B1.1  Carbohydrates and Lipids

Theme:  Form and Function

Every biological molecule's shape, bonding pattern, and chemical properties directly determine what job it can perform in living organisms. 

• Carbon's bonding creates diverse molecular shapes that directly determine biological roles. Carbon can form four bonds in various combinations, producing straight chains, branches, and rings that each serve specific functions in living organisms.
• Molecules can change form and function by building and breaking apart through condensation and hydrolysis reactions. Large molecules like polysaccharides, proteins, and nucleic acids gain specialized functions based on how their monomers are arranged, while hydrolysis allows flexible breakdown when needed.

Carbohydrates:

• Monosaccharides like glucose have ring structures that provide perfect solubility for transport, stability for storage, and accessible bonds for energy release.
• Energy storage polysaccharides (starch, glycogen) use coiling and branching to pack glucose units compactly while staying insoluble, yet allow easy glucose removal.
  
• Structural polysaccharides like cellulose use alternating glucose orientations to create straight, strong chains that bundle together for plant cell wall strength.
• Glycoproteins use specific carbohydrate shapes as molecular identification tags, enabling cell recognition through precise structural matching.

Lipids:

• Hydrophobic properties of lipids determine their roles in waterproof barriers and energy storage.
  
• Triglycerides store twice the energy of carbohydrates due to their structure, while fatty acid saturation directly affects fluidity.
• Phospholipids are amphipathic, causing them to spontaneously form membrane bilayers that control what enters and exits cells.
  
• Steroids have rigid, non-polar structures that let them pass through membranes to function as hormones.

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• 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?

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​Linking Questions:  
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• How can compounds synthesized by living organisms accumulate and become carbon sinks?
• What are the roles of oxidation and reduction in biological systems?

Key Terms to Know: 

-H
-OH
ABO Antigens
Adipose
Alpha-Glucose
Amphipathic
Beta-Glucose
Bilayer
Branched Chain
Carbon
Cell-Cell Recognition
Cellulose
Centi-
Chemical Energy Storage
Chemical Property
Chemical Stability
Compound
Condensation Reaction
Covalent Bond
Cross-Link
Double Bond
Endotherm
Fat (Molecule)
Fatty Acid

Glycerol
Glycogen
Glycoprotein
Hexose
Hydrogen Bond
Hydrolysis Reaction
Hydrophilic
Hydrophobic
Insolubility
Kilo-
Lipid
Macromolecule
Melting Point
Micro-
Milli-
Monomer
Monosaccharide
Monounsaturated
Nano-
Non-Polar
Nucleic Acid
Oestradiol
Oil
Oxidation

Pentose
Phosphate Group
Phospholipid
Physical Property
Polymer
Polymerization
Polypeptide
Polysaccharide
Polyunsaturated
Saturated
SI Unit
Single Bond
Solubility
Soluble
Solvent
Starch
Steroid
Testosterone
Thermal Insulation
Transportability
Triglyceride
Unbranched Chain
Water
Wax

B1.1.1— Chemical properties of a carbon atom allowing for the formation of diverse compounds upon which life is based.

• Outline the number and type of bonds carbon can form with other atoms.
• State what makes a molecule “organic.”
  
• Outline the cause and consequence of covalent bonds between atoms.
• Recognize common functional groups.
• List the four major classes of carbon compounds used by living organisms.
• List example molecules with branched chain, unbranched chain, single ring or multiple rings.​

B1.1.2— Production of macromolecules by condensation reactions that link monomers to form a polymer.  

• Define monomer and polymer.
• Describe condensation reactions.
• State that energy from ATP is needed to produce macromolecules by condensation reactions.
• Outline the condensation reactions that form polysaccharides, polypeptides and nucleic acids.

B1.1.3— Digestion of polymers into monomers by hydrolysis reactions.

• Define monomer and polymer.
• Describe hydrolysis reactions.
• Outline the hydrolysis reactions that digest polysaccharides, polypeptides and nucleic acids.

B1.1.4— Form and function of monosaccharides.

• Define monosaccharide.  
• Identify pentose and hexose carbohydrates from molecular diagrams.  
• Outline the properties of glucose referring to solubility, transportability, stability, and energy yield in cellular respiration. ​

B1.1.5— Polysaccharides as energy storage compounds.

• Define polysaccharide.  
• Compare the structure and function of amylose, amylopectin, and glycogen.
• Discuss the benefit of polysaccharide coiling and branching during polymerization.
• Explain how condensation or hydrolysis of alpha-glucose monomers build or mobilize energy stores.​

B1.1.6- Structure of cellulose related to its function as a structural polysaccharide in plants.  

• Compare the structure of alpha-glucose and beta-glucose. 
• Describe the structure of cellulose microfibrils. 
• Discuss the consequences of the strength of cellulose in the plant cell wall.

B1.1.7— Role of glycoproteins in cell–cell recognition. 

• Outline an example of a function of a glycoprotein. 
• Compare the structure of the A, B and O glycoproteins on the red blood cell membrane.
• Discuss the consequences of the presence of A, B and O glycoproteins during blood transfusion.

B1.1.8- Hydrophobic properties of lipids.

• Explain why lipids are hydrophobic.
• Outline the structure and function of fats, oils, waxes and steroids.

B1.1.9- Formation of triglycerides and phospholipids by condensation reactions.

• Explain the  condensation reaction connecting fatty acids and glycerol to form a triglyceride.
• Explain the  condensation reaction connecting fatty acids, glycerol and a phosphate group to form a phospholipid. 

B1.1.10- Difference between saturated, monounsaturated and polyunsaturated fatty acids.

• Describe the structure of a generalized fatty acid.
• Compare and contrast the structures and properties of saturated and unsaturated (mono- or poly-) fatty acids.
• Distinguish between the structure and properties of cis- and trans-unsaturated fatty acids.

B1.1.11- Triglycerides in adipose tissues for energy storage and thermal insulation. 

• Outline properties of triglycerides that make them suitable for long-term energy storage. 
• State the function of adipose tissue.
• Discuss the adaptation of a thick adipose tissue layer as a thermal insulator. 

B1.1.12- Formation of phospholipid bilayers as a consequence of the hydrophobic and hydrophilic regions.

• Draw a simplified diagram of the structure of the phospholipid, including a phosphate-glycerol head and two fatty acid tails.
• Define hydrophilic, hydrophobic and amphipathic.
• Outline the amphipathic properties of a  phospholipid.
• Explain why phospholipids form bilayers in water, with reference to hydrophilic phosphate heads and two hydrophobic hydrocarbon tails.

B1.1.13- Ability of non-polar steroids to pass through the phospholipid bilayer.  

• Identify steroid molecules from molecular diagrams.  
• State why steroid hormones are able to pass directly through the phospholipid bilayer.