Biological Molecules Flashcards
1
Q
What are biological molecules?
A
Molecules made and used by living organisms e.g. carbohydrates, proteins, lipids, DNA, aTP , water, inorganic ions
2
Q
What are the functions of carbohydrates?
A
- energy source
- energy store
- structure
3
Q
What are the building blocks for carbohydrates called?
A
Monosaccharides
4
Q
Examples of monosaccharides?
A
Glucose (alpha and beta)
Galactose
Fructose
5
Q
Formula for monosaccharides?
A
C6H12O6 (isomers = same formula but different arrangement)
6
Q
Difference between alpha and beta glucose?
A
On carbon 1, alpha glucose has a OH group on the bottom and beta glucose has a OH group on the top
7
Q
How are monosaccharides joined together?
A
Condensation reaction - between 2 OH groups
8
Q
Bond in carbohydrate?
A
glycosidic bond
9
Q
Example of disaccharides?
A
glucose + glucose = maltose
glucose + galactose = lactose
glucose + fructose = sucrose
10
Q
Formula for disaccharides
A
C12H22O11
11
Q
How are polymers separated?
A
hydrolysis
12
Q
What is a polysaccharide?
A
Many monosaccharides joined by condensation reaction/glycosidic bonds
13
Q
Example of polysaccharides
A
- Amylose (long chain of alpha glucose) which makes starch/glycogen
- Cellulose (long chain of beta glucose) which makes cell wall in plants
14
Q
What are polysaccharides?
A
- carbohydrates
- made of a long chain of monosaccharides joined by condensation reaction/glycosidic bonds
- 3 examples: strach, glycogen, cellulose
- starch & glycogen used as energy stores (starch in plants, glycogen in animals), they are made out of many alpha glucose which are used for respiration
- cellulose used to form cell wall in plants, made out of many beta glucose
15
Q
Properties of starch and glycogen as energy stores?
A
- Insoluble = do not affect water potential of the cell, do not diffuse out of the cell
- Coiled/Branched = compact, more can fit into a cell
- branched/chained = glucose removed from the end
16
Q
Structure of cellulose?
A
- beta-glucose arranged in a straight chain (each alternative beta-glucose is rotated 180 degrees) = cellulose straight chain
- many cellulose chains are cross linked by hydrogen bonds to form microfibrils
- many microfibrils are cross linked to from macrofibrils
- forms structure of cell wall
- strong material (prevents plant cell from bursting or shrinking)
17
Q
Test for starch?
A
add iodine, turns blue/black
18
Q
Test for reducing sugar?
A
heat with Benedict’s, turns brick red
19
Q
Test for non-reducing sugar?
A
- heat with Benedict’s - no change
- therefore, add dilute hydrochloric acid
- then add sodium hydrogen carbonate (neutralises solution)
- heat with Benedict - turns brick red
20
Q
What are 2 types of proteins?
A
Globular and fibrous
21
Q
What are globular proteins?
A
Soluble proteins with a specific 3D shape e.g. enzymes, hormones, antibodies, haemoglobin
22
Q
What are fibrous proteins?
A
strong/insoluble/inflexible material e.g. collagen and keratin
23
Q
What are the building blocks for proteins?
A
amino acids
24
Q
Structure of amino acid?
A
central carbon, carboxyl group to the right (COOH) amine group to the left (NH2), hydrogen above and R group below
25
How do amino acids differ?
Have different R groups e.g. glycine has a hydrogen in its R group - simplest amino acid
26
How are amino acids joined together?
By condensation reaction between the carboxyl group of one and amine group of another, leaves a bond between carbon and nitrogen (called a peptide bond) forming a dipeptide
27
Define primary, secondary, tertiary, quaternary structure?
- Primary = sequence of AA, polypeptide chain (held by peptide bonds)
- Secondary = the primary structure (polypeptide chain) coils to form a helix held by hydrogen bonds
- Tertiary = secondary structure folds again to from final 3D shape, held together by hydrogen/ionic/disulfide bonds
- Quaternary = made of more than one polypeptide chain
28
Examples of quaternary structure proteins?
