chapter 3 - biological molecules Flashcards
what is the composition of the body’s biological molecules
70% water
30% chemicals - carbohydrates, lipids, proteins and nucleic acids
what are the monomers of
lipids:
proteins:
carbohydrates:
lipids: fatty acid and glycerol
proteins: amino acids
carbohydrates: glucose
define organic chemistry
the study of chemical reactions that involve carbon
what happens in a condensation reaction?
a water molecule is released,
a new covalent bond is formed
a larger molecule is formed
(monomers linked)
what happens in a hydrolysis reaction?
a water molecule is used
a covalent bond is broken
smaller molecules are formed
(polymer split into monomers)
how many bonds can carbon atoms form?
4
how many bonds can nitrogen form?
3
how many bonds can oxygen form?
2
how many bonds can hydrogen form?
1
what elements are present in the biological molecules:
1. carbohydrates
2. lipids
3. proteins
4. nucleic acids
- carbohydrates - carbon, hydrogen and oxygen (usually in the ratio C6H12O6)
- lipids - carbon, hydrogen and oxygen
- proteins - carbon, hydrogen, oxygen, nitrogen and sulfur
- nucleic acids - carbon, hydrogen, oxygen, nitrogen and phosphorus
what is the difference between a cation and an anion?
cations - the atom loses electrons creating a positive ion
anion - the atom gains electrons creating a negative ion
what abnormal properties do hydrogen bonds give ice?
less dense than water - hydrogen bonds hold molecules apart
higher boiling point - strong hydrogen bonds, 2 bonds per molecule
define “high latent heat of vaporisation”
and why is it important that water possesses this?
large amount of energy to vaporise
efficient cooling mechanism
define “high specific heat capacity”
and why is it important that water has this?
large amount of energy required to raise temp of one unit of substance by 1degrees
thermally stable for aquatic organisms
what are the 7 properties of water molecules and why are they important
high latent heat of vaporisation - efficient cooling mechanism
high specific heat capacity - thermally stable for aquatic organisms
ice is less dense than water due to hydrogen bonds - insulator, reflects light, habitat for algae underneath, provides habitat for animals living on ice
efficient solvent (due to polarity) medium for enzyme controlled reactions
cohesion/adhesion - helps transpiration stream in plants
surface tension - habitat for invertebrates
transparent - allows light for photosynthesis
define cohesion and adhesion in water molecules
cohesion - attraction to water molecules
adhesion - attraction to other molecules
why is water an effective solvent
due to the polarity of the molecules
what are the main four functions of carbohydrates (give examples)
energy source - glucose in respiration
energy store - starch, glycogen
structure - cellulose
form part of larger molecules - nucleic acids or glycolipids
what three elements are carbohydrates made of?
hydrogen, oxygen and carbon
what are monosaccharides and what are some examples
simple sugars
eg. glucose, fructose, galactose, ribose
what are disaccharides and what are some examples
“double sugars” formed from 2 monosaccharides.
eg. maltose, sucrose and lactose
what are polysaccharides and what are some examples
large molecules made of many monosaccharides.
eg, starch, glycogen, cellulose
what are the properties of monosaccharides and what are the 3 main types
have between 3 and 6 carbon atoms,
are soluble in water
are sweet tasting
TRIOSE - 3 carbons
PENTOSE - 5 carbons
HEXOSE - 6 carbons (most common)
what are the properties of glucose and what are its possible structures?
- major energy source for most cells
- highly soluble
- main form in which carbohydrates are transported around the body of animals
structure
straight chain or ring
what is the difference between alpha and beta glucose structure?
the position of the -OH and H groups on carbon 1
what are the 2 isomers of glucose and what are their properties
fructose - very soluble
main sugar in fruits and nectar
sweeter than glucose
galactose - not as soluble as glucose
important in production of glycolipids and glycoproteins
what are the 3 main disaccharides, what are their monomers?
and what are they joined by
maltose - glucose + glucose
sucrose - glucose + fructose
lactose - glucose + galactose
joined by glycosidic linkage
what is the polysaccharide starch composed of?
