Lec 2. Biomolecules & Protein Synthesis

Structures of atoms

Structures of atoms

• Central atoms: nucleus has 6 protons = 6 neutrons

• Around nucleus: orbital contains electrons

What are charges of protons, neutrons, and electrons?

Protons (+), neutron : no charge, electrons (-)

T/F: Protons and neutrons are equal.

True

How many types of chemical bonds?

Three types: Ionic, covalent, and hydrogen bonds

What is ionic bonds? How do ionic bonds occur?

• Electron is transferred from one element to another

• Occurs when electronegativity of 1 atom has to be strong (really wants electrons), and the other one has to be very weak →once occurred, it is easy for an electron to be transferred from one element to the other.

• Between 2 ions w/ opposite charge

Give an example of ionic bonds?

NaCl. At outer shell, Na has 1 electron and Cl has 7 electrons. Purpose: atoms want their out shell to be filled up. Hence, Cl really wants electrons (high electronegativity) while Na does not (low electronegativity). Electrons are completely transferred from Na to Cl, then Na(+) and Cl (-) bind together since they are opposite attracted, called ionic bonds.

What is covalent bonds?

• Very common, electrons are shared

• Electronegativity: relatively equal

How many types of covalent bonds and their characteristics? Give examples.

• non-polar: equal sharing (ex: CH4)

  • H is pulled into 4 diff. directions, but still balanced → equal sharing

• polar: unequal sharing (ex: H2O)

  • H2O are sharing electrons between H and O, the electrons spend more time by the O (move around slowly), while spends less time by the H (move fast) → unequal sharing. From this, the area by O has slightly negative charge whereas the area by H has a slightly positive charge

What is hydrogen bonds? Give examples.

• Opposite partial charges on adjacent molecules → attraction

• Slight + charge (near H) and (-) charge (near O) → attraction

  • Ex: water molecules binding to each other

What is biomolecules?

• Molecules synthesized by cells

• Contain C-C covalent bonds

  • Often form ring or chain structures

How do we make biomolecules? Give examples

• Dehydration synthesis:

  • Forming covalent bonds by removal of water

  • Ex: H2O is removed via dehydration synthesis to form a new bond between glycerol and fatty acid

How do we break biomolecules?

• Hydrolysis: breaking covalent bonds by addition of water

How many types of biomolecules?

4 types:

• Carbohydrates

• Lipid

• Proteins

• Nucleic acids

What is carbohydrates and its properties?

• Contains: C, H, and O

• C + H2O → carbohydrates exists at ratio 1C : 2H : 1O

• Properties: polar → hydrophilic (water loving)

How many types of carbohydrates?

2 types: simple sugars and complex carbohydrates

What is category and functions of simple sugars?

• Function: fast energy

• Types:

  • Monosaccharides: one sugar (ex: glucose, fructose)

    • Disaccharides: 2 sugars (ex: sucrose, lactose) → 2 monosaccharides link together via dehydration to form disaccharides (ex: glucose + fructose → sucrose)

What is category and functions of complex carbohydrates?

• Function:

  • Energy storage

  • Structural support

  • Components of cell membranes

• Types:

  • Polysaccharides: chain of sugars

  • Ex: starch, glycogen, cellular, chitin

Give examples of polysaccharides?

• Starch: our body does not use for energy storage

• Glycogen: store excess glucose in blood. Once the body has excess glucose, the liver, muscle, and fat absorb the glucose into the cells and the. they take whatever they need. Later on, the leftovers are linked together to form glycogen, which is a complex carbohydrates

• Cellular: main component of plant cell wall and gives structural support

• Chitin: gives structural support, commonly found in diff fungi, main component of the exoskeleton of diff shellfish, such as shell of crabs, shell of lobster.