Collagen, antibodies, haemoglobin
29
Structure of collagen?
- strong material, used to bind tendons/ligaments/connective tissues
- primary structure mainly made up of glycine (simplest amino acid)
- secondary structure forms a tight coil (not much branching due to glycine)
- tertiary structure coils again
- quaternary structure made from 3 tertiary structures wrapped around each other like rope
- = a collagen molecule
- many of these collagen molecules make the tendons/ligaments/connective tissues
30
Test for protein?
add biuret, turns purple
31
What is an enzyme?
A biological catalyst (substance that speeds up the rate of reaction without used up - lowers activation energy)
32
What makes an enzyme specific?
Has a specific active site shape, only complementary substrates can bind to the active site to from enzyme-substrate complexes
33
Lock and Key Model vs Induced Fit Model?
LK = active site shape is rigid, only exactly complementary substrates can bind to from ES complexes
IF = active site changes shape, the substrate binds to the active site - the active site changes shape so the substrate fits exactly forming an ES complex
34
Effect of enzyme concentration on enzyme activity?
- Increase enzyme concentration, increases chance of successful collisions, increase chance of forming an ES complex, increase rate of reaction
- this continues until all the substrates are used up = maximum rate of reaction
35
Effect of substrate concentration on enzyme activity?
- increase substrate concentration, increases chance of successful collisions, increase chance of forming an ES complex, increase rate of reaction
- this continues until all the enzyme's active sites are full/saturated = maximum rate of reaction
36
Effect of temperature on enzyme activity
As temperature increases the kinetic energy increases, the molecules move faster.
Increases chance of successful collisions and increases chance of forming ES complex.
Increases rate of reaction.
Carries on till optimum,.
After optimum the bonds in tertiary structure break ( hydrogen and ionic bonds). Causes active site shape to change, so the substrate is no longer complementary, meaning that ES complexes can't be formed.
The enzyme is denatured.
37
Effect of pH on enzyme activity?
If change pH away from optimum, bonds in tertiary structure break, lose active site shape, no longer form ES complex, enzyme denatured.
38
Competitive vs Non-Competitive Inhibitors
- Competitive = a substance with a similar shape to the substrate and a complementary shape to the enzyme's active site binds to the active site, blocking it, preventing ES complexes from forming
- Non-competitive = a substance that binds to another site on the enzyme other than the active site, causes the active site to change shape, so less ES complexes can form
39
What are the 3 types of lipids?
- Triglycerides (fat for energy store, insulation, protection of organs)
- Phospholipids (to make membranes)
- Cholesterol (for membrane stability and make hormones)
40
Structure of triglyceride
- made of 1 glycerol and 3 fatty acids
- joined by condensation reaction, ester bonds
- bond is COOC
- there are two types of triglycerides: saturated fat and unsaturated fat
41
Saturated fat vs unsaturated fat
Saturated = has no carbon double bonds in the R group of the fatty acid
Unsaturated = has no carbon double bonds in the R group of the fatty acid
42
Structure of phospholipid
- Made of 1 glycerol, 2 fatty acids and 1 phosphate
- Phosphate forms a hydrophilic head, fatty acids form hydrophobic tails
- Forms a phospholipid bilayer, basic structure of membranes
43
What are nucleic acids?
Polymers made from nucleotides (2 types = DNA and RNA
44
What is DNA?
- Deoxyribonucleic Acid
- found in all organisms
- carries genes
- genes = section of DNA that codes for a protein
- all organisms are built of proteins
45
Building block of DNA
- DNA nucleotide (made of phosphate, deoxyribose sugar, nitrogenous base)
- 4 types of nucleotides
46
DNA structure
- DNA double helix
- join nucleotides by condensation reaction between sugar and phosphate to form a polynucleotide
- join 2 polynucleotides by hydrogen bond between the bases
- A + T, C + G (complementary base pairing)
- produces double strand
- then coil double strand into double helix
47
Properties of DNA structure?