amylose and amylopectin
(alpha glucose with 1-4 glycosidic bonds and a coiled structure)
what shared features do the polysaccharides starch and glycogen have
both energy storage molecules
are insoluble (don’t affect water potential of cell)
what makes up cellulose fibres
50-100 beta glucose molecules cross link via hydrogen bonds to form bundles of MICROFIBRILS
microfibrils cross link to form MACROFIBRILS,
bundles of macrofibrils make up cellulose fibres
what are the structure and function of cellulose cell walls
- provide strength to cells and the whole plant
- prevents bursting (lysis), keeps cell turgid
- apoplast - permits passage of water
- allows cells to grow or change shape
- reinforced with other substances eg. lignin to be waterproof
how are the long chains of beta glucose molecules that make up cellulose arranged?
straight chain, every alternative monomer rotated 180 degrees
what elements are lipids composed of?
carbon, hydrogen and oxygen
what is the solubility of lipids like?
soluble in organic solvents but not in water
what are 4 examples of lipids
triglycerides (fats and oils)
cholesterol
steroid hormones
phospholipids
what is the difference between fat and oil
fat is solid at room temp
oil is liquid at room temp
explain in detail the 8 functions of lipids?
give examples
energy source - used when glycogen and starch are depleted
energy store - in adipose tissue, provides more energy per gram than carbohydrates
biological membranes - phospholipid bilayer, cholesterol regulates fluidity
insulation - blubber reduces heat loss (whales + seals). electrical insulation around nerve cells (myelin sheath)
buoyancy - fat is less dense than water - marine animals
physical protection - around vital organs
waterproofing - cuticle on plant leaves, ducks produce an oil to waterproof their feathers
vitamin D, bile and steroid hormone production
what are triglycerides composed of?
a glycerol and 3 fatty acids
what is the difference between the structure of saturated and unsaturated fatty acids
saturated = straight chain, unsaturated = bent tail
what group do all fatty acids have at one end?
carboxyl group
formula for saturated fatty acids:
CnH(2n+1)COOH
what are the two types of unsaturated fatty acids and how do they differ?
cis - both hydrogen atoms bonded to the double bond of carbon from the same side - bent
trans - one hydrogen atom bonded to each side of the double carbon bond - straight structure
what is the structure of phospholipids like compared to a triglyceride?
similar structure but one fatty acid is replaced by a phosphate group
would an organism living in a cold environment have more saturated or unsaturated fatty acids?
why?
more unsaturated as can’t pack as tightly together due to bent structure - membrane remains more fluid
4 facts about cholesterol
and where are they placed for their function
- NOT formed from glycerol/ fatty acids
- 4 carbon rings
- small, narrow molecule
- hydrophobic
fit between phospholipid tails in membrane, regulates membrane fluidity and strength
2 facts and 3 examples of steroid hormones
- made from cholesterol
- lipophilic- can pass through phospholipid bilayer
- testosterone
- oestrogen
- progesterone
how do you remember the difference in structure between alpha and beta glucose?
ABBA = OH group in Alpha Below
OH group in Beta Above carbon 1
define isomer of a molecule
same chemical formula, different structure
what is the difference between amylose and amylopectin (in starch)
amylopectin has side branches with 1-6, glycosidic bonds
when is beta glucose used as monomers
when is alpha glucose used as monomers
beta = structural - cellulose
alpha = energy - starch and glycogen
what is the difference between structural vs energy carbohydrates?
structural - has hydrogen bonds (important for strength), straight chain structure, every alternative molecule flipped 180degrees.
energy - no hydrogen bonds, coiled structure
what are the 4 carbohydrate structures you need to know and draw?
ribose
deoxyribose
alpha glucose
beta glucose
what is the structural difference between ribose and deoxyribose
deoxyribose does not have the oxygen on carbon 2
what are ribose and deoxyribose found?
ribose = RNA
deoxyribose = DNA
how many water molecules are produced in the formation of a triglyceride molecule (lipids)
3 water molecules
why is glycogen such a good energy storage molecule?
- insoluble - doesn’t affect water potential of cell
- easily and quickly hydrolysed - releasing energy for functions
- lots of side branches (1-6, glycosidic bonds) - enzymes can attach
- very compact shape - high energy content for its mass
what molecule is produced when glycogen is hydrolysed?
