Biological molecules Flashcards
what is a covalent bond
atoms consist of a nucleus surrounded by shells of electrons. most atoms tend to be stable when their outermost shells have a full 8 electrons. atoms of different elements have different numbers of electrons in their outermost shells. for example, carbon has 4. by sharing electrons with other atoms, the atoms outer shells can be filled which forms a strong bond, called a covalent bond.
what is a condensation reaction
a condensation reaction occurs when two molecules are joined together with the removal of water.
what is a hydrolysis reaction
when two molecules are split apart with the addition of water
what elements (monomers) are in the molecules carbohydrates, proteins, and nucleic acids
carbohydrates= carbon hydrogen and oxygen
proteins= carbon hydrogen oxygen nitrogen and sulfur
nucleic acids= carbon hydrogen oxygen nitrogen and phosphate
describe the molecular structure of water molecules
water consists of two hydrogen atoms, each covalently bonded to an oxygen atom. oxygen, however, has a greater number of positive protons within its nucleus. so therefore it exerts a stronger attraction for the shared electrons. so oxygen becomes slightly negative and hydrogen becomes slightly positive. when this happens we call the molecule polar.
what are the liquid properties of water
as in any liquid, water molecules are consistently moving. however unlike other liquids, as they move they continually make and break hydrogen bonds. the bonds between water molecules make it difficult for molecules to escape and become a gas. so water is liquid at room temperature with a low viscosity. So water can now:
-provide habitats for living things in rivers, lakes, and seas.
- form a major component of tissues in living organisms
-provides a reaction medium for chemical reactions as well as a transport medium.
what are the density properties of water
as water becomes colder it starts to lose its density as ice begins to form which creates a lattice of bonds that leaves gaps for air. because ice is less dense than water it floats atop which allows for species to have a liquid environment throughout the winter.
ponds and other bodies of water are insulated against extreme colds, this reduces heat loss from the rest of the pond allowing for an animal habitat to be maintained underneath.
describe waters properties as a solvent
water is a good solvent for many substances found in living things. this includes ionic solutes such as sodium chloride and covalent solutes such as glucose. because water is polar, the positive and negative parts of the water molecules are attracted to the charged parts of solutes. the water molecules cluster around these charged parts and will help keep them separate. and at this point they dissolve and a solution is formed. Because of its good solvent properties molecules and ions can be transported around living things whilst dissolved in water.
what properties does water have in terms of cohesion and surface tension
water molecules at the surface are all hydrogen bonded to molecules beneath them and hence the surface of the water contracts and gives it the ability to resist the force applied to it. this is known as surface tension and cohesion. this allows for insects to walk on water and water to be pulled up xylem tissues.
what are the properties of water with its high specific heat capacity
water temperature is a measure of the kinetic energy of the water molecules. water molecules are held together tightly by hydrogen bonds. therefore you have to put in a lot of energy to increase the kinetic energy and temperature. this means that living things can have a stable environment for enzyme-controlled reactions to take place. as well as this aquatic organisms need a stable environment in which to live.
what are carbohydrates for?
carbohydrates contain carbon hydrogen and oxygen. they are hydrated carbons, meaning that for every carbon atom, there are two hydrogen atoms. the act as a source of energy(glucose), as a store of energy (starch and glycogen) and as structural units (cellulose in plants and chitin in fungi)
what is a monosaccharide
a monosaccharide is the simplest of carbohydrate. they are improtanr in living things as a source of energy, and are well suited to this role because of their high amounts of carbon and hydrogen. they are sugars meaning they are soluble in water and are insoluble in nonpolar solvents. they can exist in rings or in straight chains and often have a carbon-bonded backbone, and a double bond to oxygen to form a carboxyl group. different sugars have different numbers of carbon atoms. pentose has 5 and hexose sugars have 6.