- Double stranded = makes DNA more stable & 2 strands act as templates in semi conservative replication
- Coil into helix = more compact
- Sugar-phosphate backbone = protect bases (bases code for protein)
- Hydrogen bonds between bases = weak, so double strand separates more easily for semi-conservative replication
48
DNA Replication
Occurs in interphase before mitosis & meiosis.
| Occurs by semi-conservative replication
49
Describe semi-conservative replication
- DNA double strand separate and act as templates, producing 2 identical copies of the DNA, each has half the original strand and half the new strand
Process:
- DNA helices breaks hydrogen bonds between the complimentary bases
- double strand separates, leaves 2 template strands
- free complementary nucleotides bind to exposed bases on template strands
- DNA polymerase joins the sugar-phosphate backbone of the new strand
50
Evidence for SCR
- replicating bacterial DNA in 2 types of nitrogen isotopes, 15N and 14N
- 15N = heavy isotope
- 14N = light isotope
- Nitrogen found in nitrogenous bases of DNA
- Bacterial DNA made from 15N will have a heavy density
- Bacterial DNA made from 14N will have a light density
- Experiment = bacterial DNA made of 15N is replicated an environment of 14N - produces DNA molecules with half 15/half 14 (semi-conservative replication, original strand = 15N & new strand = 14N), therefore, DNA molecules has medium density
51
What is RNA?
- RiboNucleic Acid
- 2 types (mRNA and tRNA)
- mRNA = messenger RNA
- tRNA = transfer RNA
- both single stranded
- both made of RNA nucleotides (phosphate, ribose sugar, nitrogenous bases - AUCG)
52
What is ATP?
Adenosine triphosphate (Energy carrier molecule - delivers energy for life processes)
53
Structure of ATP
- Adenosine triphosphate
- made from 1 adenosine and 3 phosphates
- formation: ADP + Pi (+ energy used) = ATP
- condensation reaction using ATP synthase
- carries energy in its bonds
- breakdown: ATP = ADP + Pi (+ energy released)
- hydrolysis reaction using ATP hydrolase
- releases energy from its bonds
54
What makes ATP a good deliverer of energy?
- immediate source = only need to break one bond
| - manageable source = releases small amount of energy
55
Uses of ATP
- protein synthesis
- organelle synthesis
- DNA replication
- cell division
- active transport
- metabolic reactions
- movement
- maintaining body temperature
56
Role of water in biology
- found in living organisms = cytoplasm (all organisms), xylem/phloem (in plants), tissue fluid and blood (in animals)
- also acts as habitat for living organisms
57
Properties of water
- water molecules are dipolar
- hydrogen has slightly +ve charge and oxygen has slightly -ve charge therefore H2O molecules can form hydrogen bonds with each other
58
Role of water in living organisms
(I) Habitat (e.g. sea): Water has high specific heat capacity meaning that a lot of heat needs to be applied before it evaporates due to the presence of the hydrogen bonds between the water molecules. Also when water freezes it becomes Ice, which is less dense then liquid water – so it floats on the surface insulating the water beneath it, preventing it from freezing. In both cases the water remains liquid to provide an habitat for organisms.
(II) Solvent: Because H20 molecules are dipolar they can separate out solutes based on their charge, +ve Hydrogen side mixes with -ve solute and -ve Oxygen side mixes with +ve solute, so solute mixes with water and becomes dissolved. This is useful in cytoplasm of all cells and supports the reaction of these solutes, it is also useful in the processes of diffusion/active transport, and is also useful in transport such as blood and phloem.
(III)Hydrostatic Pressure: Water when pressurised can provide a strong physical pushing force. Used particularly in Mass Flow (where mass of water carries large amounts of substances e.g. tissue fluid in capillaries and phloem in plants). Also helps to support turgidity in plants.
(IV)Homeostasis: Mammals and Humans control body temperature by sweating. Sweat on the skin uses heat from the blood to evaporate, hence, cooling the individual. Because sweat/water is made up of hydrogen bonds, it has a stable structure, so requires a large amount of heat for it to evaporate. This is called Latent Heat of Vaporisation.
59
What are inorganic ions?
- Salts/minerals
- inorganic = do not contain carbon, ion = charged
- e.g. sodium ions, chloride ions
