BIO120 Exam 1 Review

What makes one element different from another?

The number of protons in the nucleus, known as the atomic number, determines the identity of an element and distinguishes it from others.

Which four elements are important for life?

Carbon, hydrogen, oxygen, and nitrogenare the four essential elements for all known forms of life.

What molecule is most common in the human body?

Water

What main types of molecules are made mostly of H, C, O & N?

Organic molecules

Emergent properties

new properties that arise with each step upward in the hierarchy of life, owing to the arrangement and interactions of parts as complexity increases

Electronegativity

the tendency of an atom to attract electrons towards itself in a chemical bond.

An element’s reactivity is influenced by what

number of electrons in its outermost shell

valence electrons

electrons in an atom’s outermost orbit

What is the role of electrons in how atoms of different elements react or interact chemically (form bonds)?

Electrons determine an atom's reactivity by influencing its ability to gain, lose, or share electrons during chemical reactions. This behavior is largely dictated by the number of valence electrons in the outermost shell.

How do hydrogen, oxygen and carbon bond to each other?

Hydrogen, oxygen, and carbon bond through covalent bonds, sharing electrons to achieve a full outer shell and stabilize their structures.

What is the role of electrons and orbitals (or valence shells) in covalent bonds?

Electrons in valence shells play a crucial role in covalent bonds by allowing atoms to share electrons, which helps them achieve full outer shells and greater stability.

What is the structure of a water molecule?

two hydrogen atoms covalently bonded to one oxygen atom, forming a bent molecular shape due to the unequal sharing of electrons resulting in a polar molecule.

What makes a water molecule polar?

A water molecule is polar because of the unequal sharing of electrons between the oxygen and hydrogen atoms, leading to a partial negative charge on the oxygen and partial positive charges on the hydrogens.

How does the structure and polarity of water affect its properties?

The structure and polarity of water contribute to its unique properties, such as high surface tension, cohesion, adhesion, and the ability to dissolve many substances, making it an essential solvent in biological systems.

What is an example of a nonpolar molecule?

Methane

Why is Methane a nonpolar molecule?

Methane is a nonpolar molecule because it has a symmetrical tetrahedral shape, which allows the individual bond polarities to cancel out, resulting in no overall dipole moment.

What happens when several water molecules come close to each other?

Cohesion and surface

What happens when several methane molecules come close to each other?

molecules exhibit dispersion forces, leading to weak interactions.

Which is a liquid and which is a gas at room temperature? Why?

Water is a liquid and methane is a gas at room temperature due to water's strong hydrogen bonding, which requires more energy to overcome, while methane has weaker dispersion forces.

How do the hydrogen bonds affect the properties of water, and specifically how water interacts with other kinds of molecules?

They significantly enhance water's cohesion, making it an excellent solvent for polar substances. This results in unique properties such as high surface tension and the ability to dissolve a variety of compounds.

Cohesion

tendency of same molecules to stick together

Adhesion

clinging of one substance to another

Surface Tension

measure of how difficult it is to stretch or break surface of a liquid

Why is carbon the element of life?

Carbon's ability to form stable bonds with many elements, including itself, allows it to create complex molecules essential for life, such as proteins, nucleic acids, carbohydrates, and lipids.

Why is carbon so good at forming many complex molecules?

Carbon has four valence electrons, enabling it to form strong covalent bonds with a variety of elements, leading to a vast array of molecular structures.

Why form polymers from monomers?

Forming polymers from monomers allows for functionality, stability, efficiency, versatility

Process that connects monomers into polymers?

Dehydration (Polymerization)

Process that breaks polymers into monomers?

Hydrolysis

What makes a polymer longer?

A dehydration reaction

What functional groups do carbohydrates consist of?

Carboxyl group + several other hydroxyl groups

How do you build a bigger carb?

With a dehydration reaction, two monosaccharides combine to form a disaccharide, and if you put many saccharides together, you make a polysaccharide

A polysaccharide’s function is what? Give an example for both.

Storage - Starch in plants

Structure - Cellulose in the cell wall

What functional groups do lipids consist of?

Carboxyl + Hydroxyl

What is fat made of?

polymers of glycerol + fatty acids

What is the reaction that links glycerol with a fatty acid?

A dehydration reaction

Why are fats not soluble in water?

Fats are nonpolar molecules, while water molecules are polar. This causes them to repel each other.

Proteins are polymers of what?

Amino acids

How many kinds of amino acids are in our bodies?

20

What determines which amino acids are hydrophobic or hydrophilic?

