biological molecules Flashcards
What is a molecule?
The complex formed when two or
more atoms bond together
What are covalent bonds?
Bond that occur when two atoms share a pair of electrons. The electrons used to form bonds are unpaired and present in the outer orbitals of the atoms
What are covalent bonds?
Bond that occur when two atoms share a pair of electrons. The electrons used to form bonds are unpaired and present in the outer orbitals of the atoms
What are the bonding rules for
carbon, nitrogen, oxygen and
hydrogen atoms?
- Carbon atoms form 4 bonds
- Nitrogen atoms form 3 bonds
- Oxygen atoms form 2 bonds
- Hydrogen atoms form 1 bonds
What is an ion?
An atom or molecule with an overall
electric charge because the total
number of electrons is not equal to
the total number of protons
What is an ionic bond?
A chemical bond that involves the donating of an electron from one atom to another, forming positive and negative ions held together by the attraction of the opposite charges
What is a cation?
An atom or molecule that loses one
or more electrons giving it a net
positive charge
What is an anion?
An atom or molecule that gains one
or more electrons giving it a net
negative charge
What are ions in solution
called?
Electrolytes
List all of the important cations
in living organisms
- Calcium ions (Ca2+)
- Sodium ions (Na+)
- Potassium ions (K+)
- Hydrogen ions (H+)
- Ammonium ions (NH4+
List all of the important anions
in living organisms
- Nitrate ions (NO3-)
- Hydrogen carbonate ions (HCO3-)
- Chloride ions (Cl-)
- Phosphate ions (PO43-)
- Hydroxide ions (OH-)
What are the following cations necessary for? 1. Calcium ions 2. Sodium ions 3. Potassium ions 4. Hydrogen ions 5. Ammonium ions
1. Nerve impulse transmission and muscle contractions 2. Nerve impulse transmission and kidney function 3. Nerve impulse transmission and stomatal opening 4. Catalysis of reactions and pH determination 5. Production of nitrate ions by bacteria
What are the following anions necessary for? 1. Nitrate ions 2. Hydrogen carbonate ions 3. Chloride ions 4. Phosphate ions 5. Hydroxide ions
1. Nitrogen supply to plants for amino acid and protein formation 2. Maintenance of blood pH 3. Balance positive charge of sodium and potassium ions in cells 4. Cell membrane formation, nucleic acid and ATP formation, bone formation 5. Catalysis of reactions and pH determination
List the 4 biological molecules
and the element present in
each of them
• Carbohydrates - carbon, hydrogen, and oxygen usually in the ration Cx(H2O)x • Lipids - carbon, hydrogen, and oxygen • Proteins - carbon, hydrogen, oxygen, nitrogen, and sulphur • Nucleic acids - carbon, hydrogen, oxygen, nitrogen, and phosphorus
What are the monomers in
carbohydrates and proteins
called?
In carbohydrates the monomers
are sugars (saccharides) monosaccharides
• In proteins the monomers are
amino acids
What are the monomers in
carbohydrates and proteins
called?
In carbohydrates the monomers
are sugars (saccharides)
• In proteins the monomers are
amino acids
Why are some molecules
polar?
• In covalent bonds the electrons are not always shared equally by the atoms of different elements • The atoms with the greater share of negative electrons will be slightly negative compared with the other atom in the bond, which will be slightly positive • Polar molecules have regions of negativity and regions of positivity
Why is water a polar
molecule?
• Oxygen always has a much greater share of electrons in an OH bond • Many organic molecules contain hydroxyl (OH) groups, and so are slightly polar; water is an example
What are hydrogen bonds, and
what causes them?
Hydrogen bonds are relatively weak interactions • They are caused by polar molecules interacting with each other and forming bonds - hydrogen bonds
List the properties of water
- Liquid
- Density
- Solvent
- Cohesion and surface tension
- High specific heat capacity
- High latent heat of vaporization
Why is water a liquid at room
temperature?
• The hydrogen bonds between
water molecules make it more
difficult for them to escape to
become a gas
What is the importance of
water being a liquid at room
temperature, to living
organisms?
• Provides habitats for living things in rivers, lakes and seas • Forms a major component of the tissues in living organisms • Provides a reaction medium for chemical reactions • Provides an effective transport medium e.g. in blood and vascular tissue
Describe how the density of
water changes, as H2O
changes state
Usually the solid is more dense than the liquid form of a substance. However ice is less dense than water because as water goes from 4C to freezing point, the water molecules form a structure that is less dense than liquid water
What is the importance of
water’s density to living
organisms?
If water was less dense, aquatic organisms would find it very difficult to float Ice floats on water so: • Aquatic organisms have a stable environment to live through in winter • Ponds are insulated against extreme cold because the ice layer reduces heat loss from the pond
Why is water a good solvent?
• As it is polar, the positive and negative parts of the water molecules are attracted to the oppositely charged parts of the solute • Water molecules cluster around the charged parts of the solute molecules or ions, which helps to separate them and keep them apar
What is the importance of
water being a good solvent to
living organisms?
• Molecules and ions can move around and react together in water e.g. as in the cytoplasm of cells, which is >70% water • molecules and ions can be transported around living things whilst dissolved in water
Describe cohesion and surface
tension of water
• Water molecules demonstrate cohesion because hydrogen bonding between the molecules pulls them together • Water molecules demonstrate surface tension because they are more attracted to the water molecules beneath them than air molecules above, so the water contacts, giving the surface of the water the ability to resist a force applied to it
What is the importance of
cohesion and surface tension
of water to living organisms?
