Topic 1 Biological Molecules Flashcards
carbs, lipids, proteins, enzymes, inorganic ions, water
What kind of molecule is water?
Polar
Meaning electrons aren’t shared equally
Dipole property of water
2 poles, oxygen is electronegative (slightly negative) , hydrogen is slightly positive
What atoms are electronegative?
Usually
Oxygen nitrogen or fluorine
Why is water a good solvent?
Weak hydrogen bonds so water easily disassociates into OH- and H+ to form other bonds
Because it is DIPOLE
pH
Why does water have a high specific heat capacity?
Takes a lot of energy to break down a lot of hydrogen bond
Stronger together
What are hydrophobic molecules and their properties
Water fearing molecules
Insoluble
Molar is not polar, so cannot form H bonds hence cannot dissolve
What are Hydrophilic molecules and their properties?
Water loving
Soluble because molecules are polar, so can form hydrogen bonds with water
Give 3 properties of water
-ice floats
-tension, cohesion and adhesion
-water in reactions (pH, solvent, hydrolysis)
-transparency (predators can spot prey)
-water as transport medium
-high SHC, thermal stability
-incompressible
Give 3 properties of water
-ice floats
-tension, cohesion and adhesion
-water in reactions (pH, solvent, hydrolysis)
-transparency (predators can spot prey)
-water as transport medium
-high SHC, thermal stability
-incompressible
What are some macromolecules?
Proteins, lipids, starch, nucleic acid
Role of nitrate ions in plants?
- supply of nitrogen to synthesize protein, nucleic acids, chlorophyll etc
Nitrate ion deficiency symptoms in plants?
Reduced chlorophyll
Leaves turn pale / yellow
Role of Magnesium ions in plants?
Make chlorophyll
Symptom of magnesium ion deficiency in plants?
- failure to synthesis chlorophyll
therefore: Stunt growth, yellowing leaves
(Since less magnesium = less p/s = less glucose for respiration = less ATP)
Role of calcium ions in plants?
Build new cell walls - Form calcium pectate for the middle lamellae
Symptom of calcium ion deficiency in plants?
stunted growth bcs of poor cell wall development
Role of phosphate ions in plants?
Make DNA, RNA, ATP
What does ATP stand for?
Adenosine Triphosphate
Give 3 differences between starch and cellulose
Starch / cellulose
Alpha glucose / beta
Is branched / not
Has 1,4-glycosidic bonds and 1,6-glycosidic bonds / 1,4 only
Same orientation / flipped glucose molecules
What is the structure and function of glycogen?
Made up of alpha glucose
1,4 and 1,6 - glycosidic bonds
In animal cells
Insoluble so no osmotic effect
Compact and branched, allows quick hydrolysis
What are the structures and functions of cellulose
Made up of beta glucose
Straight chains, only 1,4 glycosidic bonds. Alternate Beta glucose flipped 180°
Fibres held together by HYDROGEN bonds
High tensile strength , give plants structure
Polar so allows water to diffuse through
How do triglycerides form
Condensation reaction by ester bonds between a glycerol and three fatty acids
Relate structures of triglycerides to their functions
• High energy:mass ratio = high calorific value from oxidation (energy storage).
• Insoluble hydrocarbon chain = no effect on water potential of cells & used for waterproofing.
• Slow conductor of heat = thermal insulation e.g.
adipose tissue.
• Less dense than water = buoyancy of aquatic animals.
Functions of phospholipids relate to their structure
Barrier to Protect cells from external
glycerol backbone attached to 2 hydrophobic fatty acid tails & 1 hydrophilic polar phosphate head
• forms phospholipid bilayer in water = component of membranes
• tails can splay outwards = waterproofing
what are the 3 monosaccharides?
fructose, glucose, galactose
what is maltose made up of?
2 alpha glucose
what is sucrose made up of?
gluocse + fructose
what is lactose made up of?
glucose + galactose
what is a polysaccharide?
chain of many monosaccharides
what is starch made up of?
chain(polymer) of ALPHA glucose
(Amylose and amylopectin)
what is starch used for?
chloroplast stroma
energy storage in plants
what is glycogen made up of?
chain(polymer) of alpha glucose
what is glycogen used for?
muscle cells
main energy storage
what is cellulose made up of?
chain (polymer) of beta glucose
what is cellulose used for?
plant cell wall
Name the reaction involved when a disaccharide is formed
condensation reaction
name the type of bond formed when disaccharides are formed
glycosidic bonds
what is starch made up of?
