lesson 3.2

• Cell transport


  The movement of substances across the cell membrane either in or out of the cell
• Passive transport

  • Does not require energy to move substance across the cell membrane
• Diffusion


  1. The passive transport of particles from an area of high concentration to an area of low concentration

  2. Simple diffusion does not require a transport protein
• Facilitated diffusion


  Uses transport proteins to move ions and other small molecules across the plasma membrane
• Osmosis


  1. The diffusion of water across a membrane

  2. Water passes through until dynamic equilibrium is achieved
• Isotonic solutions


  • Those in which concentrations are equal on each side of the membrane
  • Water passes through in both directions at the same rate
• Hypotonic solutions

  Those in which the concentration of solutes outside the cell is lower than the concentration inside the cell
• Hypertonic solutions


  Those in which the concentration of solutes outside the cell is higher than those inside the cell
• Active transport


  Happens when a substance is moved against a concentration gradient, from a low concentration to a higher concentration
• Endocytosis


  1. The membrane forms a pocket around a particle, the pocket then breaks loose from the outer portion of the cell membrane and forms a vesicle within a cytoplasm

  2. Pinocytosis, takes on fluids and solute

  3. Phagocytosis, takes in larger substances (bacteria)
• Exocytosis


  1. The membrane of a vesicle surrounds the material then fuses with the cell membrane

  2. The contents are forced out of the cell
• Photosynthesis


  • The process by which plants capture energy from the sun to build carbohydrates through chemical pathways
  • Sun is converted to chemical energy during these reactions
  • 6CO2 + 6H2O + sunlight -> C6H12O6 + 6O2
• Light-dependent reactions


  1. Chlorophyll in the plants absorb sunlight and transfers to the photosystem which are responsible for photosynthesis

  2. Water is used to provide hydrogen ions and electrons but also produces

  3. Electrons and protons are used to produce NADPH and ATP

  4. ATP and NADPH are energy storage and electron carrier/donor molecule

  5. The chlorophyll molecule regains the lost electron from a water molecule through a process called photolysis, which releases dioxygen (O2) molecule
• Calvin cycle (light-independent reactions)

  1. Carbon fixation, one carbon atom from CO2 is added to a five carbon sugar called ribulose bisphosphate (RuBP)

  2. PGA formation, the six carbon sugar in step 1 is then split to form two molecules of phosphoglyceric acid (PGA)

  3. Use of ATP and NADPH, a series of reactions involving ATP and NADPH from the light dependent reactions converts a molecule of PGA into phosphoglyceraldehyde (PGAL) another three carbon molecule

  4. Glucose production, after several rounds of the calvin cycle two molecules of PGAL leave the cycle to form glucose

  5. ATP and PGAL replenish RuBP, some PGAL molecules reform the five carbon sugar with the help of energy from ATP
• Cellular respiration


  • The process by which mitochondria break down food molecules to produce ATP in plants and animals
  • The process by which food, in the form of sugar (glucose), is transformed into energy within cells
  • This energy is stored in ATP molecules, which then power all sorts of cellular process
  • Respiration that requires oxygen is known as aerobic respiration
  • A respiration that occurs without oxygen is called anaerobic respiration
  • C6H12O6+ 6O2 -> 6CO2 + 6H2O + Energy
• Aerobic respiration

  1. The first stage of aerobic respiration is glycolysis, where glucose molecules are broken down to create ATP in a cell's cytoplasm

  2. In the second stage, which occurs in the mitochondria of a cell, pyruvate is used to create a acetyl coenzyme A and carbon dioxide

  3. The third stage is known as the citric acid cycle or krebs cycle

  4. In the final stage, NADH, FADH2 and oxygen are used to create massive amounts of ATP trough electron transfer
• Anaerobic respiration

  1. There is no oxygen present

  2. ATP is created through other chemical processes that does not require oxygen

  3. These processes do not produce as much ATP as aerobic respiration
• Cell cycle

  • A series of events that happens in the life of a cell as it grows and divides in order to make a new cell
  • Two major phases: interphase and M phase (mitosis and cytokinesis)
• Interphase


  1. The cell grows and makes a copy of its DNA

  2. G1 (first gap phase), the cell grows physically larger and copies organelles

  3. S (synthesis phase), makes multiple copies of DNA

  4. G2 (second gap phase), cells grows more and makes proteins and organelles
• Mitotic phase

  1. Two events: mitosis, division of somatic or body cells into two new cells; cytokinesis, division of cytoplasm

  2. Happens in somatic or body cells of eukaryotes
• Prophase

  1. Chromatin condenses into chromosomes

  2. Nucleolus disappears

  3. Spindle fibers form

  4. Nuclear envelope breaks down

  5. Spindle fibers attaches to chromosomes
• Metaphase


  1. Chromosomes line up along metaphase plate

  2. Each chromosome should be attached to microtubules from the opposite ends of centrosomes
• Anaphase


  1. Sister chromatids separate

  2. Spindle fibers pull the chromatids towards the poles
• Telophase

  1. Spindle fibers disintegrate

  2. Nuclear envelopes form around both groups of chromosomes

  3. Chromosome convert to their extended form (chromatids) again
• Cytokinesis


  1. Division of the cytoplasm to form two new cell

  2. Overlaps with the final stages of mitosis

  3. May start in either anaphase of telophase

  4. Finishes shortly after telophase
• Meiosis


  • Division of reproductive or sex cell (sperm and egg) in eukaryotic organisms
  • It has two cell divisions forming four unique daughter cells