Foundations of Biology Exam 2

Atom

basic unit of chemical structure; basic unit of chemical structure

Electron

One unit of a negative charge

Proton

One unit of positive charge

Neutron

 Neutral charge

Element

Substance that cannot be broken down to other substances; Same type of atom

Molecule

2 or more atoms held together by covalent bonds

Ionic bond

occurs when electrons are transferred between 2 atoms and the 2 resulting to be attracted to one another.

Covalent bond

formed between two atoms ( with incomplete outer orbitals) which are a pair of electrons

Polar covalent bond

atoms that DON'T share electrons equally

Hydrogen bond

Weak chemical bond, when it is slightly attracted to another molecule with the opposite charge

What is an acid?

 A substance that increases the hydrogen ion concentration of a solution

What is a base?

A Substance that reduces the hydrogen ion concentration of a solution

What is a buffer?

Sets of chemicals that keep PH of a solution stable, A solution that contains a weak acid and its corresponding base. A buffer minimizes changes in pH when acids or bases are added to the solution.

Why is pH important biologically?

A measure of hydrogen ion concentration equal to -log[H+] and ranging in value from 0 to 14.

Autotroph

An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from oxidation of inorganic substances to make organic molecules from inorganic ones.

Heterotroph

Biological importance: They depend on autotrophs (like plants) for energy and carbon.  

Must eat others for energy; Examples: Humans, lions, fungi, most bacteria.

Heterotroph

Aerobic

 Refers to processes (or organisms) that require oxygen.

Requires Oxygen;

Aerobic respiration in human cells uses oxygen to completely break down glucose into carbon dioxide and water, producing lots of ATP.

Aerobic

Anaerobic

Refers to processes (or organisms) that do not require oxygen; some may even die in its presence.

 Does not Require energy;

Fermentation in yeast or human muscle cells (produces ethanol or lactic acid).

Anaerobic

Facultative Anaerobe

An organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present.

Cytoplasm

the contents of the cell bound by the plasma membrane

Flagellum

a long cellular appendage specialized for motility

Ribosomes

site of protein synthesis, composed of RNA and protein

Thylakoid membranes

• the network of infolded cell membrane where photosynthesis takes place in autotrophic bacteria

Nucleoid

the region of a prokaryotic cell where the genetic material (circular DNA) is located

Plasma membrane

regulates exchange of materials between the cytoplasm and surroundings

Respiratory membranes

infoldings of the cell membrane where cellular respiration occurs, site of ATP synthesis

Cell wall

outer layer of bacterial cells that maintains cell shape; most have peptidoglycan

Capsule

a layer of protein and/or polysaccharide that surrounds the bacterial cell wall and helps cells adhere to surfaces or each other

Plasmid

a small circular DNA molecule often carrying genes for antibiotic resistance

Simple Diffusion

Movement of small, nonpolar molecules directly across the membrane from high to low concentration.

Example: Oxygen (O₂) or carbon dioxide (CO₂).

Simple Diffusion

Simple Diffusion

No energy or transport proteins required.

Osmosis

Diffusion of water across a selectively permeable membrane.

Example: Water moving into a bacterial cell when placed in hypotonic solution.

Osmosis

Osmosis

Water moves toward higher solute concentration.

Facilitated Diffusion

Movement of molecules down their concentration gradient but using transport proteins (channels or carriers).

Example: Glucose entering a cell via a permease protein.

Facilitated Diffusion

Facilitated Diffusion

No energy required, but needs a protein "helper."

Active Transport

Movement of molecules against their concentration gradient using

Active Transport

Requires energy and proteins.

Example: Sodium-potassium pumps in some bacteria; nutrient uptake pumps.

Active Transport

Phototrophs

organisms that obtain energy from light.

Chemotrophs

organisms that obtain energy from chemicals (organic or inorganic).

What elements are common across all biological organisms? What are these elements used for?  Illustrate with specific examples.

• Nitrogen (N)

  • Role: Essential for amino acids (building blocks of proteins) and nucleotides (DNA/RNA).

  • Example: Nitrogen is part of the nitrogenous bases (A, T, G, C, U) in nucleic acids.

• Oxygen (O)

  • Role: Required for cellular respiration; major component of water and organic molecules.

  • Example: Oxygen is the final electron acceptor in aerobic respiration, enabling ATP production.

• Phosphorus (P)

  • Role: Key in nucleic acids (DNA/RNA backbone) and energy transfer molecules like ATP.

  • Example: ATP (adenosine triphosphate) stores energy in phosphate bonds.

• Sulfur (S)

  • Role: Found in certain amino acids (cysteine, methionine) and vitamins; important for protein structure.

  • Example: Disulfide bonds between cysteines stabilize protein structures like keratin in hair.

How do prokaryotes reproduce?

Prokaryotes reproduce by binary fission (asexual).

In what ways are bacteria important to society?

Food, biotechnology, waste cleanup.

In what ways are bacteria important to ecosystems?

Nutrient cycling, nitrogen fixation, oxygen production.

In what ways are bacteria important to humans?

Gut health, vitamin production, but also disease.