2a- Biological molecules: Carbohydrates and Water

What is water?

• a major component of cells

• 1 oxygen atom, 1 hydrogen atom

What bond is formed between water molecules?

hydrogen bond

Explain how bonds form in water

• Water is a polar molecule (unequal distribution of charge)

• The slightly negatively charge O2- atoms attract slightly positively charged H+ atoms of other H2O molecules.

• The hydrogen bonds formed are relatively weak but strong in large numbers

What does this image show?

3 water molecules bonding to each other

What do the pink and grey lines represent?

pink= hydrogen bond

grey= covalent bond

What are the 5 properties of water?

1. High specific heat capacity

2. Large latent heat of vaporization

3. Strong cohesion and surface tension

4. Solvent

5. Metabolite

What is the importance of water having a high specific heat capacity?

allows water to act as a buffer to sudden temp changes= can gain/ lose lots of heat without changing

What is the importance of water having a large latent heat of vaporization?

explains why sweating is an effective means of cooling= helps organisms maintain constant internal body temp

What is the importance of water having a strong cohesion and surface tension?

allows water to be pulled up xylem tissues in continuous columns in plants

What is the importance of water being a solvent?

allows metabolic reactions to occur faster in solution

allows transport of substances around an organism

What is the importance of water being a metabolite?

metabolite involves in many metabolic reaction. Used in hydrolysis and is formed in condensation. Used in photosynthesis

What is a monomer?

small repeating molecules from which polymers are made

What is a polymer?

a large chain of many similar monomers joined together

What reaction joins monomers?

condensation reactions to form polymers

What happens in condensation and hydrolysis reactions?

Condensation= 2 molecules join together forming a chemical bond, releasing water

Hydrolysis= 2 molecules separate, breaking a chemical bond using water

What is the reversible reaction for condensation and hydrolysis?

What elements are all carbohydrates composed of?

• carbon

• hydrogen

• oxygen

What is a saccharide?

a simple sugar

What are monosaccharides?

basic molecules units/ monomers of which larger carbohydrates are made. Usually soluble and sweet

What are the 3 monosaccharides?

• glucose

• fructose

• galactose

What is the chemical formula of glucose and pentose?

Glucose:

C6H12O6

Pentose:

C5H10O5

What is an isomer?

same molecular formula, differently arranged atoms

What are the 2 isomers of glucose?

• a glucose

• B glucose

What is the difference between the 2 isomers of glucose?

OH group is below carbon 1 in a glucose but above carbon 1 in B glucose

What isomer of glucose is this?

a glucose

What isomer of glucose is this?

B glucose

What are disaccharides and how are they formed?

2 monosaccharides joined together with a glycosidic bond formed by a condensation reaction, releasing water

What are the 3 common disaccharides?

• maltose

• sucrose

• lactose

What monosaccharides is maltose made from?

glucose + glucose

What monosaccharides is sucrose made from?

glucose + fructose

What monosaccharides is lactose made from?

glucose + galactose

How is a glycosidic bond formed? (diagram)

What are polysaccharides and how are they formed?

many monosaccharides joined together with glycosidic bonds formed by many condensation reactions, releasing water

What are the 3 main polysaccharides?

• starch

• glycogen

• cellulose

What is the function of starch?

energy storage (found in plants)

What is the function of glycogen?

energy storage in animals

What is the function of cellulose?

strength/ structural support to plant cell walls

What is starch?

polysaccharide of a glucose

What are the 2 polymers of starch?

Amylose:

1-4 glycosidic bonds, helical chain, unbranched

Amylopectin:

1-4 and 1-6 glycosidic bonds, branched

Explain how the structures of starch relate to its function

• Helical= compact for storage in cell

• Large and insoluble= can’t diffuse out of cell

• Insoluble in water= water potential of cell not affected (no osmotic effect)

What is glycogen?

polysaccharided of a glucose.

1-4 and 1-6 glycosidic bonds, branched.

