Chapter 5.5 Summary

• to start a chemical reaction, it is first necessary to weaken chemical bonds in the reactant molecules
• activation energy is "start-up" energy
• one way to provide activation energy is to heat up the mixture of molecules
• heating up a cell would cause many unnecessary reactions
• the main catalysts of chemical reactions in organisms are specialized proteins
• catalyst is a compunds that speed up chemical reaction
• enzyme doesn't supply activation enrgy
• each enzyme catalyzes a specific kind of chemical reaction

• the shape of each enzyme fits the shape of only particular reaction molecule
• specific reactant acted upon by an enzyme is substrate
• the substrate fits into a particular region of the enzyme is active site
• as substrate enters, the shape change slightly
• tighter grip weakens the bonds
• another way that an enzyme can lower activation energy is by accepting two reactant molecules into adjacent sites
• enzymes structure and shape are essential to its function
• enzyme changes shape depending on the enviornment

Concept Check 5.5



1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy?

Activation energy's role is to activate the reactants and triggers a chemical reaction. Enzymes does effect activation energy by lowering the energy requirement of the barrier so reactons can react at a normal temperature.



2. Describe how a substrate interacts with an enzyme.

A substrate interacts with an enzyme by entering the enzyme's active site, and active site changes shape. This help the subtrate to fit better to enzyme's active site. Then it places certain functional groups of the active site in position to catalyze the reaction.

Chapter 5.3 Summary

• hydrophobic means "water-fearing"
• the function of hydro phobic is really important in starch
• lipids act as boundary and contains watery contents of human cells
• some fat are solid at room temperature
• most animal fats are saturated fats
• the fats in fruits, vegetables, fish are unsaturated fats
• saturated fats are unhealty (large amount)
• steroids are classified a lipid
• cholesterol, a steroid, is found in membranes
• cholesterol has a bad reputation because high level of particular cholesterol-containing substances in the blood increases the risk of getting heart and blood vessel disease

Concept Check 5.3

1. What property do lipids share?

All lipids share the property of hydrophobic. Hydrophpbic means a water-avoiding molecules.

2. What are the parts of a fat molecule?

The parts of a fat molecule are the three-carbon backbone called glycerol attached to three fatty acids, which contain long hydrocarbon chains.

3. Descrive two ways that steroids differ from fats.

The steroids are different from fats in two way. Those two ways are structure and function. The steroids circulate body as chemical signals when fats stores the energy. Also, the steroids are formed from four rings.

4. What does the term unsaturated fat on a food label mean?

The term unsaturated fat on a food label means that the food contains less than the maximum number of hydrogen atoms in one or more of its fatty acid chains because some of its carbon atoms are double-bonded to each other.

Chapter 5.2 Summary

• sugar contains the elements carbon, hydrogen, and oxygen

• monosaccharide: glucose, fructose, and galactose
• sugar, usually glucose, are the main fuel supply

• disaccharide: sucrose
• body can also store glucose in larger molecules for later use
• starch chains serve as sugar stockpile
• humans and most other animals are also able to use plant starch as food by breaking it down within their digestive systems
• rich in starch: potatoes, rice, corn
• animal cells has no starch
• animal cells has glycogen
• when body needs energy, it breaks down glycogen granules, releasing glucose
• almost all carbohydrates are hydrophilic
• some starch doesn't dissolve in water
  

Concept Review 5.2

1. Explain the difference between a monosaccharide and a disaccharide. Give an exmaple of each.

Monosaccharide is simple sugars contain just one sugar unit. Example of monosaccharide are glucose, fructose, and galactose. The disaccharide is sugar with two monosaccharide. For example, sucrose are disaccharide.

2. Compare and contrast starch, glycogen, and cellulose.

Starch, glycogen, and cllulose are all polysaccharide and glucose monomers. First, the starch are only contained in the plant cell, and glycogen is only contained in the animal cells. Cellulose is containted in both plant and animal cells. Starch serves as sugar stockpiles, in the use of enrgy. The glycogen is also store for the use of energy. Finally, cellulose serves as building materials. These protect cells and stiffen the plant, preventing it from flopping over.

3. How do animals store excess glucose molecules?

The animals store excess glucose molecules by the form of polysaccharide called glycogen. For humans, the glycogen is stored usually in granules in liver and muscle cells. When human needs energy, the glycogen is broken down and released.

Chapter 5.1 Summary

• carbon can form up to four bonds
• most carbon-based molecules are classified as organic molecules
• non-carbon based molecule classified as inorganic molecules
• carbon can bond with other elements
• hydrocarbons are important fuels
• Methane: abundant hydrogen, natural gas
• Some biomolecule can be composed of hundreds or even millions of atoms
• large molecules classified in four main categories: carbohydrates, lipids, proteins, and nucleic acids
• Dehydration reaction involves removing water
• Organisms not only build polynomers, but they also have to brek them down
• water is removed to build a polynomer, and water is added to break it down
  

Concept Check 5.1

1. Draw a molecule that has a three-carbon skeleton and a hydroxyl group on the middle carbon. (Hint: The molecule's formula is C3H8O.)

2. Explain the connection between monomers and polymers.

The connection between monomers and polymer is that polynomer is a straight chain of monomers. Other polymer have branching chains. So the monomer comes together to form polymer.

3. What molecule is released during construction of a polymer? What is this reaction called?

During the construction of a polymer water molecule is released. This reaction is called dehydration reaction.

4. Draw at least three ways in which five carbon atoms could be joined to make different carbon skeletons.