Water and Its Importance in Plants and Animals

What Water and Its Importance in Plants and Animals covers

Water and Its Importance in Plants and Animals is examined in all three written papers — the specification states that Components 01, 02 and 03 can each assess content from any of the five modules, so nothing is confined to one paper. It covers the properties of water, water as a transport medium and the composition of body fluids, Detecting and measuring sugars and proteins, monomers, polymers and the carbohydrates and osmosis and water potential.

The 5 subtopics

Each one has its own page.

• The properties of waterRecall questions on the polarity of water and hydrogen bonding, its high specific heat capacity and latent heat of vaporisation, cohesion, water as a solvent and reactant, why ice floats, incompressibility, transparency and surface tension.Open →
• Water as a transport medium and the composition of body fluidsRecall questions on intracellular and extracellular fluid, the transpiration stream, cell sap and turgor, plasma, serum, tissue fluid and lymph, urine, the main electrolytes H⁺, K⁺, Na⁺, Cl⁻, HCO₃⁻ and Mg²⁺, and what glucose or protein in urine suggests.Open →
• Detecting and measuring sugars and proteinsRecall questions on the Benedict's test for reducing sugars and making it quantitative, the Biuret test for protein, choosing a colorimeter filter, blanks and calibration curves, glucose test strips with glucose oxidase, and how a glucose biosensor works.Open →
• Monomers, polymers and the carbohydratesRecall questions on monomers and polymers, condensation and hydrolysis, the elements in organic molecules, α-glucose and lactose, the structures of amylose, amylopectin and glycogen, why branching and insolubility suit storage, and the iodine test for starch.Open →
• Osmosis and water potentialRecall questions on water potential and its units, why solutes lower it, the solute and pressure equation, plant cells and erythrocytes in strong solutions, and percentage change in potato mass.Open →

What you need to know

Answer each one before you reveal it.

Take Water and Its Importance in Plants and Animals further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Plasma vs Serum

  Plasma: the liquid part of blood with all its dissolved substances present, including fibrinogen and the other clotting factors. Serum: the liquid left after blood has clotted, from which fibrinogen and the other clotting factors have therefore been removed.

• Amylose vs Amylopectin

  Amylose: an unbranched chain of α-glucose joined only by 1,4-glycosidic bonds, which coils into a compact helix. Amylopectin: a chain of α-glucose that carries 1,6-glycosidic bonds at intervals, creating side branches along its length.

• Benedict's test vs Biuret test

  Benedict's test: a blue reagent added in equal volume and heated in a boiling water bath, which forms a green to brick-red precipitate if a reducing sugar is present. Biuret test: sodium hydroxide followed by dilute copper(II) sulfate, used cold, which turns purple if peptide bonds are present.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Why is a water molecule polar?

   Model answer

   The oxygen atom attracts the shared electrons more strongly than the hydrogen atoms, so the oxygen carries a small negative charge and each hydrogen a small positive charge, and because the molecule is V-shaped these charges do not cancel out.

2. 2

   How does a hydrogen bond form between two water molecules?

   Model answer

   The slightly positive hydrogen of one molecule is attracted to a lone pair of electrons on the slightly negative oxygen of a neighbouring molecule.

3. 3

   Why are hydrogen bonds between water molecules described as individually weak but collectively strong?

   Model answer

   One hydrogen bond is only about a twentieth the strength of a covalent bond and is constantly breaking and reforming, but each molecule can form up to four of them, so in bulk water the total attraction between molecules is considerable.

4. 4

   Why does water have an unusually high specific heat capacity?

   Model answer

   A large amount of energy must be absorbed to break the many hydrogen bonds before the molecules can move faster, so a large input of heat produces only a small rise in temperature.

5. 5

   Give one biological benefit of the high specific heat capacity of water.

   Model answer

   Cells, body fluids and aquatic habitats are largely water, so their temperature changes only slowly and enzymes are protected from sudden fluctuations.

6. 6

   Why does water have a high latent heat of vaporisation?

   Model answer

   A great deal of energy is needed to break all the hydrogen bonds holding a molecule to its neighbours before it can escape as vapour.

What is inside Levo

Six ways to work the same material.

Water and Its Importance in Plants and Animals revision questions

What does Water and Its Importance in Plants and Animals cover in OCR A-Level Biology B?

5 subtopics: the properties of water, water as a transport medium and the composition of body fluids, detecting and measuring sugars and proteins, monomers, polymers and the carbohydrates and osmosis and water potential. Each one has its own page with questions and model answers.

How is Water and Its Importance in Plants and Animals organised?

By the OCR H422 specification, subtopic by subtopic, so it matches the order you are taught it in.