80% amylopectin
20% amylose
v compact
what is amylopectin’s structure?
branched
having both α-1,4-glycosidic and α-1,6-glycosidic
what is amylose’s structure?
helix structure
only α-1,4-glycosidic bonds
is starch soluble in water?
no, it is insoluble
why is amylopectin hydrolysed easier?
because it is highly branched with protruding ends, so more SA for enzymes to work on
how to test for starch?
iodine test
turns blue black precipitate
how to test for reducing sugars? (e.g. glucose fructose maltose)
Benedict’s test
water bath
turns brick red ppt
how to test for non-reducing sugars? (e.g. sucrose)
benedict’s reagent + dilute HCl
boil
dnf
what is a triglyceride made up of?
1 glycerol + 3 fatty acids
what bond is formed between glycerol and fatty acids?
ester bonds
give 3 main functions of lipids
- energy storage
- thermal insulation
- waterproofing
- buoyancy (less dense than water)
- major component of cell membranes
- cushion and protection of internal organs
what are some lipid examples?
triglycerides
phospholipids
cholesterol
what is the structure of phospholipids?
1 phosphate group + 2 fatty acids
Hydrophilic head, hydrophobic tail
is phospholipid soluble in water
the head is soluble (bcs can ionise)
but tail is insoluble (non-polar, hydrophobic)
what are 5 structures of the fluid mosaic model
- fluid phospholipid bilayer, movable
- internal/integral protein
- external/surface protein
- cholesterol
- channel protein
what are saturated fatty acids?
only single bonds between carbon atoms
(it is a -COOH carboxylic acid)
what bond is formed between 2 amino acids?
peptide bond via condensation
what are two secondary structures of polypeptides?
alpha-helix
beta pleated sheet
what are two tertiary structures of protein molecules?
globular and fibrous
which 4 bonds are used for peptide folding?
- hydrogen
- ionic
- disulfide
- hydrophilic/phobic
compare globular vs fibrous proteins
- circular vs strands
- irregular amino acid sequence vs regular
- functional vs structural
- generally soluble vs insoluble
what are some examples of globular proteins?
haemoglobin, enzymes, insulin
what are some examples of fibrous proteins?
collagen, fibrin, actin
protein synthesis vs dna replication - what is the diff?
Protein synthesis makes proteins, while DNA replication makes DNA
what does a nucleotide consist of?
phosphate, deoxyribose sugar and nitrogenous base
name 4 DNA bases and number of carbon rings they have
Adenine
Guanine - Purine - 2
(A-G-POO-TWO)
Cytosine
Thymine - Pyrimidine - 1
what bonds are formed between phosphate and deoxyribose sugar ( in DNA )
phosphodiester bond
How many H bonds between Adenine and Thymine?
2
How many H bonds between Cytosine and Guanine?
3
whats the relationship between A-T and C-G
complementary
what are the steps (+enzymes) used in DNA replication?
- DNA helicase unwinds & breaks H bonds between complementary bases
- free nucleotides match complementary bases into Okazaki fragments
- DNA polymerase adds adjacent nucleotides tgt (5’ to 3’ direction?? CHECK NOTES)
- DNA ligase seals the gaps between nucleotides
what method is used for DNA replication?
semi conservative
bcs new DNA consist of 1 new + 1 old strand
What is the evidence for the semi-conservative replication?
Meselson and Stahl
Replication of Nitrogen using ‘heavy’ isotope 15 N and ‘light’ 14N
1st Gen - each DNA made up of 1 parent + 1 new strand
after replication in 2nd Gen there were 2 layers, one lighter one heavier
what structure is DNA?
double helix
what are the stages of a cell cycle?
G1 - cellular contents replicated
S - replication of DNA
G2 - check for errors
M - mitosis
C - cytokinesis
what are enzymes?
protein that changes rate of chemical reaction without changing itself
4 major factors that influence enzyme RoR
temp
pH
enzyme conc
substrate conc
What is the induced fit hypothesis?
shape of active site changes to fit precisely around the substrate
What are cofactors? + examples?
