Module 2.2 Biological Molecules Flashcards
Calcium (Ca2+)
- Increases rigidity of bones, teeth and cartilage
- Component of the exoskeleton of crustaceans
- Clotting blood and muscle contractions
- Activator for enzymes e.g. lipase, ATPase and cholinesterase
- Stimulates muscle contractions
- Regulates transmission of nerve impulses
- Regulates permeability of cell membranes
- Important for cell wall development (in plants) and formation of middle lamellar between cell walls
Sodium (Na+)
- Helps regulate osmotic pressure
- Helps control water levels in body fluid
- Helps maintaining pH
- Affects absorption of carbohydrates in intestine
- Affects absorption of water in the kidney
- Contributes to nervous transmission and muscle contractions
- Present in vacuole which helps maintain turgidity
Potassium (K+)
- Helps control water levels in body fluid
- Helps maintain pH
- Assists active transport
- Involved in synthesis of glycogen and protein, and breakdown of glucose
- Helps keep leaves and flowers healthy
- Involved w nervous transmission and muscle contraction
- Present in vacuoles to help maintain turgidity
Hydrogen (H+)
- Involved in photosynthesis
- Involved in respiration
- Involved in transport of oxygen and carbon dioxide in the blood
- Involved in regulation of blood pH
Ammonium (NH4+)
- Component of amino acids, proteins, vitamins and chlorophyll
- Essential component of nuclei acids
- Involved in maintaining pH in the body
- Component in the nitrogen cycle
Nitrate (NO3-)
- Component of amino acids, proteins, vitamins and chlorophyll
- Essential component of nucleic acids
- Some hormones are made out of proteins which contain nitrogen e.g. insulin
- Component in nitrogen cycle
Hydrogencarbonate (HCO3-)
- Regulates blood pH
- Involved in transport of carbon dioxide in and out of the blood
Hydroxide (OH-)
-Regulates blood pH
Chloride (Cl-)
- Helps production of urine in the kidneys and maintaining water balance
- Involved in transport of carbon dioxide in and out of the blood
- Regulates affinity of haemoglobin to oxygen through allosteric effects on the haemoglobin molecule
- Involved in blood pH regulation
- Used to produce HCl in the stomach
Phosphate (PO4 3-)
- Increases rigidity of bones, teeth and cartilage
- Component of the exoskeleton of crustaceans
- Component of phospholipids, ATP, nuclei acids + several important enzymes
- Involved in blood pH regulation
- Helps roots grow in plants
Phospholipids
- Composed of glycerol and a phosphate head w 2 fatty acid tails
- Soluble head and insoluble tail in water
- Part hydrophilic, part hydrophobic
- Make up cell surface membranes
- Made up of C, H and O
- Fatty acid chains joined to glycerol w ester bonds
- Phosphate group + carbohydrate = glycolipid (used for cell signalling)
Triglycerides
- Composed of a glycerol molecule and 3 fatty acid tails
- Fatty acid chains joined to glycerol w ester bonds in a condensation reaction
- The ester bonds form at 3 OH groups on glycerol - 3 water molecules released
- Made up of C, H and O
- Hydrophobic molecule (evenly distributed charge)
- Insoluble in water (means doesn’t effect water potential of cells)
- Used as energy stores by hydrolysing ester bonds breaking down CO2 and H2O to release energy
Cholesterol
- Made up of C, H and O
- Make up cell surface membranes
- Hydrophobic molecule (evenly distributed charge)
- Insoluble in water
- Made up of a 4 carbon ring structure
- Vital to organisms - made by many cells
- Helps regulate fluidity
- Can build up causing heart disease and can clog arteries etc. It can be deposited in blood vessels causing atherosclerosis
- Produce steroid hormones e.g testosterone and oestrogen which can pass straight through membranes to target cells
Lipids
- Solid lipid = fat
- Liquid lipid = oil
- Lipids dissolve in organic solvents e.g. alcohol but not in water
Roles of lipids in organisms
- Energy source
- Energy store (lipids stored in adipose cells)
- Phospholipid bilayer
- Insulation
- Myelin sheath of neurones - electrical insulation
- Steroid hormones
- Waxy cuticle of leaves
Glycerol
- C3H8O3
- Glycerol and fatty acids are both found in 2 major groups of lipids - glycerolipids (energy store/source) and glycerophospholipids
Fatty acids
- All have an acid group at one end joined to a hydrocarbon chain (2-20 carbons long)
- Fatty acids are used to make up lipids
- An essential fatty acid is one that we can’t assemble ourselves
- 3 types - palmitic, stearic and oleic
Saturated fats
- No double bonds in the hydrocarbon chain
- Raise cholesterol
Monounsaturated fats
One C=C bond
Polyunsaturated fats
2+ C=C bonds
Are unsaturated fats more or less permeable?
