Macromolecules Flashcards
What are macromolecules?
large molecules composed of thousands of covalently linked atoms
- structure and function are inseparable
What is a polymer?
a long chain-like molecule consisting of many similar or identical building blocks linked together by covalent bonds
What is a monomer?
small building-block molecules
Synthesis of a polymer
monomer form larger molecules by bonding together through the loss of a water molecule
= condensation / dehydration reaction
Breakdown of polymer
polymers are disassembled to monomers by hydrolysis
- water is added
How is the diversity of polymers achieved?
-> arrangement of the monomers into polymers
all organisms share the same limited number of monomer types (40-50 types)
what are monosaccharides?
simple sugar
- most common: Glucose
- carbonyl group and many hydroxyl groups
- classified by the location of the carbonyl group (aldose or ketose)
- size of carbon chain (3-7)
- spatial arrangement of their parts around asymmetric carbons
- many form rings in aqueous solutions
- serve as major fuels in cells and raw material for building molecules
What is the difference between aldose and ketose?
carbonyl group is at the end of the skeleton in aldehydes
in the middle in ketones
What are disaccharides?
two monosaccharides joined by dehydration reaction
- most common is sugar (glucose+fructose)
- maltose: 2 glucose
- glycosidic linkage
What kind of bond has maltose?
1,4 glycosidic linkage
What kind of bond has sucrose?
1,2 glycosidic linkage
What are polysaccharides?
macromolecules, polymers of sugar
- storage and structural functions
structure and functions are determined by its sugar monomers and the positions of glycosidic linkages
What are the storage polysaccharides?
- plants use starch
-> excess starch is stored as granules within chloroplasts and other plastids - animals use glycogen
-> stored mainly in liver and muscle cells
both consist of glucose monomers, but have different spatial arrangements
What is starch made of?
most are linked by 1,4 linkages -> helical
- amylose, unbranched
- amylopectin, branched polymer with 1,6 linkages at branch points
What is the structure of glycogen?
branched polymer with 1,6 linkages at branch points
more branched than amylopectin
What are structural polysaccharides?
cellulose:
- in though walls of plant cells
- polymer of glucose
- beta-glucose -> straight (alpha glucose in starch -> helical)
-> can be stacked closer together
- 1,4 linkages in beta glucose monomers
about 80 cellulose molecules associate to form a microfibril, the main architectural unit of plant cell wall
What is the structure of cellulose?
- cellulose is never branched
- some hydroxyl groups on its glucose monomers are free to hydrogen-bond with the hydroxyls of other cellulose molecules lying parallel to it
-> grouped together into microfibrils - microfibrils are strong building material for plants and important for humans -> major constituent of paper and the only component of cotton
how is cellulose digested? in humans
- enzymes can digest starch by hydrolysing alpha-linkages, but cant hydrolyse beta linkages in cellulose (they have distinctly different shapes)
- humans can not digest cellulose
- cellulose passes through digestive tract as insoluble fiber -> stimulates the secretion of mucus, which aids the passage of food through the tract (ballaststoffe)
how is cellulose digested in herbivores, fungi?
- herbivores (cows, termites) have symbiotic relationships with microbes that have enzymes to digest cellulose into glucose in their stomach
(prokaryotes and protists) - eg in cows, the microbes hydrolyse cellulose in hay and grass converting into nutrients
- some fungi also digest cellulose -> aid in the recycling of chemical elements
What are lipids?
the only biomolecules that do not form polymers
- hydrophobic, due to the main component being hydrocarbon chains
- most important types:
fats, phospholipids and steroids
What are fats made of?
glycerol:
3 carbon alcohol with -OH group at each carbon
fatty acid:
-OH group attached to a long carbon skeleton (16-18C)
What is a triacylglycerol / triglyceride?
3 fatty acids joined to glycerol by an ester linkage
Why are fats hydrophobic?
mainly because of the relatively non-polar C-H-bonds in the hydrocarbon chains in fatty acids
What are the differences in fatty acids?
vary in length (number of carbons)
very in number and locations of double bonds
What are saturated fatty acids?
have the maximum number of H-atoms and no double bonds
What are unsaturated fatty acids?
have minimum one double bond
cis-double bond causes bending in structure
animal fats
are saturated and solid at room temperature
-> can be packed tightly due to their flexibility
plant and fish fats
unsaturated and liquid at room temperature
- kinks due to cis double bonds do not allow them to be packed tightly
What are hydrogenated vegetable oils?
unsaturated fats that have been synthetically converted to saturated fats by adding hydrogen
What is atherosclerosis?
plaque build up in the walls of blood vessels, causing inward bulges that impede blood flow and reduce resilience of vessels
- hydrogenating vegetable oils also creates unsaturated fats with trans double bonds -> these trans fats may contribute more than saturated fats to cardiovascular disease
What is hydrogenation?
process of converting unsaturated fats to saturated fats by adding hydrogen
- also creates unsaturated fats with trans double bonds -> trans fats
What is the major function of fats?
