Biology topic 1 part 1- Lifestyle, health and risk

How is an aqueous solution formed

When solutes are dissolved in a solvent

Why is water a powerful solvent

Water is a polar molecule, which allows it to easily dissolve ionic and polar molecules

What is meant by a polar molecule

A molecule that has regions of negativity and regions of positivity.

How do ions dissolve in water

Water molecules are attracted to the ions in contact with the water, as they are polar molecules and have negative regions and positive regions that are attracted to the positive and negative ions. This causes the water molecules to cluster around each ion, separating them from its ionic lattice (The slightly positive hydrogens are attracted to the negative ions, while the slightly negative oxygens are attracted to the positive ions). They are attracted by electrostatic forces of attraction.

Why is water a good transport medium

It can carry a range of solutes

What are some uses of water as a transport medium in animals

Can carry important substances in the blood:

Gases- Carbon dioxide and oxygen

Polar biological molecules- Amino acids, glucose, nucleotides

Inorganic ions- Sodium, chloride, potassium

What are some uses of water as a transport medium in plants

Plants use water in sap in the phloem to carry important substances like amino acids, sugars and ions

Why is water a good reaction medium

Solutes can dissolve in water, allowing them to move freely and collide and interact with each other. e.g. enzymes react with substrates to catalyse reactions

Why does water have an unusually high boiling point

It contains hydrogen bonds, which require much more energy to be broken than other inter molecular forces

Why is waters high boiling point essential for life

- It provides habitat for aquatic organisms, as it is liquid at room temperature

- It provides a medium for chemical reactions, as it allows substances to move freely and interact

- It provides a medium for transport, as ionic substances and polar molecules can easily be dissolved in it

What is specific heat capacity

The amount of energy required to increase the temperature of 1kg of a substance by 1oC

Why is it important for water to have a high SHC

- Lakes and seas are able to maintain a stable temperature for organisms to live in

- The water inside of cells can provide a stable environment necessary for enzymes to function effectively

What is latent heat of vapourisation

energy needed for a substance to change from liquid to gas

Why does evaporation have a cooling effect

When water molecules are heated, they gain kinetic energy, allowing them to break the hydrogen bonds present between them and form a gas. When these gas molecules break off, it decreases the total average energy of the remaining molecules, as it has been taken away in the form of kinetic energy

What do humans use evaporation for in the body

The evaporation of sweat. When temperatures become too high, this can cause our enzymes to denature. The body produces sweat in order to decrease body temperature. This is because the thermal energy from our surroundings is absorbed by the hydrogen bonds between the water molecules, causing them to break and evaporate.

How do plants use evaporation

Plants use evaporation to cool themselves as water evaporates from the mesophyll cells in the leaves and diffuses into the air (transpiration)

What is cohesion

Attraction between molecules of the same substance

Why is water cohesion important in plants

The water molecules are attracted to one another, so when water is taken from one end of the tube, water molecules follow behind. This is important in plants to be able to draw water up the xylem vessels in a continuous stream against the pull of gravity during transpiration

How is tension created at the surface of water and why is it important

Cohesion of water causes tension at the surface of water. At the interface between water and air, the water molecules at the waters surface is more attracted to the other water molecules than to the molecules in the air. This uneven attraction pulls the water molecules inwards toward the water below, placing the surface of the water under tension. This results in a thin "skin" at the surface of the water that is difficult to break through. This can act as a habitat for insects, such as pond-skaters.

What is adhesion

An attraction between molecules of different substances

When does water display adhesive properties

when it is attracted to other polar or charged surfaces

Why is water able to move up glass straws when they are placed in water

Glass straws are made up of materials that contain polar properties. Due to adhesion, the water molecules are attracted to the straw, and are able to move up it. This is known as capillary action. The narrower the glass straw is, the higher up the water can travel, as there is more surface in contact with the water.

What is a monomer

a molecule that can be bonded to other identical molecules to form a polymer.

