Unit 1: Chapters 1 & 2 - Introduction to Biology and Chemistry of Biology
Which elements make up the human body?
"Big 4": oxygen, carbon, hydrogen, nitrogen. Others: phosphorus, sulfur, sodium, chlorine, calcium, potassium. (Trace amounts of 15 other elements (<0.1%): minerals that you take in your diet (iron, manganese, etc.))
Draw a diagram of the electron distribution within an atom using the electron shells capacity rules for the first three rows of the periodic table.
(Shells closest to the nucleus have the least energy. The energy increases as you move out and you have more shells.)
What is the atomic mass of an atom that has an atomic number of 9 and contains 10 neutrons?
19 amu
An atom of sulfur has 16 electrons. Which statement below represents the proper positioning of those electrons within sulfur's electron shell?
2 electrons in shell 1, 8 electrons in shell 2, and 6 electrons in shell 3
Define what it means to be a good solvent.
A good solvent is able to dissolve other things.
Which things can disrupt this pH balance by either adding or removing hydrogen ions or hydroxide ions, messing with the ratio?
Acids (lemon juice, vinegar, vitamin C) can add hydrogen ions to the concentration in a solution and because they do that, they lower the pH value/level. Bases (drano, ammonia, baking soda) either release more hydroxide ions or take hydrogen ions out of the solution. They raise the pH level/value.
Water forms a meniscus inside a graduate cylinder. This feat is possible because of which characteristic of water?
Adhesion
Define the term adhesion.
Adhesion is water molecules' ability to interact with other molecules. It's the reason why water forms a meniscus inside a graduated cylinder.
Define the term anion.
Anion (-) = when an atom gains electrons, but the number of protons remains the same, so the whole ion is going to be negatively charged.
How do cohesion and adhesion take place?
As a result of the strong lattice and interaction between water molecules, the process of cohesion and adhesion take place.
Define the term atomic mass.
Atomic mass or mass of an atom is determined by the number of protons and neutrons in the nucleus or the weighted average of the atomic masses of all the different stable isotopes of an element.. Atomic mass = Number of Protons + Number of Neutrons = # P + # N
Define the term atomic number.
Atomic number is the number of protons in an atom. It tells you what specific element you're working with.
Define the term atom.
Atoms are the smallest component of an element that cannot be subdivided further without losing its properties.
Give an example of unequal covalent bonding.
Atoms get partial charges. One of the atoms is a hoarder since it wants to hoard the electrons from the other atoms. For water, oxygen is the hoarder and it kind of wants to hold onto the electrons more strongly than the hydrogens. So, oxygen is going to be a partial negative (more electronegative) and hydrogens are going to partial positives.
Explain how ionic bonding differs from covalent bonds.
Atoms interact in a way that's going to fill each other's outer shells, whether it's permanently, like an ion or temporarily, like a covalent bond. In covalent bonds, electrons are shared between atoms whereas in ionic bonds, electrons are transferred between atoms. Covalent bonds are stronger than ionic bonds.
When is an ion more likely to be a anion?
Atoms with 5, 6 or 7 e- in their outermost shell will tend to gain electrons and become - charged
How does water have surface tension?
Because water can interact with 4 other water molecules, you can create this really cool lattice system of water molecules. Strong lattice creates surface tension, which leads to tiny organisms being able to spread out their weight and walk on water.
Define the term biology.
Biology is a specific field of science that focuses on studying living things.
Define the term cation.
Cation (+) = when an atom loses electrons, but the number of protons remains the same, so the whole ion is going to be positively charged.
Define the term cohesion.
Cohesion is water's ability to stick to itself.
Define covalent bonding.
Covalent bonds: electrons are shared between atoms.
Give an example of ionic bonding.
Create salt when sodium, which has one electron in its valence shell, donates it to chlorine, which only needs to gain one more electron to have a full valence shell. Sodium loses its electron to become positively charged and chlorine gains that electron to become negatively charged. Positive charged sodium interacts with negative charged chlorine and the opposite attraction creates the ionic bond, the sodium chloride ionic compound.
How does water have a high heat capacity? And what does high heat capacity even mean?
Due to water's hydrogen bonds, it has a high heat capacity. It takes a lot of energy to raise the temperature of water to a high enough level to turn it into a gaseous state. In order to change states, all of the hydrogen bonds that connect water molecules have to be broken, which takes a lot of energy.
Define the term element.
Elements are substances that can't be broken down chemically into simpler substances. (Can break a component down into smaller and smaller pieces but each piece still has the same physical and chemical properties as any other piece.)
Define the term non-polar covalent bond and describe the charge that results in this type of bond.
Equal sharing of electrons. No charges.
State the biological significance of pH for humans and other living organisms (e.g. such as the pH of human blood or stomach).
