Molec Cell Unit 1

Eukaryote

Cells with a nucleus bounded by a nuclear membrane

Prokaryote

Class of organisms, including bacteria and archaea, that lack a true membrane-limited nucleus and other organelles

DNA

Long linear polymer, composed of four kinds of deoxyribose nucleotides, that is the carrier of genetic information

mRNA

Any RNA that specifies the order of amino acids in a protein (i.e., the primary structure). It is produced by transcription of DNA by RNA polymerase. In Eukaryotes, the initial RNA product (primary transcript) undergoes processing to yield functional mRNA

Protein

A macromolecule composed of one or more linear polypeptide chains and folded into a characteristic three dimensional shape in its native, biologically active site

The Central Dogma of Biology

Genetic information flows in one direction: from DNA to RNA, and then to proteins

Transcription

Process in which one strand of DNA molecule is used as a template for synthesis of a complementary RNA by RNA polymerase

Translation

The ribosome-mediated assembly of a polypeptide whose amino acid sequence is specified by the nucleotide sequence in an mRNA

Organelle

Any membrane-limited subcellular structure found in eukaryotic cells

Nucleus

Large membrane-bounded organelle in eukaryotic cells that contains DNA organized into chromosomes; synthesis and processing of RNA and ribosome assembly occur in nucleus

Cytosol

Unstructured aqueous phase of the cytoplasm excluding organelles, membranes, and insoluble cytoskeletal components

Plasma membrane

The membrane surrounding a cell that separates the cell from its external environment; consists of a phospholipid bilayer and associated membrane lipids and proteins

Cell Wall

A specialized, rigid extracellular matrix that lies next to the plasma membrane, protecting a cell and maintaining its shape; prominent in most fungi, plants, and prokaryotes but absent in most multicellular organisms

Endoplasmic reticulum (ER)

Network of interconnected membranous structures within the cytoplasm of eukaryotic cells contiguous with the outer nuclear envelope. The rough ER, which is associated with ribosomes functions in the synthesis and processing of secreted and membrane proteins; the smooth ER, which lacks ribosomes functions in lipid synthesis

Golgi complex

A membrane-bound cell organelle that processes, packages, and sorts proteins and lipids

Mitochondria

Large organelle that is surrounded by two phospholipid bilayer membranes, contains DNA, and carries out oxidative phosphorylation, thereby producing most of the ATP in eukaryotic cells

Chloroplast

A specialized organelle in plant cells that is surrounded by a double membrane and contains internal chlorophyll-containing membranes where the light absorbing reactions of photosynthesis occur

Lysosome

Small organelle that has an internal pH of 4-5, contains hydrolytic enzymes, and functions in degradation of materials internalized by endocytosis and of cellular components in autophagy

Peroxisome

Small organelle that contains enzymes for degrading fatty acids and amino acids by reactions that generate hydrogen peroxide, which is converted to water and oxygen by catalase

Secretory vesicle

Membrane bound sacs that store and transport proteins, hormones, or neurotransmitters before releasing them outside the cell

Cytoskeleton

Network of fibrous elements, consisting primarily of microtubules, microfilaments, and intermediate filaments, found in the cytoplasm of eukaryotic cells. The cytoskeleton provides organization and structural support for the cell and permits directed movement of organelles, chromosomes, and the cell itself

what allows cells to have different functions

• Two cells might respond differently to the same extracellular signal because one cell might not transcribe (and translate) the receptor required to bind this signal because the DNA encoding this gene is compacted in one cell but not the other cell

• Post translational protein modifications, where proteins localize, what proteins associate with, amount of protein produced, which proteins are expressed

What determines which proteins are expressed in a specific cell type? Why might cells in the same person (where DNA is the same in all cells regardless of organ) produce or “express” different proteins?

• differential gene regulation

• transcription factors, epigenetics, cell signaling, RNA splicing

What things (other than absence or presence of a protein) impact the ability of a protein to do its job?

• Mutations

• Inhibitors

• Environmental

  • Factors Temperature, pH, detergents