What is a polymer

long chain of monomers

How is water formed in condensation reactions between monosaccharides

The grouping of a hydroxyl group of one monomer and the hydrogen of another

What is the general formula for monosaccharides

(CH2O)n

What is the general formula of glucose

C6H12O6

Draw glucose

Give some useful properties of glucose

- Small so can be easily transported in and out of cells through carrier proteins

- Soluble so can be easily transported

- Less reactive than other monosaccharides so breakdown must be catalysed and therefore controlled by enzymes

What is an isomer

Compound with same atoms, but arranged differently

What are the isomers of glucose

alpha glucose and beta glucose

Draw ribose

What is the general formula of ribose

C5H10O5

How is ice less dense than water

As liquid water cools, more hydrogen bonds are formed and water becomes more dense, until its maximum density at 4 degrees. As water freezes to ice, the water molecules begin to spread out in a regular geometrical structure, in order to allow each molecule to form the maximum 4 hydrogen bonds. This means that there are less molecules in a given volume, making it less dense than water

What temperature is water at its most dense state

4 degrees

Why is floating ice essential to life

- Provides habitat for creatures that live in a cold climate

- Provides an insulating layer on lakes and rivers, which prevents it from freezing solid, allowing aquatic organisms to survive in cold external temperatures

What is maltose made out of

glucose and glucose

What is sucrose made out of

glucose and fructose

What is lactose made out of

glucose and galactose

Where is glycogen found

animals- cells with a high metabolic rate

Starch structure

amylose and amylopectin

Amylose structure

Linear polysaccharide

alpha 1-4 glycosidic bonds

What shape is amylose

helix

Amylopectin structure

1. Branched Chains of alpha glucose

2. 1-4 and 1-6 glycosidic bonds

3. With Branches

Why is amylopectin more easily broken down than amylose

It has branches, making it more accessible to enzymes to break it down into individual alpha glucose molecules.

Glycogen structure

Long, branched chain of alpha-glucose.

Similar structure to amylopectin, but has much more side branches.

Properties of starch

Amylose- coiling makes it compact and stores much more in a smaller space

Amylopectin- Branching increases surface area for enzymes to hydrolyse glycosidic allowing glucose to be released quickly

Uses of starch

Plants use starch as a way of storing excess glucose as it is too large cells and insoluble. Starch can be hydrolysed to release glucose for respiration

Cellulose structure

1. Long, unbranched chain of beta-glucose.

2. Bonds between the sugars are straight, so cellulose chains are straight.

3. Cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils.

Cellulose properties

Hydrogen bonds between the cellulose chains make the microfibrils very strong but still flexible allowing them to provide support

Cellulose uses

Major component of cell walls for rigidity and prevents call bursting, allows the cell to become turgid

How do you test for reducing sugars

1) Add the sample to a clean test tube and add an equal volume of Benedict's reagent

2) Heat the solution in a water bath for 3-5 minutes

3) If reducing sugars are present, copper (II) ions will be reduced to form copper oxide, which will change the colour from blue to orange-red

How to test for non-reducing sugars

1) Following a negative reducing sugars test, add dilute HCl to the solution and heat it in a water bath to break bonds

2) Add an alkali (sodium hydrocarbonate) to neutralise it

3) Add excess Benedict's reagent and heat to above 80 degrees

How to test for starch

1) Place the sample in a clean test tube

2) Add iodide solution and gently shake

3) A positive result will go from orange to blue/black

How to test for proteins

1) add the sample to a clean test tube and add biuret solution

2) Shake and leave at room temperature

3) If amino acids are present, it will go from blue to purple

How to test for lipids

1) add sample to ethanol

2) Add water and shake

3) if lipids are present a milky white emulsion will form

How can a colorimeter be used to do a quantative Benedict's test

Filter the solution and weigh the precipitate and use the colorimeter to measure the absorbance of the remaining solution

Triglycerides structure

glycerol + 3 fatty acids

How are ester bonds formed in triglycerides

Condensation reactions between each of the 3 OH groups on the glycerol and OH group on each fatty acid chain

Triglycerides properties

Fatty acid chains are hydrophobic, so are insoluble in water

Triglycerides uses

Used as an energy store as a lot of energy is released when the fatty acid chains are broken down

Phospholipids structure

glycerol, 2 fatty acids, and a phosphate group

How are ester bonds formed in a phospholipid

Condensation reaction between 2 OH groups on the glycerol and the OH group on each fatty acid chain

Phospholipids properties

Phosphate group is hydrophillic, while fatty acid chains are hydrophobic, which allows them to form bilayers which make up membranes

Uses of phospholipids

Membranes and hormones

What is a saturated fatty acid

One without double bonds.

What is an unsaturated fatty acid

a fatty acid with at least one double bond between carbon atoms

4 main roles of lipids in the body

insulation, energy, waterproofing, form membranes and hormones

What is a phospholipid bilayer

a two-layered arrangement of phosphate and lipid molecules that form a cell membrane, the hydrophobic lipid ends facing inward and the hydrophilic phosphate ends facing outward.

Why is it important for starch and glycogen to be insoluble

They do not affect the concentration of water in the cytoplasm, so do not affect the movement of substances in and out of the cell by osmosis