Step 1 : Overvation
    Step 2: Formulate a hypothesis
    Step 3: Devise a testable prediction
    Step 4: Conduct experiments
    Step 5: Draw conclusions, make revisions

    1. Pseudoscience: individuals make scientificsounding claims that are not supported by trustworthy, methodical scientific studies 伪科学
    2. Anecdotal observations: based on only one or a few observations, people conclude that there is (or is not) a link between two things. 只有少数实验结果，偶然性

    Water properties:

    1. Cohesion: Hydrogen bonds 氢键 make water molecules stick together - make water conhesive
    2. Large heat capacity 比热容大: water resists heating b/c heat energy from sun is used up breaking and re-forming hydrogen bonds.
    3. Low density as a solid
    4. 固体密度低 - frozen water is less dense due to arrangement of water molecules.
    5. good solvent 良好的溶剂 - water pries apart ionic bonds dissslving ionic compounds.

    Chemical basis:

    1. chemical bond 化学键: interaction of electrons between atoms that holds them together. (when atoms share electrons in order to become more stable, that is a covalent bond 共价键)
    2. Atom structure: Core(protons + 质子, neutrons 中子， electrons - 电子)
    3. ionic bonds 离子键: one atom transfers one or more electrons to another atom. 如Salt cystals: Na+ Cl-

    image.png

    carbohydrates -> simple sugars -> energy
    proteins -> amino acids -> enzymes and structural proteins
    fats -> fatty acids and glycerol 甘油
    nucleic acids 核酸-> nucleotides 核苷酸 -> DNA/RNA

    Polar and Non-polar:
    极性分子 和 非极性分子
    Polar: 1) 对称 2) 同类互溶 3)boiling point/melting point 沸点熔点 通常比非极性分子高 HCl, H2O, NH3
    Non-polar: 1)不对称 2) 同类互溶 3) 低 N2, CO2, CCl4

    Protenins structure:
    image.png

    Enzymes 酶
    Enzymes are proteins that initiate and speed up chemical reactions.

    • Activation energy: the chemical reactions need a little push in order to initiate reaction
    • Enzymes act as catalyst by lowering the activation energy
    • Enzyme activity is dependent on multiple variables, like PH and temperature, salt

    Enzymes reduce activation energy in following ways:

    1. By stressing, bending, or stretching critical chemical bonds
    2. By directly participating in the reaction
    3. By creating a microhabitat that is conducive to the reaction 创造有利于微生物的环境
    4. By simply orienting or holding substrate molecules in place so that they can be modified

    lactose

    • Without enzymes, the reaction to break down lactose 乳糖( which is a sugar found in milk, lactose intolerant 乳糖耐受 people cannot break it down) or synthesize lactose would be very slow.

    gluten
    gluten - gliadins 麦胶蛋白 and glutenins 谷蛋白, the gliadins are responsible for the problems in celiac disease

    • celiac disease: a disease in which the small intestine 小肠 is hypersensitive to gluten, leading to difficulty in digesting food.
    • Untreated celiac disease results in atrophy 萎缩 of the intestinal villi 小肠绒毛—projections of the small intestinal wall that facilitate efficient absorption of nutrients. This atrophy can lead to long-term dietary deficiencies and increased risk of other disorders such as lymphoma淋巴瘤
    • lipase 脂肪酶, amylase 淀粉酶, proteases and peptidases 蛋白酶 肽酶

    Membranes 细胞膜组成成分
    image.png
    plasma membrane细 胞质膜
    phosphate group 磷酸基团 亲水 hydrophilic
    fatty acid 脂肪酸 疏水, hydrophobic

    Plasma Membrane proteins 膜蛋白
    (cholesterol 胆固醇 帮助细胞膜保持流动性flexibility)

    • receptor proteins 受体蛋白 接受外部受体 eg. “beta blockers” reduce anxiety
    • transport proteins 转运蛋白
    • recognition proteins 识别蛋白: provide a fingerprint for the cell, so it can be recognized by other cells; eg. transplants
    • membrane enzyme 膜酶

    image.png
    Quiz: why fatty acid tails of a phospholipid hydrophobic? fatty acids are non-polar, and they are composed of carbon-hydrogen bonds

    Cystic Fibrosis (CF )囊性纤维化
    Airway with CF: thick, sticky mucus blocks the airway
    Symptoms: Weight loss, chronic lung infections
    Treatment: break up mucus, antibiotics, digestive enzymes
    image.png

    Reason for CF:
    chloride 氯离子 is trapped in the cell 因此细胞膜内浓度大，会吸收细胞膜外的水分，使外部变成粘液
    Excess salt in the cells would cause them to suck in water from surrounding mucus, leaving it sticky and thick, allowing infection to set in. The excess salt also accounted for the salty sweat —all defining features of CF.

    • distinct mutations make the CF be difficult to cure

    CF TYPES:
    image.png

    Cardiovascular disease

    Angioplasty: procedure used to restore blood flow through the artery
    Coronary Artery Bypass Graft: 心脏搭桥

    Lipidids:
    Typical features:

    • non-polar molecules that do not dissolve in water
    • greasy to the touch
    • can be a significant source of energy storage

    Types:

    • Fats 脂肪 long-term energy storage and insulation
    • sterols 固醇类 regulate grouth and development
    • phospholipids 磷脂 form cellular membranes 细胞膜组成成分

    Saturated vs. unsaturated fats

    image.png
    Saturated fats: pack closer together, solid in room temperature.
    Unsaturated fats: disrupting close packing, liquid at room temperature.

    • rancid foods 腐臭的食物 results from cleavage of double bonds in unsaturated fats 双键断裂

    HOW TO SAVE UNSATURATED FATS LONGER?
    -> Hydrogenation: hydrogenation is the artificial addition of hydrogen atoms to an unsaturated fat in order to make the fat more saturated.

    • Partially hydrogenated fats = trans-fats

    Cholesterol 胆固醇

    • important component of most cell membranes
    • liver produce almost 90% of the ciculating cholesterol

    eg. Steroid hormones 类固醇激素, bile acids 胆汁, vitamin D
    image.png

    Diabetics
    Type 1: 无法分泌胰岛素insulin. Glucose cannot enter cells. All energy must be derived from fats.
    Type 2(mainly): insulin is produced but the insulin-signaling pathway is not responsive, a condition referred to as insulin resistance. 胰岛素受体基因突变, target cells become insulin resistant
    image.png
    Advanced Glycated End products (AGE) 进一步糖化最终产物

    • Hyperglycemia 高血糖

    image.png

    Cancer cell

    1. contact inhibition
    2. divided indefinitely
    3. less stickiness

    Tumor develops:
    image.png

    Recombination and Independent assortment:
    Recombination - homologous chromosomes exchage genetic information
    Independent assortment - random separation of maternal and paternal homomologous chromosomes.