Food Chem

Question 1

Amino acid

Answer 1

A alpha carbon which has a carboxyl group and a amino group

Question 2

Peptide

Answer 2

Amino acids which has undergone condensation. Condensation creates peptide link thus now a peptide.

Question 3

Protien

Answer 3

A chain of amino acids consisting of 50 or more amino acids, each joined by peptide links

Question 4

Primary structure

Answer 4

A sequence of amino acids

Question 5

Secondary structure

Answer 5

Alpha helixes and beta pleated sheets, derived from hydrogen bonding between N-H and C=O group. Slightly positive H in N-H hydrogen bonds with slightly negative O in C=O

Question 6

Tertiary structure

Answer 6

Overall 3D structure of the protein is derived from intermolecular interactions between groups in amino acid side chains. Looks at how the alpha helixes and beta pleated plates interact. Dispersion forces, Hydrogen bonds, dipole bonds, ionic interactions and disulphide bridge in cys-cys

Question 7

Quaternary structure

Answer 7

How protein with other proteins in 3D

Question 8

Rancidity of fats + antioxident

Answer 8

Two stages:

Initiation: C=C oxidizes and forms a free radical

Propagation: chain reaction (auto-oxidation) forming harmful short chains containing aldehyde and keytones, the smell is from aldehyde

An antioxidant oxidizes in preference to the C=C thus, preventing/delaying rancidity of fat or donating H+ to prevent oxidation

To prevent rancidity:
-lower temperature thus lower rate of reaction
-use lean meats, avoid fat
-use saturated fats

Question 9

Glycemic index

Answer 9

The rate of release of glucose into the bloodstream within two hours. Pure glucose has a relative GI of 100.

Question 10

Starch (carbohydrate)

Answer 10

Amylose: Straight thus more dispersion forces hence harder to break down by amylase into maltose. Low GI

Amylopectin: Branches thus fewer dispersion forces hence easier to breakdown by amylase into maltose. High GI

Made of alpha glucose

Question 11

Glycogen

Answer 11

Extremely branched, used for energy storage. Since it is so branched it can be easily broken down into glucose. Made due to excess glucose

Made of alpha glucose

Question 12

Celluose

Answer 12

Not branched thus very strong bonds. Humans cannot ingest cellulose due to lack in cellulase.

Celluose made from Beta glucose

Question 13

Maltose

Answer 13

A disaccharide that is made from two alpha glucose

Question 14

Sucrose

Answer 14

A disaccharide that is made from glucose and fructose

Question 15

Lactose

Answer 15

A disaccharide that is made from galactose and glucose

Question 16

Glucose

Answer 16

Alpha glucose has OH on the first C facing down

Beta glucose has OH on the first C facing up

Question 17

Fructose

Answer 17

Pentagonal structure

Question 18

Galactose

Answer 18

fourth C’s OH is facing up compared to glucose

Question 19

Vitamin

Answer 19

Polar
-More OH groups
-Dissolved in blood
-Blood pass through the liver and thus is excreted
-lots needed
-C and B

Non-Polar
-Little OH groups
-Stored in fatty tissue
-Not needed in large quantities because fat is not easily ridden

Question 20

Digestion of carbohydrates

Answer 20

Amylose and amylopectin are broken down into maltose by amylase in salvia. Crushing the food increases surface area thus higher rate of reaction

Maltose is broken down into glucose by maltase in the small intestine

Question 21

Digestion of protiens

Answer 21

Proteins or polypeptides, start digestion in the stomach. Pepsin breaks it down into dipeptides

Dipeptides are broken down into amino acids for the body to absorb by proteas in small intestine

Question 22

Digestion of triglycerides

Answer 22

Triglyceride is broken down by lipase in the small intestine.

In the small intestine, bile drips down from the pancreas, emulsifying the fat globule

Smaller fat droplets form as a result as bile surrounds it thus it increases in surface area

Lipase enters the small intestine from the pancreas catalyzing the hydrolysis process of fat droplets

Lipase is polar and thus can only interact with the surface of the nonpolar fat droplet however due to droplet size it can react with the whole thing

Question 23

Enzyme + Co enzymes

Answer 23

Enzymes:
- catalyze reaction thus rate of reaction increase and not equilibrium point
- lock and key model predicts that enzyme has specific shape for specific substrate
- induced fit model predicts that enzyme can slightly alter shape by the binding of the substrate however it is still highly specific and can normally only change shapes for isomer of substrate
-Does not change as a result of reaction

Co enzymes
- acts as a proton donor or small molecule donor
- helps substrate physically fit into enzyme as coenzyme changes the tertiary structure of enzyme protein
-can change as a result of the reaction

Question 24

Denaturisation of enyzme

Answer 24

Enzyme is denaturized through extreme pHs or temperatures

Secondary and tertiary structures are broken as a result of breaking the intermolecular bonds

At low pH, the COO group will not ionise thus it will not be negatively charged

AT high pH, the NH3 will not act as base thus it will not be charged

High temperatures literally break the tertiary structure of protein however primary structure is not affected as it is the peptide links.

High temperatures cause the unfolding of the protein chain/s thus causing them to clump together afterward. This known as coagulation

Question 25

Calorimetry

Answer 25

E=VIt (J) E=mcΔT (J) E=Δh x n (J) CF= E/ΔT (J/Degree) Energy Content = E/m (J/g) In a realistic temperature-time graph, the ΔT is best calculated by drawing a line of best fit through when the temperatures start dropping and then finding the difference between the temperature when the current and the temperature when the current turn on on the line of best fit