Helper to enzymes, required to function properly
e.g. coenzymes, inorganic ions and prosthetic groups
What is an inhibitor?
substance that slows RoR
What is a competitive inhibitor?
competes with the substrate for the active site of the enzyme
is competitive inhibitor reversible or no?
reversible
what is a non-competitive inhibitor?
they bind to allosteric sites of enzymes, changing the active site of enzymes, so fewer/no ES complexes formed
what is the change of graph if there are competitive inhibitors?
RoR decreases but plateaus at about the same time
is non-competitive inhibitor reversible or no?
irreversible, permanent change
what is the change of graph if there are non-competitive inhibitors?
RoR slows
plateaus earlier
what is catabolism?
breaking large molecules into smaller ones
e.g. digestion
what is anabolism?
building up smaller molecules to larger ones
e.g. muscle growth
why are carbohydrates vital in humans?
energy source
why are fibres vital in humans?
helps w digestion
why are proteins vital in humans?
muscle growth and repair
found in DNA
why are lipids vital in humans?
energy storage
thermal insulation
used for plasma membrane
why are vitamins and minerals vital in humans?
help w immunity, chemical reactions
why is water vital in humans?
- temp control
- transport substances
- chemical reactions (metabolism)
what does DNA polymerase do?
line up nucleotides and join them via phosphodiester bonds (condensation reaction)
what is the only direction DNA polymerase can travel in?
5’ to 3’
What breaks hydrogen bonds between complementary bases?
DNA helicase
in where is Uracil used instead of Thymine?
(t)RNA
What bond is formed to bind nucleotides together?
phosphodiester bond
What do ribosomes do in protein synthesis?
bind to mRNA, read code 3 bases at a time aka codon
what is the shape of tRNA?
clover leaf shape
what are exons and introns?
exons - coding part of gene
introns - non-coding part of gene
Why do mutations occur?
mutagen exposure in our environment eg UV light
randomly occurs
How does one get sickle cell anaemia?
base substitution (A replaces T) in beta haemoglobin chain
changing shape of haemo.
what is the issue of sickle cell anaemia?
haemoglobin stop carrying oxygen so efficiently, causing blockages in small blood vessels
why are mutations sometimes good?
advantageous mutations allows positive evolution
what are monomers?
single small molecule that can join together and form a polymer
e.g. nucleic acids
What are buffers?
they resist changes to pH
how to test for proteins?
Biuret’s reagent
blue to purple
how to test for fat/lipids?
dissolve in ethanol
emulsion test
there will be emulsion/greasy patch produced in comparison to water
are lipids polar?
NO! generally hydrophobic
what are the 2 types of fatty acids?
saturated and unsaturated
How do 2 monosaccharides join together to form a disaccharide?
Glycosidic bond forming condensation reaction
Compare phospholipids and triglycerides…
Phospholipids are polar
Triglycerides are non-polar
What bonding is present in both secondary and tertiary structures of proteins?
Hydrogen only
Give the meaning of a tertiary structure of a protein (2 marks)
3D shape of protein
Held together by bonds between R groups
What are the steps of translation? (4 marks)
- mRNA attaches to ribosomes
- tRNA attached to specific amino acids
- tRNA anticodon binds to mRNA codon
- peptide bonds form between amino acids
- process involves start/stop codons
What is it meant by secondary structure of protein? 2 marks
Folding of primary structure
Into alpha helix or beta pleated sheet
From formation of hydrogen bonds
Explain how a primary structure of a hormone determines its’ properties. 4 marks
- sequence of amino acids determining tertiary structure
- because determines position of R group bonds
- eg hydrogen, ionic, disulfide
- final structure has to be specific, complementary to receptor molecules
Why are globular proteins soluble in water? (3 marks)
- folded so hydrophilic groups are facing the outside
- exposed R groups are polar
- so can form H bonds with water
- because water is a polar solvent
Which enzyme in DNA replication forms phosphodiester bonds?
DNA polymerase AND ligase
P-P
What are 2 things about calcium pectate?
Found in middle lamallae
Hold Cell walls together
What ions are needed to make amino acids?
Nitrate
What ions are needed to make amino acids?
Nitrate
What ions are needed to make amino acid and DNA?