The chemical properties of the side chain (R-group) of amino acids

What is the process of making a protein (polypeptide)?

Carboxyl group + Amino group

Dehydration Reaction = Polypeptide

Primary structure of a protein

Precise sequence of amino acids

Function = determines shape and function of overall protein

Secondary structure of protein

Segments of coil (alpha helices) or fold (beta sheets)

Function = stability and framework

Tertiary structure of protein

Three-dimensional

Function = determines the specific shape required for the protein’s biological activity

Quarternary structure of protein

Arrangement of multiple polypeptide chains

Function = provides functional complexity by allowing subunits to work together cooperatively

What are nucleic acids?

information rich polymers

What are nucleic acids made up of?

Nucleotides (nucleic acid monomers)

Examples of polynucleotide polymers

DNA, RNA

The bonds that hold together the two polynucleotide polymer strands together to form the double helix are:

Hydrogen bonds between base pairs

What is cell theory?

all living things are composed of cells and all cells come from other cells

We have seen that most cells (that are not egg cells) are pretty small. What is most important reason why cells stay small?

Small cells are better able to take up sufficient nutrients and oxygen to provide for their needs

How many micrometers in a mm?

1,000

About how many human eggs could line up to make a millimeter?

10 human eggs

Why are most cells so small?

Larger surface area/volume ratio allows more oxygen to diffuse through its membrane per unit volume

Is oxygen need in proportion to volume or surface area?

volume

Is oxygen flow into cell in proportion to volume or surface area?

surface area

What are the two main types of cells?

Prokaryotic and Eukaryotic

Which is a key difference between prokaryotes and eukaryotes?

Eukaryotes have a nucleus, prokaryotes do not

Which organelle does not contain DNA?

Lysosomes

The endosymbiosis theory suggests that:

The ancestors of mitochondria may have been symbiotic prokaryotes living inside a larger cell.

Is the plasma membrane permeable?

Yes, but semipermeable

Why do particles move?

Particles move due to thermal energy

Why is equal concentration called equilibrium?

because it represents a state where the movement of particles in and out of a region is balanced

What is osmosis?

diffusion of water across a membrane

What is diffusion?

the movement of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached

What is active transport and what does it require?

the movement of molecules or ions across a cell membrane against their concentration gradient, from an area of lower concentration, to an area of higher concentration; requires ATP

Hypertonic solution

lower concentration inside the cell than outside the cell

Isotonic solution

equal concentration inside the cell as outside the cell

Hypotonic solution

higher concentration in the cell than outside the cell

What are aquaporins?

channel protein that allows water molecules through a membrane

What are aquaporins responsible for?

osmoregulation

What solves the problem of moving ions against a concentration gradient?

Active transport

How do organisms, and the cells that make them up, transform energy for life’s processes?

Organisms get energy from various sources (sunlight, food, chemicals), convert it (photosynthesis, cellular respiration) into usable forms (mainly ATP), store it for future use (as glycogen, starch, or fat), and then use it for a wide range of life processes, including metabolism, movement, growth, and repair.

Exergonic reaction

releases energy

Endergonic reaction

absorbs energy

Exergonic reaction example

A cell breaking down glucose to CO2 and water in cellular respiration

Endergonic reaction example

Plants using light to make glucose from CO2 and water in photosynthesis

The synthesis of ATP from ADP plus a phosphate…

stores energy in a form that can drive cellular work

Nucleus

control center of the cell

Chromatin

tangled, spread out form of DNA found inside the nuclear membrane

Nucleolus

structure where ribosomes are made

Cytoplasm

jelly-like substance the organelles outside the nucleus float in

Rough Endoplasmic Reticulum (ER)

membrane enclosed passageway for transporting materials such as the proteins synthesized by the ribosomes

Smooth Endoplasmic Reticulum (ER)

has no ribosomes

Vesicles

vehicles for proteins and other materials to emerge from the endoplasmic reticulum

Golgi Apparatus

receives the vesicles from the ER, folds the proteins into usable shapes or adds other materials (lipids, carbohydrates)

Vacuoles

sac-like structures that store different materials

Lysosomes

the garbage collectors that take in damaged or worn out cell parts; they are filled with enzymes that break down the cellular debris

Mitochondria

powerhouse of the cell; make ATP molecules that provide the energy for all of the cell’s activities

Cytoskeleton

how the cell holds it shape; includes microfilaments (threads) and microtubules (tubes)

Chloroplast (plant cell)

where photosynthesis happens

Chlorophyll

green pigment inside the chloroplast

Cell Wall

outside the cell membrane; shapes, supports, and protects the plant cell