F3 Food and Humans


ID# 4287
1.

The characteristics of life

Nutrition【營養】

Respiration【呼吸】

Reproduction【繁殖】

Organisms【生物】

Excretion【排泄】

Growth

Movement【移動 】

Sensitivity【靈敏度】

Organisms

  1. Nutrition【營養】
  2. Reproduction【繁殖】
  3. Growth
  4. Movement【移動 】
  5. Sensitivity【靈敏度】
  6. Excretion【排泄】
  7. Respiration【呼吸】
2.

Food requirements of humans

Why do we need food? Food provides us with :

  1. energy to keep our body warm and support daily activities【支持日常活動】;
  2. raw materials for growth and repair【修復】 of body tissues【身體組織】;
  3. substances that keep us healthy.

The seven major food substances are:

Primary food substances【基本食物物質】 that are essential【必需】 to life

  1. carbohydrates【碳水化合物】
  2. lipids【血脂】
  3. proteins【蛋白質】
  4. water

Protective food substances【保護性食物物質】 that keep us healthy and help prevent diseases.

  1. vitamins【維他命 】
  2. minerals【礦物質】
  3. dietary fibre【膳食纖維】
3.

Carbohydrates【碳水化合物】

Carbohydrates are organic substances【有機物質】 which are made of carbon, hydrogen and oxygen.

There are three major types of carbohydrates – monosaccharides, disaccharides and polysaccharides, which differ in their molecular complexity【分子復雜性】.

Monosaccharides

e.g. glucose【葡萄糖】 and fructose【果糖】 in fruits, galactose【半乳糖】

  • small molecules【小分子】 -> properties【特質】
  • soluble【溶於】 in water -> properties
  • readily absorbed【吸收】 in the intestines【腸】
  • transported【輸送 】 in the blood to every part of the body

Disaccharides

e.g. sucrose【蔗糖】 in table sugar, lactose【乳糖】 in milk, maltose【麥芽糖】

  • too large to be absorbed directly【直接地】 in the intestines

Polysaccharides

e.g. starch【澱粉】 in cereals, taros, maize and potatoes

  • made up of long chains【長鏈】 of glucose unit【葡萄糖單位】
  • size is too large for absorption【吸收】
  • broken down into【分解成】 monosaccharides by hydrolysis【水解】
4.

Metabolism【代謝】 Of Carbohydrates【碳水化合物】 In The Human Body

Monosaccharides

e.g. glucose

  • is broken down during respiration to release【釋放】 energy.
  • provides immediate【即時】 energy source【能量源】 for body activities.

glucose【葡萄糖】

+

oxygen

Respiration【呼吸】
————->

energy

+

carbon dioxide

+

water

glucose【葡萄糖】 + oxygen –> (Respiration【呼吸】) –> energy + carbon dioxide + water

Disaccharides

  • broken down into【分解成】 monosaccharides before absorption【吸收】 by hydrolysis【水解】.
  • for hydrolysis to happen, suitable enzyme is required.

maltose【麥芽糖】

+

water

maltase【麥芽糖酶】
————->

glucose【葡萄糖】

+

glucose【葡萄糖】

sucrose【蔗糖】

+

water

sucrase【蔗糖酶】
————->

glucose【葡萄糖】

+

fructose【果糖】

lactose【乳糖】

+

water

lactase【乳糖酶】
————->

glucose【葡萄糖】

+

galactose【半乳糖】

 

maltose【麥芽糖】 + water –> (maltase【麥芽糖酶】) –> glucose【葡萄糖】 + glucose【葡萄糖】

sucrose【蔗糖】 + water –> (sucrase【蔗糖酶】) –> glucose【葡萄糖】 + fructose【果糖】

lactose【乳糖】 + water –> (lactase【乳糖酶】) –> glucose【葡萄糖】 + galactose【半乳糖】

Polysaccharides

  • different types of enzymes are required to break down a starch molecule【澱粉分子】 to form glucose.
Part of a starch molecule

amylase catalyses【催化】 the breakdown of starch to maltose

maltose molecules

maltase【麥芽糖酶】 catalyses【催化】 the breakdown of maltose to glucose

glucose molecules
5.

