Science AHSGE

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Science AHSGE

• Standard V-1, Part 2- Cell Processes

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Homeostasis

• The ability of an organism or cell to maintain
  internal balance and stability by adjusting its
  physiological processes.
• If normal state is not restored, death might
  occur.
• Processes involved in homeostasis
• Nutrition- Use of nutrients
• Digestion- Break down of materials into usable
  substances
• Absorption- Ability of an organism/cell to take
  in materials from the outside environment
• Transport- Movement of substances within an
  organism/cell
• Biosynthesis- Making new compounds for growth,
  repair, or reproduction

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Homeostasis

• Homeostasis processes contd
• Secretion- Release of substances within an
  organism/cell
• Respiration- Release of energy from the breakdown
  of chemical compounds in the mitochondria
• Photosynthesis- Autotrophic production of glucose
  from CO2 and H2O
• Excretion- Rid of waste products to the outside
  of the organism/cell
• Response- Reaction due to a stimulus
• Reproduction (Fission)- Production of new cells
  by one cell dividing (mitosis and meiosis)

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Passive Transport

• Passive Transport- The diffusion of a substance
  across a biological membrane.
• Diffusion- The net movement of particles from an
  area where there are many particles of the
  substance to an area where there are fewer
  particles of the substance.
• High concentration to lower concentration
• Requires no energy
• Will continue until all concentrations are the
  same
• Dynamic equilibrium- Particles will continue to
  move without an overall change in concentration.

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Diffusion
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Diffusion

• 3 factors affect rate of diffusion
• Concentration (amount of a substance)
• Temperature (average kinetic energy of the
  particles)
• Pressure (Force of particles against the area of
  membrane)
• In each case, the higher, the faster
• More collisions occur causing diffusion to occur
  faster

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Facilitated Diffusion

• Facilitated diffusion- Uses transport proteins to
  move other ions and small molecules across the
  plasma membrane
• Passive transport because it does not require
  energy
• Water can diffuse across the membrane, but most
  other substances can not
• Can use water-filled transport (channel) proteins
  or
• Carrier proteins (change shape as material passes
  through)

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Osmosis

• Osmosis- Diffusion of water across a selectively
  permeable membrane
• In a solution, a solute is dissolved into a
  solvent.
• Water is the solvent in a cell and its environment

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Osmosis

• Hypotonic Solution- Solution has a lower
  concentration of solute and higher concentration
  of solvent.
• Cell will be cell will be hypertonic
• Net movement of water will be into the cell,
  causing the cell to swell
• In pure solvents, cells will burst
• Ex Distilled water, pure vinegar

• Hypertonic solution- Solution has a higher
  concentration of solute and a lower concentration
  of solvent.
• Cell will be hypotonic
• Net movement of water will be out of the cell,
  causing the cell to shrink

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Osmosis

• Isotonic Solution- The solution has the same
  concentrations of solutes and solvents as the
  cell.
• Cell is also isotonic
• Water will enter and leave the cell at equal
  rates, allowing for the cell to remain unchanged.

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Osmosis Practice
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Active Transport

• Active transport- Movement of substances across
  the membrane from an area of lower concentration
  to an area of higher concentration against the
  concentration gradient.
• Requires energy
• Uses carrier proteins called pumps
• Maintains the proper balance of substances it
  needs to maintain homeostasis

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Active Transport

• Sodium-potassium ATPase Pump
• Found in cell membrane of animal cells
• Uses energy to transport 3 sodium ions out, while
  moving two potassium ions in (decreases sodium
  concentration inside the cell)
• Coupled transport- Sugar molecules attach to
  sodium ions to be transported into the cell
  without energy through the coupled channel

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Active Transport

• Endocytosis- Cell surrounds a substance in the
  outside environment, enclosing it in a portion of
  the membrane.
• Pinches off into a vacuole
• Pinocytosis- Cell drinking
• Phagocytosis- Cell eating
• Exocytosis- Vesicles surround waste inside the
  cell, attach to the cell membrane, and expel
  materials to the outside environment.