Key Concepts in Biology: Elements, Bonds, and Processes

Four elements in living organisms

Carbon, Hydrogen, Oxygen, Nitrogen

Proton

Positive charge - Located in nucleus

Neutron

Neutral charge - Located in nucleus

Electron

Negative charge - Located in electron cloud/orbitals

Covalent bond

Sharing of electrons between atoms

Polar covalent bond

Sharing of electrons is unequal due to differences in electronegativity. One atom is slightly more positive, the other more negative.

Ionic bond

Electrons are transferred from one atom to another, creating oppositely charged ions that attract.

Hydrogen bond

Weak attraction between a slightly positive hydrogen atom and a slightly negative atom (often oxygen or nitrogen).

pH scale

Measures hydrogen ion (H⁺) concentration

pH unit difference

Each difference in one pH unit represents a 10x difference in H⁺ concentration. Example: pH 2 is 1000x more acidic than pH 5.

Buffer

Maintains pH by neutralizing small amounts of acids or bases.

Dehydration synthesis

Builds molecules (removes water)

Hydrolysis

Breaks down molecules (adds water)

Unsaturated fatty acids

Fatty acids with double bonds.

DNA vs RNA

DNA is double-stranded; RNA is single-stranded. DNA has deoxyribose sugar; RNA has ribose sugar. DNA has thymine; RNA has uracil.

Phospholipid

Made of a glycerol, two fatty acid tails, and a phosphate group.

Hydrophilic

Water-loving (polar)

Hydrophobic

Water-fearing (nonpolar)

Prokaryotic chromosomes

Prokaryotes have circular chromosomes.

Eukaryotic chromosomes

Eukaryotes have linear chromosomes in a nucleus.

Plant cell organelles

Chloroplasts, Central vacuole, Cell wall.

Animal cell organelles

Centrioles, Lysosomes (more prominent).

Nucleus function

Stores DNA, controls the cell.

Plasma membrane function

Regulates what enters/exits the cell.

Golgi apparatus function

Packages and ships proteins.

Photosynthesis equation

6CO2 + 6H2O → C6H12O6 + 6O2

Products of photosynthesis

One molecule of glucose (a six-carbon sugar) and six molecules of oxygen.

Reactants of photosynthesis

6CO2 and 6H2O.

Osmosis

Diffusion of water; Type of transport: Passive.

Exocytosis

Vesicles fuse with the plasma membrane to release contents.

Phosphorylation

Term for adding phosphate with ATP.

Enzymes

Speed up (catalyze) chemical reactions by lowering activation energy.

Aerobic respiration

Requires oxygen.

Anaerobic respiration

Does not require oxygen.

ATP production

Aerobic respiration makes more ATP.

Yeast

Facultative anaerobe.

Cristae

Structure that increases surface area in mitochondria.

ATP synthase

Enzyme for ATP production.

Cell cycle

Includes interphase and mitosis phases.

G1 phase

Cell growth, makes proteins.

S phase

DNA replication.

G2 phase

Prepares for division, copies centrosomes.

G0 phase

Cell exits cycle and stops dividing.

Prophase

Chromosomes condense, spindle forms.

Metaphase

Chromosomes line up at center.

Anaphase

Chromatids separate.

Telophase

Nuclear membrane reforms.

Cytokinesis

Cytoplasm splits (cleavage furrow in animals, cell plate in plants).

Benign tumor

Does not spread.

Malignant tumor

Invades tissues, can metastasize.

Prophase I of Meiosis

Crossing over - exchange of genetic material between homologous chromosomes.

Nondisjunction example

Extra chromosome #23: Klinefelter syndrome (XXY).

Alleles

Found at the same locus on homologous chromosomes.

Incomplete dominance

One allele doesn't fully mask another - produces intermediate phenotype (e.g., red + white = pink).

Codominance

Both alleles are fully expressed (e.g., AB blood type).

Sex-linked traits in males

They have only one X chromosome, so recessive traits on it are expressed without a second X to mask it.

Mutation

Change in DNA nucleotide sequence.

Dolly the sheep cloning

A differentiated cell nucleus still retains the full genetic potential to develop an entire organism.

Restriction enzymes in bacteria

Protect bacteria by cutting up foreign (e.g., viral) DNA.

Homologous structures

Suggest common ancestry between organisms.

Population

Group of the same species living in the same area.

Natural selection

Process that causes the 'fittest' to survive.

Allopatric speciation

New species form due to geographic separation.

Sympatric speciation

New species form without geographic isolation (e.g., due to behavioral or reproductive barriers).

Types of selection

Includes directional, stabilizing, and disruptive selection.

Producer

Makes energy from sun (plants).

Primary consumer

Eats producers (herbivore).

Secondary consumer

Eats primary consumers (carnivore).

Decomposer

Breaks down dead matter (fungi, bacteria).

Keystone species

Species that has a large impact on ecosystem balance.

Products of Krebs Cycle

6 NADH, 2 FADH2, 4 CO2, 2 ATP

Reactants of Krebs Cycle

2 Acetyl CoA

Reactants of Glycolysis

glucose, 2 ATP, 2 NAD+

Products of Glycolysis

2 ATP, 2 NADH, 2 pyruvate

Reactants of Calvin Cycle

CO2, ATP, NADPH

Products of Calvin Cycle

glucose, ADP, NADP+