AP BIOLOGY-Unit 2 Notes

• Passive Transport is the net movement of molecules down their concentration gradient. Requires no energy input

  • Simple Diffusion-movement of molecules from high concentration to low concentration

    • small nonpolar molecules pass freely (Nitrogen, oxygen, carbon dioxide)

    • small amounts of very small polar molecules, like water, can diffuse across a cell membrane

      • water has a slight charge to be able to sneak across the membrane

  • Facilitated Diffusion-movement of molecules from high concentration to low concentration through transport proteins

    • large polar molecules

    • charged ions, including Na+ and K+, require channel proteins/carrier proteins

    • does not require energy

• Osmosis is the diffusion of water across a selectively permeable membrane

  • Large quantities of water move via AQUAPORIN (any of several proteins that are found in cell membranes).

  • goes from an area of high water potential to a low water potential

  • Differences in relative solute concentrations can facilitate osmosis

• Osmolarity: unit of measurement for solute concentration

  • the numbers of moles of solute per liter of solution

• Active transport- moves molecules and/or ions against their concentration gradient, from low concentration to high concentration

  • protein pumps are used in active transport

  • requires metabolic energy (such as ATP)

  • establishes and maintains concentration gradients

  • creates a higher concentration gradient

• Endocytosis- process used by cells to import large molecules, such as antibodies, across the plasma membrane

  • cell uses energy to take in macromolecules and particle matter by forming new vesicles derived from the plasma membrane

    • types of endocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis

• exocytosis-remove large molecules from the cell

  • internal vesicles use energy to fuse with the plasma membrane and secrete large macromolecules out of the cell

-How can a cell maintain a high concentration of Na+ in the environment surrounding the cell? Na+ ions are being actively transported from the inside of the cell to the outside of the cell through a membrane protein.

• Key Takeaways

  • Passive transport is the net movement of molecules from high concentration to low concentration without direct input of metabolic energy

  • water is transported in small amounts across the membrane by simple diffusion and in large amounts via facilitated diffusion through aquaporins embedded in the membrane

  • active transport requires direct input of energy to move molecules from regions of low concentration to regions of high concentration

  • large molecules and large amounts of molecules are moved into the cell by endocytosis and out of the cell by exocytosis

Cell Compartmentalization

• Cellular Compartments allow for various metabolic processes and specific enzymatic reactions to occur simultaneously, increasing the efficiency of the cell

• membranes minimize competing interactions

  • For example, lysosomes contain hydrolytic enzymes that are involved in chemical digestion. Still, these enzymes need to function in an acidic environment, which is available in the membrane of the lysosomes. By compartmentalization, the inside of the lysosome can maintain a more acidic environment and allow for efficient hydrolysis, while the rest of the cytoplasm can remain in a more neutral environment.

• membrane folding maximizes the surface area for ATP reactions to occur

  • electron transport and ATP synthesis occur in the inner mitochondrial membrane

  • folding. The inner membrane increases surface area, allowing for more ATP to be made. The same thing happens with thylakoids in chloroplast.

Cell Structure and Function

• broken down proteins get turned into Urea

• H+ ions regulate the cell’s pH

• Tonicity (plant cells)

  • in plants, tonicity can affect the structure of the whole plant

    • the large central vacuole will exert outward pressure on the cell wall, called turgor pressure, this gives plants their structure and shape

• Dynamic Study Module Notes

  • Middle Lamella: in plants, is a thin layer of adhesive extracellular material, primary pectin found between the primary walls of adjacent young cells

    • the extracellular matrix of the animal cell has all the following molecular components except a middle lamella

      • animals cells do have an extracellular fluid called ECM

  • The network of fibers that organizes the structures and activities in a cell is the cytoskeleton

    • composed of microtubules, microfilaments, and intermediate filaments

      • Components of the cytoskeleton often mediate the movement of organelles within the cytoplasm

      • cell mobility refers to both changes in the cell location and more limited movement of parts of the cell

      • Microfilaments function is cell motility and muscle contraction, amoeboid movement, and cytoplasmic streaming in plants

  • Peroxisomes: membrane bound metabolic compartments that produce hydrogen peroxide, and it’s conversion of water

  • cells are small because of the geometric relationship between surface area and volume

  • Nucleoid: region of a bacterial cell that contains the genetic material

  • Animals cells have a unique organelle called centrosomes that are composed of structures called centrioles

  • Cell junctions in plants cells are called plasmodesmata, and communicating junctions in animal cells are called gap junctions

  • Central Vacuole (plant cells): storage of inorganic ions such as potassium and chloride

  • All cells have voltages across their membranes. This voltage is called membrane potential and is often maintained by electronic pumps

  • How does the “fluid mosaic model” describe the structure of the plasma membrane

    • proteins in membrane contribute to mosaic quality of the membrane, while the lateral and rotational movements of phospholipids contribute to it’s fluidity

    • Hypotonic: in a hypotonic solution, a cell takes up water and burst

    • Hypertonic: a cell, in a hypertonic solution, would lose water and shrink

  • Isotonic: a cell in an isotonic solution would exhibit lower turgor pressed and be flaccid

• How does cholesterol affect the membrane fluidity?

  • at body temperature, it makes the membrane less fluid

• Peripheral Proteins: these proteins are found only on the surface of the plasma membrane

• Proteins embedded in two layers of phospholipids allow them to play their role in selective transport of polar molecules

  • Carbohydrates are located primarily on the outer surface of the membrane, in this location they function in cell to cell recognition

• Exocytosis and smooth and rough ER accounts for the replacements of lipids and proteins lost from the plasma membrane

• Plasmolysis refers to the shriveling of plant cells when they are placed in a hypertonic environment

  • the plant cell will lose water to the environment and shrink

  • the plasma membrane pulls away from the cell wall, leading to wilting and possible death

• Integral Proteins: these proteins exhibit both hydrophilic and hydrophobic properties