B1.1 Carbohydrates and Lipids - Page-by-Page Notes
Page 1
Topic: B1.1 Carbohydrates and lipids (Core only)
Guiding questions:
In what ways do variations in form allow diversity of function in carbohydrates and lipids?
How do carbohydrates and lipids compare as energy storage compounds?
Linking questions:
How can compounds synthesized by living organisms accumulate and become carbon sinks?
What are the roles of oxidation and reduction in biological systems?
Key idea: Carbohydrates and lipids exhibit a wide variety of structures that underpin diverse biological functions, with contrasting roles in energy storage and insulation, and with important implications for metabolism and cellular architecture.
Page 2
Theme and Level of Organisation:
Theme B: Form and function – Adaptations are forms that correspond to function. These adaptations persist from generation to generation because they increase the chances of survival.
Level of Organisation: Molecules
Key idea: Focus on molecular structures that enable function in living systems, linking form to biological role.
Page 3
Content Statement and Guidance (1 of 2) SL & HL
B1.1.01 Chemical properties of a carbon atom allowing for the formation of diverse compounds upon which life is based
Students should understand the nature of a covalent bond.
Carbon can form up to four single bonds or a combination of single and double bonds with other carbon atoms or non-metal atoms.
Include examples of molecules with branched or unbranched chains and single or multiple rings.
B1.1.02 Production of macromolecules by condensation reactions that link monomers to form a polymer
Students should be familiar with examples of polysaccharides, polypeptides, and nucleic acids.
B1.1.03 Digestion of polymers into monomers by hydrolysis reactions
Water molecules are split to provide -H and -OH groups that are incorporated to produce monomers (hence the term hydrolysis).
B1.1.04 Form and function of monosaccharides
Recognize pentoses and hexoses as monosaccharides from ring diagrams.
Use glucose as an example: link between monosaccharide properties (solubility, transportability, chemical stability) and energy yield from oxidation.
B1.1.05 Polysaccharides as energy storage compounds
Include starch in plants and glycogen in animals.
Emphasize coiling and branching during polymerization, relative insolubility due to large size, and ease of adding/removing α-glucose units by condensation and hydrolysis to build/mobilize energy stores.
B1.1.06 Structure of cellulose related to its function as a structural polysaccharide in plants
Include alternating orientation of β-glucose monomers, giving straight chains that group in bundles cross-linked by hydrogen bonds.
Key concepts: Covalent bonding and carbon's tetravalence; polymerization via condensation; hydrolysis; monosaccharide structure; energy storage (starch, glycogen); structural polysaccharides (cellulose).
Page 4
Content Statement and Guidance (2 of 2) SL & HL
B1.1.07 Role of glycoproteins in cell–cell recognition
Include ABO antigens as an example.
B1.1.08 Hydrophobic properties of lipids
Lipids are substances that dissolve in non-polar solvents but are sparingly soluble in water.
Lipids include fats, oils, waxes and steroids.
B1.1.09 Formation of triglycerides and phospholipids by condensation reactions
One glycerol molecule can link to three fatty acids (triglyceride) or to two fatty acids and one phosphate group (phospholipid).
B1.1.10 Difference between saturated, monounsaturated and polyunsaturated fatty acids
Define: number of C=C double bonds; effect on melting point.
Relate to prevalence in oils/fats used for energy storage in plants and endotherms.
B1.1.11 Triglycerides in adipose tissues for energy storage and thermal insulation
Properties make triglycerides suited to long-term energy storage.
Relate triglycerides to thermal insulation in body temperature and habitat.
B1.1.12 Formation of phospholipid bilayers as a consequence of hydrophobic and hydrophilic regions
Use the term “amphipathic.”
B1.1.13 Ability of non-polar steroids to pass through the phospholipid bilayer
Include oestradiol and testosterone as examples.
Students should identify compounds as steroids from molecular diagrams.
Key implications: Glycoprotein-mediated recognition; lipid properties driving membrane structure; triglycerides vs phospholipids; saturation, branching, and structural features affecting function; steroid permeability and signaling.
Page 5
B1.1.01 NOS: Standards of science knowledge
Students should understand that scientific conventions are based on international agreement.
SI metric unit prefixes include “kilo,” “centi,” “milli,” “micro,” and “nano.”
Note: Emphasis on international standardization of units to enable consistent communication of measurements.
Page 6
Application of Skills
This page denotes an application-focused section (page number only).
