Chemistry for biologists Flashcards
Why might a covalent molecule be slightly polarized
electrons are not evenly shared in the molecule. This separation of charge is known as a dipole and results in the molecule being slightly polarized.
these tiny charges are represented by S- and S+
What is dissociation
splitting of molecule into smaller atoms, molecules, or ions, especially by a reversible process.
example: dissolving an ionic substance in water
Is water a polar or non-polar molecule?
polar
Why is water a polar molecule
electrons are held closer to the oxygen atoms than the hydrogen atoms, resulting in a separation of charge
What is a hydrogen bond
weak electrostatic interMOLECULAR bonds formed between polar molecules containing at least 1 hydrogen atom
How does water form hydrogen bonds
slightly negative oxygen atom of one water molecule will attract the slightly positive hydrogen atoms of other water molecules in a weak electrostatic attraction
Why does water have a high melting and boiling point compared to other molecules of a similar size
it takes a lot of energy to break all of the hydrogen bonds that hold the molecules together
Why is water important
polar solvent
transport medium
Enables organisms to live in water, even in countries where it gets cold enough for the water to freeze in winter
Prevents the temperature of large bodies of water from changing drastically throughout the year, making it a good habitat
Important factor in hydraulic mechanisms in living organisms
Important in plant transport and in surface tension
Surface tension of water is important in plant transport systems and life on the surface of water masses
Why is water a polar solvent
Its covalent nature means water dissolves covalent compounds, its
polar nature means it dissolves ionic compounds
Why is water a good transport medium
dipole nature of water allows many substances to dissolve in it
How does water enable organisms to live in water, even in countries where it gets cold enough for the water to freeze in winter
At 4 degrees Celsius, water reaches its maximum density and as it cools further, molecules become more widely spaced and the water freezes into ice. Ice is less dense than water and floats above the water, forming an insulating layer helping to prevent the water beneath from freezing. Ice will also melt quickly as it is at the top and exposed to the sun
How does water prevent the temperature of large bodies of water from changing drastically throughout the year
water has a high specific heat capacity
Why is water an important factor in hydraulic mechanisms in living organisms
water cannot be compressed
What property of water is important in the movement of water from the roots to leaves of plants
water molecules are cohesive- the forces between the molecules mean they stick together
what property of water is important in plant transport systems and water tension
water molecules are adhesive- they are attracted to other different different molecules
Why does water have very high surface tension
attraction between water molecules, including hydrogen bonds, is greater than the attraction between water molecules and air. As a result, water molecules hold together forming a thin skin of surface tension
What is a dipole
The separation of charge in a molecule when the electrons in covalent bonds are not evenly shared
What is a macromolecule
a very large molecule formed by polymerization where monomers bond with many other similar units to make a very large molecule
What are carbohydrates made of
Carbon, Hydrogen and Oxygen
What are the three groups of carbohydrates
monosaccharides, disaccharides, and polysaccharides
General formula of monosaccharides
(CH2O)n
importance of triose sugars
important in mitochondria where the respiration process breaks down glucose into triose sugars
importance of pentose sugars
ribose and deoxyribose (which are pentose sugars) are important in the nucleic acids deoxyribonucleic acid and ribonucleic acid which make up the genetic material
what are the hexose sugars
best known monosaccharides, including glucose, fructose, and galactose. They have a ring structure
What are the isomers of glucose
a-glucose
B-glusose
What is the difference between the two isomers of glucose
have different arrangements of the atoms on the side chains of the molecule. The different isomers form different bonds between neighboring glucose molecules, and this affects the polymers that are made
What is a disaccharide
a sugar made up of two monosaccharide units joined by a glycosidic bond, formed by a condensation reaction
What is a condensation reaction
a reaction in which a molecule of water is removed from the reacting molecules as a bond is formed between them
what is a glycosidic bond
a covalent bond formed between two monosaccharides in a condensation reaction, which can be broken by a hydrolysis reaction to release the monosaccharide units
What is sucrose’s source and its monosaccharide units
stored in plants such as sugar cane
glucose + fructose
What is lactose’s source and its monosaccharide units
milk sugar- this is the main carbohydrate found in milk
glucose + galactose
What is maltose’s source and its monosaccharide units
malt sugar- found in germinating seeds such as barley
glucose + glucose
How are reducing sugars tested with benedicts reagent
Benedicts solution is a chemical reagent containing copper (ii) ions. Sugars such as glucose react when heated gently are reduce the copper (ii) ions into copper (i) ions forming a precipitate that changes colors from blue to orange and are hence called reducing sugars. All of the monosaccharides and disaccharides are reducing sugars except sucrose. it is known as a non-reducing sugar
How are non-reducing sugars tested with benedicts reagent
