Mid semester content

• Photosynthesis


  Using the energy provided by light to build carbohydrates
• Photosynthesis


  Combining 6 water molecules and 6 carbon dioxide molecules using light to build glucose and produce oxygen gas
• Photosynthesis


  • Water enters the plant through the roots
  • Carbon dioxide enters the leaves through stomata
  • Oxygen leaves the plant through stomata
• Chloroplast


  The organelle that carries out photosynthesis
• Mitochondria


  The organelle responsible for cellular respiration
• Photosynthesis


  Converts carbon dioxide and water with light energy into glucose and oxygen
• Cellular respiration


  Takes glucose and oxygen and converts it into carbon dioxide and water, releasing energy
• Chlorophyll


  The pigment that absorbs light energy
• Chlorophyll absorbs blue and red light, but reflects green light</b>
• Photosynthesis


  1. Light dependent reactions

  2. Light independent reactions (Calvin cycle)
• Light dependent reactions


  • Occur in thylakoids
  • Produce oxygen, ATP, and NADPH
• Light independent reactions (Calvin cycle)


  • Occur in stroma
  • Convert carbon dioxide into glucose using ATP and NADPH
• Light dependent reactions


  1. Photosystem 2 excites electrons in chlorophyll

  2. Electrons flow through electron transport chain

  3. Oxidizes water to oxygen

  4. Reduces NADP+ to NADPH

  5. Produces ATP via chemiosmosis
• Calvin cycle


  1. Carbon dioxide fixation

  2. Reduction using ATP and NADPH

  3. Regeneration of RuBP
• The Calvin cycle converts 3 CO2 molecules into 1 G3P molecule, requiring 18 ATP and 12 NADPH
• To produce 1 glucose molecule, the Calvin cycle requires 6 CO2, 18 ATP, and 12 NADPH
• Aerobic respiration


  1. Steps leading up to the electron transport chain

  2. The electron transport chain (the main event)
• Electron transport chain


  A series of proteins and other molecules embedded in the inner membrane of the mitochondrion that transport electrons
• The vast majority of ATP is made in the electron transport chain
• Electron transport chain


  • Transports electrons
  • Releases energy gradually as electrons move through protein complexes
  • Uses this energy to pump hydrogen ions across the inner membrane
• Electrons moving


  Provides the energy to drive protein pumps that transport hydrogen ions
• Oxygen accepts the electrons and hydrogens from the matrix, making water
• If the electron transport chain stops

  You won't be able to make enough ATP to keep you alive and you die
• ATP synthesis

  1. High concentration of hydrogen ions in the intermembrane space

  2. Hydrogen ions flow through ATP synthase from high to low concentration

  3. ATP synthase spins like a turbine and produces ATP
• The electron transport chain happens over and over again, making 30 to 34 ATP molecules for every glucose that entered respiration
• Receptor


  A molecule, such as a protein, where a signal molecule can bind
• Ligand


  A smaller molecule that binds to a typically larger molecule (the receptor)
• General sequence of cell signaling

  1. Reception (signal molecule binds receptor)

  2. Transduction (receptor gets activated, often by changing shape)

  3. Response (e.g. transcription of DNA)
• Cell signaling


  • Can involve intracellular signaling (within the cell) and intercellular signaling (between cells)
  • Distance matters - some cells are close with direct contact, others use paracrine or endocrine signaling
• Types of cell signaling

  • Gap junction (direct cell-cell contact)
  • Paracrine (signal molecule diffuses between close cells)
  • Synaptic (neurotransmitters in a synapse)
  • Endocrine (signals carried in bloodstream)
  • Autocrine (cell signals itself)
• Steroid hormone signaling


  Steroid hormone (ligand) travels through cell membrane, binds to intracellular receptor, receptor travels to nucleus and binds DNA to regulate transcription
• Ligand-gated ion channel


  Ligand (signal molecule) binds to receptor (which is the channel protein), causing the channel to open and allow ions to flow through, triggering a cellular response
• Cell signaling is critical for processes that keep you alive, from regulating heartbeat to neuron communication in the brain
• Disorders like cancer and diseases caused by pathogens can involve problems with cell signaling
• Scientific theory


  An explanation of a scientific event supported by scientific evidence, that is testable and tested over and over again
• Theories can be changed or even disproven, but there are a lot of facts behind them
• Endosymbiotic theory


  Explains how eukaryote cells could have evolved from prokaryotic cells that lived in symbiosis
• Prokaryotes


  • No nucleus
  • No membrane-bound organelles
• Eukaryotes


  • Have a nucleus
  • Have membrane-bound organelles
• Both prokaryotes and eukaryotes are cells and have a cell membrane, cytoplasm, ribosomes, and genetic material