Columns of water in plant vascular tissue are pulled up the xylem tissue together from the roots due to cohesion • Insects like pond-skaters can walk on water due to surface tension
Why does water have a high
specific heat capacity?
• Water molecules are held together quite tightly by hydrogen bonds • Therefore you need to put in a lot of heat energy to increase their kinetic energy and temperature • This means that water doesn’t heat up or cool down easily
What is the importance of the
high specific heat capacity of
water to living organisms?
• Living things need a stable temperature for enzyme-controlled reactions to happen properly • Aquatic organisms need a stable environment in which to live
Why does water have a high
latent heat of vaporisation?
Because the water molecules are held together by hydrogen bonds, a relatively large amount of energy is needed for water molecules to evaporate
what is the importance of the
high latent heat of
vaporisation of water to living
organisms?
Water can help to cool living things and keep their temperature stable e.g. • Mammals are cooled when sweat evaporates • Plants are cooled when water evaporates from mesophyll cells
What is the importance of
water’s role as a reactant to
living organisms
It is a reactant in reactions such as photosynthesis, and in hydrolysis reactions such as digestion of starch, proteins and lipids • Plays a very important role in the digestion and synthesis of large biological molecules
What are carbohydrates?
Organic polymers composed of the elements carbon, hydrogen and oxygen, usually in the ration Cx(H2O)y. Also known as saccharides or sugars
Define the following:
- Monosaccharide
- Disaccharide
- Polysaccharide
1. A single sugar molecule e.g. glucose, fructose and ribose 2. A molecule comprising two monosaccharides joined together by a glycosidic bond 3. A polymer made up of many monosaccharides e.g. glycogen, cellulose and starch
Describe glucose
• C6H12O6 • Hexose monosaccharide (because it has 6 carbons) • Polar and soluble in water due to the hydrogen bonds that form between the OH group and water molecules • Means glucose is dissolved in the cytosol of the cell 2 variations • Alpha glucose - OH group is below carbon 1 • Beta glucose - OH group is above carbon 1
How do alpha glucose
molecules react with each
other?
• The OH groups on C1 and C4 reacted forming a 1,4 glycosidic bond (covalent) • Condensation reaction because a water molecule is formed (lost)
What do the following combinations form? 1. a-glucose + a-glucose 2. a-glucose + fructose 3. B-galactose + a-glucose 4. B-glucose+ B-glucose
- Maltose
- Sucrose
- Lactose
- Cellobiose
What are pentose
monosaccharides? Give
examples
• Sugars that contain 5 carbon atoms • e.g. ribose which is the sugar present in RNA nucleotides • e.g. deoxyribose which is the sugar present in DNA nucleotides
What is starch?
A polysaccharide formed from alpha
glucose molecules either joined to
form amylose or amylopectin. Found
in plants
Describe amylose
• Found in plants • Alpha glucose • Glycosidic bonds between C1 andC4 • Coils into a spiral shape held together by hydrogen bonds • OH groups on C2 inside of the coil, making the molecule less soluble and allowing hydrogen bonds to form to maintain the coil’s structure
Describe amylopectin
• Found in plants • Alpha glucose • Has glycosidic bonds between C1 and C4, and also has branches formed by glycosidic bonds between C1 and C6 • Coils into a spiral shape held together by hydrogen bonds, but with branches coming out of the spiral
What is glycogen?
A branched polysaccharide formed
from alpha glucose. A chemical
energy store in animal cells
Describe glycogen
• Found in animals • Like amylopectin with glycosidic bonds between C1 and C4, and branches formed by glycosidic bonds between C1 and C6 • The C1 C4 bonded chains are smaller than in amylopectin so glycogen has less tendency to coil • Has more branches than amylopectin making it more compact • Easier to remove monomer units as there are more ends
How do beta-glucose
molecules react with each
other?
• The OH groups on C1 and C4 are to far away to react, so each alternate beta glucose molecule must be turned upside down to reach • It is unable to could or form branches • A straight chain molecule called cellulose is formed
Describe cellulose
• Cellulose molecules make hydrogen bonds with each other forming microfibrils • Microfibrils join together to form macrofibrils that combine to produce fibres • The fibres are strong and insoluble and are used to make cell walls
Why is cellulose a good
material for cell walls?
Microfibrils and macrofibrils have very high tensile strength because of the glycosidic bonds and hydrogen bonds • macrofibrils run in all directions, criss-crossing the wall for extra strength • Space between macrofibrils for water and mineral ions to pass in and out of the cell, making the cell wall full permeable
What are lipids?
Non-polar macromolecules contains the elements carbon, hydrogen and oxygen. Soluble in alcohol rather than water. Include triglycerides, phospholipids and sterols
Formation of a triglyceride
What are triglycerides?
Lipids composed of one glycerol (C3H8O3) molecule and three fatty acids. Fatty acids are carboxylic acids that consist of a carboxyl group (-COOH) which a hydrocarbon chain attached.
How are triglycerides formed?
• The hydroxyl groups in the fatty acid molecule and glycerol molecule react • This leads to the formation of 3 water molecules and bonds between the fatty acid and glycerol molecule • The bonds are called ester bonds, and the reaction is called esterification • Esterification is an example of a condensation reaction
What is the difference between
saturated and unsaturated
triglycerides?
• Fatty acid chains that have no double bonds between the carbon atoms are saturated, and vice versa • If there’s 1 double bond = monounsaturated • If there’s 2 or more double bonds = polyunsaturated
Phospholipid
Amino acid
