Chemical Component of Cells Flashcards
What is an atom?
The smallest fundamental unit of matter
Everything comes from the atom. Atom are require to build elements, and elements are required to build organic compound such as water, fat, etc.
What makes an atom?
- Nucleus consist of protons and neutrons
- Electron surrounds the nucleus
The number of protons determine its atomic number and electron, meaning the number of protons determine the identity of the atom.
What is the differences between atomic number and atomic weight
Atomic Number: The number of proton an atom has
Atomic Weight: The number of proton and neutron an atom has in its nucleus
Types of Chemical Bonds
Strong Bonds: Covalent Bond and Ionic Bond
Weak Bonds: Hydrogen Bond, Hydrophilic Bond, Van der Waals
What is a covalent bond?
Electrons are shared between two elements.
For example: HCL
Both Chlorine and Hydrogen only needs one more electron to complete its outer shell. Therefore, they will share their last electron with each other to complete their outer shell.
What is an Ionic Bond?
Electrons are transferred from one atom to another.
Why is it better to transfer electrons in a ionic bond?
Electrons are transferred because it is more favorable for metal atoms to lose their electrons and nonmetals to gain electrons, rather than sharing the electrons.
Example: NaCl
It is better for Na to lose one electrons than to gain 7 electrons. Vice versa, it is better for Cl to gain one electron than to lose electrons. If Na, lose one electron, it will become stable because its outermost shell will be complete and if Cl gain one more electron, it will complete its outershell.
Why does chemical bond occur?
Atoms want to fill their incomplete shell because an incomplete shell is less stable than a complete shell. Therefore, atoms with incomplete outer shell tend to gain or lose electrons to fill their outer shell.
Describe the relationship between the number of chemical bond and how that affects bond strength.
Single bonds are longer but weaker than double and triple bond. More bond prevents rotation, producing a more rigid and less flexible arrangement of atoms. Moreover, the more bond a molecule has, the stronger its attractive force, causing the length to be shorter but stronger. Therefore, the stronger the bond, the more energy is needed to invest to break the bond.
Why is the strength of ionic bonds greatly affected by water but covalent bonds are not?
Water consist of dipole moments that are attracted to the cations and anions in an ionic bond. The partial negative dipole of oxygen is attracted to the cation and the partial positive dipole of hydrogen is attracted to the anion. This cause the salt to dissolve, causing a partially shield charge between ions, separating the salt (which dissolve the salt ).
What is a hydrogen bond?
An electrostatic attraction between a hydrogen atom in one polar molecule and a small electronegative attraction in another atom.
How does a hydrogen bond work?
In each water molecule, there is a slight positive charge on the hydrogen atom because its electron is being attracted by the oxygen atom, resulting a slightly negative charge on the oxygen atom. Therefore, the partial positive charge of the hydrogen is attracted to another slightly negative charge of another atom (usually the oxygen in another water molecule), forming a hydrogen bond.
What is a hydrophobic interaction?
The interaction between non-polar molecules and water that results in the attractions between multiple non-polar molecules.
How does Hydrophobic Interaction work?
Non-polar molecules are repelled in the presence of water molecule until it is attracted to other non-polar molecules to minimize polar contact in its environment.
Example: Fat mixing together in water
Fat molecules tend to clump together to minimize water contact.
What are the properties of water? What is responsible for water’s unique properties?
- Water is polar because of its asymmetrical charge distribution, uneven distribution of molecule from the oxygen. This produces dipole molecules.
Many properties depend on water’s ability to make hydrogen bond
Unique properties of water
- Liquid at room temperature; if the molecule were straight, the charges would cancel each other out, and water would be a gas.
- High Boiling Point; bonding causes linkages in the water molecules which result in the boiling point of water is more than that of the other compounds.
- High Specific Heat; The bonding between other water molecule contributes to water’s high specific heat.
- Surface Tension; Due to water’s dipole moment, the partial charges of water cause a strong electrostatic attraction between other water molecule.
- Lower Density as Solid; the orientation of hydrogen bonds causes molecules to push farther apart, lowering the density
What is an acid?
Any molecule capable of releasing (donating) a hydrogen ion (proton).
What are the characteristic of an acid?
- Acid affects pH by lowering the pH. The higher the concentration of hydrogen ion in a solution, the lower the pH.
- All acid have a conjugate base
Strong Acid: lose their proton easily
Weak Acid: holds on to their proton in the presence of water
-Weak Acids will give up their protons more readily if the H+ concentration is low (and the pH is high) and will hold onto their protons (or accept them back) when the H+ concentration
is high (and the pH is low).
What is a base?
Any molecule capable of accepting a hydrogen ion (proton).
What is the characteristic of a base?
- Raises the concentration of hydroxyl (OH–) ions by removing a proton from a water molecule. This cause pH to rise.
- All base have a conjugate acid.
Strong Base: Fully dissociate in water to form OH- ions.
Weak Base: Partially dissociate in water
What is a Buffer
A solution that consist of a mixture of weak acid and weak base that can resist pH change upon the addition of an acidic or basic components.
What is the application of buffer?
In a cell setting, a buffer keeps the pH of the cell relatively constant under a variety of conditions.
For enzymes, they depend on a buffer to prevent a rapid change in pH that may cause denaturalization.
What are the four major class of biological molecules?
sugar, fatty acid, amino acid, nucleotide
