WORKSHEET REVIEW

The Molecules of Cells

WORKSHET DISCUSSION

1a. What is Homeostasis? The maintenance of a relatively stable internal

environment. It may fluctuate slightly within a normal range.

What are the Main body systems involved?The nervous system & the Endocrine System

Question 1b)

b) What is Negative Feedback?

A stimulus causes a particular response and the body reacts to counter the initial reaction

The effect of the stimulus is offset to return to homeostasis

1c) Examples of Negative Feedback? Blood glucose levels 100mg/100ml pH of blood 7.4 Blood Pressure 120/80 Body Temperature 37 degrees C

Examples of Positive Feedback? Childbirth Lactation Blood Clotting

Q5.

Elements: pure substances made of one type of atom

Compounds: more than one type of atom joined together

Most Common elements: “CHNOPS”

Common Compoundx: NaCl etc etc

3. What is the difference between an atom and an ion?

An atom is neutral so the number of protons is equal to the number of electrons. An ion is charged, therefore the number of protons does NOT equal the number of electrons

What is one common atom found in the human body? Lots of possible answers! Ex: CarbonWhat is one common ion found in the human body? Lots of possible answers! Ex: H+, HCO3

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Draw Bohr Models for the following atoms and ions:

a) Sodium atom

b) Chlorine atom Chloride ion

5. How do you determine if an atom would become an anion or a cation? Explain the difference between these two types of ions.

An anion is an ion that has a negative charge. It has more electrons than protons, therefore an overall negative charge.

A cation is an ion that has a positive charge. It has LESS electrons than protons, therefore an overall positive charge.

You can predict if an anion or cation will form by counting how many electrons are in the atom’s outermost shell. If it must gain electrons to obtain a full shell it will become an anion. If it must lose electrons to become an ion it will become a cation.

6.Complete the following Venn Diagram comparing ionic bonds and covalent bonds:

Ionic Covalent-electrons transferred -electrons shared-electrons lost or gained-usually metal & non metal -usually 2 non-metals

BOTH:-form a force of attraction that holds

compounds together-Both involve electrons

7. Explain redox reactions. Provide an example of an element that is oxidized and an example of an element that is reduced.

Redox reactions refer to chemical reactions where electrons are lost and a substance is oxidized and when a substance gains electrons and becomes reduced. The entire reaction is called a “redox” reaction because oxidation must occur for reduction to occur. The two happen simultaneously.

Ex) Many possible answers (any ionic bond)NaCl forms and Na becomes Na+ (oxidized) and Cl becomes Cl- (reduced)

8. If magnesium were to form a compound (ionic bond) with oxygen the formula would be MgO. Which element is oxidized? Which element is reduced? Explain.

Magnesium is oxidized because it loses 2 electrons to become an ion and obtain a full outer shell.

Oxygen is reduced because it gains two electrons to become an ion and obtain a full outer shell.

9.Why, or how, are redox reactions important in the body system? Provide an example.

In the human body, compounds are constantly forming, breaking down and reforming.

For atoms to join together and to form the molecules need for life electrons must continually be lost and gained (or shared) in order for chemical bonds to be formed.

There are many examples of redox reactions especially related to metabolic reactions in the cell and in the body. Ex) Digestion: Food reacts with O2 and to release energy and make CO2 and H2O