Key idea: Apply understanding of structure–function relationships in carbohydrates and lipids to real-world contexts and problems.
Page 7
SL & HL B1.1.01 Chemical properties of a carbon atom (repeated emphasis)
Reiterate: carbon’s covalent bonding capabilities and tetravalence.
Include example of carbon forming branched/unbranched chains and rings.
Some terms to know (glossary starter):
Chemical ELEMENT: pure substance with one type of atom (distinguished by atomic number).
ATOM: basic unit; nucleus with protons and neutrons; electron cloud.
ION: atom with unequal numbers of electrons and protons; Cations (+) and Anions (-).
IONIC BOND: attraction between oppositely charged ions.
MOLECULE: two or more atoms joined by covalent bonds.
COVALENT BOND: sharing electron pairs between atoms.
Basic chemistry reminder: the key ideas of elements, atoms, ions, and bonds underpin the biological macromolecules discussed later.
Page 8
Structure of the Atom (illustrative content)
Helium atom example: nucleus with protons and neutrons; electron cloud distribution.
The atomic number gives the number of protons/electrons.
Mass of an element derives from proton and neutron masses.
1 mole of atoms weighs the atomic mass in grams.
Note: This page provides foundational chemistry context for understanding elemental composition of biological molecules.
Page 9
SI Units (Base quantities)
Seven base quantities and their units:
Length — symbol: m
Mass — symbol: kg
Time — symbol: s
Electric current — symbol: A
Temperature — symbol: K
Amount of substance — symbol: mol
Luminous intensity — symbol: cd
Rationale: Standardized units enable clear communication in science.
Page 10
SI Prefixes
Prefixes and factors (applied to base units) to handle large/small values:
yotta (Y) 10^24, zetta (Z) 10^21, exa (E) 10^18, peta (P) 10^15, tera (T) 10^12, giga (G) 10^9, mega (M) 10^6, kilo (k) 10^3, hecto (h) 10^2, deka (da) 10^1
deci (d) 10^-1, centi (c) 10^-2, milli (m) 10^-3, micro (µ) 10^-6, nano (n) 10^-9, pico (p) 10^-12, femto (f) 10^-15, atto (a) 10^-18, zepto (z) 10^-21, yocto (y) 10^-24
Practical note: Prefixes help avoid unwieldy numbers in scientific communication.
Page 11
B1.1.01 Chemical properties of a carbon atom (elemental overview)
Bulk elements – 11; Trace elements – 15; Other – 6; Life is built from a small subset of elements.
Page contains a breakdown of element counts in living systems and emphasizes carbon as a central element in organic chemistry.
Page 12
Elemental abundance visualizations
Three graphs show common elements by mass in:
Earth’s crust
Seawater
A living organism (human)
Key takeaway: Organisms contain similar C and N profiles to seawater but differ from crust, supporting the idea that life originated in water.
Page 13
Why is Carbon important for life?
Atoms gain favourable energy status by filling the outer electron shell.
Carbon has 4 valence electrons; it needs 4 more electrons to fill the shell.
It achieves this by sharing valence electrons with other atoms, forming covalent bonds.
Carbon is the basis for molecular diversity in life.
Chemical facts:
Symbol: C; Atomic number: 6; 6 protons in nucleus; 2 electrons in first shell; 4 in second shell; Valency = 4.
Page 14
Carbon’s tetravalence and basic organic structures
Methane (CH4) as the simplest organic molecule: central carbon forms four covalent bonds with hydrogen atoms.
Structural diagrams often show carbon at the center with lines to other atoms representing covalent bonds.
Key idea: Carbon can form long chains by sharing electrons with other carbon atoms; other electrons remain available to bond with other elements or carbon.
Page 15
Carbon–carbon bonding and multiple covalent bonds
Carbon can form single bonds (C–C) and share electrons to form double bonds (C=C).
Example: carbon–carbon–oxygen double bond (C=C=O style illustration) and carbon–carbon double bonds.
Carbon can form rings, enabling cyclic organic compounds.
Highlight term: carbon–carbon bond.
Page 16
Carbon can form rings and multiple bonds
Carbon can form rings by linking to other carbon atoms, creating cyclic structures.
Double bonds (e.g., C=C) increase structural variety and reactivity.
Visual: Rings and carbon–carbon bonding expand the diversity of organic molecules.