More permeable
What bond joins glycerol to a fatty acid?
An ester bond
Haemoglobin
- Conjugated protein
- 4 polypeptides
- 2 alpha, 2 beta
- Prosthetic haem groups have an affinity for oxygen (each one can attract 1 oxygen molecule)
- Fe2+ ions
- Function - to carry oxygen from the lungs to tissues for aerobic respiration
- Globular - for metabolic reactions
- Primary structure - amino acids
- Secondary structure - mostly alpha helices
- Tertiary structure - alpha chains and beta chains
- Quaternary structure - 2 alpha and 2 beta chains
Collagen
- Structural protein
- Fibrous
- Quaternary structure - 3 polypeptide chains tightly wound around each other
- H bonds give strength
- Every 3rd amino acid on each peptide chain is glycine - small - tiny R group - allows close packing
- Covalent bonds across peptide chains (cross linkage) helps to form a collagen fibril - staggered cross linkage adds strength
- Many fibrils make up a fibre
Functions of collagen (protein)
- Lines arteriole walls - prevents bursting at high pressure
- Tendons allow movement
- Bones - collagen reinforced to make them hard
- Cartilage and connective tissue
- Used in cosmetic treatments
Properties of collagen (protein)
- High tensile strength
- NOT elastic
- Flexible
- Insoluble
Comparing collagen and haemoglobin (both proteins)
Collagen:
- Fibrous
- Insoluble
- No prosthetic group
- Structural
Haemoglobin:
- Globular
- Soluble
- Prosthetic haem group
- For transporting oxygen
Secondary structure of proteins
- As polypeptides form, to stabilise them, they are coiled (a-helix) or pleated (ß-pleated sheets)
- These are held in place by H bonds
Why is the secondary structure of proteins dependant on the primary structure?
- Primary structure = unique sequence of amino acids in the protein
- Different proteins have different combinations of amino acids which each have different R groups and different properties
- Different proteins have H bonds formed in different places in the pleats/coils meaning some are more or less pleated/coiled than others
Tertiary structure
- 3D shape
- When coils/sheets are folded into their final shape
- Tertiary structure is 🔑 to the protein’s function
Tertiary structure - disulfide bonds
- The amino acid cysteine contains sulfur
- Where 2 cysteines are found close to each other, a covalent bond forms
Tertiary structure - ionic bonds
- The strongest 💪🏻
- R groups sometimes carry a charge (either +ve or -ve)
- When oppositely charged amino acidsare found close to each other, an ionic bond forms
Tertiary structure - Hydrogen bonds
-Form when slightly positively charged groups are found close to slightly negatively charged groups
Tertiary structure - Hydrophilic and hydrophobic interactions
- In a water-based environment, hydrophobic amino acids are most stable if they are held together w water excluded
- Hydrophilic amino acids tend to be found on the outside in globular proteins w hydrophobic amino acids in the centre
Globular proteins
- Ball shaped
- Soluble - the hydrophobic groups are found in the centre of the ball w hydrophilic on the outside
- For metabolic reactions
- E.g. enzymes, plasma proteins, antibodies, haemoglobin
Fibrous proteins
- Looks like fibres
- Insoluble
- Structural
- E.g. collagen and keratin
Denaturation
- Heat energy gives molecules KE
- KE makes molecules vibrate and can break bonds
- Heating proteins can break bonds in the tertiary structure
- Once the tertiary structure is lost, the protein is no longer properly functional
Which bond joins a glucose and a fructose unit to make sucrose?
1,4 glycosidic
General formula for carbohydrates
Cx(H2O)y
Elements that carbohydrates contain
C, H and O
3 types of sugar
- Hexose
- Pentose (in DNA - ribose)
- Triose
Maltose
a + a
Lactose
a + ß galactose
Sucrose
a + fructose
Cellubiose
ß + ß
Amylose
a + a + a and so on…
Cellulose
ß + ß + ß etc
2 sugars are joined by a what bond?