Functions Of Carbohydrates In The Human Body

  1.  as main source of energy (especially glucose) for metabolism【代謝】 in the body
    • 1g of carbohydrates -> 17.1kj of energy
  2. as energy storage
    • excess【過多的】 carbohydrates are converted【轉化為】 to glycogen【糖原】 or lipids【血脂】
    • glycogen: stored in liver【肝】 and skeletal muscles【骨骼肌】
  3. as a building block【組件】 of larger molecules
    • e.g. nucleic acids【核酸】
  4. cellulose【纖維素】 as a source of dietary fibre【膳食纖維】
    • can’t be digested【被消化】 in human body
    • keeps the digestive system【消化系統】 healthy
6.

Lipids【血脂】

Organic food substances【有機物質】
  • made up of carbon, hydrogen and oxygen
  • insoluble【不溶於】 in water
  • soluble【溶於】 in organic solvent【有機溶劑】. For example, ethanol【乙醇/酒精】

Triglycerides【甘油三酸酯】

One main group of lipids is triglycerides.

Saturated fats【飽和脂肪】

  • at room temperature -> solid
  • main sources -> animals
  • examples -> butter, lard【豬油】, cheese and fatty meat

Unsaturated fats【不飽和脂肪】

  • at room temperature -> oily
  • main sources -> plants and fish
  • examples -> corn oil, olive oil, and salmon
Saturated fats【飽和脂肪】 Unsaturated fats【不飽和脂肪】
At Room Temperature solid oily
Main Sources animals plants and fish
Examples butter, lard【豬油】, cheese and fatty meat corn oil, olive oil and salmon

Metabolism【代謝】 of lipids

A triglyceride molecule is formed from one glycerol【甘油】 molecule and three fatty acid【脂肪酸】 molecules by condensation【凝結】. Before absorbed【吸收】 directly in the digestive tract【消化道】, it must first be broken down【分解】 into smaller molecules by hydrolysis【水解】, in the presence of water and a suitable enzyme【酶】.

Function of lipids

  • source of energy
    • 1 gram of lipid produces 38.9 kJ of energy
  • excess lipids
    • stored in adipose tissues【脂肪組織】 in the body as an energy reserve
    • under the skin as subcutaneous fat【皮下脂肪】 which acts as an insulating layer【絕緣層】 to reduce heat loss
    • around internal organs【內臟】 to act as shock-absorbers【減震器】.
  • transport and storage of fat-soluble vitamins【脂溶性維他命】
    • e.g. vitamin A & D
  • cholesterol【膽固醇】 is a raw material for producing lipid hormones【脂質荷爾蒙】
    • e.g. sex hormones

Bad fats and good fats

Bad fats Good fats
Saturated fats Unsaturated fats
Effects
  1. increase the level of bad cholesterol【膽固醇】 in the blood
  2. bad cholesterol deposits【沉積】 on the inside walls of blood vessels【血管】 and block【堵塞 】 the blood flow【血液流動】
  3. eventually, lead to cardiovascular diseases【心血管疾病】
  1. lower the blood glycerol level【血糖水平】
  2. control blood clotting【血液凝結】
  3. lower blood pressure【血壓】
Examples animal fats, cheese, milk …… egg, avocado, almond ……

Bad Fats / Saturated Fats

  • effects
    1. increase the level of bad cholesterol【膽固醇】 in the blood
    2. bad cholesterol deposits【沉積】 on the inside walls of blood vessels【血管】 and block【堵塞 】 the blood flow【血液流動】
    3. eventually, lead to cardiovascular diseases【心血管疾病】
  • examples
    • animal fats, cheese, milk ……

Good Fats / Unsaturated Fats

  • effects
    1. lower the blood glycerol level【血糖水平】
    2. control blood clotting【血液凝結】
    3. lower blood pressure【血壓】
  • examples
    • egg, avocado, almond ……
7.

Proteins【蛋白質】

Organic substances【有機物質】
  • large complex【複雜】 molecules
  • made up of carbon, hydrogen, oxygen andnitrogen【氮】.
  • some contain sulphur【硫】
  • amino acid【氨基酸】
    • subunits【亞單位】 of protein
    • human requires 20 different types of amino acid to synthesize【合成】 proteins.
      • 11 types are non-essential【非必須】 amino acids, which can be made using other compounds【化合物】 in our body.
      • 9 types are essential【必需】 amino acids, which cannot be made in our body and must be included in our diet.
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