Cell

• A cell is the basic living unit of all organisms and contains different regions: cell membrane, cytoplasm, nucleus, and organelles
• Cell metabolism involves chemical reactions within cells collectively called cell metabolism, which includes synthesis of molecules and communication between cells
• Cells produce and receive chemical/electrical signals that allow them to communicate with each other
• Each cell has a copy of the genetic information of the individual, and specialized cells transmit that genetic information to the next generation
• The cell membrane forms the boundary between the material inside (intracellular fluid) and outside of the cell (extracellular fluid) and is composed of phospholipids, cholesterol, and proteins
• The cell membrane is not stationary and has protruding proteins responsible for receptors and transport of structures and particles in and out of the cell
• Mechanisms of transport include passive mechanisms like diffusion, facilitated diffusion, and osmosis, as well as active mechanisms like active transport and vesicular transport
• Diffusion transports small, nonpolar molecules directly through the lipid bilayer, moving solutes from a higher concentration to a lower concentration until equilibrium is reached
• Osmosis is the diffusion of water through a selectively permeable membrane from an area of higher water concentration to one of lower concentration
• Facilitated diffusion provides passage for certain substances through a channel, allowing larger molecules that cannot pass through the membrane pores to move through
• Active transport requires ATP and can move substances in and out of cells from low to high concentration, against the concentration gradient, and can exchange one substance for another
• Secondary active transport involves the active transport of one substance across the cell membrane, establishing a concentration gradient that provides the energy to transport a second substance
• Vesicular transport includes phagocytosis, pinocytosis, and exocytosis for the ingestion of particles, extracellular fluid, and movement of large molecules from inside to outside the cell
• The cytoplasm is a jelly-like substance that holds organelles and is enclosed by the cell membrane, with cytoplasmic organelles positioned by movements along the polymers of the cytoskeleton
• The cytoskeleton, made of protein polymers, determines cell shapes, plays a role in organelle movements, and allows the movement of entire cells through microtubules, microfilaments, and intermediate filaments
• The nucleus contains the cell’s hereditary units, called genes
• Centriole is a microtubule that assists in the separation of daughter chromatids during anaphase
• The nucleus contains the cell’s hereditary units, called genes, which are arranged in chromosomes (mitotic stage) and chromatin (when the cell is not dividing)
• The nucleus is bounded by a double membrane barrier called the nuclear envelope or nuclear membrane
• The nucleus contains nuclear pores where fragments of DNA and RNA pass through
• Nucleolus are sites where cell structures called ribosomes are assembled
• Ribosomes are macromolecular machines that assemble proteins from amino acids
• The core of ribosome contains ribosomal RNA (rRNA)
• Attached ribosomes are active in protein synthesis
• Endoplasmic Reticulum functions include synthesis, transport, storage, and detoxification
• The Golgi Apparatus is a morphologically complex system where proteins and other molecules made in the RER undergo further modification and sorting into specific vesicles
• Lysosomes are sites of intracellular digestion and turnover of cellular components
• Peroxisomes contain peroxidase, an enzyme that breaks down H2O2, a product of fatty and amino metabolism
• Mitochondria are organelles specialized for aerobic respiration and production of adenosine triphosphate (ATP)
• Transcription occurs in the nucleus and is the process by which genetic information encoded in DNA is copied onto a strand of RNA to direct protein synthesis
• During transcription, the double strands of DNA separate, and one DNA strand serves as a template for mRNA synthesis
• Combination of 3 nucleotide triplets forms the codon, which encodes for a particular amino acid
• Translation occurs in the ribosomes, consisting of large and small subunits, and tRNA serves to match specific amino acids
• Cell division is a process by which cells reproduce themselves, with two major periods: interphase and cell division
• Interphase has 3 phases: G1 phase, S phase, and G2 phase
• Mitosis is the process of dividing a nucleus into two daughter nuclei with exactly the same genes as the “mother” nucleus
• Mitosis has 4 phases: Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis
• Cells undergo distinction and differentiation, all derived from the zygote
• Apoptosis is programmed cell death, eliminating damaged cells, virus-infected cells, and potential cancer cells