Chemical Elements and Water
1. State that the most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen. (or)
State that a variety of other elements are needed by living organisms, including sulphur, calcium , phosphorus, iron and sodium. (or)
State one role for each of the elements mentioned above
2. Outline the difference between an atom and an ion and a polypeptide
An atom is a single particle of a chemical element. When an atom either gains or loses an electron it then becomes an ion. Ions are charged, while atoms are uncharged. An Ion has either a negative or positive charge depending if it gained or lost an electron. On the other hand a polypeptide chain is a chain of amino acids joined through peptide bonds, the amino acids are molecules that are formed through the combination of ions.
3. Outline the properties of water that are significant to living organisms, including transparency, cohesion, solvent properties and thermal properties. Refer to the polarity of water molecules and hydrogen bonding when relevant.
4. Explain the significance to organisms of water as a coolant, transport medium and habitat in terms of its properties
State that a variety of other elements are needed by living organisms, including sulphur, calcium , phosphorus, iron and sodium. (or)
State one role for each of the elements mentioned above
- Nitrogen: Required by proteins. (Remember, nitrogen is included in the amino acid structure) Essential to enzymes required for plant function.
- Calcium: The mineral that strengthens bone and teeth uses calcium. Also important in nerve synaptic transmission of nerve impulses and muscle contraction. Regulates the cell wall construction in plants.
- Phosphorus: Part of the phosphate groups in ATP and DNA molecules. In plants it is needed for cell reproduction and division. It is part of the cell membrane.
- Iron: found in the structure of haemoglobin and essential for the production of red blood cells. It is involved in the light energy transferring compounds involved in photosynthesis in plants.
- Sodium: Major ion associated with the propagation of a nerve impulse. Can replace potassium in some plants.In membrane function.
- Sulfur: It is a component of amino acids.
2. Outline the difference between an atom and an ion and a polypeptide
An atom is a single particle of a chemical element. When an atom either gains or loses an electron it then becomes an ion. Ions are charged, while atoms are uncharged. An Ion has either a negative or positive charge depending if it gained or lost an electron. On the other hand a polypeptide chain is a chain of amino acids joined through peptide bonds, the amino acids are molecules that are formed through the combination of ions.
3. Outline the properties of water that are significant to living organisms, including transparency, cohesion, solvent properties and thermal properties. Refer to the polarity of water molecules and hydrogen bonding when relevant.
- Water is transparent which allows light to filter into aquatic environments, and thus aquatic plants can absorb light and perform photosynthesis. Since the ancestor of all plants originated in the ocean, the transparency of water has had an immeasurable influence on life as we know it.
- Water is also cohesive, that is it binds to itself, due to the polarity of the water molecule. The positive, hydrogen side of the molecule binds to the negative, oxygen side of another water molecule. This bond is called a hydrogen bond. Water is also adhesive, that is it binds to other things around it. This property allows for transport of water against gravity in plants. The water adheres to the xylem tube of plants and is able to be drawn up in long columns up the stem due to its strong cohesive force
- Water's solvent properties allows molecules to dissolve in it. This means that water can transport minerals up the xylem tube and sugars up the phloem tubes in plants. Blood in animals consists largely of water, allowing the transportation of oxygen, urea and glucose throughout the body. Water also is the site of metabolic reactions because reactions can occur between dissolved compounds.
- Water's polarity also inhibits movement of its molecules. Since all the molecules are connected, they cannot freely move about as other, non-polar molecules do. Heat, the kinetic energy of molecules, is thus restricted and so water has a high specific heat (it must absorb large amounts of energy in order to change states). This means that water can serve as a temperature insulator, and does so in organisms of all kinds.
- Water's high latent heat of vaporization is due to strong hydrogen bonds existing between water molecules. A large amount of heat is released when water in the liquid state vaporizes into the gaseous state.
4. Explain the significance to organisms of water as a coolant, transport medium and habitat in terms of its properties
- 'Coolant: Allows us to perform homeostasis. (We sweat to cool ourselves down). Additionally, water's high heat of vaporization allows water molecules to absorb large amounts of energy from the body before evaporating - thus, the sweating individual loses heat.
