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P1 – Cell ChemistryBiomacromolecules
Key knowledgeThe nature and importance of biomacromolecules in the chemistry of the cell
Synthesis of biomacromolecules through the condensation reaction
Structure and function of lipids Structure and function of DNA and RNA, their
monomers and complementary base pairs The structure and functional diversity of proteins, their
levels of organisation and the nature of the proteome.
Organic vs. Inorganic Organic: a compound which has the
elements carbon and hydrogen. The atoms of carbon and hydrogen are bonded together within that molecule
eg: glucose.
Inorganic: a compound where carbon and hydrogen aren’t bonded together eg: water, carbon dioxide etc.
Different kinds of bonding
Different kinds of bonding
Properties of Water:
Classes of MACROMOLECULES
Macromolecule Subunit
1. PROTEINS Amino Acid
2. NUCLEIC ACIDS Nucleotide 3. complex CARBOHYDRATES Simple
sugar (monosaccharide) 4. LIPIDS Triglyceride and
chains of fatty acids
Class of biomacromolecule
Sub units / monomers
Cellular functions
Lipids (hydrophobic)Lipids are not polymers
Fatty acids & glycerolEster Bonds between subunits
Energy store, component of cell membranes, signalling molecules
Complex carbohydratesInsoluble PolysaccharidesStarch, glycogen, cellulose, chitin
GlucoseGlycosidic bond between monomers
Energy store, structural components of cells
Nucleic AcidsPolynucleotidesDNA, RNA (various forms)
NucleotidePhosphodiester bond between monomers
Information molecules that constitute an organisms genetic material
ProteinsPolypeptides
Amino AcidPeptide bond between monomers
Proteins have many diverse roles. They control and regulate cellular processes, assist in transport of substances, act as receptors and as structural components
Synthesis of biomacromolecules Autotrophs – synthesise their own
organic requirements through chemical processes other than photosynthesis. Called chemosynthetic autotrophs.
Heterotrophs – have to synthesise their own biomacromolecules from existing organic compounds. E.g. we need to take in lots of organic compounds from food and then break them into smaller, simpler substances.
Biomacromolecules Mono (one) mer (unit) Poly (many) mer (units)
Monomers join up together to create a polymer.
The process by which this happens is known as condensation polymerisation.
Monomer ------------------- Monomer -------------------- Monomer
Building a polymer
As the polymer is built a H from one monomer joins with the OH of the next monomer
releasing a water molecule.
Biomacromolecules
Lipids are a macromolecule, however, they aren’t polymers.Not made up of similar subunits. They are made up of fatty acids and glycerol.
Monomer PolymerAmino Acid ProteinMonosaccharide Polysaccharide/
CarbohydrateNucleotide Nucleic Acid
Glycerol A water molecule is condensed out when the acid group reacts with the alcohol group. An ester bond is formed that links the two molecules together
Fatty acid Hydrocarbon chain
Fatty acid Hydrocarbon chain
Fatty acid Hydrocarbon chain
Glycerol has three OH groups. Hence each glycerol molecule can only accept a total of three fatty acids. There is no repetitive linkage: so lipids are NOT polymers
Carbohydrates/Polysaccharides Formula: nCH2O e.g. Glucose C6H12O6
Subunit: monosaccharide Monosaccharide + monosaccharide = disaccharide Monosaccharide + disaccharide = polysaccharide
Monosaccharide = fructose, glucose, hexose Disaccharide= sucrose, lactose, maltose Polysaccharide= glycogen, cellulose, chitin
Can join with other atoms or groups eg: glycoproteins (carbohydrate and protein)
GlucoseGlucose C6H12O6
Carbohydrate ratio: 1:2:1
In solution glucose forms a ring structure as shown
*Note the number of OH groups in each molecule. These OH groups make glucose highly soluble in water
Monosaccharide (simple sugar)
Eg: Maltose (grains), Sucrose (table sugar, sugar cane), Lactose (milk)
Disaccharide (sucrose)
Eg: Maltose (grains), Sucrose (table sugar, sugar cane), Lactose (milk)
Polysaccharide (cellulose)
Eg: Cellulose (structural component in plant cells most common organic chemical on Earth), Starch (plants – energy storage), Glycogen (animals – energy storage in muscles and liver), Chitin (exoskeleton of insects and crustaceans, cell walls of fungi).
