Biological Molecules Flashcards
What is a monomer?
a small unit which larger molecules are made from
What is a polymer?
molecules made from large numbers of monomers joined together
Carbohydrates, proteins, lipids, and nucleic acids contain which elements? (2)
Carbon and Hydrogen
What type of bond can carbons form? and how many per carbon?
4
What are the three types of carbohydrates?
Monosaccharides, Disaccharides and Polysaccharides
What is a monosaccharide?
A single sugar monomer
What is the function of a monosaccharide?
energy for respiration, building blocks for polymers.
What are two examples of monosaccharides?
Ribose and Glucose
What is a Disaccharide?
Two monosaccharides joined together via a condensation reaction (which forms a glycosidic bond)
What is the function of a Disaccharide?
Sugar found in germinating seeds (maltose), mammal milk sugar (lactose)
What are two examples of Disaccharides?
Maltose, Sucrose, Lactose
What is a Polysaccharide?
A polymer formed by many monosaccharides joined by a glycosidic bond in a condensation reaction
What is the function of a Polysaccharide?
energy stores in plants, structural- cell wall
When does a condensation reaction occur?
When monomers combine together by covalent bonds to form polymers (polymerisation) or macromolecules and water is removed
What happens in the hydrolysis of polymers?
Covalent bonds are broken when water is added
What is a reducing sugar?
A sugar that can donate electrons
What happens when reducing sugars donate electrons?
The carboxyl group becomes oxidised and the sugars become the reducing agent
What is the test for sugars?
Benedict’s test
Why can reducing sugars be detected via Benedict’s test?
They reduce the soluble copper sulphate to insoluble brick-red copper oxide
What are two examples of a reducing sugar?
glucose, fructose, galactose
What is a non-reducing sugar?
A sugar that can’t donate electrons or be oxidised
How are non-reducing sugars detected?
They are hydrolysed and then put through benedict’s test
Why are non-reducing sugars hydrolysed before they are tested with Benedict’s solution?
To break the disaccharide into its two monosaccharides
What is an example of a non-reducing sugar?
Sucrose
What is the molecular formula for glucose?
C6 H12 O6
What are the two types of glucose?
α (alpha) glucose, β (beta) glucose
What is the difference between α and β glucose?
The hydroxyl group on the right side of the ring is below the ring in α glucose, and in β glucose it is above the ring
What is removed from the glucose when a glycosidic bond is formed?
one water molecule
What type of reaction forms glycosidic bonds?
condensation reaction
How is a glycosidic bond broken?
When water is added in a hydrolysis reaction
What are the three ways the chains in a polysaccharide can be organised?
Branched/unbranched, Folded, Straight
What is starch?
The storage polysaccharide of plants
What is glycogen?
The storage polysaccharide for plants and fungi
What are the two groups of lipids?
Triglycerides and phospholipids
What is a triglyceride?
Three fatty acid chains attached to a glycerol molecule
What are the monomers of a triglyceride?
Glycerol and fatty acids
What are the two types of fatty acids?
Saturated and unsaturated
What type of bonds are in a saturated fatty acid?
the bonds between the carbons in the ‘tail’ are all single bonds
What are the two types of unsaturated fatty acids?
Mono-unsaturated and Poly-unsaturated
What is a mono-unsaturated fatty acid?
A fatty acid that has single bonds between carbon atoms
What is a poly-unsaturated fatty acid?
A fatty acid that has double bonds between carbon atoms
What are the functions of triglycerides?
Energy storage, Insulation, Buoyancy, Protection
What is a phospholipid?
two fatty acids bonded to a glycerol molecule with a phosphate group
Which part of the phospholipid is hydrophobic and which part is hydrophilic?
The head (glycerol and phosphate group) is hydrophilic and the tails are hydrophobic.
What is the role of a phospholipid?
It’s the main component of cell membranes
What is the chemical test for lipids?
The emulsion test
Describe the chemical test for lipids and the positive and negative results.
Add ethanol to the sample being tested and then shake it, then add the mixture to a test tube of water. If lipids are present, the solution will turn cloudy, and the more lipid present, the cloudier the solution will be. If there is no lipid present, the solution remains clear.
