Biological Molecules Flashcards
What are the 4 elements that all things are made out of?
carbon, hydrogen, oxygen, nitrogen
How many bonds does carbon form?
4
How many bonds does nitrogen form?
3
How many bonds does oxygen form?
2
How many bonds does hydrogen form?
1
What are the two reactions that water is needed for?
condensation and hydrolysis reactions
Why is water a polar molecule?
Water consists of elements hydrogen and oxygen. Oxygen has a greater affinity to the electrons, giving it a slight negative charge. Hydrogen is left with a slight positive charge. Because of these two charges within one molecule, water is polar (specifically dipolar)
How does cohesion work in water?
Water is cohesive because the slight negative charge of the oxygen atom attracts the slight positive charge of the hydrogen atoms from other water molecules. The many hydrogen bonds give it a stable structure
Why is it good that water molecules are cohesive?
It means it is able to flow so it is good at transporting substances. It helps water move through plant stems through the transpiration stream
What is hydrophilic?
Substances that become a part of waters’ hydrogen bonded structure therefore dissolving in water
What is hydrophobic?
Substances that can’t become a part of waters’ hydrogen bonded structure therefore not dissolving in water
Why does water have a high specific heat capacity?
The hydrogen bonds between water molecules can absorb a lot of heat so it takes a lot of energy to heat it
Why is it good that water has a high specific heat capacity?
The organisms that live in water can spend less energy regulating their body temperature, as water doesn’t experience rapid temperature changes
Why does water have a high specific latent heat?
Because it takes a lot of energy to break the hydrogen bonds between the water molecules
Why is it good that water has a high specific latent heat?
Because it means that water is good for cooling things. This is why humans sweat because when it vaporises, we cool down
What are the good properties of water?
It’s a solvent (good for transportation) , it’s cohesive (good for movement of water), resistant to rapid temperature changes (good for organisms living in it), it’s transparent (light can be let through for algae to photosynthesise)
Why is the fact that water is denser than ice beneficial for organisms?
Ice can float which is good for animals to get land, layers of ice can form on top of the water to act as an insulating layer. This means that the animals beneath can spend less energy on having to control their body temperatures
What is a monomer?
Smaller units which can bind together to create larger molecules (polymers)
What is a polymer?
Made from lots of monomers bonded together
Give examples of a monomer and the name(s) of the polymers it forms
Monomer- glucose
Polymer it forms- starch, cellulose, glycogen
Monomer- amino acids
Polymer it forms- protein
Monomer- nucleotide
Polymer it forms- DNA and RNA
What elements do carbohydrates contain?
carbon, hydrogen and oxygen
What are monosaccharides and give examples?
monosaccharides are the monomers that make up carbohydrates (sugars)
examples: glucose, fructose, galactose
What are disaccharides and give examples?
Two monosaccharides joined together by glycosidic bonds
examples: sucrose, maltose, lactose
What are polysaccharides and give examples?
Lots of monosaccharides joined together by glycosidic bonds
examples: starch, cellulose, glycogen
What is an isomer?
When they have the same chemical formula but they are arranged different structually
What are the two isomers of glucose?
alpha glucose and beta glucose
What is the difference between alpha and beta glucose?
The hydroxyl (OH) group are in different places
Alpha is below the carbon ring and beta is above the carbon ring
How are glycosidic bonds formed?
When the hydroxyl group of two monosaccharides react in a condensation reaction. Water is produced as a by-product. These glycosidic bonds join monosaccharides together to form disaccharides and polysaccharides
What two monosaccharides react to make maltose?
glucose + glucose -> maltose + water
What two monosaccharides react to make lactose?
glucose + galactose -> lactose + water
What two monosaccharides react to make sucrose?
glucose + fructose -> sucrose + water
What is a condensation reaction?
Joining two molecules together by removing water and a chemical bond is formed
What is a hydrolysis reaction?
Splitting apart molecules through the addition of water and a chemical bond is broken
What are the three main polysaccharides?
starch, cellulose, glycogen
What are the uses of the three main polysaccharides?
starch- storage of glucose in plants
cellulose- structural strength in plants
glycogen- storage of glucose in animals
What monomer is starch made up of?
alpha glucose
What bonds are between the monomers in starch?
Formed from a mix of amylose and amylopectin
Amylose is 1-4 glycosidic bonds of alpha glucose
Amylopectin can have 1-4 and 1-6 glycosidic bonds of alpha glucose
What is the structure of starch?
