2. Biological molecules

What is a solution?

Homogenous mixture of a solvent and a solute

What is a solvent?

Substance in which a solute is dissolved to form a solution

What is a solute?

Dissolves in a solvent to form a solution

What is solvation?

The interaction between a solvent and a solute

What happens when a solute dissolves in water?

Solute particles interact with water particles through hydrogen bonding

What happens when polar molecules dissolve in water?

Hydrogen bonds form between water and other polar molecules

What happens when ionic compounds dissolve in water?

Water molecules surround ions of the compound

What are hydration shells?

When polar solvents orientate themselves towards polar solutes and ions to form hydrogen bonds/ion-dipole forces

What is concentration?

Quantity of a solute in a given quantity of solution

What is a hypertonic solution?

Higher concentration of solutes compared to another solution.

What is an isotonic solution?

Same concentration of solutes compared to another solution. No net mass change

What is a hypotonic solution?

Lower concentration of solutes compared to another solution.

What is osmosis?

Passive movement of water molecules down concentration gradient from a hypotonic solution (low solute concentration) to a hypertonic solution (high solute concentration) through a partially permeable membrane

What is a dynamic equilibrium?

When there is equal movement of water in and out of cell

What happens to animal cells in a hypertonic solution?

Cells lose water (crenation) → flaccid → plasmolysis → mass decreases, cell shrinks → death

What happens to animal cells in a hypotonic solution?

Cells gain water → turgid → tissue mass increases → plasma membrane bursts (cytolysis)

What are contractile vacuoles?

Structures in amoeba (live in hypotonic habitats) - excess water will be continuously collected and pumped out of organism to maintain osmotic concentration

Why are animal cells very sensitive to osmotic changes?

They lack cell walls

What is turgor pressure?

When the expanding protoplast (living part of cell inside cell wall) pushes against cell wall and pressure builds up inside cell

What is osmoregulation?

A form of homeostasis - maintenance of constant osmotic pressure in fluids of an organism by the control of water and salt concentrations

What are some medical applications of isotonic solutions?

1. Transporting organs

2. Intravenous fluids

What is the general structure of amino acids?

Amine group, hydrogen attached to central alpha carbon, carboxyl group, side chain (R group)

Which structure is the only difference between amino acids?

R group - determines chemical properties and behaviour of amino acid

How many amino acids are there?

20

How do amino acids form dipeptides?

Condensation reactions: Amino Acid + Amino Acid → Dipeptide + Water

Where are peptide bonds formed?

Between carboxyl of 1 amino acid and amine of another

What is a polypeptide?

Long chain of amino acids

How are polypeptides formed?

Many condensation reactions at a ribosome during the process of translation

What is the role of proteins in human diet?

Broken down to amino acids by digestive system which are used to synthesise proteins for the body

What are essential amino acids?

9 amino acids that humans require, cannot be synthesised by an animal so must be consumed in the diet

What are non-essential amino acids?

11 amino acids that animals can synthesise using metabolic pathways that transform one amino acid into another

What are considered complete proteins?

Meat and animal products - contain all 9 essential amino acids

What is denaturation?

A change in the shape of a protein, resulting in the loss of function

What is the number of possible combinations of a protein?

Infinite

How does extreme heat cause denaturing of proteins?

Heat disrupts weak bonds → loss of 3D conformation → function lost

How do extreme pH changes cause denaturing of proteins?

Changes R-group charges → disrupts ionic bonds

What happens to enzymes when they denature?

Lose active site shape and stop functioning

What is the covalent bond between monosaccharides called?

Glycosidic bond

What is the covalent bond between glycerol and fatty acids called?

Ester bond

What is the covalent bond between amino acids called?

Peptide bond

What is the role of structural proteins?

Proteins that create a framework for the body's structure and function - membrane, collagen fibres

What are functional proteins?

Biologically active proteins that help to maintain and support normal immune function - enzymes, some hormones

Why are there thousands of protein molecules?

1. Types of amino acids

2. Sequence of amino acids

3. Number of amino acids

How is a polymer formed?

Condensation of monomers

How is a polymer broken down?

Hydrolysis into monomers

What are some examples of lipids in living organisms?

Fats, oils, waxes, steroids

What atoms do lipid macromolecules contain?

Carbon, hydrogen, oxygen

What is the polarity and solubility of lipids?

Hydrophobic, non-polar. Insoluble in water

What are triglycerides composed of?

1 glycerol molecule and 3 fatty acid molecules

How are triglycerides formed?

3 condensation reactions between glycerol and 3 fatty acids, releasing 3 water molecules

What is a phospholipid composed of?

1 glycerol molecule attached to 2 fatty acids and 1 phosphate group

How are phospholipids formed?

Esterification - ester bond forms between the hydroxyl (-OH) group of a glycerol molecule and the carboxyl group (-COOH) of a fatty acid

Condensation reaction - 3 water molecules are released

What is the polarity and solubility of phosphate and fatty acids?

• Amphipathic

• Phosphate head: polar, hydrophilic

• Fatty acid tails: non-polar, hydrophobic

What are fats?