What are proteins?
polymers made of amino acids
What determines the function of amino acids?
The sequence, type and number
What do proteins make up?
Enzymes, cell membranes, hormones, immunoproteins, transport proteins, structural proteins, contractile proteins
How are dipeptides formed?
Condensation reaction between two amino acids
How are polypeptides formed?
Condensation reaction between 3 or more amino acids
How are peptide bonds broken?
In a hydrolysis reaction- the water breaks the peptide bond and it gets broken down into amino acids
How many levels of structure are there in proteins?
4- primary, secondary, tertiary, quaternary
What is the primary structure of proteins?
Amino acids bonded by covalent peptide bonds
What is the secondary structure of proteins?
It happens when the negatively charged nitrogen and oxygen atoms form with a positively charged hydrogen atom to form hydrogen bonds
What shapes can form in secondary structured proteins due to the hydrogen bonds>
α-helix and β-pleated sheet
When does the α-helix shape occur?
When the hydrogen bonds are formed between every fourth peptide bond
When does the β-pleated sheet shape form?
When the protein folds so that two parts of the polypeptide chain are parallel to each other so hydrogen bonds form between the parallel peptide bonds
What types of proteins have secondary structures?
Fibrous proteins (collagen and keratin)
What does the secondary structure relate to?
The hydrogen bonds forming between the amino group and the carboxyl group
How can the hydrogen bonds be broken in secondary structured proteins?
High temperatures and pH changes
What is the tertiary structure of proteins?
The 3D configuration when R groups interact
How is the tertiary structure different from the secondary structure of proteins?
The tertiary structure has additional bonds forming between the R groups
What are the additional bonds in the tertiary structure of proteins? (Where are they found?)
Hydrogen (between R groups), Disulphide (only found between cysteine amino acids), Ionic (found between charged R groups), Weak hydrophobic interactions (found between non-polar R groups)
In what type of protein is the tertiary structure most common?
Globular proteins
When does a protein have a quaternary structure?
When they have more than one polypeptide chain working together as a functioning macromolecule
What is an example of a protein with a quaternary structure?
Haemoglobin
How can disulfide bridges be broken?
Reduction (gaining electrons)
What is the test for proteins?
The biuret test
How is the biuret test carried out?
A few drops of a copper sulphate solution are added to the sample
What does a positive test for proteins look like?
The solution changes from blue to lilac in colour when protein is present
What are some features of globular proteins?
They are compact, spherical, and soluble in water
Why are globular proteins spherical?
The non-polar hydrophobic R groups are in the center (away from the aqueous surroundings) the polar hydrophilic R groups are on the outside of the protein.
What are fibrous proteins?
Long strands of polypeptide chains that have cross-linkages due to hydrogen bonds
Do fibrous proteins have tertiary structures?
They have little or none
Why are fibrous proteins insoluble in water?
They have large numbers of hydrophobic R groups
What type of structure does haemoglobin have? (why?)
It has a quaternary structure (because it has 4 polypeptide chains (they are globin proteins and each has a prosthetic haem group))
How are the 4 globin chains held together?
By disulphide bonds
How are the globin chains arranged?
The hydrophobic R groups are facing inwards (to preserve the 3D spherical shape) and the hydrophilic R groups are facing outwards (helps to maintain solubility)
What does the prosthetic haem group contain that makes it able to combine with an oxygen molecule?
It contains an iron II ion (Fe2+)
How many oxygen molecules can each haemoglobin carry?
Each of the four haem groups can carry 4 oxygen molecules (so 8 oxygen atoms total)
True or false: Collagen is the most common structural protein found in vertebrates.
True
What type of protein is collagen?
Fibrous protein that is also insoluble
How many polypeptide chains are needed to form collagen?
3
What holds those polypeptide chains together in collagen and what shape does it form?
Hydrogen bonds and it forms a triple helix
What other type of bond is present in collagen?
Covalent bonds
Why are the covalent bonds there?
To form cross-links between R groups of amino acids in interacting triple helices. The cross-links hold the collagen molecules together to form fibrils
Why are the collagen molecules positioned in the fibrils?
So that there are staggered ends
What is an enzyme?
