2.2 - Biological molecules Flashcards
What are the elements that make up proteins?
C, H, O, N, S
Explain the polar nature of water
O is more negative than H therefore there is an unequal share of electrons so the electrons spend more time orbiting around O than H
Give regions of slight positive and negative
What allows water molecules to have cohesive and adhesive properties?
Hydrogen bonds
Describe the structure of amylose, including the bonds involved and the shape
1,4-glycosidic bonds, straight helix
Describe the structure of amylopectin, including the bonds involved and the shape
1,4 and 1,6 glycosidic bonds, branched
What are the two structures that make up starch?
Amylose and amylopectin
What are the 3 types of polysaccharides that α-glucose can form?
- Amylose
- Amylopectin
- Glycogen
Where are 1-6 glycosidic bonds found?
Amylopectin & Glycogen
Where is beta glucose found?
Cellulose
How are the monosaccharides in cellulose arranged?
Alternative β-glucose molecules are turned upside down inverted 180°
Why do cell walls provide strength and support to plant cells?
- Cellulose molecules form H bonds with each other to make microfibrils
- microfibrils join to make macrofibrils
- macrofibrils join to make fibres
- fibres are insoluble and tough
What does the Benedict’s test test for?
Reducing sugars
How is a positive result formed in Benedict’s test?
Reducing sugar reacts with blue Cu2+ (copper)
–> to make brick-red Cu+ (copper)
How can we test for starch?
Iodine solution
How can we use a colorimeter to do a quantitative Benedict’s test?
- Colorimeters measure the absorbance or transmission of light by a coloured solution
- More concentrated solution = more light absorbed / less light transmitted
- Compare to data table
What are the two parts that make up a carboxylic
acid?
Carboxyl group and hydrocarbon chain
What is another term for the condensation reaction that makes lipids?
Esterification
What is the difference in structure between saturated and unsaturated lipids?
- Saturated (SINGLE) : all single C-C bonds in fatty acid chain
- Unsaturated (DOUBLE): 1 or more double C=C bonds in fatty acid chain
[Poly unsaturated would have multiple double C=C bonds while mono unsaturated fatty acids would have a singular double C=C bond]
Draw a water molecule and label the charges on the atoms
O-
/ \
H+ H+
What is the difference between adhesion and cohesion?
Adhesion is when water molecules stick to other
surfaces
Cohesion is when water molecules stick to each other
Why do oils contain unsaturated triglycerides rather than saturated? (How is it shown)
- Unsaturated fatty acids cause the molecule to kink/bend
- Cannot pack closely together (ie. Cannot form more H bonds)
What is the difference in structure between triglyceride and phospholipid?
- phospholipid: 2 fatty acid chains + 1 phosphate group
- Triglyceride: 3 fatty acid chains
What is the structure and function of triglycerides?
Structure: Made up of a glycerol backbone and three fatty acid tails
Function: Triglycerides are a type of lipid used for long term energy storage in the body
What is the structure and function of a phospholipid?
Structure: A phospholipid is made up of two hydrophobic fatty acid tails and a hydrophilic
phosphate group head
Function: A phospholipid is a type of lipid molecule that
is the main component of the cell membrane
What is the phospholipid bilayer arrangement?
- Hydrophilic heads point outwards
- Hydrophobic tails point inwards (shielded from aqueous environment)
What are 2 similarities and 1 difference between phospholipids and sterols?
Similarities: both have dual hydrophilic/hydrophobic characteristics & both make up the plasma membrane
Difference: sterols are complex alcohol molecules; phospholipids are lipids
What are the steps in identifying lipids and state the positive result?
Emulsion test
- mix sample with ethanol to dissolve the lipid
- mix solution with water and shake
- if a white emulsion layer is formed therefore lipids are present
What is the monomer of a protein?
Amino acids
What are the components that make up an amino acid?
Amine group + Central carbon + Carboxyl group + H atom + R group
What is the bond formed between two amino acids?
Peptide bond
What is the primary structure of a protein?
The sequence and number of amino acids
What is the secondary structure of a protein?
- The coiling and folding of the amino acid chain
- The bonds used are alpha-helix + beta-pleated sheets
- Stabilised by hydrogen bonds in the main chain
What is the tertiary structure of a protein?