Where is glycogen found?

liver cells and muscle tissue in animals

Explain how the structures of glycogen relate to its function

• Coiled/ compact= store lots of glucose in small space

• Branched= quickly hydrolysed= release glucose for respiration to make ATP for energy release

• Large + insoluble= can’t diffuse out of cell

• Insoluble in water= water potential of cell not affected= no osmotic effect

What is cellulose?

polysaccharide of B glucose

1-4 glycosidic bonds, straight unbranched chains

What type of reaction is involved in joining cellulose (B glucose) molecules?

condensation

Name the additional molecule forming during the reaction of joining B molecules

water

Draw 2 B glucose molecules to form cellulose

Explain how the structures of cellulose relate to its function

• Every other B glucose molecule is inverted= long, straight, unbranched chain

• Chains run parallel to each other and hydrogen bonds form cross linkages between chains to form microfibrils

• Many hydrogen bonds are strong= provide high tensile strength= makes cell wall rigid and prevents osmotic lysis

Name the monomer, shape of polymer, types of bonds, and solubility in water for…

STARCH

• a glucose

• amylose= helical, amylopectin= branched

• glycosidic

• insoluble

Name the monomer, shape of polymer, types of bonds, and solubility in water for…

GLYCOGEN

• a glucose

• branched

• glycosidic

• insoluble

Name the monomer, shape of polymer, types of bonds, and solubility in water for…

CELLULOSE

• B glucose

• straight long chains forming microfibrils

• glycosidic (hydrogen between chains)

• insoluble

What is the food test for starch?

Add iodine solution and colour changes from brown/ orange to blue-black

What is a reducing sugar?

those with the ability to donate electrons/ hydrogen (has spare hydrogen)

What is the food test for reducing sugars?

Add benedicts solution to sample. Heat in water bath. If reducing sugar present, colour will change blue to red

What are the 5 reducing sugars?

• glucose

• fructose

• galactose

• maltose

• lactose

What is the food test for non-reducing sugars?

1. Do benedicts test and result stays blue

2. Boil fresh sample with dilute HCl (acid)

3. Neutralise with alkali

4. Heat in water bath with benedicts solution

5. Positive result turns red

What is the only non-reducing sugar?

sucrose

Explain the quantitative benedicts reagent test

more concentration of glucose solution= more white precipitate

> remove precipitate= more transparent solution

What readings do you get from the quantitative benedicts reagent test?

• Transmission %= increases as increase glucose

• Absorbance= decreases as glucose increases

What are some issues related to the benedicts tests and how are they resolved?

• Non-specific (doesn’t tell us the reducing sugar)= a biosensor can test for specific sugars

• Qualitative (can’t obtain a value from the concentration)= spectrum of concentrations

• Subjective= use a colourimeter and a calibration curve

How do you use a colourimeter and a calibration curve?

• Make sugar solutions of known concs (series of dilutions).

• Heat a set volume of each sample with benedicts solution.

• Use colourimeter to measure absorbance of each conc.

• Plot calibration curve quantitative benedicts reagent test (conc=x, absorbance=y)

• Repeat on unknown sample.

• Read off calibration curve to find conc associated with unknown sample’s absorbance

What is an inorganic ion?

an ion that has a charge

Where are inorganic ions found in the body?

in solution in cytoplasm and body fluid, same in high concs and low concs

What are the 4 main ions?

• Iron (FE2+/ FE3+)

• Sodium (Na+)

• Phosphate (PO4 3+)

• Hydrogen (H+)

Describe the role of hydrogen ions

• Affects pH levels= high conc= low pH

  > affects enzyme rate of reaction as can cause enzyme denaturation

Describe the role of sodium ions

• Involved in absorbance of glucose and amino acids in small intestine (co-transport)

Describe the role of iron ions

• Component of haem group of haemoglobin= allows oxygen to bind for transport

Describe the role of phosphate ions

• Component of DNA, ATP (an energy-containing molecule used by cells) and phospholipids