FOOD CHEMICALS

Chemical Makeup: 99% CHON; Next 1% = Na/K; Mg/Ca; P/S/ClHumans: 47 elements present; 24 at are necessary

AN AVERAGE ADULT NEEDS 2400 kcal (2000-3000) PER DAY = 100 kcal/hour

NOTE: One food Cal = 1 kcal (= 4.8 kJ)

ONE POUND OF FAT = ~4000 kcal ~ 2 days food 1 KILO OF FAT = 9000 kcal ~ 4 days food

fat uses up the daily calorie intake rapidly and it takes a lot of exercise to get rid of!

cycling 20 km/h for 1 h: ~ 600 kcalwalking up hill ~300m height gain: ~ 600 kcal

Resting metabolic rate (4am sleeping): ~ 50 kcal/hNon energetic stuff: ~ 70-100 kcal/h

CARBOHYDRATES Cn(H2O)m hence name

Monosaccharides have ONE sugar: egs. glucose, fructose, ribose

Disaccharides have TWO sugars: egs. sucrose, maltose, lactose

Oligosaccharides have a FEW sugars: eg. raffinose

Polysaccharides have MANY sugars: egs. starch, cellulose

Carbohydrates store water as well as being an energy source

MONOSACCHARIDESGLUCOSE C6H12O6

O

OH

H OH

HOH

H

CH2OH

H

HO

O

HO

HOH

HHO

H

HOCH2

H

OH

Mirror

OH

OH

H OH

H

CH2OH

H

HO CHO

O

OH

H OH

HH

OH

CH2OH

H

HO

water

water

-(+)-D-glucosenote = up

(-)-L-Glucose(not found in nature)

open form(low conc)

-(+)-D-glucosenote = down

and glucose are two different chemicals

Glucose = blood sugar = dextrose: needs no digestion, can be used IV

in reality rings are not flathave a chair like structurebonds are equatorialor axial

OOH

HOHHOHO

HOCH2

H

H

HH

NOTE: in glucose all the H’s are axial, all the OH equatorial

If we flatten the ring, then noticethe groups alternate – this is one way to recognize glucose!

O

OH

H OH

HOH

H

CH2OH

HH

HO

IF YOU SWITCH AN OH GROUP, YOU CHANGE THE SUGAR

O

OH

H OH

HOH

H

CH2OH

HO

H

(+)-D-Galactose note: this can still be or

has this OH changed we show this with a wiggly line:

O

OH

H OH

H

CH2OH

HO

HOH

We will meet this sugar later in lactose (milk)

SOME SUGARS HAVE THE SAME FORMULA BUT MAKE 5-membered rings: eg. FRUCTOSE

O

H

HO

HO

H

HOCH2

HO

H

CH2OH(-) - D- Fructose (levulose), happens to be a (-) sugar present in invert sugar, fruit sugar

Sweetest sugar: ‘high fructose corn syrup’ need less to sweetenBUT fructose stimulates liver to release fats in to blood stream just like insulin, leads to insulin resistance promotes type II diabetes

C6H12O6

O

H

HO

H

OH (H)

HOCH2

HOOH

(-) - D- Ribose used in RNA

(deoxyribose, used in DNA, has H instead of OH)

DI-SACCHARIDES most important in foods

R-OH + HO-R'- water

R-O-R'

OHO OH

OHO OH+

OOH

OHO O

two molecules of a mono-saccharide can ‘condense’ with loss of a molecule of water to form a disaccharide:

2 (C6H12O6) - H2O = C12H22O11

acetal

MALTOSE uses two glucose molecules, (+) sugar

-Glu-4-Glu

all animals can easily cleave links (eg. we have the enzymes in our

saliva) back to (in this case) 2 glucoses link 4-link

123

O

OH

H OH

H

CH2OH

OH

O

OH

H OH

HH

O

CH2OH

H

HOH 4

Other saliva enzymes cleave starch to maltose:try chewing some bread it gets sweeter as you chew

Note: this link is not interconvertible once formed, i.e. stays , stays

SUCROSE: Table sugar (>80M tons/y)

O

H

HO

HO

H

HOCH2 H

CH2OH

O

OH

H OH

HH

O

CH2OH

H

HO-Glu-(2)-Fru

(+) sugar

link

So we can split this to glucose and fructose – we can only directly metabolize monosaccharides

The liver can inter-convert glucose and fructose as needed but as before too much fructose is not good!