-Further folding of the amino acid chain into a 3D shape
-Caused by interactions between R groups
-Ionic bonds are present between positive and negative charges
-Disulphide bridges are present with covalent bonds connecting cysteines together
[More of these interactions are present if the proteins are stable]
-Hydrophobic (on the inside) and hydrophilic (on the outside) interactions
What is the quaternary structure of a protein?
- Multiple polypeptide chains
- The binding with other subunits
- For example the binding of the 2 Alpha and 2 Beta subunits in haemoglobin in a tetromer
What is the bond involved in the primary structure of a protein?
Peptide bonds
What is the bond involved in the secondary structure of a protein?
Hydrogen bonds
What are the bonds involved in the tertiary structure of a protein?
ionic, covalent, hydrogen, hydrophobic interactions, disulphide bridges
What is the bond involved in the quaternary structure of a protein?
ionic, covalent, hydrogen, hydrophobic interactions, disulphide bridges
What are three monosaccharides?
Alpha glucose, Beta glucose and Ribose
What biological molecule makes up the smooth and rough endoplasmic reticulum?
Lipids
What are the properties of water molecules?
-Good solvent (especially to polar substances) - due to the polar nature, as the different charges allow other molecules to bind easily to break them down
-Cohesion - water molecules stick together
-Adhesion water molecules stick to other things
-Surface tension - for wildlife to stand on top of water
-Water is less dense than ice - so ice floats and
insulates the water underneath it providing a habitat for animals
-Water has a high specific heat capacity - water maintains its temperature even with supplying or taking a away lots of energy, this meaning it is useful for creating stable environments
-Water has a high latent heat of vaporisation - it requires a lot of energy to evaporate water meaning that it is useful for cooling the body in sweat as it takes heat energy away from the body, while it also allows habitats to be more permanent as it is hard for the water to evaporate
How is water used and produced in certain types of reactions?
- In a condensation reaction water is released
- In a hydrolysis reaction water is used to split the molecule apart (sometimes along side an acid catalyst)
What is the formulae for simple sugars? (Monosaccharides)
(CH2O)n:
n=3, triose
n=5, pentose
n=6, hexose
What type of sugar is glucose?
Hexose
What is the difference in the structure of alpha and beta glucose?
Alpha glucose = H
OH
Beta glucose = OH
H
What are the three hexose monosaccharides?
- Glucose
- Fructose
- Beta galactose
What is the monomer of carbohydrates?
Monosaccharides
How are disaccharides joined together?
A condensation reaction will join the two monosaccharides with an oxygen in the middle as the H2O is released
What are all the disaccharides and what are they made up from? (SCLM)
- Lactose = Beta galactose + Alpha glucose
- Cellobiose = Beta glucose + Beta glucose
- Maltose = Alpha glucose + Alpha glucose
- Sucrose = Glucose + Fructose
Why are some people lactose intolerant?
Some people lack the enzyme (Lactase) that is used to break down the 1-4 glycosidic bond in lactose
-This means that they are lactose intolerant
What is the polymer of monosaccharides?
Polysaccharides
What bonds are found in each polysaccharide?
Amylose = 1-4 glycosidic bonds Amylopectin = 1-4 & 1-6 glycosidic bonds Glycogen = 1-4 & 1-6 glycosidic bonds
What is the test used to identify when amylose is present?
Amylose = Iodine solution [The iodine atom fits within the spiral of amylose and goes from brown to blue/black when amylose is present]
What is the function of the storage polysaccharides?
Amylose & Amylopectin = Form starch and used as an energy store in plants
Glycogen = Used in animals for energy storage as it is a branched polymer so there are more ends that are easily hydrolysable for quick access to energy
Why are amylose, amylopectin and glycogen suitable for energy storage?
- They are all compact polymers meaning that you can fit a lot of glucose in them in a tight space
- They are non-soluble meaning that you can store lots and lots of glucose molecules together in the polymer inside the cell without it affecting water potential and osmosis
- They are readily hydrolysable so energy can easily be accessed for metabolic processes and respiration
What is the fourth non-storage polysaccharide and what is it used for?