Page 17
The chemical nature of carbon enables molecular diversity
The carbon atom’s properties underpin the almost unlimited diversity of organic molecules that constitute living matter.
Page 18
Functional groups
Beyond C–C and C–H bonds, certain recurring groupings (functional groups) govern characteristic chemical reactions.
Functional groups participate in reactions in a similar way regardless of the molecule’s size.
Example: Methyl group – CH3 (one functional group illustration).
Key concept: Functional groups confer specific chemical behavior to organic molecules and thus influence metabolism and bioactivity.
Page 19
Condensation and hydrolysis (B1.1.02, B1.1.03)
Macromolecules are built from repeating units called MONOMERS.
Condensation reactions link monomers to form dimers, oligomers, and polymers, releasing water: Monomer ⇌ Dimer ⇌ Oligomer ⇌ Polymer with condensation producing water as a byproduct.
Hydrolysis reverses this process by adding water to break bonds and release monomers.
Macromolecules are formed by repeated condensation (polymerization).
Visual simplification:
OH groups on monomers are involved; during condensation, a water molecule is released; during hydrolysis, water is added to break the bond.
Notation:
Condensation reaction generally yields water: Monomer + Monomer → Dimer + H2O; and so on for polymers.
Page 20
Families of Organic Molecules
Biomonomers ↔ Biopolymers ↔ Polymerization process
Common monomers and their polymers:
Amino acids → Polypeptides (proteins) via peptide bonds (a type of condensation)
Monosaccharides → Polysaccharides via glycosidic bonds
Nucleotides → Polynucleotides via phosphodiester bonds
Bond types:
Amino acids → Polypeptides: Peptide bond (a condensation bond)
Monosaccharides → Polysaccharides: Glycosidic linkages
Nucleotides → Nucleic acids: Phosphodiester bonds
Key idea: Three major biomolecule families (proteins, polysaccharides, nucleic acids) are assembled from simple monomer units via condensation reactions.
Page 21
B1.1.04 Form and function of monosaccharides
Monosaccharides to recognise: Hexoses (6 carbons) and pentoses (5 carbons).
Examples: Glucose and fructose are hexoses; ribose and deoxyribose are pentoses.
Monosaccharides in ring form; glucose properties highlighted: high solubility, transportability, chemical stability, and energy yield upon oxidation.
Ring form recognition: β-D-ribose is an example; orientation of –OH at C1 differs (anomeric forms: α/β).
Practical takeaway: Glucose is highly soluble due to multiple –OH groups; provides energy via oxidation, commonly yielding up to ~38 ATP per molecule in cellular respiration.
Page 22
Monosaccharide forms and isomerism
Monosaccharides can exist as α- or β- forms; example: β-D-Ribose.
Structural implications: configuration at carbon-1 (anomeric carbon) determines the ring form.
Key idea: Isomerism in monosaccharides alters properties and metabolic uses, with ring forms prevalent in biological systems.
Page 23
Properties of glucose
Glucose is highly soluble due to many hydroxyl groups forming hydrogen bonds with water.
Solubility aids transport in blood (blood sugar).
Glucose is chemically stable and can be oxidized in respiration to release energy.
Energy yield: 1 glucose molecule can yield up to approximately 38 ATP molecules.
Page 24
Monosaccharide and disaccharide structures
General formula for carbohydrates: Cx(H2O)x for many monosaccharides (empirical formula resembles a carbohydrate).
Disaccharides example: Sucrose: C12H22O11 (C12(H2O)11).
Glyceraldehyde: C3H6O3 (an aldose) or C3(H2O)3; glycerol: C3H8O3 (not a sugar).
Key formula relationships:
Monosaccharide: Cn(H2O)n (empirical composition)
Disaccharide: formed via condensation of two monosaccharides with loss of H2O; e.g., maltose as two glucose units.
Note: Condensation forms glycosidic bonds between monosaccharides; hydrolysis splits them again.
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Example: Disaccharide formation
Maltose formed by condensation of two glucose molecules.
Visual: short animation showing maltose formation (described verbally).
Key concept: Disaccharides arise from the linkage of two monosaccharides via a glycosidic bond through a condensation reaction.
Page 26
Polysaccharides as energy storage compounds (B1.1.05)
Starch (plants) and glycogen (animals) as energy storage polysaccharides.
Structural features:
Amylose: long chains of α-glucose linked by α-1,4 glycosidic bonds; tendency to form a spiral.
