Bailey Bio 130 Final

Phospholipid bilayer

A double layer of phospholipids that makes up plasma membranes; consists of hydrophilic heads and hydrophobic tails.

Fluid-Mosaic model

Describes the cell membrane as a dynamic structure with proteins floating in or on the fluid lipid bilayer.

Permeability

The ability of a membrane to allow substances to pass through it.

Diffusion

The movement of particles from an area of higher concentration to an area of lower concentration.

Osmosis

The diffusion of water across a selectively permeable membrane.

Solute

A substance that is dissolved in a solution.

Concentration gradient

A difference in the concentration of a substance across a distance or membrane.

Membrane channel

Protein pore that allows specific ions or molecules to pass through the membrane.

Carrier protein

A membrane protein that binds to a specific molecule and changes shape to transport it across the membrane.

ATPase/pump

An enzyme that uses ATP hydrolysis to transport ions against their concentration gradient (active transport).

Passive transport

Movement of substances across a membrane without the use of energy (down concentration gradient).

Simple diffusion

Movement of small/nonpolar molecules directly through the phospholipid bilayer.

Facilitated diffusion

Movement of specific molecules across membranes through protein channels or carriers.

Active transport

Movement of molecules against their concentration gradient requiring energy (ATP).

Primary active transport

Direct use of ATP to transport molecules against a gradient.

Secondary active transport

Use of an electrochemical gradient (created by primary transport) to move other substances.

Hypertonic

A solution with a higher solute concentration compared to another solution (causes cell to shrink).

Hypotonic

A solution with a lower solute concentration compared to another solution (causes cell to swell).

Isotonic

Solutions with equal solute concentrations (no net movement of water).

Virus

An infectious agent consisting of genetic material (DNA or RNA) inside a protein coat.

Capsid

The protein shell of a virus.

Enveloped virus

A virus with an outer lipid membrane layer derived from the host cell.

Naked virus

A virus consisting only of a nucleocapsid (no envelope).

Oxidation

Loss of electrons.

Reduction

Gain of electrons.

Mitochondrial matrix

The innermost compartment of the mitochondrion; site of the Citric Acid Cycle.

Intermembrane space

The space between the inner and outer mitochondrial membranes; H+ accumulates here.

ATP synthase

Enzyme that creates ATP from ADP and inorganic phosphate during oxidative phosphorylation.

Electron transport chain

Sequence of carrier molecules that transfer electrons and release energy used to pump H+.

NAD+/NADH

Electron carrier involved in cellular respiration (NAD+ is oxidized, NADH is reduced).

FAD/FADH2

Electron carrier produced in the Citric Acid Cycle.

Glucose

A simple sugar that is an important energy source in living organisms.

Pyruvate

The end product of glycolysis (3-carbon molecule).

Acetyl CoA

The entry compound for the Citric Acid Cycle, formed from pyruvate.

Glycolysis

Metabolic breakdown of glucose into pyruvate; occurs in the cytoplasm.

Citric Acid Cycle (Krebs)

Series of reactions in the mitochondrial matrix that breaks down Acetyl CoA to produce NADH, FADH2, and ATP.

Oxidative phosphorylation

Production of ATP using energy derived from the redox reactions of an electron transport chain.

Chloroplast stroma

Fluid-filled space within the chloroplast; site of the Calvin Cycle.

Thylakoid space

The interior of the thylakoid discs; site of H+ accumulation during photosynthesis.

Photosystem I & II

Protein-pigment complexes in thylakoid membranes that capture light energy.

NADP+/NADPH

The electron carrier used in photosynthesis.

Calvin Cycle

Light-independent reactions in the stroma that convert CO2 into glucose using ATP and NADPH.

Photorespiration

A metabolic pathway where Rubisco reacts with O2 instead of CO2, reducing sugar production.

Stomata

Pores on the leaf surface that allow gas exchange (CO2 in, O2/water out).

C3 plants

Plants that fix CO2 directly into a 3-carbon compound (standard photosynthesis).

C4 plants

Plants that physically separate carbon fixation and the Calvin cycle to minimize photorespiration.

CAM plants

Plants that temporally separate carbon fixation (night) and the Calvin cycle (day) to save water.

