Biology

• Cell


  Smallest unit of living things
• Prokaryotic cells


  • Simple cells without organelles
• Eukaryotic cells


  • Complex cells containing organelles with specific functions
• Characteristic


  • Prokaryotic
  • Eukaryotic
• Cell Part or Organelle


  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Mitochondria
  • Endoplasmic reticulum
  • Smooth or rough
  • Ribosome
  • Golgi body/complex
  • Lysosome
  • Vacuole
• Cell cycle

  Sequence of phases consisting of cell growth and division; timing and rate are critical to an organism's normal growth and development; cell division frequency varies by cell type
• Phase


  • G₁: intense growth and enzyme production
  • S: DNA synthesis/replication
  • G₂: growth and preparation for cell division
  • Mitosis
• Eukaryotic cell


  • Animal cell with organelles
• Cell membrane


  • Surrounds cell; controls what enters/leaves cell; recognizes other cells; maintains homeostasis
• Cytoplasm


  • Suspends organelles in a eukaryotic cell; enclosed within the cell membrane
• Nucleus


  • Controls the cell's activities; contains chromosomes made of DNA
• Mitochondria


  • Breaks down food to release energy
• Endoplasmic reticulum


  • Moves substances within the cell (pipe-like structures)
• Ribosomes


  • Make proteins; round structures located on rough endoplasmic reticulum
• Golgi complex


  • Changes and packages cell products
• Lysosome


  • Contains enzymes (proteins that speed up digestion and chemical reactions)
• Vacuole


  • Holds materials like water; large in a plant cell
• Organelles found only in plant cells


  • Cell wall
  • Chloroplast
• Homeostasis


  Regulation of conditions (like pH or temperature) within a cell which allows for stable, "normal" internal equilibrium (balance)
• Energy conversion


  During photosynthesis, plant cells use energy from the sun to make a sugar called glucose; during aerobic cellular respiration, mitochondria release energy from molecules like glucose
• Molecule transportation


  Molecules move in and out of cells across the cell membrane by various means; active transport (like transport proteins) requires energy, but passive transport (like diffusion) does not
• Synthesis of new molecules

  Cells can create new molecules from simpler molecules, like when proteins are made from amino acids
• Virus


  Tiny non-living structure with no metabolism that depends on a host cell and causes diseases
• Virus features


  • Structure: head with nucleic acids (DNA or RNA) surrounded by protein coat (capsid)
  • Reproduction: attaches to host cell and releases its nucleic acids; host cell makes viruses and dies
• Viruses cannot be treated with antibiotics
• DNA


  Holds the genetic information that controls what a cell can do and what molecules it can make
• Examples of Specialized Plant Cells and Functions

  • Leaf cells containing chloroplasts for photosynthesis; guard cells control size of stomates (pores) allowing gas transfer
  • Xylem cells move water and minerals and phloem cells move nutrients like glucose throughout the plant using pipe-like structures (provide support for leaves, branches, and flowers)
  • Epidermis cells on root hairs increase surface area to allow for the absorption of water and mineral nutrients
• Mitosis


  Phase during the cell cycle in which the nucleus is divided, resulting in identical daughter cells with the same genetic information found in the original nucleus; process is critical for an organism's growth
• DNA molecule


  Contains genetic information; structure is double helix of two strands of complementary nitrogen base pairs
• DNA replication


  Process that transforms one DNA molecule into two identical copies; enzymes help DNA strands unwind and separate; each DNA strand serves as a template for a new, complementary strand to form
• Disruption of cell cycle


  Loss of control within the cell cycle can lead to diseases like cancer
• Cell differentiation


  Process by which genetically identical cells become more specialized and different from each other; DNA, RNA, and environmental factors can influence which genes are transcribed and expressed
• Biomolecules


  • Lipid
  • Carbohydrate
  • Protein
  • Nucleic acid
• Organic molecule


  Molecule that is found in living systems; contains carbon atoms, usually in rings or long chains
• Organic molecule formation and organization

  Small organic molecules (monomers) can link together to form longer and more complex molecules (polymers)
• Nucleotide


  Three-part structure that makes up nucleic acid molecules (DNA and RNA)
• Nitrogen bases


  Often symbolized by base's first letter; bases that bond together are complementary
• DNA (deoxyribonucleic acid)


  Carries genetic information from parent cell or parents' egg and sperm cells; controls a cell's activities and specifies the organism's traits; structure is two strands twisted into a double helix with ladder-like connections between complementary nitrogen bases
• RNA (ribonucleic acid)


  Uses genetic information from DNA to produce proteins (protein synthesis); structure is double helix
• Codon


  Formed from a sequence of three nucleotides; different codons specify one of twenty different amino acids