what are the two isomers of the carbohydrate glucose
-Alpha glucose
-Beta glucose
what disaccharide is formed with the condensation of two alpha glucose molecules
maltose
what disaccharide is formed with the condensation of an beta glucose molecule and a beta glucose molecule
cellobiose
what disaccharide is formed with the condensation reaction of a beta galactose and alpha glucose molecule
lactose
what disaccharide is formed with the condensation reaction of an alpha glucose molecule and a fructose molecule
sucrose
what type of bond is formed when two hydroxyl groups lone up next to each other, from which a water molecule is removed which leaves an oxygen atom acting as a link between two monosaccharide units
glycosidic
what is the process called when a disaccharide is broken to make two monosaccharides units
hydrolysis
what type of sugar is alpha and beta glucose
hexose sugars
what type of sugar is ribose or deoxyribose
pentose
what is the difference between alpha and beta glucose
alpha glucose has the hydrogen molecule above the plane of the ring of carbon 1 while beta glucose has the hydrogen molecule below the plane of the ring of carbon 1 ( meaning that the OH group sits above the plane in beta glucose, but below in alpha glucose)
what is the molecular formula of maltose
C6,H22,O11
what s the difference between ribose and deoxyribose
ribose molecular formula has one more oxygen atom than deoxyribose. making deoxyribose’s formula- C5,H10,O4 while ribose’s is C5,H10,O5
what is a polysaccharide
a polysaccharide is a polymer of monosaccharide. they are made of thousands of monosaccharide monomers bonded together. if they are made entirely out of one monomer they are called homopolysaccharides, while those that have more than one monomer are known as heteropolysaccharides.
what makes polysaccharides good energy stores
-glycogen and starch are compact, which means they do not occupy large amounts of space.
-polysaccharides hold glucose molecules in chains so they can easily be snipped off from the chain in hydrolysis during respiration
-some chains are branched (amylopectin and glycogen)
these branches allow for more glucose to be snipped off at one time as well as the fact that they are more compact in their structure.
As well as this the polysaccharides are less soluble in water than monosaccharides. meaning that they do not disrupt the water potential within cells.
describe the polysaccharides found within plants
- amylose, this molecule is a long chain of alpha glucose molecules, like maltose it has glycosidic bonds between carbons 1 and 4.
coiled structure with no branches.
-amylopectin, is like amylose, with glycosidic bonds between 1 and 4 but also carbon 1 and 6 . Itdes coils into a spiral shape but with branches emerging
describe the polysaccharides found within animals
glycogen. this molecule is like amylopectin with glycosidic bonds 1 and 4 and with branches formed by glycosidic bonds between carbon 1 and 6. This has more branches than amylopectin making it more efficient and compact.
what is cellulose
cellulose is found within plants’ cell walls. it is tough, insoluble, and fibrous. it is a homopolysaccharide of up to 15000 Beta glucose molecules bonded by glycosidic bonds.
why does the bonding of cellulose prevent the molecules spiraling
-hydrogen and hydroxyl groups on carbon 1 are inverted in beta glucose. this means that every other beta glucose molecule in the chain is rotated 180 degrees, this bondage prevents spiraling. As well as this there are hydrogen bonds between each rotated beta glucose molecule which helps support the chain and stop it from spiralling. and finally, the hydroxyl group on carbon 2 sticks out enabling hydrogen bonds to be formed between chains which adds additional strength in spiral prevention.
what is the term used to describe 60 to 70 cellulose chains bound together
microfibrils
what is the term used to describe a bundle of 400 microfibrils bonded together.
macrofibrils
what are pectins
pectins are what microfibrils are embedded within to form the cellulose cell wall in plant cells.
why is cellulose a good material for plant cell walls
microfibrils and macrofibrils have very high tensile strength, both because of the strength of the glycosidic bonds but also the hydrogen bonds between the chains.
-macrofibrils also run in all directions along the cell wall for extra strength.
As well as strength there is space between macrofibrils for water and mineral ions to pass in and out of the cell making it fully permeable.