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Medicine LibreTexts

1.12: Worksheet Answers

1. What is the most abundant molecule in the cell?

Water (H2O). Roughly 70% of a cell consists of water.

2. Name one inorganic molecule in the cell.

One of: Sodium chloride (NaCl), potassium chloride (KCl), water (H2O), oxygen (O2) etc.

3. What is the difference between inorganic and organic molecules?

All organic molecules contain carbon (C) while inorganic molecules can contain any atom except carbon.

4. Name the 4 different types of organic molecules to be found in the cell.

1.Carbohydrates
2. Fats
3. Proteins
4. Nucleic acids

5. What is the characteristic of carbon atoms that makes them so versatile?

They can bond with 4 other atoms allowing them to make rings and chains and thus form large, complex molecules.

6. Name the 3 atoms that are always found in carbohydrates.

Carbon (C)
Hydrogen (H)
Oxygen (O)

7. Fats and carbohydrates both contain the same atoms. What distinguishes carbohydrates from fats?

In carbohydrates H and O are in the ratio 2:1. There is no such relationship in fats.

8. Give the 3 main functions of carbohydrates.

1. As an energy store e.g. as glycogen stored in the liver.
2. Providing energy in the cell
3. Making structures of the body e.g. in cartilage, bone
Plus other functions

9. Which of the following is NOT one of the main types of carbohydrate.

Monosaccharide / Polysaccharide / Sucrose / Disaccharide. Sucrose is a disaccharide.

10. Monosaccharides: (Indicate if true (T) or false (F))

  • are sweet to taste T
  • are insoluble in water F
  • provide energy T
  • form important structures in the cell or animal F
  • are not easily digested in the gut of mammals F
  • are found in grains and potatoes F
  • are found in fruits and energy drinks T
  • include sucrose, maltose and lactose F
  • can be absorbed into the blood directly from the gut without the need for digestion T
  • include glucose T
  • are formed when disaccharides are split T

11. Disaccharides:

  • are sweet to taste. T
  • are soluble in water. T
  • provide energy. T
  • form important structures in the cell or animal. F
  • are not easily digested in the gut. F
  • are found in grains and potatoes. F
  • are found in milk, malt and your sugar bowl. T
  • include sucrose, maltose and lactose. T
  • can be absorbed into the blood directly from the gut without the need for digestion. F
  • include glucose. F
  • are formed when 2 monosaccharides are joined. T

12. Polysaccharides:

  • are sweet to taste. F
  • are soluble water. F. Some are but most are not
  • provide an energy store. T. Starch is the energy store in plants while glycogen is in animals. cellulose (plant cell walls) is digested by herbivores and provides them with their energy.
  • form important structures in the cell or animal's bodyT. e.g. cellulose plant cell walls, lignin is wood and chitin forms the outer skeleton of insects.
  • can be absorbed into the blood directly from the gut without the need for digestion. F
  • are found in grains and potatoes. T
  • include sucrose, maltose and lactose. F
  • do not need to be digested in the gut. F
  • include glucose. F
  • are formed when monosaccharides are joined in long strings. T
  • include cellulose, starch and glycogen. T

13. Fats:

  • are soluble in water. F
  • are only soluble in solvents like ethanol. T
  • contain hydrogen and oxygen in the ratio 2:1. F
  • include triglycerides, phospholipids, and some vitamins. T
  • provide the body’s most concentrated source of energyT. Fats provide approximately 2 1/2 times more energy than the equivalent weight of carbohydrate.
  • are formed by the joining of several glucose molecules. F
  • are found in nuts, seeds and dairy produce. T

14. Give 2 differences between saturated and unsaturated fats.

Saturated fats contain the maximum number of hydrogen atoms, come from animals, and tend to be solid at room temp. Unsaturated fats can incorporate more hydrogen into their structures, come from plants and fish (and poultry) and tend to be liquid at room temperature.

15. Proteins:

  • are formed from carbon, hydrogen and oxygen molecules. F
  • all contain nitrogen. T
  • are made up from many fatty acids. F
  • are made up from many amino acids. T
  • are very small molecules. F. Proteins form some of the largest and most complex molecules in the body.
  • are very stable molecules and can withstand heating, etc. F. Proteins are very sensitive to heat, acid/base balance (pH) and solvents which can destroy their molecular shape (denaturation) causing them to lose their function in the cell or body.
  • are digested in the gut by the enzymes pepsin, trypsin, peptidases and proteases. T
  • are digested in the gut by amylases.
  • have a major role in the cell is as enzymes. T
  • have a major role in the cell is to provide energy. F. Note that proteins can provide energy in some circumstances (e.g. during starvation) and in some animals (e.g.the cat) but generally they are not used for energy.
  • are found in cream, potatoes and fruit. F
  • are found in meat, nuts and cheese. T

16. These statements are true of amino acids:

  • There are 20 different amino acids. T
  • All of these can be found in plants. F. Only something like 10 of them (non essential amino acids) are found in sufficient quantities in all plants to provide a balanced diet.
  • The amino acids not found in plants can be made by the body. F. These essential amino acids can not be made in the body. They must be taken into the body in the diet.
  • Only meat and dairy produce contain all the essential amino acids. T
  • The bond joining amino acids together is called a protein bond. F. It is called a peptide bond.

17. Which is the odd one out?

  1. proteins / fats / glucose / carbohydrates / nucleic acids. Glucose is a type of carbohydrate. All the others are major types of organic molecule.
  2. glucose / starch / amino acids / fatty acids. Starch is formed from many glucose molecules while the others in the group are all the smallest subunits of carbohydrates, proteins and fats respectively.
  3. starch / cellulose / glycogen / glucoseGlucose is the only molecule in the group that is not a polysaccharide.
  4. carbon / iron / hydrogen / oxygen. All except iron are found in all carbohydrates.
  5. enzymes / plasma membrane / antibodies / plant cell wall (cellulose). All except cellulose are made of protein.

Contributors

  • Ruth Lawson (Otago Polytechnic; Dunedin, New Zealand)