Amylopectin: linear α-1,4 linked chains with occasional α-1,6 branches; branches roughly every 20–30 glucose units.
Amylose and amylopectin combine to form starch; typical amylose content varies by plant.
Glycogen: highly branched, with α-1,4 linkages along chains and α-1,6 branch points about every 8–10 glucose units; more branched than amylopectin to allow rapid mobilization of glucose.
Consequences: High molecular size leads to insolubility; multiple terminal glucose units enable rapid addition/removal of glucose units by condensation/hydrolysis for energy release.
Key idea: The structure (coiling/branching) of storage polysaccharides determines solubility and rate of energy release, matching the energy needs of organisms.
Page 27
Glucose storage: Glycogen structure
GLYCOGEN: principal storage polysaccharide in animals.
Highly branched structure ensures many non-reducing ends for rapid enzyme access to release glucose when needed.
Branching pattern: 1→4 linkages with occasional 1→6 linkages; glycogen branches every ~8–10 glucose units.
Implication: Efficient, rapid mobilization of glucose for short-term energy needs.
Page 28
Structure of cellulose related to its function as a structural polysaccharide
Cellulose uses β-glucose monomers.
Alternating orientation of β-glucose units results in straight chains.
Chains bundled and cross-linked by hydrogen bonds; these bundles form cellulose microfibrils.
Microfibrils are interwoven with other polysaccharides (e.g., pectin, hemicelluloses) to form plant cell walls.
Key idea: The β-1,4 linkage yields straight, rigid fibers that provide mechanical strength to plants.
Page 29
Cellulose and disaccharide formation (cellobiose) as an illustration
Cellobiose: disaccharide formed from two β-glucose units via a β-1,4 glycosidic linkage.
Structural detail: In β-glucose, the hydroxyl at C1 points above the plane of the ring, affecting linkage type.
Hydrolysis/forming disaccharides can illustrate how specific glycosidic bonds influence polymer properties.
Page 30
Glycoproteins and cell–cell recognition
Glycoproteins: proteins with short saccharide chains (2–10 monosaccharide units).
Locations: often on cell membranes, roles in inter-cell recognition, binding sites for hormones, molecules taken up by endocytosis, binding sites for neurotransmitters, and involvement in self/non-self (immune recognition).
Example: ABO blood group antigens are glycoprotein/oligosaccharide structures that determine blood type.
Page 31
ABO blood group mechanism (illustrative details)
O-type glycoprotein: core H antigen present, with a chain of four monosaccharides ending in galactose.
A-type glycoprotein: an extra monosaccharide added to the final galactose, forming A antigen.
B-type glycoprotein: an extra monosaccharide added to the final galactose, forming B antigen.
Blood type outcomes:
Type O: O individuals (no A/B antigens); universal donor in some contexts but can receive only O blood.
Type A: A antigen; can receive A or O.
Type B: B antigen; can receive B or O.
Type AB: both A and B antigens; universal recipient.
Extra note: There are rare genetic variations (e.g., h/h genotype) affecting transfusion compatibility; the H antigen is present in most individuals.
Page 32
ABO antigen genetics (brief)
Gene on chromosome 19 controls ABO antigens (IA, IB alleles; i allele).
IA leads to galactosamine addition to H antigen (A phenotype).
IB leads to galactose addition to H antigen (B phenotype).
If neither IA nor IB is present, the H antigen remains (O phenotype).
Practical note: Rare genotypes may complicate transfusions.
Page 33
Review of Lipids (Intro to Lipids section)
Lipids include FATS, OILS, WAXES, and STEROIDS.
Two main groups:
Fatty acid-based lipids (Triglycerides and Waxes)
Steroids
Focus on triglycerides and phospholipids for membrane biology; steroids for signaling and membrane composition.
Page 34
Visual: Triglyceride (simple diagram)
A triglyceride consists of glycerol linked to three fatty acids via ester (condensation) bonds.
Fatty acid chains may be the same or different.
Skeletal diagrams omit explicit carbon skeletons, focusing on C–C bonds and C=C bonds where present.
Page 35
Lipids: Triacylglycerols and fatty acid diversity
Energy storage lipid class: triglycerides (triacylglycerols).
Number of possible triglycerides depends on number of fatty acid varieties: n^3 combinations for triacylglycerols using n fatty acids.
Example: Milk contains >400 fatty acids identified; potential triglyceride variety could be up to 3,400, but the common fatty acid repertoire is closer to ~40.
