Topic 1 - A level BIology

• What are carbohydrates made out of?

  carbon, hydrogen and oxygen
• What is a monosaccharide (with examples of 3)?

  Carbohydrates with a single sugar unit, such a glucose, fructose and ribose
• What is a disaccharide (with 3 examples)?


  A carbohydrate with two sugar units, including maltose, sucrose or lactose.
• What is a true polysaccharide (with three examples)?

  A long chain of sugars that has been made through condensation polymerisation, these include glycogen, starch and amylose. It contains 11+ sugar units. It doesn't have the sweet taste of many mono and disaccharides.
• What is the monosaccharide equation

  (CH2O)n
• How many carbons do monosaccharides have and what do we call each monosaccharide (with examples)?

  Between 3 and 6.

  3 carbons - triose sugar (C3H6O3) In respiration, glucose is broken down into triose sugar

  5 carbons - pentose sugar (C5H10O5), ribose and deoxyribose are both pentose sugars and make up genetic material.

  6 carbons - hexose suagr (C6H12O6), often tastes sweet and include glucose, galactose and fructose.
• Why are carbohydrates important?

  They store energy in plant, fungi and bacterial cells. They also make up an important part of the cell wall. The best known carbohydrates are sugars and starch. Sucrose is a white crystalline sugar, glucose supplies energy in sports drinks, starch is found in flour and potatoes. They can come in the form of monosaccharides, disaccharides, oligosaccharides and polysaccharides.
• What is a dissacharide? Give an example.

  A molecule formed from the combination of two monosaccharides through a condensation reaction where water is lost. A covalent bond called a glycosidic bond forms between the two molecules. The reaction can be reversed by adding in water ( hydrolysis ). Sucrose is table sugar ad is formed by alpha glucose joining to a fructose.
• What is the source and monosaccharides of sucrose?

  source = stored in plants such as sugar cane

  monosaccharides = alpha glucose + fructose
• What is the source and monosaccharides of lactose?

  source = milk sugar - main carbohydrate found in milk

  monosaccharides = alpha glucose + beta glucose
• What is the source and monosaccharides of maltose

  source = malt sugar - found in germinating seeds such as barley

  monosaccharides - 2 alpha glucose molecules
• How do we test for reducing sugars? How ca we make a non- reducing sugar test positive?

  We use a solution called Benedict's solution. It is bright blue and contains copper (II) ions. When heated gently, the Benedict's copper (II) ions are reduced to copper (I) ions. A precipitate is formed, turning the solution from bright blue to orange. All monosaccharides are a reducing sugar and some disaccharides are too.

  With non-reducing sugars, you can add a few drops of hydrochloric acid to hydrolyse the glycosidic bonds. Allow to cool then neutralise with sodium hydrogen carbonate which will now give a positive result as the sugars been broken down into its monosaccharide units.
• What is an isomer?

  compounds with the same molecular formula but different structural formulas
• Draw alpha glucose and beta glucose

  
• Draw a ribose molecule

  
• What is an oligosaccharide?

  a carbohydrate with 3-10 monosaccharide units
• Why do polysaccharides form good storage molecules?

  - Can form very compact molecules meaning a cell can store a large number of them.

  - Glycosidic bonds can be easily broken, allowing from the quick release of monosaccharide units for cellular respiration.

  - Not very soluble in water meaning they have little effect on water potential within a cell and causes no osmotic water movements.
• Where does hydrolysis occur?

  During digestion in the gut and in muscle and liver cells when carbohydrate stores are broken down to release sugars in cellular respiration.
• Where is starch found, what is it made of and what is its role.

  Starch is found in plants and stores energy. Sugars produces in photosynthesis are quickly converted into starch . It is insoluble, compact and can be rapidly broken down to release glucose when needed. It is made up of amylose and amylopectin.
• What is amylose and amylopectin?

  Amylose = Unbranched polymer made up of 200 and 5000 glucose molecules. As the chain lengthens the molecule spirals, making it more compact for storage.

  Amylopectin = Branched polymer of glucose molecules. Branching chains have many terminal glucose molecules that can be broken off rapidly when energy is needed.
• What are the differences and similarities between amylose and amylopectin?

  Both are made of purely alpha glucose molecules.