Alpha glucose
what is the difference between the functional groups of glucose and fructose molecules
fructose = ketone functional group (C=O)
glucose = aldehyde functional group (CHO)
why can bacteria not break down the carbohydrate agarose?
because the bacteria doesn’t contain the correct enzymes to digest agarose,
agarose does not have complimentary shape to the active site on bacteria
suggest the purpose of a control test alongside your experiment
eg. an experiment without the presence of the substance you are investigating
to ensure that the positive result is due to the independent variable you are testing and not another factor
to ensure the reliability of the experiment
suggest 2 ways in which reliability of an experiment can be improved
- repeat the experiment
- test the samples more than once for each category
what bonds are formed during the condensation of lipids?
ester bonds
what bonds are formed during the condensation of proteins
peptide bonds
what bonds are formed during the condensation of sugars/ carbohydrates
glycosidic bonds
what tissue is composed of lipids
adipose tissue
Define heteropolysaccharide
A polysaccharide containing multiple different monosaccharides
Define heteropolysaccharide
A polysaccharide containing multiple different monosaccharides
what are some examples in which hydrogen bonds are found in biological molecules (5)
- water
- between cellulose fibres
- adjacent collagen chains
- proteins - secondary, tertiary and quaternary structure
- strands of/ bases in DNA
what are the roles of cholesterol in living organisms (5)
1.regulate plasma membrane fluidity
2.converted to steroid hormones
3.producing vitamin D
4.making bile (salts)
5.waterproofing the skin
what are ways that the molecular structure of cholesterol is similar to that of a carbohydrate
contains carbon, oxygen and hydrogen
has OH/ hydroxyl groups
has a six membered ring/ hex
what 2 molecules combine with cholesterol to form LDLs (low density lipoprotein)
saturated lipids/ fats/ triglycerides
proteins / polypeptides
suggest why diets with high red meat are associated with high blood cholesterol
red meat contains large amounts of saturated fat/ fatty acids
which leads to an increased number of LDLs
list some of the differences between the structures of glycogen and cellulose
G: no hydrogen bonding
C: hydrogen bonding
G: 1,4- + 1-6 glycosidic bonds
C: 1,4 glycosidic bonds ONLY
G: branched
C: unbranched - linear
G: no fibres/fibrils
C: fibres/fibrils
G: granules
C: no granules
how is collagen’s structure similar to that of haemoglobin
collagen has amino acid chain/ sequence, peptide bonds, helix/helical
3 bonds / interactions from hydrophobic & hydrophilic, ionic, hydrogen, disulfide
quaternary structure; more than one polypeptide / subunit
how do sodium and hydrogen ions help a cut plant live longer
sodium regulates water potential
hydrogen regulates pH
why is glucose easily transported into the blood stream
its soluble in water
how can you estimate glucose concentration without a colorimeter?
carry out benedict’s test, allow precipitate to form and sink to the bottom. filter the solution and weigh the mass of solid precipitate
what is the difference between DNA and RNA
DNA contains deoxyribose
RNA contains ribose
DNA contains: Thymine, Adenine, Cytosine and guanine
RNA contains Adenine, Cytosine, Guanine and Uracil
define molecule
what is produced when 2 or more atoms chemically bond together
which type of glucose molecule makes up structural carbohydrates and which makes up energy source carbohydrates
alpha = energy = starch and glycogen
beta = structural = cellulose
why does benedict’s solution turn red when heated with a reducing sugar
because the blue cu2+ ions are reduced to brick-red cu+ ions
therefore the higher reducing sugar concentration, the more red precipitate formed
how do you use the benedict’s test for non-reducing sugars?
boil the sugar with hydrochloric acid first,
then neutralise with a base
then the sugar will react with the benedict’s solution as the sugar has been hydrolysed by the acid to reducing sugar monomers
what is the alternative way to benedict’s solution for testing for reducing sugars?
what is the advantage for this method
reagent strips
with the use of a colour-coded chart, the concentration of glucose can be calculated
what are the 3 basic components of a biosensor
- molecular recognition - a protein or single strand of DNA is immobilised to a surface. This will interact with, or bind to, the specific molecule in question
- transduction - this interaction causes a change in the transducer. The transducer detects a change and produces a response. e.g. an electric current on a glucose testing machine
- display - this then produces a visible qualitative or quantitative signal such as colour on a test strip or readings on a machine
why do the presence of saturated and unsaturated fatty acids cause fats to be solid and oils to be liquid
saturated fatty acids - the carbon-to-carbon double bond causes the molecule to kink or bend and can therefore not pack together as tightly. making them liquid at room temperature and described as oils rather than fats
What would be the results for tests of starch and sucrose
Biurets:
Benedict’s:
Iodine in potassium iodide:
Blue
Blue
Blue-black
What property of water is the main factor enabling homeotherms (endotherms) to adapt to a range of environments
High heat of vaporisation