- Cellulose is the fourth polymer
- Cellulose is a structural polysaccharide made up of Beta glucose
What is the structure of cellulose?
- Cellulose is a polymer of Beta glucose meaning that the hydroxyl group is flipped
- The cellulose chain is very straight due to the 180 degree inversions
- The straight cellulose chains line up and they connect to other adjacent and parallel chains via hydrogen bonds to form microfibrils
- Microfibrils are bonded together to make macro fibrils which make up the cell wall with a high tensile strength to resist the high pressure of osmosis
How does the arrangement of macro fibrils allow the cell to be semi permeable?
- The macro fibrils are criss-crossed around the outside of the cell
- This provides strong structural support but allows the cell to be permeable as water molecules can go between the gaps
What are lipids?
Macromolecules that are:
- Alcohol soluble
- Non-polar
- Lots of Carbon and Hydrogen not much Oxygen, this allows for a lot of energy to be packed inside the triglycerides
- Lipids are more energy dense than sugars or carbohydrates
What is the structure of lipids?
Glycerol and fatty acid joined together via an ester
bond
What is a triglyceride and what is their structure?
- Fats used for storage
- 1 glycerol
- 3 fatty acids
Why are the heads of phospholipids polar and the tails non-polar?
- The heads are polar (hydrophilic) as they are heavily charged due to the phosphate group
- The tails are non-polar (hydrophobic) because they are not as charged
- This means the phospholipid is amphipathic
What is the impact of introducing unsaturated fatty acids into a phospholipid bilayer?
- The unsaturated fatty acids have a kink in the molecule, this means the neighbouring fatty acid cannot be as close
- This causes the membrane to be more fluid as it is more spaced out
Why are unsaturated fatty acids such as olive oils used?
They have a low melting point
What is the purpose of cholesterol in the phospholipid membrane?
Cholesterol is a hydrophobic molecule that fits in with the fatty acid tails of the phospholipid membrane and regulates the membranes fluidity
What are some examples of the different proteins and their roles?
Collagen, a structural protein
Enzymes, biological catalyst proteins
Haemoglobin in RBC’s, a transport protein
What determines the properties and type of amino acid that is made?
The R group can make 20 different amino acids
How is a peptide bond formed?
O H
I I I
C – N
What is the test for proteins and what shows a positive result?
- A biuret reagent is used
- The test will go from blue to purple if peptide bonds are present
What does it mean if there are more ionic interactions and more disulphide bridges present in a proteins tertiary structure?
- Ionic interactions and disulphide bridges are the stronger bonds
- Proteins with more of these bonds and interactions are more stable (potentially at higher temperatures)
What are the stronger bonds/interactions in a proteins tertiary structure and what are the weaker bonds/interactions?
- Ionic interactions and disulphide bridges are the stronger bonds/interactions
- While hydrogen bonds and hydrophilic/hydrophobic interactions are the weaker bonds/interactions
How is the quaternary structure with all the subunits combined formed?
-Each individual polypeptide is coded for at the ribosome
-They are stuck together after being modified and
packaged at the golgi apparatus
-This is how the subunits are formed and combined to make the quaternary structure of the protein
What is a conjugated protein?
A protein that contains other types of chemical groups that are joined via permanent covalent bonds
What is the structure of conjugated haemoglobin proteins?
-Made up of 4 haem groups
-Contains 4 Fe2+ ions that allow the binding of the O2
(one on each haem group)
What is the mathematical variability of a protein caused by the 20 different available amino acids?
1 Amino acid = 20 2 Amino acids = 20 x 20 3 Amino acids = 20 x 20 x 20 4 Amino acids = 20 x 20 x 20 x 20 If there are 1000 amino acids in a polypeptide chain then there are 20^1000 possible combinations and types of proteins that could be coded for
What is the structure of glycogen?
- Made up of alpha glucose molecules
- Held together by 1-4 & 1-6 glycosidic bonds
- More branched structure than amylopectin
- Branched polymer so there are more ends that are easily hydrolysable for quick access to energy
What are the fibrous proteins?
- Collagen
- Elastin
- Keratin
What are the globular proteins?
- Haemoglobin
- Insulin
- Catalase
