Carbohydrate

elements: $C$, $H$, $O$

Function

  • Quick energy: glucose in animal; sucrose in plant
  • Short-term storage: glycogen in animal; starch in plant
  • Structure: cellulose in plant

Notes

Simple: Glucose(葡萄糖), Sucrose(table sugar)(蔗糖), Lactose(乳糖)
Complex: Starch(淀粉), Glycogen(糖原), Cellulose(纤维素)

[!Note]
Complex carbohydrate are made from simple carbohydrate.
Glucose is the monomer (subunit) of glycogen, cellulose, starch
Complex carbohydrate are insoluble
broken down by enzymes in organism

Testing

[!Starch]
for Starch: Reagent used: Iodine solution
(blue black for positive else yellow brown)

[!glucose]
for glucose/reducing sugar(还原糖): Reagent used: Benedict’s Solution(copper (II) sulphate and the Cu2+ ions) with HEAT
(brick red for positive, green&orange for slightly positive, else blue)

[!warning]
glucose: (葡萄糖)
glycogen: (糖原)
glycerol: (甘油)

Fats

elements: $C$, $H$, $O$

Function

  • Long-term Storage
  • Thermal insulation
  • Buoyancy for marine animals
  • Component of cell membrane

Example : triglyceride(甘油三酯) (1 glycerol ($C_{3}H_{8}O_{3}$), 3 fatty acids(脂肪酸))
Fat and oil are insoluble
-phobia : fear of something

Testing

[!Lipids]
Ethanol Emulsion Test, Reagent used: ethanol and water

  1. food sample is placed in a test tube with ethanol
  2. test tube is shaken and the fat dissolves into the ethanol. Add water and shake
  3. RESULT: Cloudy for Positive and Transparent for Negative

Proteins

elements: $C$, $H$, $O$, $N$

Function

Growth and repair of tissues
Transport: Part of RBC
Protection: Part of immune system

Example:

Enzymes(酶), antibody(抗体), insulin(胰岛素)

Notes

Proteins are made up of amino acids(氨基酸) (20 different types of amino acid)

Tests

[!Proteins]
Reagent used: Biuret Solution
purple for Positive and blue for Negative

[!Vitamin C]
Reagent used: DCPIP Solution
Add food juice into DCPIP
Transparent for Positive and blue for Negative

This reaction is a redox reaction: vitamin C (ascorbic acid) is oxidized to dehydroascorbic acid, and DCPIP is reduced to the colorless compound DCPIPH2
DCPIP (blue) + H+ → DCPIPH (pink)
DCPIPH (pink) + vitamin C → DCPIPH2 (colorless)

Water

[!Note]
solvent
essential for digestion to provide a medium for enzymes to act in
transport solutes around the body and transport waste products to be excreted

DNA

Notes

Structure: double helix(双螺旋)
Subunit: nucleotide(核苷酸)
Three components of a nucleotide:

  • sugar - deoxyribose(脱氧核糖) ($H−(C=O)−(CH_{2})−(CHOH)_{3}−H$)
  • phosphate(磷酸盐)
  • base

Sugar + phosphate

Sugar phosphate backbone (糖-磷酸骨架)

Bases

base sequence makes up genes, which code for proteins
Function: storing, coding and transferring biological information though its unique structure.
Four types: A, T, C, G
Base pairing: A to T, C to G, complementary(互补)
Example: ATTCGCTA - TAAGCGAT