Lipids CHO (N and P, much less O than carbohydrates)Subunit: fatty acid and glycerol (therefore lipids are not polymers) make
triglycerides
Synthesised by Smooth Endoplasmic Reticulum
Generally hydrophobic, but some lipids possess a polar end, making the whole molecule partially polar (hydrophilic) and some lipids are both - amphipathic.
Use: Energy storage (stores 2 times more energy than carbohydrates) Structural component Transmission of signals
Saturated vs. Unsaturated
Animal Plant
At least one double bond between carbon atoms
Lipid Types: fats, oils, terpenes, waxes Phospholipid – phosphate is
hydrophilic, fatty acid tail is hydrophobic.
Cholesterol – structural, prevents solidification of membrane at cold temps. Belongs to steroid group. Glycolipids – communication,project from membranes and arespecialised to detect and bindwith signalling molecules.
Lipids in membranesPhospholipids, another kind of fat, have two fatty acids attached to a glycerol molecule. They also have a phosphate group attached to the glycerol molecule
The phosphate ‘head’ of a phospholipid molecule is attracted to water (hydrophilic). The fatty acid tails extend away from water (hydrophobic). Because of these properties, the molecules align so that they develop double-layered sheets, which are the cell membranes found in every living cell.
Lipid functionENERGY Lipids have a high proportion of Hydrogen atoms relative to Oxygen atoms and yield more energy
than the same mass of carbohydrates. Excess triglycerides are stored as adipose tissue.
THERMAL INSULATION Triglycerides conduct heat very slowly. Marine animals often have a thick layer of subcutaneous
fat (located under the skin) called blubber which keeps metabolic heat inside the body.
ELECTRICAL INSULATION The axon of a nerve cell is surrounded by a fatty material called myelin. It helps maintain nerve
conductivity by preventing signal loss. It also increases speed of nervous conduction by increasing the diameter of the axon.
HOMEOSTASIS Steroid hormones have a lipid component e.g. estrogen and testosterone.
BUOYANCY Triglycerides are less dense than water. Marine organisms with a high lipid content are highly
buoyant.
Cell membrane
Nucleic Acid CHNOP Subunit: Nucleotide Made of 3 parts: phosphate, attached to a
sugar, which is attached to a nitrogenous base.
Codes for production of proteins – genetic material
Structural & Chemical Differences between DNA & RNA
RNA: Nitrogenous base Thymine (T) is replaced with Uracil (U)
DNA sugar (deoxyribose) = one less oxygen atom
DNA & RNADNA RNA
Double Stranded Single Stranded
Deoxyribose Sugar Ribose Sugar
Found in nucleus Found in nucleus, cytoplasm and ribosomes
Nitrogenous bases: Adenine, Guanine, Cytosine and THYMINE
Nitrogenous bases: Adenine, Guanine, Cytosine and URACIL
Linear (eukaryotes) or circular (prokaryotes)
3 types: mRNA, tRNA, rRNA
Involved in Transcription (protein synthesis)
Involved in Transcription and Translation (protein synthesis)
Base PairingChromosomes are made up of genes that are made up of DNA.
DNA is double stranded.Bases undergo complementary base pairing.
Adenine-Thymine and Guanine-Cytosine
RNA doesn’t have T, it has U instead: A-U
DNA: G T C C T A T T A C G T A GDNA: C A G G A T A A T G C A T CRNA: G U C C U A U U A C G U A C
Phosphodiester bond
RNA Important in protein synthesis
Takes the information from the DNA strand and makes proteins – Gene expression
Information from genes on DNA are transferred to messenger RNA (mRNA)
Ribosomes read mRNA, one triple (codon) at a time and with the help of transfer RNA (tRNA) an amino acid chain is formed.
RNA is necessary to make a protein from the DNA instructions that can’t leave the nucleus.
Ribosomal RNA is found in the ribosomes (rRNA)
Proteins
Protein are large molecules made of amino acidsEach amino acid has one part of it’s molecule different from other amino acids.