Triglycerides, solid at room temperature, high melting points, saturated fatty acids

What are oils?

Triglycerides, liquid at room temperature, low melting points, unsaturated fatty acids

What are fatty acids composed of?

Carboxyl group, hydrocarbon chain, methyl group

What are the properties of saturated fatty acids?

• Single bonds between carbon atoms in hydrocarbon tail

• Each carbon atom is bonded to 2 hydrogen atoms

• Straight molecules - increases melting point, used as storage molecules in animals

What are the properties of unsaturated fatty acids?

• Not all single bonds

• Each carbon atom in carbon-carbon double bond can only bond to 1 hydrogen atom

• Kinked/bended hydrocarbon tail

What are monounsaturated fatty acids?

Fatty acid with one carbon-carbon double bond (C=C)

What are polyunsaturated fatty acids?

Fatty acid with many carbon-carbon double bonds (C=C)

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have higher melting points than unsaturated fatty acids

Why are lipids ideal for long term energy storage?

• Contain 2x more energy per gram than most carbs

• Insoluble - not transported around body easily, remain in storage cells

• More water is produced during respiration than carbs - metabolic water, can be used as dietary water source

Where are lipids stored?

In adipose tissue under skin and around organs

How are triglycerides used in thermal insulation?

Low thermal conductivity → provides insulation, cushioning, and water-repellent energy stores e.g. blubber layer in endotherms

What are endotherms?

Animals that rely on metabolic reactions to generate heat to maintain a constant internal body temperature

What are steroids?

Lipids with 4 fused carbon rings and a hydrocarbon chain

What are the properties of steroids?

Hydrophobic, non-polar - can pass through membranes

What are examples of steroid hormones?

Oestradiol and testosterone

What is the role of cholesterol within steroid hormoens?

Strengthens membranes

Why is water required for life?

It is:

• The medium for metabolic reactions (universal solvent)

• A transport medium

• Involved in many chemical reactions

Why is water the medium for life?

• The first cells evolved in a watery environment (deep oceans, close to hydrothermal vents in Earth’s crust)

• Water and solutes trapped within a membrane

• Chemical reactions occurred in membrane-bound structure

• Led to evolution of cells

What is the polarity of water?

Polar covalent molecule

What is the structure of water?

2 hydrogen atoms form covalent bonds with 1 oxygen atom

What is the unequal sharing of electrons?

Pair of electrons spend most time near Oxygen as it has a higher affinity to attract electrons (slightly negative) than Hydrogen (slightly positive charge)

What bond forms between water molecules?

Hydrogen bonds (weaker than covalent bond)

What is cohesion?

Attraction between the same kind of molecules

What is adhesion?

Attraction between different kinds of molecules

What is surface tension?

Property of a substance to resist an external force

How does cohesion enable strong surface tension of water?

Hydrogen bonds occur between top layer of water molecules to create film on body of water

How does cohesion enable transport in the xylem?

Water forms a continuous column moving up the stem of plants

What is capillary action?

The ability of water to flow against gravity in a narrow space

How does adhesion enable strong capillary action in soil?

Water adheres to porous and polar soil particles and moves up the soil towards the roots of plants

How does adhesion enable strong capillary action in cell walls?

Cellulose in cell walls is porous and polar - polar water adheres to polar cellulose

What are hydrophilic substances?

Charged, polar substances that mix and dissolve with water

Why is water the transport medium in plants and animals?

Many polar molecules and ions dissolve in water e.g. polar organic particles, ions, ionic materials, organic molecules

What is metabolism?

Complex network of interdependent and interacting chemical reactions occurring in living organisms

What are enzymes?

Biological catalysts which speed up the rate of chemical reactions

What are hydrophobic substances?

Uncharged, non polar substances that do not readily mix with water

How does adhesion enable transport in the xylem?

Adhesion between water and cellulose prevents water column from dropping down when there is no cohesion during nighttime

What is an aqueous solution?

Any solution that has water as the solvent (cytoplasm - metabolism can occur efficiently)

What is the importance of water in living organisms?

1. Metabolic reactions

2. For transportation within the body

3. Reactant in some reactions

4. Movement

5. Give mechanical support

What is buoyancy?

Upward force exerted by a fluid on an object immersed in the fluid

How does water’s buoyancy affect aquatic animals?

Denser than air - provides greater buoyancy for aquatic animals and allows them to float or swim more easily

What is viscosity?

Measure of a fluid’s resistance to flow

How does water’s viscosity affect aquatic animals?

Higher than air - black-throated loon have streamlined body shape to move smoothly through water

What is thermal conductivity?

A substance’s ability to conduct heat

How does water’s thermal conductivity affect aquatic animals?

Higher than air - ringed seals have insulating blubber to prevent heat loss, black-throated loons insulated by feathers coated with hydrophobic oil

What is specific heat capacity?

Energy required to raise temperature of 1g of a substance by 1K

How does water’s specific heat capacity affect aquatic animals?

Lower than water (4.18Jkg⁻¹K⁻¹) - temperature more stable, animal cells in endotherms resistant to temperature change

What are covalent bonds?

When valence electrons are shared between two non-metal elements.