Notation example:
A, B, C denote three fatty acid moieties in a triglyceride: ABC, ACB, etc.
Real-world note: Milk demonstrates potential molecular diversity, illustrating functional flexibility of lipids.
Page 36
Hydrophobic properties of lipids: partition coefficient (log P)
Lipids are hydrophobic due to a lack of polar bonds and high C–H content.
Partition coefficient P = ratio of solute concentration in two immiscible solvents (water vs non-polar solvent, often 1-octanol).
Log P is used to express hydrophilicity/hydrophobicity: higher log P indicates more hydrophobic compounds.
Practical setup: separatory funnel diagram illustrating distribution of a compound between aqueous and hydrophobic phases.
Page 37
Why triglycerides are hydrophobic
Triglycerides have almost no polar bonds; C=O bonds are only slightly polar and few in number, leading to overall hydrophobic character due to many non-polar C–H bonds.
Page 38
Steroids and membrane signaling
Steroids are organic compounds with four fused rings (A, B, C, D).
Two main roles:
Membrane components that influence membrane fluidity (e.g., cholesterol).
Signaling molecules (e.g., sex hormones estradiol and testosterone).
Attachment of functional groups alters hydrophobicity and interactions with membranes.
Example: Cholesterol contains an –OH group capable of hydrogen bonding, influencing its interaction with phospholipids; testosterone has hydrophilic ends enabling limited water interaction.
Overall: Steroids are hydrophobic; they move through membranes via diffusion.
Page 39
Non-polar steroids crossing the phospholipid bilayer (process overview)
1) Steroid diffuses through membrane into the cell.
2) Binds to intracellular receptor protein.
3) Receptor-steroid complex translocates to the nucleus and interacts with DNA, altering gene expression.
Sex-specific receptors: males (testosterone receptors) vs females (oestradiol receptors).
This outlines the pathway linking steroid uptake to genomic effects.
Page 40
Waxes
Waxes are long-chain fatty acids esterified to long-chain alcohols.
Very hydrophobic and water-insoluble.
Common function: water repellence on leaves, feathers, and insect cuticles.
Page 41
Phospholipids: condensation to phospholipid formation
Phospholipids arise when one fatty acid of a triglyceride is replaced by a polar, water-attracting phosphate-containing group.
Result: Amphipathic molecule with a polar (hydrophilic) head and non-polar (hydrophobic) tails.
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Phospholipid formation (continued)
A fatty acid is removed from a triglyceride and replaced by a phosphate-containing molecule.
This biosynthetic pathway transforms triglycerides into phospholipids with a polar head and non-polar tails.
Page 43
Phospholipid bilayer structure and amphipathicity
A phospholipid is depicted as a circle (glycerol + phosphate head) with two hydrophobic tails.
Head: polar (hydrophilic) and interacts with water.
Tails: non-polar (hydrophobic) and avoid water.
This amphipathic nature leads to bilayer formation in aqueous environments.
Three common arrangements for phospholipids in water: micelles, liposomes, and bilayer sheets.
Page 44
Membrane aggregation in water
In water, phospholipids self-assemble to minimize free energy: tails exclude water, heads contact water, forming structures such as micelles, liposomes, or bilayer sheets that separate two water compartments.
Page 45
Fatty acid structure and saturation (intro)
Fatty acids: long chains of carbon with hydrogen; terminal carboxyl group (–COOH).
Saturated fatty acids: all C–C bonds are single; straight chains.
Monounsaturated fatty acids: one C=C double bond (one kinking point).
Polyunsaturated fatty acids: more than one C=C double bond.
Effect of saturation:
Saturated chains are straight, allowing tight packing and higher melting points.
Unsaturated chains are kinked, reducing packing efficiency and lowering melting points.
Relevance: Variation in saturation influences properties of fats and oils in plants (energy storage) and endotherms (e.g., mammals).
Page 46
Difference between saturated, monounsaturated and polyunsaturated fatty acids (visual cues)
Visual examples show typical shapes: saturated (straight), mono- (one kink), polyunsaturated (multiple kinks).
Naming convention uses C:D notation, where C is the number of carbons and D is the number of double bonds.
Page 47
Fatty acid nomenclature (C:D notation)
Common notation: e.g., 16:0, 18:0, 18:1, 18:2, 18:3, etc.
The first number is the number of carbon atoms; the second is the number of C=C double bonds.