Made of two polymers mixed:
amylose- unbranched helix (coil)
amylopectin- branched molecule because of the 1-6 bonds
How does the structure of starch lead to its function?
-The helix can compact to fit a lot of glucose into a small space
-Branched structure increases surface area for rapid hydrolysis back to glucose
-Insoluble
What monomer is cellulose made up of?
beta glucose
What bonds are between the monomers in cellulose?
1-4 glycosidic bonds
What is the structure of cellulose?
The polymer forms long, straight chains as each alternate beta glucose has to be flipped 180 degrees so that the hydroxyl groups are close enough to react and form bonds. These straight chains are then held in parallel by hydrogen bonds to form fibrils
How does the structure of cellulose lead to its function?
-The many hydrogen bonds provide collective strength
-Insoluble
What monomer is glycogen made up of?
alpha glucose
What bonds are between the monomers in glycogen?
1-4 and 1-6 glycosidic bonds
What is the structure of glycogen?
A highly branched molecule
How does the structure of glycogen lead to its function?
-branched structure increases surface area for rapid hydrolysis back to glucose
-insoluble
What are the reducing sugars?
all monosaccharides and some disaccharides (maltose, lactose)
Give an example of a non-reducing sugar
sucrose
How to test for reducing sugars
add benedicts reagent to a sample and heat it in a water bath thats been brought to the boil
if reducing sugars are present,
colour change of precipitate:
blue , green, yellow, orange, brick red
How to test for non-reducing sugars
if the result of the reducing sugars test is negative there could still be non reducing sugars present.
add dilute HCL and gently heat in a water bath thats been brought to the boil to hydrolise the sugar. then add sodium hydrogencarbonate to neutralise it. then carry out the benedicts test for reducing sugars as normal.
What are proteins made of?
amino acids
What are the groups in an amino acid?
amine group, carboxylic acid group, hydrogen and the R group
(you have to know the structure of an amino acid)
What are the four structural levels of amino acids?
primary, secondary, tertiary and quaternary
describe the primary structure of a protein
the order of amino acids in the polypeptide chain with no intramolecular bonds
describe the secondary structure of a protein
the sequence of amino acids in the primary structure causes parts of a protein molecule to bend into alpha helix (coil) or fold into beta pleated sheets
What holds together the secondary structure shapes
hydrogen bonds formed between the oxygen from the COOH group and the hydrogen from the amine group
describe the tertiary structure of a protein
the secondary structure is bent and folded to form a precise 3D shape. the 3D shape is held together by four different bonds which are created by the R groups interacting.
What are the four bonds that hold together the tertiary structure proteins?
-hydrophobic and hydrophilic interactions (weak interactions between polar and non polar R groups)
-hydrogen bonds (the weakest bonds formed)
-ionic bonds (are stronger than hydrogen bonds and form between oppositely charged R groups
-disulfide bonds/bridges (these are covalent and the strongest of the bonds but only form between R groups that contain sulfur atoms e.g. cysteine)
describe the quaternary structure of a protein
when a protein is made up of more than one polypeptide chain
what are the bonds that hold together amino acids and describe how they are formed
peptide bonds.
two amino acids bond together in a condensation reaction. the amino group of one amino acid bonds with the carboxyl group of another. this creates a peptide bond with a by-product of water as the OH from the carboxyl group reacts with the H from the amino group
What are the 3 types of proteins?
globular, conjugated and fibrous
what are globular proteins?
they are in a spherical shape. Their hydrophobic R group is on the inside and the hydrophilic is on the outside which makes them soluble in water.
globular proteins include transport proteins, enzymes and hormones
give an example of a globular protein and describe it
insulin
it is a hormone that helps to regulate blood glucose concentration
it has a tertiary structure
hormones need to be soluble as they’re transported in blood
hormones need to have a specific shape as they need to fit into receptors on cell membranes for them to work
what are conjugated proteins?
conjugated proteins are globular proteins that contain a non protein group called a prosthetic group
give examples of conjugated proteins and describe them
haemoglobin
-its the red oxygen-carrying pigment in blood cells
-it is a quaternary protein formed from four polypeptides; 2 alpha and 2 beta subunits
-each subunit contains a prosthetic group (haem)
-the iron 2 ions in the haem group are able to combine with oxygen
- this is how haemoglobin transports oxygen around the body
catalase
-it’s an enzyme
- it’s a quaternary protein containing four haem prosthetic groups
-the iron 2 ions in the haem groups allow catalase to interact with hydrogen peroxide to speed up the breakdown
-hydrogen peroxide is a by-product of metabolism but can damage cells if its builds up so catalase stops this from happening
what are fibrous proteins?
