deck_5661103 Flashcards
What is a condensation reaction?
When two molecules are joined together with the removal of water
What is a hydrolysis reaction?
When a molecule is split into two smaller molecules with the addition of water
How do almost all condensation reactions happen?
When two -OH groups react together-this reaction involves the breaking and formation of covalent bonds
In condensation reactions, what molecules are joined together?
Monomers
What if formed when lots of monomers join together?
Polymers
What do carbohydrates contain?
Carbon, hydrogen and oxygen. The monomer is a monosaccharide and the polymer is a polusaccharide
What do proteins contain?
Carbon, hydrogen, oxygen, nitrogen and sulfur. The monomer is amino acids and the polymer is polypeptides and proteins
What do nucleic acids contain?
Carbon, hydrogen, oxygen, nitrogen and phosphorus. The monomer is nucleotides and the polymer is DNA and RNA
What does water consist of?
Two hydrogen atoms covalently bonded to one oxygen atom, however the oxygen atom has a greater number of protons in it’s nucleus which exerts a stronger attraction for the shared electrons, so the oxygen atom becomes slightly negative and the hydrogen become slightly positive, the molecule is polar
What is a hydrogen bond?
A weak interaction which happens wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom. It is weaker than a covalent bond however some polymers have thousands of hydrogen bonds that form between chains of monomers, helping stabilise the structure of some biological molecules
How are hydrogen bonds represented in diagrams?
With a dotted line
What are the properties of water?
Latent heat of evaporation, density, transparent, dipolar, surface tension, incompressibility, temperature, specific heat, viscosity, solvent, metabolic, capillarity and state
What is latent heat of evaporation?
Water molecules absorb heat energy from surfaces as they evaporate, cooling them down eg sweating and transpiration
What is density?
Water supports aquatic organisms. Ice floats on water allowing organisms to survive below it in liquid. Polar bears live in an environment of floating ice planks
What is transparent?
Allows the transmission of light eg photosynthesis in aquatic organisms
What is dipolar?
Has positive and negative charges
What is surface tension?
Water has a strong surface film allowing small organisms to be supported on or in it
What is incompressibility?
Provides a hydrostatic skeleton with a surrounding strong wall provides support and protection eg earthworm body cavity, human abdomen and plant cells
What is temperature?
Carries away heat energy when it evaporates from a surface. This cools the surface and helps to lower the temperature
What is specific heat?
High specific heat so gains and loses heat slowly, good for temperature control of aquatic environments
What is viscosity?
Allows free flow for transport of materials inside and outside the organisms
What is solvent?
Universal solvent to dissolve many substances
What is metabolic?
Water takes part as a reactant in some chemical processes-hydrolysis and photosynthesis
What is capillarity?
Water rises in small tubes against gravity because polar molecules are attracted to themselves and to surfaces, useful in plants eg xylem and phloem
What is state?
Solid at 0ºc and vapour above 100ºc provides a wide temperature range as a liquid
What are ‘hydrated carbon’?
For every carbon there are two hydrogen atoms and one oxygen atom. Carbohydrates are hydrated carbon
What are the functions of carbohydrates?
They act as a source of energy (glucose), as a store of energy (starch/glycogen) and as structural units (cellulose in plants and chitin in insects). Some are also part of other molecules such as nucleic acids and glycolipids
What are the three main groups of carbohydrates?
Monosaccharides, disaccharides and polysaccharides (common monosaccharides and disaccharides all have names ending in -ose)
What are monosaccharides?
They are the simplest carbohydrates and are particularly important in living things as a source of energy
How are monosaccharides well suited to their role?
Because they have a large number of carbon-hydrogen bonds
What are the properties of monosaccharides?
They are sugars, which taste sweet, are soluble in water and are insoluble in non-polar solvents
What is the structure of monosaccharides?
They can exist as straight chains or in ring/cyclic forms. They have a backbone of single bonded carbon atoms, with one double-bonded to an oxygen atom to form a carbonyl group
What are the different sugars with different numbers of carbon atoms?
Hexose sugars have six carbon atoms, pentose sugars have five carbon atoms and triose sugars have three carbon atoms
What is an example of a monosaccharide hexose sugar?
Glucose, these types are the monomers of more complex carbohydrates, and they bond together to form disaccharides or polysaccharides
What are triose and tetrose sugars like in solution?
They exist as straight chains
What form are pentoses and hexoses more likely to be found as?
Ring or cyclic form
What are isomers?
Molecules with the same formula, but whose atoms are arranged differently, glucose in both forms can exist as a number of different isomers
How are isomers formed in straight chains?
The -H and -OH can be reversed
How is the ring shape formed?
When the oxygen attached to carbon 5 bonds to carbon 1. Because the -OH and -H on carbon 1 can be above or below, there are two isomers (a- and b-glucose), the small difference seems insignificant but becomes very important when glucose polymerises into starch or cellulose
What are the properties of disaccharides?
They are sweet and soluble
What are the most common disaccharides?
Maltose and lactose with are reducing sugars, and sucrose which is a non reducing sugar
How are disaccharides made?
When two monosaccharides join together
What is a-glucose plus a-glucose?
Maltose
What is a-glucose plus fructose?
Sucrose
What is b-glucose plus a-glucose?
Lactose
What is b-glucose plus b-glucose?
Cellobiose
What happens when the monosaccharides join?
A condensation reaction occurs to form a glycosidic bond. Two hydroxyl groups line up next to each other, from which a water molecule is removed, leaving an oxygen atom acting as a link between the two monosaccharide units
How are disaccharides broken into monosaccharides?
By a hydrolysis reaction which requires the addition of water. The water provides a hydroxyl group -OH and a hydrogen -H which help the glycosidic bond to break eg cellobiose is obtained by the hydrolysis of cellulose
Explain a-glucose
All -H’s are above the C, except for at C3. Molecular formula is C6H12O6. It is an energy source/component of starch/glycogen which acts as energy stores. It is a hexose sugar
Explain b-glucose
-OH are above at carob 1 and 3. Molecular formula is C6H12O6. It is an energy source/component of cellulose with provides structural support in plant cell walls. It is a hexose sugar
Explain ribose
Molecular formula is C5H10O5. It is a component of RNA, ATP and NAD. It is a pentose sugar
Explain deoxyribose
Molecular formula is C5H10O4. It is a component of DNA. It is a pentose sugar
What are polysaccharides?
Polymers of monosaccharides made of hundreds/thousands of monosaccharides bonded together
What are homopolysaccharides?
Polysaccharides made solely of one kind of monosaccharide
What are heteropolysaccharides?
Polysaccharides made up of more than one monomer
What is an example of a homopolysaccharide?
Starch
What is an example of a heteropolysaccharide?
Hyaluronic acid
Why is glucose a source of energy?
It is a reactant in respiration. The energy released is used to make ATP, which is the energy currency of the cell
How can you create a store of energy?
By joining lots of glucose molecules together into polysaccharides, this is what living things do
How do plants store energy?
As starch in chloroplasts and in membrane bound starch grains
How do humans store energy?
As glycogen in cells of the muscles and liver
Why are glycogen and starch (amylose and amylopectin) good energy stores?
They are compact so they don’t occupy a large amount of space. They both occur in dense granules within the cell