A biological catalyst
What is a catalyst?
Something that speeds up the rate of chemical reactions without being used up or changed
What type of protein are enzymes?
Globular proteins
What happens at an enzyme’s active site?
It is where the specific substrate binds to the enzyme which forms an enzyme-substrate complex
What type of enzymes are produced and function inside the cell?
Intracellular enzymes
What type of enzyme catalyses reactions outside cells?
Extracellular
What type of enzyme normally carries out digestion? (Why?)
Extracellular enzymes (because macromolecules being digested are too large to enter the cell
What can denature an enzyme’s active site?
Extremes of heat or pH
What must happen for the reaction to occur when the substrate hits its respective enzyme?
It must hit it at the right orientation and speed
What determines the shape of the active site?
The complex tertiary structure of the protein that makes up the enzyme
True or False: the enzyme-substrate complex is formed permanently
False- it is temporary and the products are released
What are the two types of enzyme reactions?
Catabolic and anabolic
What is a catabolic reaction?
It is the breakdown of complex molecules into simpler products (more than one product is released)
What are examples of catabolic reactions?
Cellular respiration and hydrolysis
What is an anabolic reaction?
The building of more complex molecules from simpler ones by drawing two or more substrates into the active site and forming bonds between them and releasing a single product
What are two examples of anabolic reactions?
Protein synthesis and Photosynthesis
How do enzymes work in relation to energy change?
They lower the activation energy of a reaction which provides an alternative energy pathway.
Why are enzymes highly specific?
Because of their globular shape (tertiary structured protein)
Describe the induced fit model.
The substrate doesn’t fit perfectly into the active site at the start so the active site changes shape (conformational change) to allow the substrate to bind. The enzyme then breaks the substrate down and releases the products
What happens if an enzyme is at a temperature which is lower than its specific optimum temperature?
-Molecules move slowly
-Lower frequency of successful collisions
-Substrate and enzymes collide with less energy, making it harder to form bonds
What happens if an enzyme is at a temperature higher than its specific optimum temperature?
Reactions are faster as:
-Molecules move more quickly
-Higher frequency of successful collisions
-Substrate and enzymes collide with more energy (more likely that bonds are going to be formed)
What happens when the enzyme becomes denatured?
-Bonds holding the enzyme molecule in its specific shape break
-Tertiary structure of protein changes
-Permanent damage to the active site- substrate can no longer bind to it
What happens to enzymes at extremes of pH?
Hydrogen and ionic bonds (which are holding the tertiary structure of the protein) break because of an excess of H+ ions and OH- ions
-Alters the shape of the active site
What do you use to investigate the effect of pH on the rate of an enzyme-catalysed reaction?
Buffer solutions of specific pH values
What happens if you have a high concentration of enzymes?
There are more active sites so there is a higher chance of an enzyme-complex formation
The greater the substrate concentration the ______ rate of reaction
higher
What is the point of active site saturation?
Where all of the enzymes are being used but there are still substrates.
What are the two types of enzyme inhibitors?
Competitive and non-competitive
What is a competitive inhibitor?
A molecule that has a similar shape to the substrate molecules sp it ~competes~ with the substrate for the enzyme’s active site.
What is a non-competitive inhibitor?
A molecule that binds to the enzyme at an alternative site which alters the shape of the site and stops the substrate from binding to it
What is the role of DNA?
To store genetic information
What is the role of RNA?
Transfer genetic code to ribosomes
What are the components of DNA nucleotides?
-Deoxyribose sugar with hydrogen
-Phosphate group
-a nitrogenous base (A,C,G,T)
What are the components of RNA nucleotides?
-a ribose sugar with hydroxyl group
-a phosphate group
-one nitrogenous base (A,C,G,U)
What are the complimentary base pairs of DNA?
A+T
C+G
Where are ribosomes located in cells?
In the cytoplasm or attached to the rough endoplasmic reticulum
What happens at ribosomes?
Protein synthesis
What is semi-conservative replication of DNA?
Where a parent cell copies its DNA before it divides so each of the 2 daughter cells get a single strand each from the parent cell
Why is retaining one DNA strand important?
Genetic continuity