LACTOSE, Milk sugar (+)

123

4 O

OH

H OH

H

CH2OH

OHH

O

OH

H OH

H

CH2OH

HO

H

O

H

Galactose

-Gal-4-Glu

All babies have lactase which can cleave the -link, when weaned all animals and most humans (except those of European descent) LOSE this enzyme and so do not tolerate lactose well

link

Lactose goes to colon, where bacteria convert it to gas + lactic acid (CH3CHOHCOOH), which irritates bowel and causes diarrhea; human milk ~ 7.5 g lactose/100 mL; cows ~ 4.5

Sweetness(relative): Fructose 1.7; Sucrose 1; Lactose 0.16

POLYSACCHARIDES

STARCH, Amylose = water soluble portion of starch (20-25%)

O

O

O

O

O

O

O

O

n

AMYLOSE

-Glu-4-Glu-]n-

ALL -links n = 15-250

rest is AMYLOPECTIN

1000-5000 Glu units (3D) cross-linked using the CH2OH

Plants store STARCH for energy usage (plus a lot of water - they do not have to move!)

Animals use GLYCOGEN: stored in liver and muscles in small amounts (otherwise too much water): more branched and cross-linked than amylose, but still all -links for fast breakdown to glucose for usage

Starch cannot pass thru intestine, so to be absorbed, it is broken down by maltase into MALTOSE

Amylose when heated & cooled sets to gel: PUDDINGS, CANDIESAmylopectin goes more pasty: GRAVIES, SAUCES

Both form an intense blue colour with Iodine/iodide (I3-) - test

UTILIZING STARCH

a) All creatures can convert glucose ↔ fructose → pyruvic acid CH3COCOOH

Then we use pyruvic acid in the Kreb’s cycle, WITH O2, to convert ADP to ATP, CO2 + H2O + energy If there is insufficient O2 (eg. in starved muscles), pyruvic acid converts to CH3CHOHCOOH (lactic acid) + energy

Lactic acid causes pain in muscles (cramps): slowly reconverts to pyruvic acid in the presence of O2

b) To make beer:Barley contains enzymes that convert starch to maltose during the 1-2h cooking time of the ‘mash’Yeast enzymes then convert maltose to ethanol, CO2 and heat

CELLULOSE

O O O O O OO O

n

-[--Glu-4-Glu-]n-

all -links

Most creatures do not have cellobiase which can cleave the -links

Cows, goats, horses, termites, etc. have bacteria in their rumens (2nd stomach) which have the enzymes to cleave cellulose so can eat grass, etc.

Theoretically, could cleave the -link in the lab with aqueous acid to liberate glucose but it is too expensive to remove the sugar from acid to be practical

Paper, rayon, cotton, cellophane: cellulose chains with H-bonds

Weaken in water (can shape) but stiffen when dry (stale bread)Can stiffen cotton with starch; can use starch to paste paper

Most foods have too much sugar: eg. ketchup, 29%

Consumption: 50-60 kg sugar/year per person

Excess sugar consumption: obesity, atherosclerosis, dyspepsia, diabetes

Diabetes: Type 1 too LITTLE (or no) insulintoo much sugar in blood

Type 2 insulin resistance

Hypoglycemia: too low blood sugar (tired, poor thinking ability)

GALACTOSEMIA (rare: 10-20 / million of population)unable to convert galactose to glucose in liver; Gal deposits in eye, get cataracts

BAKED BEANS

have 0.5-10% galactose as the trisaccharide RAFFINOSE = Gal--4-Glu-Fru no enzymes for this so it goes to the intestines where bacteria convert it:

smelly gas! (mostly H2S/Me2S2/MeSH ) from S-containing amino acids (proteins)

People who require colon surgery have a polyethyleneglycol purge to clean pipes to prevent colonic detonations during surgery (spark-methane)!!!

BEANO: contains the enzyme alpha galactosidase to allow people to break down Raffinose; has been added to beer to break down complex sugars – lower carb beer but less flavour and less head