  
  

  Amylose - Alpha glucose molecules joined by 1,4 glycosidic bonds which leads to ling, unbranched monomers

  Amylopectin - Alpha glucose molecules are joined by 1,4 glycosisdic bonds with a few 1,6 bonds. This leads to branching chains
• Why is carbohydrates good to eat before sports?

  Foods like pasta contain starch which is made of amylose and amylopectin. The amylopectin is branched, meaning branches can be quickly broken off to release glucose for cellular respiration. The amylose releases glucose over a longer period of time, keeping you going for longer.
• What does amylose look like?

  
• What does amylopectin look like?

  
• What is glycogen?


  Glycogen is sometimes referred to as 'animal starch'. It is the only carbohydrate energy store found in animals and is also found in fungi. It consists of alpha glucose and is very compact. It can be broken down rapidly meaning it is an ideal glucose source for active tissues that have a high rate of cellular respiration such as muscle and liver cells.
• What is the difference and similarities between glycogen and starch?

  Glycogen has far more 1,6 glycosidic bonds than starch. Both contain only alpha glucose but starch contains alpha glucose that has been arranged in two separate ways, meaning it can provide both long and short term energy. On the the hand, glycogen only provides short term energy. Glycogen forms granuals ad starch forms grains.
• How much of a starch grain is amylopectin?

  70-80% with the rest being amylose
• What is cellulose made of?

  Beta-glucose monomers joined by beta-1,4-glycosidic linkages
• What is the role of cellulose and where is it found?


  It makes up the majority of the cell wall which provides strength and support to plants. It forms long, straight chains with considerable strength.
• What makes cellulose similar to starch and glycogen?

  All there polysaccharides are made up of long chains of glucose joined by glycosidic bonds.

  
• What bonds the monomers of cellulose?

  Condensation reactions join beta glucose monomers. One beta monomer inverts, meaning the hydroxyl (-OH)group sticks out on both sides of the monomer. The hydrogen bonds form between partially positive charged hydrogen ions of the hydroxyl groups and the partially negatively charged atoms in other parts of the glucose monomers. This is called cross linking
• Why is cellulose not digested by many animals?

  They do not contain the needed enzymes to break down the 1,4 glycosidic bonds in the cellulose. It acts as roughage or fibre, meaning it is still important even though it cannot be digested.
• What is a lipid?


  A biological molecule with low solubility in water.It is used as an energy store and in cell membranes. It is made up of carbon, hydrogen and oxygen but has less oxygen than carbohydrates.
• What are the two organic chemicals that make up lipids?

  Fatty acids and glycerol (C3H8O3)
• What is the structure of a fatty acid like?

  A long hydrocarbon chain with a carboxyl group attached to the end.
• How can fatty acids vary?


  - Their length can differ but is often between 15 and 17 carbon atoms long.

  - They can be saturated or unsaturated
• What is the different between a saturated and an unsaturated fatty acid?

  A saturated fatty acid is when each carbon atom is joined to the next one by a single covalent bond, like in stearic acid. An unsaturated fatty acid, has one double bond and a polyunsaturated acid has more than one double bond, such as in linoleic acid.
• What is esterification?


  The process of triglyceride formation. It is when a condensation reaction occurs between the carboxyl group of a fatty acid and the hydroxyl group of glycerol. Water is removed and an ester bond is formed. If a saturated fatty acid was involved, the lipid is likely to be solid at room temp than those containing unsaturated fatty acids.
• How is a triglyceride formed?

  ~ By a condensation reaction between fatty acids and a glycerol

  ~ Ester bond is formed and a molecule of water is removed

  
• What is the use of lipids and why are they suited to each purpose?

  - Their hydrophobic nature makes them important in waterproofing mammals and birds, along with the surfaces of plants and insects.

  - They are good insulators meaning they can be used in the sheath of nerves, making the impulses travel faster.

  - Insulate animals against heat loss, like with whales where the blubber keeps them warm.

  - Dissolve organic solvents meaning they do not interfere with water based reactions in the cells cytoplasm.

  - Storing energy ( can store 3X that of carbohydrates )

  - Oxidation of lipids produces carbon dioxide and oxygen which can be used to drive the production of ATP