Carbohyrdrates & Lipids

Carbohydrates (CH2O)

sugars, starches, cellulose and other fibers, glycogen, chitin (arthropods), etc

Carbohydrates roles in humans 

Chemical energy ➟ ATP
• Short-term energy storage (glycogen)
• ID tags for cells/biomolecules
• Dietary fiber
• Feed gut microbes
• Slow sugar absorption
• Bulk feces and promote defecation

Lipids (CHO)

fatty acids, triglycerides,
phospholipids, steroids, sebum, etc.

Lipids roles in humans 

Chemical energy ➟ ATP
• Long-term energy storage (fat)
• Membrane structure
• Hormones (e.g., sex, stress)
• Insulation (thermoregulation)
• Cushion reducing physical trauma
• Barrier to water loss (osmoregulation)

saccharides

sugars immediately metabolized to
transfer energy to ATP OR metabolized into larger
biomolecules (e.g., DNA)

Monosaccharides (e.g., glucose)

sugars whose
carbon skeletons routinely assume a single ring shape

aldoses

aldehyde sugars (e.g., glucose) —end

ketoses

ketone sugars (e.g., fructose) —middle

Disaccharides

(e.g., grains —maltose,
fruits —sucrose, and milk —lactose)

Polysaccharides

(e.g., starches, glycogen)

Ring

metabolized into more complex
molecules OR polymerized via dehydration
synthesis reactions to form:

Human use enzyme (-ase)..

facilitated hydrolysis
reactions to depolymerize during digestion:

maltase

maltose ➟ glucose + glucose

Sucrase

sucrose ➟ glucose + glucose

Lactase

lactose ➟ glucose + galactose

Plant Polysaccharides

Plants polymerize excess glucose into
starches (e.g., amylose, amylopectin)
• stored energy and source of glucose
when photosynthesis rate ↓ and/or
energy needs ↑ (e.g., reproduction)

Amylases

starches ➟ glucose

plants make what to strengthen cell walls?

cellulose, but animals lack enzymes to
hydrolyze it (but microbes can...)

Animals Polysaccharide

Animals polymerize glucose into glycogen
(large, branched polysaccharide) during
glycogenesis when energy demands ↓
and/or blood glucose ↑

Animals use many enzymes to … 

carry out
glycogenolysis (hydrolysis of glycogen)
when energy demands ↑ and/or blood
glucose ↓

Fatty acids monomers bond…

with glycerol
via dehydration synthesis reactions to form:
• Triglycerides

Monounsaturated fats

e.g., olives, peanuts) ↑ HDL-C

Polyunsaturated fats

(e.g., fatty fish, nuts, seeds, soy)

Phospholipids

Biota bond only 2 fatty acids with glycerol

Steroids

lipid molecules with a 4-ring
sterol carbon skeleton with various functional
groups

Cholesterol

steroid synthesized only by
animals from acetyl-coA to help build cell
membranes