Page 48
Omega (n) naming and cis/trans isomerism
Omega (ω) number: indicates the position of the first double bond counting from the omega (methyl) end.
Example: Oleic acid: 18:1 ω-9 or 18:1 n-9 (same structure).
More than one double bond: list double bond positions in parentheses, e.g., linoleic acid 18:2(9,12).
Isomerism:
Unsaturated fatty acids can be cis or trans isomers.
In nature, cis configuration predominates; trans is formed during industrial hydrogenation (e.g., margarine production) and is associated with health concerns.
Page 49
Cis vs. Trans isomerism in unsaturated fatty acids
Cis: hydrogen atoms on the same side of the double bond cause a bend in the chain.
Trans: hydrogens on opposite sides; chain is less bent, more linear.
Health note: Trans fats are associated with negative health effects; natural fats are predominantly cis.
Page 50
Consequences of cis and trans configurations
Cis unsaturated fatty acids: bends reduce packing efficiency, lowering melting points and increasing fluidity.
Trans unsaturated fatty acids: more linear, pack more tightly; higher melting points; can be less fluid.
Page 51
Comparison of cis and trans unsaturated fats (continued)
Trans fats generally have higher melting points than cis fats with similar chain lengths, and thus behave more like saturated fats in some contexts.
The physical properties (melting point) depend on both degree of unsaturation and double-bond geometry.
Page 52
Fatty acid examples and practical implications
Examples of common saturated and unsaturated fatty acids:
Saturated: Arachidic, Stearic, Palmitic acids.
Monounsaturated: Erucic, Oleic acids.
Polyunsaturated: Linoleic (18:2), Linolenic (18:3), Arachidonic (20:4).
Note: Most naturally occurring unsaturated fatty acids are cis.
Page 53
Physical properties of lipids and fatty acid chains
Physical properties (melting point, fluidity) depend on the nature of fatty acids.
Intermolecular forces (intra- and inter-molecular) between hydrophobic chains influence solid/liquid state at a given temperature.
Short chains have fewer IMF; bent chains have fewer IMF than straight chains.
Page 54
Melting points: saturated fatty acids (example data)
Relationship between carbon number and melting point for saturated fatty acids is shown (illustrative data).
Hypothesis: shorter chains have lower MP; longer chains have higher MP.
Implication: Chain length influences whether fats are solid or liquid at body temperature.
Page 55
Melting points: general trend for saturated fatty acids
The longer the hydrocarbon chain, the higher the melting point (more likely to be solid at a given temperature).
Page 56
Melting points of unsaturated fatty acids and isomer effects
Data visualization comparing MP for mono-, di-, and polyunsaturated fats.
Trans fatty acids have higher MP than cis fats with the same chain length.
Position of double bonds also affects MP.
Overall: Unsaturation lowers MP relative to saturated, but geometric isomerism (cis/trans) modulates this effect.
Page 57
Triglycerides in adipose tissue for energy storage and thermal insulation (summary)
Lipids serve multiple roles in animals:
Steroids: hormones and membrane components (cholesterol for membrane stability).
Waxes: water repellents on surfaces.
Fatty acids: used for phospholipid formation in membranes.
Triglycerides: long-term energy storage in adipose tissue.
Triglycerides: electrical insulation in nerves (myelin sheath).
Triglycerides: thermal insulation in mammals and birds (blubber).
Conclusion: Triglycerides are particularly suited for long-term energy storage and insulation due to high energy density and hydrophobicity.
Page 58
Energy release from triglycerides vs carbohydrates (oxidation)
Energy release via oxidation: oxygen is added as C–H and C–C bonds are broken to form CO2 and H2O.
Example respiration equations:
Triglyceride:
Carbohydrate (sucrose-like size):
Observation: The lipid has a higher C:O ratio in the original molecule, meaning more energy per gram is released upon complete oxidation because lipids are less oxidized initially.
Page 59
Anhydrous nature of lipids and implications for storage
Lipids do not form hydrogen bonds readily; C–H bonds are nonpolar.
Lipids do not attract water; carbohydrates are hydrophilic due to many O–H groups and form hydrogen bonds with water.
Implication: Lipids store energy with much less water mass, enabling greater energy density per gram.
Estimation example: A 70-kg man may store roughly 11 kg of energy reserves as lipids; storing the same energy in glycogen would add about 55 kg to body mass.