R is a variable compound, it can be hydrophobic or hydrophilic resulting in some proteins being soluble while others are not.
Peptide bond –releases a water molecule
Proteins CHNOPS eg: C708H1130N180O224S4
Subunit: amino acid (20 used to make proteins and are obtained through diet)
Examples and use: Enzymes – speed up cellular reactions Haemoglobin – transport oxygen Insulin – lower glucose levels Antibodies – immune response Keratin and Collagen – structure – provides
strength and support Actin and myosin - muscle movement.
Function of Proteins
Amino Acids – subunit of a proteinAll have same basic structureA central carbon atom attached to a hydrogen atomA carboxyl acid group (COOH)An amine group (NH2)R group
The R group differentiates one amino acid from anotherR group can be polar or charged (hydrophilic on the outside of protein molecule) or non polar (hydrophobic – inside of protein molecule)
Amino Acids – subunit of a protein
Type
*Non Polar =hydrophobic regions*Usually inside protein molecule away from aqueous external environment
R GroupType
*Polar = hydrophilic regions*Usually on surface of protein molecule because they like aqueous
external environment
R Group
Amino Acids ProteinsAdditional bonding: covalent, ionic, hydrogen and disulphide bridges are used to create 3D shape.
Amino Acids (AA) Proteins 4 Levels from Amino Acid to Protein
Primary Structure (the order of AA in the polypeptides) DNA determines sequence of AA in the
polypeptide (protein). AA bond together by condensation
polymerisation and form peptide bonds between each AA
Amino Acids (AA) Proteins Secondary Structure
Hydrogen bonding causes coiling & folding Tight coils = α-helices Folding forms = β-sheets Coils & Sheets connected by random loops. Random Loops remain unchanged. β-sheets & random loops = basis of active site in enzymes
Amino Acids (AA) Proteins Tertiary Structure - (Determines the function of the protein – biological functionality.)
“Like attracts like” Hydrophilic R groups attract hydrophilic R groups Hydrophobic R groups attract other hydrophobic R groups. This causes further folding and coiling into the proteins
functional shape.
R group interactions ionic bonds, hydrogen bonds & disulfide bridges between adjacent cysteine amino acids.
Protein molecules with the same AA sequence will fold into the same shape. One AA change will change the shape of the protein & possibly its function.
Amino Acids (AA) Proteins Quaternary Structure
Some large protein structures can consist of 2 or more polypeptide chains.
Chains are held together by hydrogen, ionic and covalent bond.
Makes their shape and function more complex.
haemoglobin
Protein channel
Fibrous or GlobularFibrous Proteins Basic tertiary structure. Long parallel
polypeptide chains. Cross linkages at
intervals forming long fibres or sheets.
Usually insoluble. Many have structural
roles. E.g. keratin in hair and
the outer layer of skin, collagen (a connective tissue).
Globular Proteins Have complex tertiary
and sometimes quaternary structures.
Folded into spherical (globular) shapes.
Usually soluble as hydrophobic side chains in centre of structure.
Roles in metabolic reactions.
E.g. enzymes, haemoglobin in blood.
Changing the nature of proteins Proteins are functional due to their 3D
conformation. This CAN be compromised.
High Temperatures Strong Salty Solutions Acidic or Alkaline Conditions
Such things denature or change the shape of the protein
Minor changes may be reversed, major changes cannot.
Important: Low temperatures can slow protein activity, but does not alter shape or denature the protein.
Proteome This is the structure and properties of all the
proteins produced by an organisms genetic material (genome).
Proteomics is the study of the structure and function of proteins, including the way they work and interact with each other inside cells.
It is important to study proteins together as they interact with one another.
Protein Synthesis DNA codes for proteins.
RNA is needed to copy the DNA sequence in order to get proteins made.
Two types of RNA needed for protein synthesis: mRNA and tRNA
Protein Synthesis occurs in two stages:
1. Transcription: Occurs in the nucleus and involves DNA and mRNA
2. Translation: Occurs in the cytoplasm and involves mRNA, ribosomes, tRNA and amino acids
Questions
Complete the following Questions in your workbook
Heinemann Biology 2 Textbook:Questions 14 – 17a, 18, 19. Page 19