The sucrose is heated with a few drops of HCl, cooled, and the solution is neutralized with sodium hydrogen carbonate to hydrolyze the glycosidic bonds. This produces monosaccharide units of the sugar, which give a positive benedicts test
What are oligosaccharides
molecules with between 3-10 monosaccharide units (only molecules with 11 or more monosaccharides are known as true polysaccharides)
What is hydrolysis
a reaction in which bonds are broken by the addition of a molecule of water
What is ATP
adenosine triphosphate supplies energy and comes from the breakdown of the monosaccharide glucose, using oxygen, in the process of cellular respiration where chemical energy is TRANSFERRED from the glucose molecule to the ATP molecules
which foods are good sources of relatively instant energy
foods containing monosaccharides and disaccharides
however, they cannot be stored as they are chemically active and are very soluble in water, so they will affect the water balance of cells
why are polysaccharides ideal as energy storage molecules within a cell
1) very compact molecules which take up very little space
2) physically and chemically inactive, so they do not interfere with the other functions of the cell
3) not very soluble in water, so have almost no effect on water potential within a cell and cause no osmotic water movements
What are the two compounds that starch is a mixture of
amylose
an unbranched polymer that spirals more as the chain lengthens which makes it more compact for storage. It has 1,4-glycosidic bonds
amylopectin
a branched polymer of glucose units with many terminal glucose units that can be broken off rapidly when energy is needed. Many glucose molecules are joined by 1,4-glycosidic bonds and also a few 1,6-glycosidic bonds, resulting in the branching chains
they are both long chains of a-glucose units
Difference between amylopectin and glycogen
glycogen has many more 1,6-glycocidic bonds, giving it many more branches and allowing it to be broken down very rapidly
What elements are lipids made of
hydrogen oxygen and carbon
(almost no oxygen)
how does the amount of energy from lipids compare to that of carbohydrates
for the same amount of mass, lipids, especially triglycerides have almost 3 times as much energy
List 2 differences between fats and oils
fats are solids at room temperatures and come mainly from animal sources
oils are liquids at room temperature and come mainly from plant sources
What are lipids made up of
fatty acids and glycerol (propane-1,2,3-triol)
How are lipids combined
using ester bonds
what is glycerol’s formula
C3H8O3
how are fatty acids structured
long hydrocarbon chain and a carboxyl group
how can fatty acids vary
1) the length of the carbon chain can differ
2) the fatty acid may be saturated or unsaturated
What is a saturated fatty acid
a fatty acid in which each carbon atom is joined to next one to it in the hydrocarbon chain by a single covalent bond
What is an unsaturated fatty acid
a fatty acid in which the the carbon atoms in the hydrocarbon chain have one or more double covalent bonds in them
What is a monosaturated fatty acid
a fatty acid with only one double bond in the hydrocarbon chain
what is a polysaturated fatty acid
a fatty acid with two or more double covalent bonds between carbon atoms in the hydrocarbon chain
How is triglyceride formed
when glycerol combines with 3 fatty acids in a condensation reaction between the carboxyl group of the fatty acid and the hydroxyl group of the glycerol. A molecule of water is removed and the bond formed is known as an ester bond. This type of condensation reaction is known as esterification
Difference in the formation of solid and liquid lipids
lipids containing saturated fatty acids and have longer chain fatty acids are more likely to be solid at room temperature
uses of proteins (7)
1) making hair, skin and nails
2) proteins make up the enzymes for metabolism and digestion
3) proteins make the hormones that control the different body systems
4) proteins enable the muscle fibers to contract
5) proteins make antibodies to protect you from disease
6) proteins helps blood to clot
7) protein, in the form of hemoglobin, transports oxygen
Describe a single amino acids structure
A central carbon atom with a side group ( aka R group) (such as sulfur and selenium), an amine group (-NH2), a carboxyl group (-COOH), and hydrogen
What is the role of the R group
it is not involved in the reactions which join the amino acids together, but the structure of the R group affects the way the amino acids interacts with others within the protein molecule. This mainly depends on whether the R group is polar or not
What elements make up proteins
C, H, O, N and sometimes S
How do amino acids join together
by a condensation reaction between the amino group one amino acid, and the carboxyl group of another, releasing a molecule of water. resulting in the formation of a dipeptide
What is the name of the bond between 2 amino acids
a peptide bond
What is a polypeptide
a long chain of amino acids joined by a peptide bond
what is a dipeptide
two amino acids joined by a peptide bond
when does a polypeptide form a protein
when the structure of the chain changes by folding or coiling or associates with other polypeptide chains
how do hydrogen bonds form in amino acids
in amino acids,tiny negative charges are present on the oxygen of the carboxyl groups and tiny positive charges are present on the hydrogen atoms of amino groups. when these charged groups are s are close to each other, the opposite charges attract, forming a hydrogen bond.
Hydrogen bonds are weak but, potentially, they can be made between any two amino acids in the correct position, so there are many of them holding the protein together very firmly
Why are hydrogen bonds important in proteins
important in the folding and coiling of polypeptide chains
why are proteins affected by Ph and temperature
Hydrogen bonds break easily
and reform if pH or temperature conditions change.
