biological molecules Flashcards
why is water described as a dipole?
It has positively charged end (hydrogens) and a negatively charged end (Oxygen) but no overall charge
therefore is a polar molecule
hydrogen bonds in water
H bonds form between the hydrogen atom on one molecule and another oxygen from another molecule. They are weak.
Properties of water- solvent
Water molecules attract charged particles and other polar molecules. These then dissolve in water so chemical reactions take place. Water can transport substances- plasma transports dissolved substances in animals and water transports minerals in plants.
properties of water- transparent
Allows light to pass through, allowing photosynthesis to occur
Properties of water- metabolite
used in biochemical reactions as a reactant eg. hydrolysis and condesation
Properties of water- high specific heat capacity
large amount of heat energy is needed to change the temp. As H bonds restrict movement of water molecule (resisting increase in KE) therefore resisting increase in temp.
prevents large fluctuations in water temperature and keeps habitats stable
properties of water- high latent heat of vaporisation
large amount of heat energy is needed to evaporate water. Important in temp control- heat vaporises water from sweat, cooling body
Properties of water- cohesion
Water molecules attract each other forming hydrogen bonds, molecules stick together in a lattice allowing columns of water to be drawn up xylem vessels
properties of water- surface tension
Cohesion between water molecules at the surface produces surface tension
properties of water- high density
is denser than air, which provides support and buoyancy. Maximum density is 4 degrees. Ice is less dense as hydrogen bonds hold the molecules further apart than they are in liquid water therefore ice floats on water. It is a good insulator and prevents large bodies of water losing heat and freezing therefore organisms can survive below the surface.
Monosaccharides
an individual sugar molecule
Building blocks for larger carbohydrates
General formula (CH2O)n
Roles of monosaccharides
- source of energy for respiration- C-H and C-C bonds are broken to release energy transferred into ATP
- building block for larger molecules to make polysaccharides
- intermediates on reactions
- constituents of neculotides
Disaccharides
composed of 2 monosaccharides bonded together with condensation and glycosidic bond
Examples of disaccahrides
maltose- glucose + glucose
Sucrose- glucose + fructose
Lactose- glucose + galactose
Purpose of disaccharides
Maltose: Reducing sugar, catalysed by amylase, digesting starch into maltose, found in the gut of mammals and germinating seeds
Sucrose: non reducing sugar transport in pholem of flowering plants, very soluble, reactive hydrolysed by HCL
Lactose: found in milk
Testing for the presence of sugars
Benedict test detects reducing sugars in solution. Reducing sugars will donate an electron to reduce copper (II) ions in a copper sulphate solution (blue to brick red)
Benedict’s tests method
Equal volumes of Benedict’s reagents and solution being tested are heated In a beacon of boiling water- If it changes from blue to brick red it is a reducing sugar.
If a non reducing sugar is present the solution will remain blue therefore it can only be detected if it is hydrolysed eh. Heated with HCL. Reagan needs alkaline conditions to work so alkali is added, reagent is then added and heated as before. Red- non reducing is present
Polysaccharides
Large complex polymers
Formed from very large monosaccharide units linked by glycosidic bonds
Structure to function of starch and glycogen
suitable for storage than glucose:
- Insoluble (Being soluble would increase concentration of cell content) Therefore doesn’t exist an osmotic effect
- Cannot diffuse out of cell
- Compact molecule so they can be stored in small spaces
- Carry a lot of energy in c-h and c-c bonds
Starch
Plant storage carbohydrates. Made up of alpha glucose bonded together forming amylose and amylopectin
Structure of amylose and amylopectin
Amylose: Linear, unbranched molecule with Alpha (1-4) glycosidic bonds
Chain coils into a helix
Amylopectin: chains of glucose monomers joined with Alpha (1-4) glycosidic bonds. Cross linked with Alpha (1-6) glycosidic bonds and sits into amylose. Branches are formed because of (1-6) linkages
Testing for the presence of starch
iodine and potassium iodide test.
Iodine dissolved in aqueous potassium iodide and interacts with starch
Turns from orangey brown to blue black
structure of glycogen
Animal storage carbohydrate
Similar to amylopectin
Has (1-4) and (1-6) bonds
Glycogen has shorter 1-4 linked chains than amylopectin so is more highly branched and coiled
Structure of cellulose
Structural polysaccharide- cell walls, beta glucose units
Joined by (1-4) glycosidic bonds to make straight unbranched chains
Links rotates adjacent glucose molecules by 180 to make straight chains
H bonds between OH groups of adjacent parallel chains- strength and stability
parallel cellulose molecules become tightly cross linked by H bonds to form microfibrils which form a fibre.