Meiosis

Cell division that produces reproductive cells (gametes) with half the number of chromosomes.

Gamete

A haploid reproductive cell (sperm or egg).

Zygote

A diploid cell resulting from the fusion of two haploid gametes.

Diploid (2n)

Containing two complete sets of chromosomes, one from each parent.

Haploid (n)

Containing only one set of chromosomes.

Tetrad (Bivalent)

Structure containing 4 chromatids that forms during meiosis (paired homologous chromosomes).

Random alignment

The random arrangement of homologous chromosome pairs at the metaphase plate during Meiosis I.

Independent assortment

Alleles of different genes are distributed independently of one another during gamete formation.

Crossing over

Exchange of genetic material between homologous chromosomes during Prophase I of meiosis.

Gene

A distinct sequence of nucleotides forming part of a chromosome.

Allele

An alternative form of a gene.

Genotype

The genetic constitution of an individual organism.

Homozygous

Having two identical alleles of a particular gene.

Heterozygous

Having two different alleles of a particular gene.

Phenotype

The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Recessive

An allele that is masked when a dominant allele is present.

Dominant

An allele that expresses its phenotype even in the presence of a recessive allele.

Codominant

A condition in which both alleles for a gene are fully expressed.

Linked genes

Genes located close enough together on a chromosome that they tend to be inherited together.

mRNA

Messenger RNA; carries instructions from DNA in the nucleus to the ribosome.

Template strand

The DNA strand that provides the template for ordering the sequence of nucleotides in an mRNA transcript.

Coding strand

The DNA strand that has the same sequence as the mRNA (except T instead of U).

Transcription

Synthesis of an RNA molecule from a DNA template.

RNA polymerase

Enzyme that links together the growing chain of RNA nucleotides during transcription.

Transcription factors

Proteins that help regulate the transcription of genes.

Promoter

Region of DNA that indicates to an enzyme where to bind to make RNA.

Enhancers

Regulatory DNA sequences that, when bound by specific proteins, enhance the transcription of an associated gene.

Termination signal

A specific sequence of DNA that marks the end of a gene.

mRNA processing

Modification of RNA primary transcripts (splicing, capping, tailing) before leaving the nucleus.

5' cap

A modified guanine nucleotide added to the 5' end of pre-mRNA.

Poly(A) tail

A sequence of 50-250 adenine nucleotides added onto the 3' end of a pre-mRNA molecule.

Translation

Process by which mRNA is decoded and a protein is produced.

Ribosome

Cytoplasmic organelles at which proteins are synthesized.

tRNA

Transfer RNA; carries amino acids to the ribosome.

Start codon

Codon (AUG) that signals to ribosomes to begin translation.

Stop codon

Codon (UAG, UAA, or UGA) that signals to ribosomes to stop translation.

Release factors

Proteins that recognize stop codons and cause the release of the polypeptide chain.

Amino acid R groups

The side chains of amino acids that determine their chemical properties (hydrophobic, hydrophilic, charged).

Silent mutation

A mutation that changes a single nucleotide, but does not change the amino acid created.

Missense mutation

A base-pair substitution that results in a codon that codes for a different amino acid.

Nonsense mutation

A mutation that changes an amino acid codon to one of the three stop codons.

Frameshift mutation

Mutation that shifts the "reading frame" of the genetic message by inserting or deleting a nucleotide.

Anticodon

Group of three bases on a tRNA molecule that are complementary to an mRNA codon.

DNA 5' and 3'

Directionality of DNA strands; phosphate group at 5' end, hydroxyl group at 3' end.

Anti-parallel

The opposite arrangement of the sugar-phosphate backbones in a DNA double helix.

DNA polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule.

Helicase

An enzyme that untwists the double helix of DNA at the replication forks.

Primase

An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.

Semi-conservative replication

Method of DNA replication in which parental strands separate, act as templates, and produce molecules of DNA with one parental DNA strand and one new DNA strand.

Leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

Lagging strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments.

Replication bubble

an unwound and open region of a DNA helix where DNA replication is being performed.

Replication fork

A Y-shaped region on a replicating DNA molecule where new strands are growing.