Chap 4 Bio Molecules Flashcards
What roles do water have in living organisms? [4]
- As a solvent for chemical reactions eg. photosynthesis and hydrolysis
- As a key component of tissues e.g. protoplasm
- Controlling body temperature
- Transporting dissolved substances
What roles do water have especially for plants?
Essential for photosynthesis
Needed to keep cells turgid or firm
Needed to transport mineral salts (through the xylem) and food substances (through the phloem)
Define “carbohydrates” and what they may be classified as.
Carbohydrates are organic molecules made up of the elements carbon, hydrogen and oxygen. The hydrogen and oxygen atoms are present in the ratio 2:1. They may be classified as monosaccharides, disaccharides, or polysaccharides.
What are the purpose of carbohydrates?
Carbohydrates are needed as a source of energy and to synthesise other organic compounds such as cellulose, amino acids, fats, nucleic acids (e.g. DNA), lubricants and nectar.
Name examples of monosaccharides.
Glucose, fructose, galactose
Name examples of monosaccharides.
Glucose, fructose, galactose
Name examples of disaccharides
Maltose, lactose, and sucrose. Maltose is formed from two glucose molecules joining together to form maltose, with the removal of one molecule of water.
Name examples of polysaccharides
Starch, glycogen and cellulose
What are the stores of glucose? What are their features?
Glycogen and starch are stores of glucose. Starch is the store of glucose in plants, whereas glycogen is the store of glucose in animals. Glycogen is stored mainly in the liver and muscles.
Insoluble in water. Does not change water potential in cells.
Large molecules. Cannot diffuse through cell membranes and will not be lost from the cell.
Can easily be hydrolysed to glucose when needed.
In the hydrolysis of starch, the bonds within the polysaccharide are broken and glucose molecules are released.
Have compact molecule shapes. Occupies less space to allow for more to be stored.
This makes glycogen and starch suitable storage materials.
What are the functions of carbohydrates
Carbohydrates are a substrate for respiration to provide energy for cell activities.
Forms supporting structures like cell walls in plants
Can be converted into other organic compounds like amino acids and fats
Needed to form nucleic acids such as DNA
Synthesise lubricants like mucus
Synthesise nectar in some flowers (nectar is a sweet liquid that is produced to attract insects).
What are fats?
Fats are organic molecules made up of carbon, hydrogen and oxygen. They contain much less oxygen in proportion to hydrogen, unlike carbohydrates.
What can fats be broken down into?
Fats can be broken down into fatty acids and glycerol through hydrolysis.
Fat molecule + three water molecules → Glycerol + three fatty acid molecules.
What are the functions of fats?
Fats are a source and store of energy.
An insulating material that reduces excessive heat loss (e.g. blubber in animals)
As a solvent for fat-soluble vitamins and other substances like hormones
Essential constituent of cell membranes
A way to reduce water loss from the skin surface by being secreted as an oily substance forming a thin layer over skin surfacing, reducing water evaporation and reducing the rate of heat loss.
What are proteins?
Proteins are organic molecules made up of the elements carbon, hydrogen, oxygen, nitrogen and (depends) sulfur. Proteins are always present in protoplasm, and are the largest and most complicated.
What are proteins made up of? [2 para]
Protein molecules are built up from simpler compounds known as amino acids, which is made up of an amino group, an acidic group, and a side chain. There are many different amino acids, and they can be combined in various ways to form millions of different protein molecules.
Amino acids link up to form polypeptides. The bond between two amino acids is known as a peptide bond.
These polypeptides are long, three-dimensional folds that cannot be quickly absorbed if not broken down by enzymes in digestion, which is a series of hydrolytic reactions.