formed from parallel polypeptide chains held by cross-links. the hydrophobic R group is on the outside and the hydrophilic on the inside making them insoluble in water
give examples of fibrous proteins and describe them
keratin
-present in hair, skin and nails
- it has lots of cysteine (sulfur containing amino acid)
-this results in lots of disulphide bonds creating strong, inflexible and insoluble materials
-the degree of disulfide bonds determines the flexibility
-the bad smell when skin and hair burns is because of the sulphur presence in the proteins
elastin
-found in the elastic fibres that are present in the walls of blood vessels and in the alveoli of the lungs (elastin allows these to expand when needed and return back to its normal shape)
-its a quaternary protein
collagen
-it’s a connective tissue found in skin, tendons, ligaments and the nervous system
-its made of three polypeptides wound together in a long, strong rope-like structure and it is flexible
how can peptide bonds be broken back into the original amino acids
hydrolysis. water can be added back in and this reaction can be catalysed by protease
what is a dipeptide?
two amino acids joined
what is a polypeptide?
multiple amino acids joined together
draw a peptide bond
O H
II I
C - N
what are the functions of lipids?
- store energy
- insulator
- lipids make adipose which is a tissue that surrounds organs like the kidney that cushions and protects it
- structure of cell membranes
what are the two categories of lipids?
triglycerides and phospholipids
what is the structure of triglycerides?
a molecule of glycerol bonded to three fatty acids
differences between unsaturated fatty acid and saturated fatty acid
unsaturated:
one or more double covalent bond between the carbon atoms
this creates bends within the chain meaning they are less tightly packed so their melting points are lower and they are liquid at room temperature (oil)
saturated:
single covalent bonds between the carbon atoms. this means they are able to pack closely together leading them to have higher melting points meaning that they are solid at room temperature
monounsaturated definition
one double covalent bond between the carbon atom in the fatty acid
polyunsaturated definition
more than one double covalent bond between the carbon atoms in a fatty acid
saturated definition
no double covalent bonds between the carbon atoms in a fatty acid
describe the formation of triglycerides
there is a condensation reaction between the hydroxyl groups of the glycerol and fatty acids
this creates an ester bond, forming the triglyceride
when water is added and lipase is present it gets broken down through hyrolysis
why are triglycerides insoluble
they are non-polar meolecules so they are hydrophobic and do not dissolve in water
What is the key structural difference between phospholipids and triglycerides?
Phospholipids have a glycerol molecule bonded to two fatty acids and a phosphate group, while triglycerides have three fatty acids.
What charge does the phosphate group in a phospholipid carry, and what does this mean?
The phosphate group is negatively charged, making it polar and hydrophilic (attracts water).
Why is the phosphate group in phospholipids hydrophilic?
Because it is negatively charged, making it polar and capable of interacting with water molecules.
How are phospholipids represented in simpler diagrams?
The polar, hydrophilic head represents the phosphate group, and the nonpolar, hydrophobic tails represent the two fatty acids.
How do phospholipids behave in water?
The hydrophilic head interacts with water, while the hydrophobic tails cluster together, avoiding water, forming a phospholipid bilayer.
What structure do phospholipids form in water, and why is it important?
Phospholipids form a bilayer, which is essential for creating cell membranes.
What is cholesterol, and to what family of lipids does it belong?
Cholesterol is a lipid that belongs to the sterol family.
What are the two key features of a cholesterol molecule?
The hydroxyl group is hydrophilic, and the rest of the molecule is hydrophobic.
How does cholesterol interact with cell membranes?
The hydrophilic hydroxyl group interacts with the phospholipid head groups, while the hydrophobic part interacts with the fatty acid tails.
What role does cholesterol play in cell membranes?
Cholesterol helps regulate the fluidity of cell membranes.
What are the functions of cholesterol in living organisms?
Cholesterol is a precursor for hormones (e.g., estrogen, testosterone), produces vitamin D in the skin, and is used by the liver to make bile for lipid digestion.
How does cholesterol contribute to hormone production?
Cholesterol is the starting point for hormones like estrogen and testosterone, which can pass through cell membranes to interact with internal receptors.
How is cholesterol involved in the production of vitamin D?
Cholesterol is converted into vitamin D in the skin in response to ultraviolet light, which is essential for bone development.
What is the role of cholesterol in the liver?
Cholesterol is used to produce bile, which helps in the digestion of lipids by increasing the rate at which lipase breaks them down.