Freely permeable but there are spaces between fibres and water/ Solutes can penetrate through these spaces in cell wall all the way to the cell membrane
structure of chitin
Structural polysaccharide- exoskeleton of insects
Long chains of B(1-4) linked monomers
Strong waterproof and lightweight
monomers rotated throuch 180
Long parallel chains are cross linked to each other by hydrogen bonds forming microfibrils
On common two, OH is swapped out for an N acetyl group- allows more hydrogen bonding between the chain
lipids
C,H,O (less oxygen)
Non polar (insoluble)
Dissolve in organic solvents eg. Alcohol
Triglycerides
1 glycerol molecule and 3 fatty acids
Forms Ester bonds
phospholipids
one of fatty acids replaced with Phosphate group
P group is associated with another polar group forming a hydrophyllic end
Fatty acids tails are hydrophobic- Does it have any oxygen atoms and are non-polar
Molecules will orientate itself so hydrophyllic head is in water and tails are out.
Saturated fatty acids
Hydrocarbon chain has one single c-c bonds
All carbon atoms are linked to max possible number of hydrogen atoms.
forms straight chains and molecules can align readily so fats are solid
Remain semi-solid at body temperature, storage for animals
Unsaturated fatty acids
contains double c=c bonds
Has a kink
Molecules can’t align uniformly and lipid doesn’t solidify readily.
Unsaturated lipids are oils
Role of lipids
Energy store: plants & animals, lipids contain more c-h bonds than carbohydrates
Thermal installation: when stored under skin, lipids insulate against heat loss or heat gain
Protection: Fat is often stored around organs eh. Kidney
producing metabolic water: What are released from body’s chemical reactions. It’s produced a lot when oxidised
Water proofing
Test for fats and oils
emulsion test
Sample mixed with absolute ethanol- Dissolves any lipids present. Shaken with equal volumes of water.
Forming an emulsion- sample cloudy white
implications for saturated fats
cause of heart disease- Fatty Deposits on the inner wall of Coronary arteries (atherosclerosis) and high blood pressure (hypertension)
High saturated fats cause high blood cholesterol causing plaque formation in atherosclerosis, blocking arteries to the heart.
HDLs
unsaturated
If diet has a high proportion of unsaturated fat the body makes more high density lipoprotein (HDL)
carries harmful fats away to the liver for disposal.
The higher the ratio HDL:LDL in a persons blood, the lower their risk of cardio vascular and coronary heart disease.
LDLs
sagturatted
If diet is high in saturated fats low density lipoprotein (LDL) builds up and causes harm
Atheroma gets deposited in coronary arteries, restricting blood flow. Therefore Oxygen delivery to the heart. Results in angina and if vessel is completely blocked. A myocardial infraction/ heart attach occurs
Proteins
C,H,O,N
Sometimes S and P
Polymers made up of amino acids (monomers)
Chains of amino acids- polypeptide
20 different polypeptides are used to make proteins
amino acids
R
H2-N-C-OH=O
H
amino group
carboxl group
R- variable region
zwirtterion ion
a PH 7, cell gains a H and becomes positively charged. amino groupl#
The carboxyl group is acidic and at pH 7, it loses a H and becomes negatively charged. Therefore amino acid has both charges.
formation of a peptide bond
condensation reaction forms a dipeptide
peptide bond between 2 amino acids
primary structure of a protein
primary structure:
number and sequence of amino acids in a polypeptide chain determined by the base sequence of one DNA strand
secondary structure of a protein
folding of the primary structure to form a alpha helix or beta pleated sheet
tertiary structure of a protein
folding of the secondary structure due o hydrogen bonds, ionic bonds, disulphide bridges and hydrophobic interactions between he R groups
forms complex 3D shapes
quaternary structure
protein are made up of 2 or more polypeptide chains joined togeher eg. haemoglobin
globular proteins
-compact and folded into complex 3D shapes
tertiary
-soluble in water. different functions eg. enzymes, antibodies
- EG haeomogoblin globular protein, 4 folded polypeptide chains at the centre of each is iron containing group, haem
fibrous proeins
- long thin molecules, shape makes them insoluble in water, structural function eg bones
- polypeptide are in parallel chains or sheets, with many cross linkages forming long fibres eg. kertain
-strong and tough
collagen
fibrous protein
Provides strength and toughness in tendons
Single fibre consists of three identical polypeptide chains twisted
Repetitive primary sequence of glycine-proline-alanine
Forms long unbranched chains
Forms triple helix with cross bridges (Linked with H Bonds) For additional strength
Many helices form a fibre
Test for proteins
Biuret test
Add biuret solution
Sodium hydroxide and copper sulphate react to make blue copper hydroxide
If protein is present: Blue to purple
iorganic ions functions
Mg,Fe, P group, Ca
Mg- component of chlorphll
Fe- component of haemogloblin; emzme co factors
Phosphate- found in phosolipids, membrane, component of nucleic acids
Ca- bone/ teeth,
