosidic bonds
What is glycogen?
It is the way alpha glucose is stored in animals and fungi
More branched than amylopectin
More compact for storage so it can be broken down quicker
How can you bond two B-glucose molecules?
Flip alternate molecules 180 degrees so the OHs are next to each other in order to bond
What is cellulose made up of?
Long chains of B-glucose molecules (1000-10000)
Describe the structure of a cellulose chain.
It is a long straight chain due to the molecules alternating by flipping 180 degrees each time
What is glucose?
Hexose monosaccharide with a ring structure
Soluble molecule that is used for respiration, stored as glycogen or starch as energy reserves, or used in structural molecules
What is the chemical test for proteins?
Biuret test is added to the sample in solution.
Set timer for 5 mins then record observations.
Positive result is purple.
Compare to a control such as distilled water
What if the function of Calcium ions (Ca 2+)?
Nerve impulse transmission
Muscle contraction
What is the function of Sodium ions (Na +)?
Nerve impulse transmission
Kidney function
What was the function of Potassium ions (K +)?
Nerve impulse transmission
Stomatal opening
What is the function of ammonium ions (NH4 +)?
Production of nitrate ions by bacteria
What is the function of hydrogen ions (H +)?
Catalysis of reactions
pH determination
What is the function of nitrate ions?
Nitrogen supply to plants for amino acids and protein formation
What is the function of hydrogen carbonate ions?
Maintenance of blood pH
What is the function of Chloride ions?
Balance positive charge of sodium and potassium ions in cells
What is the function of Phosphate ions?
Cell membrane formation
Nucleic acid and ATP formation
Bone formation
What is the function of Hydroxide ions?
Catalysis of reactions
pH determination
How are polymer bonds formed?
Condensation reactions
Produces water
How do you test for starch?
Iodine test
Add a few drops to substance
Orange-brown = no presence
Blue-black = presence
How do you test for reducing sugars?
Benedicts test for reducing sugars
Place sample into boiling tube
Add equal volume of benedicts regent
Heat gently in a boiling water bath for 5 mins.
Blue -> Green -> Yellow -> Orange -> Red
Blue = no reducing sugars
Red = high concentration of reducing sugars
OR
Regent test strips can be used for semi-quantitative results
How do you test for non-reducing sugars?
Benedicts test for non-reducing sugars
Benedicts regent doesn’t react directly with non-reducing sugars
Substance boiling with dilute HCl
Then warm with benedicts regent
Blue -> Green -> Yellow -> Orange -> Red
Blue = None
Red = High concentration
What is a lipid?
Non-polar
Not soluble in water
Large complex molecules known as macromolecules
What is a triglyceride?
One glycerol (alcohol)
Three fatty acids (carboxyl)
Ester bonds
What is a saturated fatty acid chain?
Fatty acid with no double bonds between carbon atoms
What is a mono-unsaturated fatty acid chain?
Fatty acid with one double bond between carbon atoms
What is a polyunsaturated fatty acid chain?
Fatty acid with more than one double bond between carbon atoms
What is a phospholipid?
Modified triglyceride
Found in cytoplasm of every cell
Phosphate group hydrophilic head (charged)
Two fatty acid hydrophobic tails (non polar)
Describe the structure of phospholipids in the plasma membrane.
Form the phospholipid bilayer
Tails face inwards touching each other
Heads face outwards
Layer of two phospholipids
What is a sterol?
Steroid alcohol
Complex alcohols
Four carbon ring structure with a hydroxyl (OH) group at one end
e.g. Cholesterol
Describe cholesterol.
Sterol
Important in formation of cell membranes
What are the roles of lipids?
Membrane formation and creation of hydrophobic barriers
Hormone production
Electrical insulation of impulse transmission
Waterproofing
What are specific roles of triglycerides?
Thermal insulation to reduce heat loss
Cushioning to protect vital organs
Buoyancy for aquatic animals
Describe the general structure of amino acids.
Amine group
R-group
Carboxyl group
How are amino acids synthesized?
By the amine and carboxylic acid groups
R-group not involved
Peptide bonds
Condensation reaction to bond
Hydrolysis reaction to break bonds
What is a dipeptide?
Two amino acids joined together by a peptide bond
What is a polypeptide?
Many amino acids joined together by a peptide bond
Describe the primary structure of a protein.
Sequence where amino acids are joined
Only involved peptide bonds
Determines the structure of the polypeptide and further levels of protein structure
Encoded by DNA and mRNA
Describe the secondary structure of a protein.
Hydrogen bonds may form within the amino acid chain
Can form an alpha helix or beta pleated sheet
Describe the tertiary structure of a protein.
Folding of protein into final shape
Secondary structure brings R-groups close enough together to interact causing the folding
What are the interactions between R-groups?
Hydrophobic and hydrophilic interactions
Hydrogen bonds
Ionic bonds
Disulfide bonds
Describe hydrophobic and hydrophilic interactions.
Weak interactions between polar and non-polar R-groups.
Describe hydrogen bonds.
Weakest bonds
Formed between hydrogen and oxygen atoms
Describe ionic bonds.
Stronger than hydrogen bonds and form between oppositely charged R-groups
Describe disulfide bonds.
Covalent and strongest of the bonds but only form between R-groups that contain sulfur atoms
Describe the quaternary structure of a protein.
Similar interactions to the tertiary structure except it is between different protein subunits
What is a globular protein?
Spherical shape
Water soluble as they have R-groups on the inside that are hydrophobic and hydrophilic ones on the outside
Involved in metabolic processes
What is haemoglobin?
Globular protein
Carries oxygen
Conjugated protein
Made of four polypeptide chains and four haem prosthetic groups that contain iron
What is insulin?
Globular protein
Involved in carrying blood glucose
Made of two polypeptide chains which are joined by disulfide bonds
Specific to the shape of cell membrane receptors
What is pepsin?
Globular protein
Enzyme that functions in the stomach
Has a few basic R-groups, hydrogen bonds and a disulfide bond.
What is a fibrous protein?
Usually made of long polypeptide chains that form fibers
Insoluble as they have amino acids with hydrophobic R-groups
Very strong, yet flexible
What is collagen?
Fibrous protein
Found in bones and tendons
Withstand large pulling forces
Found in artery walls to help withstand high pressure
What is keratin?
Fibrous protein
Strong molecule
Large number of cysteine amino acids and many disulfide bonds
Found in hooves, horns and fingernails
What is elastin?
Fibrous protein
Elastic
Found in walls of blood vessels, lungs and bladder
What is the calculation for Rf value?
Rf = distance moved by solute / distance moved by solvent