Every organism has its optimal pH level. If it's beyond its optimal pH level, then things aren't going to work properly. For example, we can start disrupting bonds within molecules and if it's a big enough change, it can actually kill the organism. Our stomachs actually have a pH that's between one and two. It's highly acidic and it helps us with digestion.
Give an example of a polar covalent bond.
For water, oxygen is the hoarder and it kind of wants to hold onto the electrons more strongly than the hydrogens. So, oxygen is going to be a partial negative (more electronegative) and hydrogens are going to partial positives.
Define the term hydrogen bonds.
Hydrogen bonds are interactions between two different water molecules due to the polarity of atoms.
How do hydrogen bonds compare to covalent and ionic bonds?
Hydrogen bonds are relatively weaker than covalent and ionic bonds. However, a lot of water molecules have an overall strength.
How does an atom become an ion?
If an atom is not complete, it will be reactive. When the atom is reactive, it reacts and either gains electrons totally or loses them totally. An atom becomes an ion (charged) when it either gains or loses electrons.
How do you differentiate between acids and bases on the pH scale?
If you're higher than 7 for the pH value, it's called a basic solution (more hydroxide ions). If you're lower than 7, it's called an acidic solution (more hydrogen ions). The smaller the pH level, the more hydrogen ions you have. The larger the pH level, the more hydroxide ions you have. If you're adding something to water that doesn't add hydrogen ions or hydroxide ions or doesn't influence those ions in any way, you're not going to change the pH. Every time that you increase pH level, you're actually decreasing (dividing) the hydrogen ion concentration by 10. 0 pH level = 1M hydrogen ion concentration. 14 pH level = 1M hydroxide ion concentration
Define the term pH and be able to state what ions influence the pH of a solution.
In pure water, there'll be an equal number of hydrogen ions (H+) and hydroxide ions (OH-). If you don't have an equal amount of these two ions, then you're going to be either acidic or more basic depending on what type of change you made to the pH. pH is a way for us to examine these changes in ions. It's specifically measuring just the hydrogen ions, but it'll be influenced by the ratio of H+ and OH-. pH is going to measure the negative log of the hydrogen ions: pH = - log [H+ ].
Explain the process of ionic bonding to form ionic compounds.
Ionic bonds: ions are attracted to each other to form ionic bonds. Positive ions attracted to negative ions. Form when one or more electrons are transferred between ions in order for them to have complete valence shells and become stable.
Define the term ion.
Ions are atoms with an electrical charge: positive or negative.
How do ions dissolve differently than polar covalent molecules?
Ions are dissolved through electrostatic attractions, whereas polar covalent molecules that have other partial charges are going to dissolve through hydrogen bonding.
Define the term isotopes.
Isotopes are atoms with the same number of protons (because the atoms come from the same element), but they have a different number of neutrons. Mass number changes.
You add NaCl to water that dissociates as shown below. What will happen to the pH of the solution when this is added (increase/raises, decrease/lowers, or stays the same)? NaCl-> Na^+ + Cl^-
It stays the same
How many elements make up the human body?
Only 10 elements make up 99.9% of the human body.
When is an ion more likely to be a cation?
When an atom has 1, 2 or 3 e- in its outermost shell, it will tend to lose those electrons and become + charged
Define the term buffer and explain how buffers help organisms maintain pH homeostasis within bodily fluids..
Our bodies have a way of protecting us from pH change. The ways that we protect ourselves are through molecules called buffers. Buffers resist pH changes by acting as sponges. They absorb excess ions in solution to make sure that we keep the pH at the level we need it to be. Our bodies need to maintain pH levels that are optimum for our homeostasis. Our blood and respiratory tract have this carbonic acid-bicarbonate buffer system. Humans need the pH value to be between 7.35 and 7.45. If we're too much outside that range, we can be damaged, our cells can be damaged, and there can be problems. When our blood is too acidic, buffers will take up extra hydrogen ions, bringing us back to the neutral pH level. When our blood is too basic, buffers can release hydrogen ions to bring us back down to neutral condition.
Explain the process of forming hydrogen bonds and how the polarity of certain atoms in a molecule can result in formation of hydrogen bonds.
Partial charge on oxygens and hydrogens allows water to interact very well with other water molecules. It creates polarity. So, the partial positive charge of a H atom on one water molecule can interact with the oxygen partial negative of another water molecule. Each water molecule can create 4 hydrogen bonds.
Name the three principal subatomic components that make up the atomic structure and know the location of each within the atom.
Proton (in nucleus) Neutron (in nucleus) Electron (in electron cloud)
Describe the charge and mass of each of the three principal subatomic components that make up the atomic structure.