Nitrate and phosphate ions
how does the dipole nature of water enable muscle layers of worm to push against cavity and change the shape of earthworm? 3 marks
- water is tightly bonded together
- via H bonds
- so they are incompressible
- change body shape since pressure increases, but volume stays the same
what components are found in phospholipids?
glycerol and phosphate in the head
fatty acid in tail
what properties of water result in surface tension? 3 marks
- polar molecules
- can form H bonds
- therefore cohesive
Why does respiration of lipid generate more energy than carbs?
More C-H bonds and H bonds
Does amylose or amylopectin hydrolyse quicker? Why?
Amylopectin because it is branched with 1,4 and 1,6-glycosidic bonds!
What is the relationship between sweating (heat loss) and dipole nature of water?
Dipole is H is positively charged, forming weak H bonds between molecules
Lots of energy needed to break this bond
Water evaporate, taking heat w it )(high latent heat evaporation)
What happens when you freeze water?
Expands
Lots of H bonds
Explain how a structure of cellulose is adapted for its function in cell walls. (3 marks)
- straight chain of molecules
- held tgt by H bonds
- prevent cell bursting
- polar, so allows water to diffuse through
what are the steps of translation
(+ release)
- mRNA leaves via nuclear pores
- attach to ribosomes (on rER)
- codon pair with anticodons on tRNA + brings amino acid
- peptide bonds formed between amino acids
(- enter Golgi to modify - travel in vesicles
- exocytosis)
what are ribosomes made of?
ribosomal RNA and protein
what is the role of tRNA in protein synthesis?
during translation, it brings a specific amino acid to the ribosome by binding its anticodon to mRNA codon
What is the role of a ribosome in protein synthesis?
holds mRNA-tRNA complexes tgt
- so condensation reactions can form between amino acids
- peptide bonds can form between carboxylic acid and amine groups
what is the difference in structures of mRNA and tRNA?
mRNA / tRNA
carry info from genes to produce polypeptides/ transport amino acids to ribosomes
linear / clover shape
larger + size varies / smaller, same size
no amino acid binding site / yes
has codons / has anticodon
what are the differences between DNA replication and transcription? (there are 5)
DNA rep / transcription
involves DNA polymerase / RNA polymerase
DNA nucleotides / RNA nucleotides
semi conservative / is not
2 template strands / 1
uses double stranded molecule / single
Describe the structure of globular proteins. (3 marks)
- 3D spherical shape
- hydrophilic R groups on the outside
- hydrophobic on the inside
- ionic / hydrogen / disulfide
Name the covalent bond formed between two polypeptide chains.
Disulfide
Describe how a molecule of mRNA is formed during transcription. (4 marks)
- DNA unwinds
- RNA mononucleotides line up and attach to template
- between complementary bases
- form phosphodiester bonds
- condensation reaction
- using RNA polymerase, DNA helicase, DNA ligase
- mRNA detaches from DNA
Explain how a poly protein molecule is converted into ten separate molecules. (2 marks)
- hydrolysis of peptide bonds
- by protease
Explain why the non-competitive inhibitor has decreased the maximum rate of reaction. (2 marks)
- due to fewer enzyme substrate complexes formed
- as some active sites are no longer complementary
Give 3 differences between the structure of collagen and haemoglobin. (3 marks)
collagen / haemoglobin
fibrous / globular
3 polypeptides / 4
little to no 3° structure / has 4°
doesn’t / has haem group
hydrophobic R group on surface / opposite, hydrophilic
What is the role of mRNA in protein synthesis? (2 marks)
- is a copy of antisense
- made up of codons
- used in translation
- binds to ribosomes
What is the role of tRNA in protein synthesis? (2 marks)
- transports specific amino acid
- binds to mRNA
- bring amino acids together
Act D inhibits transcription.
Explain why pollen tubes could still grow in the presence of act D. (2 marks)
- some mRNA in pollen grain
- so some translation / protein synthesis can take place
Describe how monomers are bonded to a polypeptide chain during the synthesis of actin. (2 marks)
Peptide bonds formed
Between amino and carboxyl group
By condensation reaction
What happens in the rough endoplasmic reticulum?
Protein synthesis
Explain how the properties of starch make it suitable as an energy store in cell. (2 marks)
- branched
- so easily hydrolysed to release ATP for respiration
Or - tightly packed
- a lot can be stored in a small space
Or - insoluble
- so does not have osmotic effect