Ch.5 The Working Cell

WHY DO CELLS USE ATP WHEN SUGAR MOLECULES HAVE MORE ENERGY?

Cells use sugars because all of energy origins are from glucose. However the cell breaks down the glucose and stores the energy in ATP. The reason why it stores energy in ATP is that because the cell can only use a little bit of energy to work at one time. Therefore, if it just directly uses glucose to do work, there will be a large amount of energy released, and all the energy it cannot use will just escape as heat. So by storing the energy in smaller amounts in ATP, not as much energy is wasted as heat.

HOW DO ANIMALS AND PLANTS PERFORM OSMOREGULATION?
Osmoregulation keeps the body's fluids from becoming too concentrated. Animals must maintain the right concentration of solutes and amount of water in the body fluids. There is no specific osmoregulation organs in higher plants. Control of water intake and loss means those internal and external factors, which affect the rate of transpiration. Plants share with animals the problems of obtaining water and in disposing of the surplus. Some plants develop methods of water conservation. Xerophytes are plants in dry places. They have better qualities of osmoregulation. Cactus have water stored in large parenchyma tissues so they can get more water. Other plants have leaf modifications to keep water.


WHAT ARE THE DIFFERENCES BETWEEN EXOCYTOSIS AND ENDOCYTOSIS?
Exocytosis is the process by which a cell expels molecules and other objects that are too large to pass through the cellular membrane. Endocytosis is the process by which a cell takes in molecules and other objects that are too large to pass through the cellular membrane. The basic mechanism of those are pretty much the same. Both make use of vesicles for their molecular transport. Vesicles are used for storage and transport. Since they are enclosed by a membrane, inside they can have a completely different composition than that of their cell.

KEY TERMS:
-Diffusion: the tendency for particles of any kind to spread out evenly in an available space, moving from where they are more concentrated to regions where they are less concentrated
-Passive Transport: diffusion across a cell membrane does not require energy
-Fluid Mosaic: the surface appears mosaic because of the protein embedded in the phospholipids and fluid because the proteins can drift about in the phospholipids
-Osmosis: a physical model of the diffusion of water molecules across a selectively permeable membrane
-Aquaporins: the very rapid diffusion of water into and out of certain cells, such as plant cells, kidney clls and red blood cells, is made possible by transport proteins
-Active Transport: moving a solute against its concentration gradient using energy
-Thermodynamics: the study of energy transformations that occur in a collection of matter
-Cellular Respiration: a chemical process that uses oxygen to convert the chemical energy stored in fuel molecules to a form of chemical energy that the cell can use to perform work
-Energy Coupling: the use of energy released from exergonic reactions to drive essential endergonic reactions. It is a crucial ability of all cells
-Cofactors: many enzymes that require nonprotein helpers

SUMMARY:
Membranes are composed of phospholipids and proteins and they are described as fluid mosaic. Phospholipids are made of fatty acids kinks which are unsaturated. Membranes exhibit selective permeability. Non polar molecules cross more easily than polar molecules because polar molecules are not soluble in lipids. Phospholipids can spontaneously self-assemble into simple membranes. Particles move in concentration gradient to less concentration gradient. This movement without energy is called passive transport. Osmosis moves water across a membrane down its concentration gradient until the concentration of solute is equal on both sides of the membrane. Animal cells can maintain their water balance by osmoregulation. However plant and prokaryotic, and fungal cells have different issues because of their cell walls. Cells don't let any substances across the membrane. They require the help of aquaporins. They assist in facilitated diffusion, which is a type of passive transport. In active transport, they move particles against its concentration gradient. They always require the energy in the form of ATP. When cells move large molecules across membrane, they use exocytosis to export bulky molecules, and endocytosis to import substances useful to the livelihood of the cell.
There are two kinds of energy for the capacity to do work and cause change. Kinetic energy for motion and potential for resulting of its location. There are two important laws of thermodynamics. The first law is energy in universe is constant. It cannot be created or destroyed. The second law is energy conversions increase the disorder of the universe. So it cannot be recycled. Exergonic reaction is a chemical reaction that releases energy. Also cellular respiration releases energy and heat and produces products but is able to use the released energy to perform work.
Living things produce many endergonic and exergonic chemical reactions. Those are all called metabolism. One cell mainly does three types of cellular work; chemical work, transport work, and mechanical work. ATP is used when a cell needs energy immediately. It is  renewable source of energy. Energy that is available to break bonds and form new ones is called EA. EA can be speed up by enzymes. They require the certain conditions for them such as temperature, and pH. They also need cofactors and coenzymes. They can be inhibited by competitive inhibitors and noncompetitive inhibitors.

This is a diagram of endocytosis. The plasma membrane takes a particle into a cell, and it will turn a food valuole. Those are the main functions of endocytosis.
-Receive nutrients
-Entry of pathogens
-Cell migration and adhesion
-Signal receptors

This is a diagram of exocytosis. It releases enzymes, hormones, proteins, and glucose to be used in other parts of the body. Also those are the main functions of exocytosis.

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• -Neurotransmitters (in the case of neurons)
• -Communicate defense measures against a disease
• -Expel cellular waste

5 FACTS:

1) To make the concentration equal, passive transport and active transport occur. Active transport requires energy.

2) Tonicity describes the ability of a solution to cause a cell to gain or lose water.

3) Many substances are necessary for viability of a cell do not freely diffuse across the membrane. 

4) Kinetic energy performs work by transferring water. Example, heat is a kinetic energy associated with the random movement of atoms.

5) The first law of thermodynamics: energy in the universe is constant. It cannot be created or destroyed. The second law of thermodynamics: energy conversions increase disorder of the universe.