- Transport medium: Digestion, also important to help transport blood. Phloem in plants transport nutrients dissolved in water using the cohesive and adhesive properties.
- Habitat: Organisms need water; the ready availability of it is essential in the choosing of a habitat. Water's high heat capacity (the amount of energy needed to increase the temperature of 1gm of water by 1 Degrees Celcius) and high heat of vapourization (amount of energy absorbed by 1gm of liquid to be converted to the gaseous form) prevents from plants and animals from overheating and dying.
Carbohydrates, Lipids, and Proteins.
1. Define organic
- Organic compounds are defined as compounds containing carbon that are found in living organisms.
- Compounds are considered inorganic when they contain carbon but are widely found in the environment (carbon dioxide and hydrogen).
6. Outline the role of condensation and hydrolysis in the relationship between monosaccharides, disaccharides, and polysaccharides; fatty acids, glycerol and glycerides; amino acids, dipeptides, and polypeptides.
7. List three examples for each of monosaccharides, disaccharides, and polysaccharides
8. State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants.
10. Discuss the use of carbohydrates and lipids in energy storage.
11. Explain the four levels of protein structure
Primary structure
12. Outline the difference between fibrous and globular proteins, with references to two examples of each protein type
Fibrous proteins (such as keratin, collagen)
- In a condensation reaction, two molecules work together and form one big molecule along with water, because water is released during this reaction. So, two amino acids could join together and form a dipeptide and this would be a condensation reaction. Same applies for monosaccharides becoming dissaccharides, you get the drift.
- Now in a hydrolysis reaction, water molecules are used up to make a large molecule into a small molecule. Think about it- "hydro" means water and "lysis" means splitting. So, water is used up to split a disaccharide into a monosaccharide.
7. List three examples for each of monosaccharides, disaccharides, and polysaccharides
- Monosaccharide: Glucose, Fructose and ribose
- Disaccharide: Maltose (Glucose + Glucose) and Sucrose (Glucose + Fructose), and lactose.
- Polysaccharide: Starch (made of glucose subunits) and Glycogen (made of glucose subunits, but linked differently from starch). (Plants use mostly starch, humans use mostly glycogen) and cellulose.
8. State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants.
- Animals
- Glucose: metabolized for energy.
- Lactose: provides energy to mammalian young.
- Glycogen: longer term energy in muscles and liver.
- Plants
- Fructose: sweetens fruit to disperse seeds
- Sucrose: energy storage
- Cellulose: cell wall structure
- Energy storage: Fat in humans. Oil in plants.
- Heat insulation: A layer of fat under the skin reduces heat loss.
- Buoyancy: Lipids are less dense than water.
10. Discuss the use of carbohydrates and lipids in energy storage.
- Lipids and carbohydrates are excellent for storing energy in living organisms. Carbohydrates are usually used to store energy in the short-term while lipids are used for the long-run.
- Contain more energy per gram. Therefore lighter to store.
- Lipids are insoluble in water; do not interfere with osmosis.
- More easily digested, so energy is released more easily from them.
- Carbohydrates are soluble in water, so easier to transport.
11. Explain the four levels of protein structure
Primary structure
- A linear sequence of amino acids joined by peptide linkages. There are about 20 different amino acids.
- α -Helix is maintained by hydrogen bonds. The helix makes up keratin (skin, nails, hair).
- β -Pleated Sheet: flat zig-zag amino acid chain. The sheets make up fibroin (silk.)
- Folded polypeptide chains into specific shapes. This means that tertiary proteins are globular (hormones, enzmyes, membrane proteins).
- Two or more polypeptide chains joined (e.g. haemoglobin).
12. Outline the difference between fibrous and globular proteins, with references to two examples of each protein type
Fibrous proteins (such as keratin, collagen)
- Chain extended
- Insoluble
- Resistance to pH/temperature changes
- Structural material
- Chain folded
- Soluble/colloidal
- Susceptible to pH/temperature changes
- Compact, rounded molecules