Glycosidic bond
Pentose
Ribose (in mRNA)
Deoxyribose (in DNA)
Polysaccharides you need to know
Amylose Cellulose Amylopectin Glycogen Starch (amylose + amylopectin)
Amylose
1,4 glycosidic bonds
No branches
a-glucose
Spiralled
Amylopectin
1,4 glycosidic bonds and 1,6 glycosidic bonds
Branched
Proteases
- Enzymes that break down peptide bonds
- E.g. pepsin in the stomach
- Used in digestion and to break down hormones so that their effect isn’t constant
Elastin
- Protein
- Coiled and cross linked for strength
- Found in skin, the lungs, the bladder and blood vessels
Pepsin
- Single polypeptide chain
- 327 amino acids
- Symmetrical tertiary structure
- Mainly acidic R groups (stable)
Insulin
- 2 polypeptide chains
- a-chain begins w alpha helicies
- b-chain ends w beta
- Tertiary structure held together by disulphide links
Transcription
- DNA helicase unwinds the double helix of DNA
- Free nucleotides attach by comp. base pairing (RNA polymerase joins the nucleotides together)
- mRNA moves away
- The 2 strands of DNA are zipped back together
- mRNA leaves via a nuclear pore and enters the cytoplasm
Translation
- mRNA enters ribosome
- tRNA enters the ribosome and brings a specific amino acid that corresponds to the codon on the mRNA strand
- The tRNA anti-codon matches the mRNA codon (complimentary)
- The amino acids join by peptide bonds
- Polypeptide chain made
Functions of proteins
- Structural e.g. muscle or bones
- Carrier/channel proteins
- All enzymes
- Many hormones
- Antibodies
Basic structure of amino acids
- Amine group
- Acid group
- R group
Explain why glycogen is referred to as an energy store
- Can be hydrolysed to release a-glucose in aerobic respiration
- Polysaccharide of glucose
- Branched
Name the 2 parts of starch
Amylose
Amylopectin
Describe the structure of a cellulose microfibril
- ß-glucose flipped 180*
- H bonds between chains
What bonds hold polysaccharides together?
Glycosidic
Formula of pentose sugars
C5H10O5
a and ß glucose have different shapes but the same formula - what term is used to describe this?
Isomer
3 things that happen in a condensation reaction
Larger molecules form
Covalent bonds form
Water used
How do a glucose and b glucose differ?
a : OH below the plane of the ring
b : OH above the plane of the ring
Peptidoglycan (murein)
Bacteria cell walls
Chitin
- Exoskeleton of insects
- Surgical thread (strong and flexible)
Starch
- Found in plants
- Polysaccharide of a-glucose
- Mix of unbranched, coiled amylose and branched amylopectin
- Insoluble
- Forms grains
- Energy storage
Glycogen
- In animals e.g. liver and muscle cells
- Polysaccharide of a-glucose
- 1,4 and 1,6 glycosidic bonds
- Insoluble
- Forms granules
- V branched
- Shorter chains
- Energy storage
Cellulose
- In plants - cell wall
- ß-glucose
- Insoluble
- V strong
- Unbranched, long, straight
- 1,4 glycosidic bonds
- Structural
- Polysaccharide formed in condensation reactions
- Every ß-glucose is flipped 180* from the last to form a glycosidic bond
Cell walls
- H bonds form between OH groups of neighbouring chains
- Cellulose chains become cross linked to form a microfibril
- Microfibrils are held together by H bonds to form macrofibrils
Macrofibrils
- Embedded in pectin (polysaccharide)
- H bonds
- Criss cross structure allows water through
- Macrofibrils v strong = turgid when too much water
Aerobic respiration
C6H12O6 + 6O2 –> 6CO2 + 6H2O
Maltose and amylose
- a-glucose + a-glucose = maltose
- The same reaction thousands of times forms amylose - held together by 1,4 glycosidic bonds - spring shape - H bonds - unbranched - compact - insoluble
Starch
- Iodine gets caught in the spring like shape of amylose (orange –>blue/black)
- Made up of amylose and amylopectin
- Amylopectin - branches of a-glucose w 1,4 glycosidic bonds joined at the ends to another chain w 1,6 glycosidic bonds
- Store of energy - broken down into a-glucose for resp in hydrolysis reactions
Glycogen
- Polysaccharide
- a-glucose
- Hydrolysis reactions are used to break it down to release glucose for respiration
Comparing glycogen and starch
- Glycogen - 1,4, shorter, more branched, more compact
- Both insoluble
- Both store glucose in chains
Carbohydrates
C,H, O
Monomer- monosaccharides e.g. glucose
Polymer- polysaccharides e.g. starch
Proteins
C, H, O, N and S
Monomer- amino acids
Polymer- polypeptides (proteins)
Nucleic acids
C, H, O, N and P
Monomer- nucleotides
Polymer- DNA and RNA
Condensation reactions
- Link monomers
- Covalent bond forms
- Larger molecules formed
- Water released
- OH group needed
Hydrolysis reactions
- Covalent bonds broken
- Smaller molecules formed
- Water used
H bonds
- When a slightly positive and slightly negative charge come close
- Weak
- Easily broken
Monosaccharides
- Contain 3-6 carbons
- Small
- Soluble in water
- Sweet tasting
- Form crystals