Page 60
Why lipids are efficient long-term energy stores
Lipids are more energy-dense per gram than carbohydrates.
They are anhydrous, reducing water weight in storage.
Triglycerides can be packed tightly, reducing volume per gram.
Page 61
Lipids and thermal insulation (continued)
Warm-blooded animals minimize heat loss via fur/feathers and a layer of adipose tissue.
Lipids contribute to insulation by stored fat beneath the skin and, in marine mammals, a specialized blubber layer.
Page 62
Blubber and marine insulation
Blubber: dense, vascularized fat layer beneath the skin in marine mammals; provides thermal insulation and energy reserve.
Composition: rich in triacylglycerols; relatively low melting points; allows phase changes with temperature changes for heat retention.
Variability: thickness varies (a few cm in small seals to around 0.5 m in large whales).
Page 63
Lipids in plants and endotherms as energy storage molecules
In plants, seeds often store energy as lipids (seed oils) to supply energy for germination.
Seed oil composition varies by climate:
Tropical seeds: tend to have shorter-chain saturated fats.
Temperate seeds: tend to have longer-chain unsaturated fats.
In endotherms (mammals), animal fats are typically more saturated, contributing to higher melting points which help maintain structural integrity at body temperature.
Page 64
Comparative fat profiles across seeds and plants (dataset summary)
Examples: Coconut, Palm oil, Safflower, Sunflower.
Data (percentages) for Saturated, Monounsaturated, Polyunsaturated fatty acids illustrate variability across tropical vs temperate seeds.
Trend: Tropical seeds tend to have more saturated fats; temperate seeds more unsaturated fats.
Additional note: Fruits vs seeds have different roles for fats; fats in seeds provide energy for germination, while fats in fruit help attract animals for seed dispersal.
Page 65
Animal fats vs seed oils (continued)
Animal fats (e.g., pig, beef, goose, butterfat) generally have higher saturated fat contents than seed oils.
Across these fats, saturated fats often dominate; monounsaturated and polyunsaturated fats vary by species.
Page 66
Why seed oils are highly variable and evolutionary considerations
Energy costs of unsaturated fats: desaturase enzymes introduce double bonds, which costs cellular energy.
Seeds in temperate climates benefit from unsaturated fats that remain liquid at lower temperatures, aiding germination in early spring.
Theoretical perspective (Linder 2000): The widespread presence of unsaturated fats in temperate seeds may confer a competitive advantage for germination timing and establishment.
Page 67
B1.1 Carbohydrates and Lipids – Key Vocabulary (You should be able to use these terms in answers unprompted)
adipose tissue
Phospholipid
Starch
Cellulose
lipids
Polymer
Condensation reaction
macromolecules
polypeptides
Disaccharide
Microfibrils
Polysaccharide
Fatty acid
Monomer
Polyunsaturated fatty acid
glucose
Saturated fatty acid
testosterone
Glycerol
Steroid
Triglyceride
glycogen
Monounsaturated fatty acid
Monosaccharide
glycoproteins
nucleic acids
hydrolysis
Glycosidic linkage
oestradiol
Unsaturated fatty acid
hexose
oxidation
amphipathic
Pentose
- waxes
B1.1 Vocabulary Quizlet
A ready-reference list of terms for quick study and recall.
Summary of key equations and concepts (LaTeX-formatted on-page references)
Condensation formation of water during polymerization:
Monomer + Monomer → Dimer + H2O
Oligomer + Monomer → Polymer + H2O
Hydrolysis reaction (reverse):
Polymer + H2O → Monomer + Monomer (example schematic)
Glucose oxidation energy yield (cellular respiration sketch):
ATP yield per glucose: approximately up to (under ideal conditions; actual yield may vary)
Lipid oxidation example (triglyceride):
Sucrose formation (disaccharide):
(illustrative for condensation)
Phospholipid bilayer arrangement: amphipathic property leads to bilayer formation in water.
General fatty acid nomenclature: C:D notation (carbons:double bonds), e.g., 18:1 (oleic acid).
Omega (ω) numbering for double bonds: e.g., 18:1 ω-9 equals 18:1 n-9.
These equations summarize the core chemical processes underpinning carbohydrate and lipid biology covered in the transcript.
If you’d like, I can tailor these notes to a specific exam format (e.g., short answer prompts, practice questions, or a condensed study sheet). Also tell me if you want any page’s notes expanded with more examples or simplified explanations for easier recall.