Proton is positive and its mass is 1 amu. Neutron is neutral and its mass is 1 amu. Electron is negative and its mass is 9x10^-31 amu (ignored).
You have the two solutions, which is more acidic? Solution 1 has an [H+] = 10^-3 M Solution 2 has an [H+] = 10^-5 M
Solution 1 = 10^-3 M
How is a stable isotope different than an unstable isotope?
Stable isotope = number of neutrons is the same as the number of protons. Unstable isotope = radioactive isotopes = number of neutrons isn't the same (usually more than) as the number of protons. These isotopes decay and break down to become more stable. In the process of doing so, they emit radiation.
How does capillary action take place?
The combination of cohesion and adhesion allows water to move against gravity: capillary action (i.e. allows water to move up a tree from the roots as other water molecules evaporate from the leaves).
Give an example of equal covalent bonding.
The number of electrons shared varies depending on how many each atom needs to gain. Hydrogen gas is just 2 hydrogen atoms bound together. They each share their individual electrons to make them both temporarily complete (2 electrons in valence shell) at any point. Electrons are shared equally because they are the same type of atom: non-polar covalent bond.
Define the term hydrophilic.
Things that have partial or ionic charges are hydrophilic: they like water and will dissolve in it.
Define the term hydrophobic.
Water can't dissolve every substance! Non-polar substances cannot dissolve in water because they have no charges to be attracted to the water molecules. Hydrophobic things don't like water. For example: Vegetable oil will completely separate from water and will not dissolve if placed together (hydrophobic).
How is water a good solvent?
Water is a good solvent because it can dissolve any molecule with polar (partial charges) covalent bonds or ionic bonds (full charges) due to hydrogen bonding. The more polar covalent bonds that you have on a molecule, the more it's going to be able to dissolve in water.
Define the term polar covalent bond and describe the charge that results in this type of bond.
Unequal sharing of electrons. Atoms can get partial charges. One of the atoms is a hoarder since it wants to hoard the electrons from the other atoms. So, the hoarder has negative charge and the other atom has positive charge.
Identify whether an atom is stable ("inert") or unstable ("reactive") based on its electron distribution.
We can tell a lot about how an atom is going to be able to react depending on how many electrons it has in its outermost shell. Atoms behave as though they "want" to have a full outer shell. Atoms with full, complete outer shells are non-reactive or inert. (noble gases on far right side of periodic table). Atoms that do not have full outer shells will interact with other atoms to fill those shells. They are reactive. (octet rule)
Describe the pH levels scale.
We have a range of values for pH; it generally goes from 0 to 14 units. There will be differing values of the H+ and OH- ions at different pH levels. pH of 7 is going to be a neutral condition: equal number of H+ and OH- ions.
What happens to the density of water when it freezes? Why?
When water is a solid, it's actually less dense than it is at a liquid state. Frozen solid water will be on top of liquid water. Water molecules interact more in a liquid state and this causes there to be less spacing. However, as water starts to freeze, it forms a lattice that more regularly spaces the molecules, expanding the size of the solid crystal lattice. This is why solid water is less dense than liquid water, which allows it to float on liquid water.
A solution with a pH of 5.0 is considered acidic, basic or neutral?
acidic
All matter on Earth, both living and non-living is made up of ______.
atoms
Certain molecules act like bank accounts for H+ ions because they can absorb excess H+ ions to keep a solution from becoming too acidic and release H+ ions to keep the solution from becoming too basic. Such molecules are called
buffers
Evaporation from the leaves of a tree will pull water up through the roots as an unbroken column throughout the entire height of the tree. This feat is possible because of which characteristic of water?
cohesion
Which of the following statements about chemical bonds is true? A. ionic bonds are formed when two atoms share electrons B. hydrogen bonds occur from the result of an attraction between a positively charged ion and a negatively charged ion. C. covalent bonds form when two atoms share electrons D. covalent bonds form when a hydrogen atom interacts with an oxygen or nitrogen atom due to the attraction between their positive and negative charges.
covalent bonds form when two atoms share electrons
Water molecules form which type of bond with other water molecules?
hydrogen bonds
Which of the following pH values would be classified as an acidic solution? A. pH = 12.0 B. pH = 8.0 C. pH = 3.0 D. pH = 7.0
pH = 3.0
You add H2SO4 to water that dissociates as shown below. What will happen to the pH of the solution when this is added (increase/raises, decrease/lowers, or stays the same)? H2SO4 -> 2H^+ + SO4^2-
pH level on scale decreases because you just added the acid to water. you increase the hydrogen ions in the solution and make it more acidic.
What subatomic particle(s) is/are located inside the nucleus of an atom? _______
protons and neutrons
Relative to protons, electrons have ________.
significantly less mass
