Chapter Five: The Working Cell

Questions:

1. What is passive transport?

  A: A big part of passive transport is diffusion, the tendency for particles of any kind to spread out evenly in an available space.  The molecules move from wehre they are more concentrated to regions where they are less concentrated.  Because a cell does not perform work when molecules diffuse across its membrane (does not exert energy) this process is called passive transport.


2. What is it called when water diffuses?

  A: Osmosis is the diffusion of water across a membrane.  For example, an experiment we performed involved a dialysis bag filled with a glucose/starch solution placed into a beaker of water.  Because the water concentration in the bag (semi-permeable membrane) was low, the water molecules slowly began to seep into the bag.  This was an example of osmosis.

3. What in the world is exocytosis?

  A: Exocytosis is used to export bulky materials such as proteins or polysaccharides.  A transport vesicle filled with macromolecules buds from the golgi apparatus and moves to the plasma membrane.  It then fuses with the membrane and the vesicle contents spill out of the cell while the vesicle becomes one with the membrane, keeping out unwanted particles.  Crying is an example of exocytosis.  (oooooh, okay.)


Five Main Facts From The Reading:

1. Membranes are a fluid mosaic of phospholipids and proteins.
2. Passive transport is diffusion across a membrane with no energy investment.
3. Water balance between cells and their surroundings is crucial to organisms.
4. Cells transform energy as they perform work.
5. Enzymes speed up the cell's chemical reactions by lowering energy barriers.

Ten Key Terms:

Diffusion- the tendency for particles of any kind to spread out evenly in an available space.
Aquaporins- a transport protein.
Endocytosis- a transport process that is the opposite of exocytosis
Phagocytosis- a cell engulfs a particle by wrapping extensions called pseudopodia around it and packaging it within a membrane sac large enough to be called a vacuole.
Pinocytosis- the cell "gulps" droplets of fluid into tiny vesicles.
Energy- the capacity to perform work.
Kinetic energy- the energy of motion.
Heat- (thermal energy) a form of kinetic energy associated with the random movement of atoms or molecules.
Potential energy- stored energy that an object possesses as a result of its location or structure.
Exergonic reaction- a chemical reaction that releases energy.


This chapter was mostly about the different ways cells work to gain energy and the way the energy is used.  It explored in detail different ways that cells can take in outside particles to provide themselves with energy, such as endocytosis, phagocytosis, pinocytosis, ect.
It also talked about the different kinds of energy, kinetic (which is the energy of motion,) and potential (which is stored energy that an object possesses as a result of its location.)
Chapter five is about "The Working Cell."