Biology Concepts: Chemistry, Cells, Genetics, and Evolution

Nucleic acid elements

Identifying elements include carbon, hydrogen, oxygen, nitrogen, and phosphorus (CHONP).

Nucleic acid structure

A long, chain-like macromolecule (DNA or RNA) built from repeating subunits called nucleotides.

Pentose sugar in DNA

Deoxyribose.

Pentose sugar in RNA

Ribose.

Phosphate group

Links the sugars of neighboring nucleotides through phosphodiester bonds, forming the sugar-phosphate backbone.

Nitrogenous bases in DNA

Purines: adenine (A), guanine (G); Pyrimidines: cytosine (C), thymine (T).

Nitrogenous bases in RNA

Purines: adenine (A), guanine (G); Pyrimidines: cytosine (C), uracil (U).

Chemical bond changes in reactions

Bonds can either break (requires energy) or form (releases energy).

Energy release in reactions

If a reaction releases energy, it's more likely to happen on its own.

Energy absorption in reactions

If a reaction absorbs energy, it needs a source of energy to occur.

Role of enzymes

Enzymes are catalysts that accelerate reactions by reducing activation energy.

Cell theory main points

All living things are made of cells, cells are the basic units of structure and function, new cells are produced from existing cells.

Eukaryotic cells

Have membrane-bound organelles, including a nucleus.

Prokaryotic cells

Do not have a nucleus and have different DNA structures.

Cell nucleus role

Controls cell activities and contains DNA.

Organelles for protein transport

Ribosomes, rough endoplasmic reticulum, and Golgi apparatus.

Vacuoles function

Store water, salts, and proteins.

Lysosomes function

Break down waste and old cell parts.

Lysosomes

Break down waste and old cell parts.

Cytoskeleton

Supports cell shape, movement, and transport.

Chloroplasts

Photosynthesis (in plants).

Mitochondria

Cellular respiration (energy production).

Cell membrane

Regulates what enters and exits the cell; provides protection and support.

Passive transport

Movement of molecules without energy, from high to low concentration (e.g., diffusion, osmosis).

Active transport

Movement of molecules using energy, from low to high concentration (e.g., endocytosis, protein pumps).

ATP

Provides energy, allowing them to power essential processes like muscle contraction, nerve impulse transmission, and chemical synthesis. Stores and releases energy quickly for cell functions.

Photosynthesis

Plants convert sunlight, water, and CO₂ into glucose and oxygen.

Pigments

Absorb light energy (e.g., chlorophyll absorbs blue/red light, reflects green).

Electron carrier molecules

Molecules that use energy to transport electrons to another place. Transport high-energy electrons (e.g., NADP⁺ → NADPH).

Reactants and products of photosynthesis

CO₂ + H₂O + light → C₆H₁₂O₆ + O₂.

Light-dependent reactions

Occur in thylakoids; produce ATP, NADPH, and O₂.

Light-independent reactions

Occur in the stroma; they use ATP and NADPH to make glucose from CO₂.

Factors affecting photosynthesis

Light intensity, temperature, CO₂ concentration, and water availability.

Cellular respiration

A process that releases energy by breaking down glucose in the presence of oxygen.

Relationship between photosynthesis and cellular respiration

Opposite processes—photosynthesis stores energy; cellular respiration releases it.

Glycolysis

Glucose is broken into 2 pyruvate molecules; 2 ATP are made; this occurs in the cytoplasm.

Krebs Cycle

Pyruvate is broken down; CO₂ is released; makes NADH and FADH₂; occurs in mitochondria.

Electron transport chain

Uses high-energy electrons to generate ATP; oxygen is the final electron acceptor.

ATP generated by cellular respiration

36-38 ATP per glucose molecule.

Anaerobic respiration

Cells use fermentation (e.g., lactic acid or alcoholic) to produce small amounts of ATP when oxygen is not available.

Body ATP production during exercise

Short-term: ATP from stored energy and lactic acid fermentation. Long-term: Cellular respiration with increased oxygen intake.