- energy storage as hydrocarbons are rich in energy (1g of fat stores twice as much as 1g of polysaccharides)
- in adipose cell
- adipose tissue also serve as cushions for vital organs and insulate the body
What is the structure of phospholipids?
2 fatty acids + phosphate attached to glycerol
fatty acids (tail) is hydrophobic, head (phosphate) is hydrophillic
What happens to phospholipids in aqueous solutions?
assemble to a bilayer because of their hydrophobic and hydrophillic traits
Steroids
lipids with characteristic carbon skeleton consisting of 4 fused rings
- vary in their chemical groups attached to the rings
Cholesterol: component in animal cell membrane and precursor of some hormones
- high levels are risk of cardiovascular disease
What are proteins?
= biologically functional molecules that consists of one ore more polypeptides
-> coiled or folded into a specific 3D structure
- make up more than 50% of the dry mass of most cells
- functions include transport, enzymes, structure, communication, storage, movement, immune system
What is an enzyme?
catalyse a reaction, without being altered by the reaction
- can perform their function repeatedly
- active site for the substance
What are polypeptides?
unbranched polymers built from the same set of 20 amino acids
- peptide bond
What are amino acids?
organic molecules with a carboxyl and amino group connected to a central alpha carbon
- have different properties due to different side chains (r groups)
- functional r group determine the unique characteristics of a particular amino acid -> affects its functional role in a polypeptide
-> non polar side chain: hydrophobic
-> polar side chain: hydrophillic (acidic due to carboxyl group, basic due to amino group)
how are the amino acids linked together?
by peptide bonds in dehydration reaction
- carboxyl group + amino group
How is the function of a protein determined?
- the amino acid sequence of a polypeptide determines the 3D structure of the protein
- the protein’s structure determines its function -> the function of a protein usually depends on its ability to recognise and bind to some other molecule
Primary structur
unique sequence of amino acids in a polypeptide
secondary structure
folding or coiling of the polypeptide into a repeating configuration
- stabilised by H-bonds between atoms of repeating parts of the polypeptide back bone
- alpha helix and beta-pleated sheets
tertiary structure
3D shape of polypeptide
- interactions (h-bonds, van der waals, ionic bonds, hydrophobic interactions) between amino acids and r groups
- disulfide bridges ( covalent bonds) may reinforce the structure
- ‘ the sentences’
- stabilised by side chain interactions
quaternary structure
- association of multiple polypeptides, forming a functional protein
- results from combination of two or more polypeptide subunits
sickle cell disease
- change in primary structure -> a single amino acid substitution
- inherited blood disorder
- hemoglobin tends to crystallise, deforming some of the cell to sickle shape
What are the factors affecting protein structure?
-> physical and chemical conditions of its environment
- pH
- Temperature
- salt concentration
What is denaturation?
protein unravels and loses its natural shape
-> protein is biologically inactive
What are chaperonins?
protein molecules that help the proper folding of other proteins
misfolding could lead to alzheimers, parkinsons
What are the methods to determine a protein’s 3D structure?
- X ray crystallography
- nuclear magnetic resonance (NMR)
- cryogenic electron microscope (cryo EM)
- bioinformatics
what is a gene?
a unit of inheritance in DNA
What is DNA?
- 2 strands of polynucleotides spiraling around forming a double helix
- backbones run in opposite 5’->3’ direction -> antiparallel arrangement
- strands held together by h-bonds between the bases (a+T, G+C)
- sugar phosphate backbone on the outside, nucleotide base on the inside
- semiconservative replication
Watson and Crick
- introduced the double helical model for DNA
- Franklins Xray crystallised images helped watson to deduce the helical shape, the width of the helix and the spacing of the nitrogenous bases
- structure revealed its function
What is RNA
single stranded
- complementary pairing might occur between 2 RNA molecules or between parts of the same molecule
- Uracil instead of Thymine
- RNA are variable in form
what is a nucleotide
- nitrogenous base
- pentose sugar
- phosphate group
what is a nucleoside
- nitrogenous base
- pentose sugar
what is the nitrogenous base?
- one or two rings of carbon with nitrogen atoms
-> N-atoms take up H+, acting as bases - pyrimidines: cytosine, thymine and uracil
have 6 C rings - purines: adenosine and guanine
have 6 + 5 rings fused
What is the pentose sugar?
desoxyribose in DNA and ribose in RNA
desoxyribose lacks o-atom at the 2nd carbon of the ring
phosphodiester bind
covalent bond between the OH group of 3’ C of sugar and phosphate group of 5’ C
-> creates the backbone of sugar-phosphate units with nitrogenous bases as attachments
What are the ends of the polynucleotides?
- 5’ end with phosphate group
- 3’ end with OH group of sugar
DNA and proteins as tape measures of evolution
- molecular comparison in molecular biology help biologists sort out the evolutionary connections between species
- comparing the amino acid sequence of proteins between different species
-> the more related the two species are, the more similar the amino acid sequence of their proteins is
Bioinformatics
use computer software and other computational tools to deal with the data resulting from sequencing many genomes
genomics
analysing large sets of genes or even comparing whole genomes of different species
proteomics
similar analysis of large sets of proteins including their sequences