Difficulties faced by growing cells

Less efficient transport; DNA overload. Places more demand on its DNA.

Asexual reproduction

Has an exact copy of itself, making 2 genetically identical cells.

Sexual reproduction

Has DNA from 2 different parents, genetically different.

Role of chromosomes during cell division

Carry genetic information and ensure accurate distribution during division.

Main events of the cell cycle

Interphase: G1 (Gap 1), S phase (Synthesis - DNA replication), G2 (Gap 2).

M Phase

The phase of the cell cycle where mitosis occurs.

Mitosis

The process of cell division that results in two identical daughter cells.

Prophase

Chromosomes condense and become visible; the nuclear envelope breaks down; spindle fibers begin to form from centrioles.

Metaphase

Chromosomes line up in the middle of the cell (the metaphase plate) and spindle fibers attach to the centromeres of chromosomes.

Anaphase

Sister chromatids separate and move to opposite ends of the cell, resulting in each side having a complete set of chromosomes.

Telophase

Chromosomes uncoil back into chromatin; nuclear envelopes form around each set of chromosomes; spindle fibers disappear.

Cytokinesis

The process where the cytoplasm divides, forming two separate daughter cells; in animal cells, the cell membrane pinches in (cleavage furrow), while in plant cells, a cell plate forms.

Cancer Cells

Cells that divide uncontrollably and ignore signals to stop dividing.

G0 Resting Phase

A phase where cells are in a state of dormancy and do not divide.

Gregor Mendel

The scientist known for his work on the inheritance of traits in pea plants, establishing the laws of inheritance.

Genes

Units of heredity that are inherited from parents and determine unique characteristics of an organism.

Segregation

The process during gamete formation where different forms of a gene are distributed to offspring.

Independent Assortment

The principle that alleles for different genes segregate independently when genes are on different chromosomes.

Dominant Traits

Traits that are expressed in the phenotype even when only one copy of the allele is present.

Recessive Traits

Traits that are expressed in the phenotype only when two copies of the allele are present.

Incomplete Dominance

A pattern of inheritance where the phenotype is a blend of the two parental traits.

Codominance

A pattern of inheritance where both alleles in a heterozygote are fully expressed.

Polygenic Traits

Traits that are controlled by multiple genes, resulting in a continuous range of phenotypes.

Sex Linked Inheritance

Inheritance patterns where genes are located on sex chromosomes.

Diploid

Cells that contain two sets of chromosomes, typical of adult organisms.

Haploid

Cells that contain one set of chromosomes, typical of gametes.

Meiosis I

The first division in meiosis where homologous chromosomes separate.

Meiosis II

The second division in meiosis where sister chromatids separate.

DNA

The molecule that carries genetic information and is composed of sugar, phosphate, and nitrogen bases (A, T, C, G).

DNA Polymerase

The enzyme that adds new nucleotides during DNA replication.

RNA

A single-stranded nucleic acid that contains ribose sugar and replaces thymine (T) with uracil (U).

Transcription

The process by which RNA is synthesized from a DNA template using RNA polymerase.

Codons

Three-letter codons specify amino acids.

Ribosome

Links amino acids to form proteins.

Molecular Biology

Shows how DNA → RNA → Protein connects genetics and function.

Mutations

Point mutations, insertions, and deletions.

Gene Mutation Effects

Can change protein function or be silent; some lead to disease.

Natural Selection

Theory of natural selection.

Biodiversity Patterns

Species vary globally, locally, and over time.

Earth's History

Earth is old; geological processes shape life.

Lamarck's Proposal

Proposed acquired traits (later disproved).

Population Growth

Populations grow faster than resources.

Artificial Selection

Humans breed traits they find desirable.

Natural Selection Conditions

Variation, heritability, overproduction, differential survival.

Unity and Diversity of Life

Common ancestry explains both unity and diversity.

Geographic Distribution

Related species adapted to different environments.