Download CHAPTER 2: CELL FUNCTION 2.1.

CHAPTER 2: CELL FUNCTION
2.1. (p. 45)
1. Explain how just a few elements can make up all living things.
The most common elements making up all living things are Carbon, Oxygen, Hydrogen, Nitrogen and
Phosphorus. These few elements are combined as atoms into molecules that form different compounds. They
are the building blocks of life and the ingredients of cell function.
2. What functions do proteins, carbohydrates, lipids, and nucleic acids perform?
Proteins are made of amino acids and control chemical reactions in cells and support cell growth and repair.
Lipids are made up of fatty acids and glycerol which repel water. Cell membranes are composed of lipids.
Carbohydrates are C-H-O sugars and provide the cell with energy. Cellulose is a carbohydrate made by plants
that provides the plant with necessary structural support.
Nucleic acids are the basis of DNA and RNA and contain instructions for cell reproduction.
3. What does it mean to describe water molecules as being polar?
They have slightly charged ends, one positive and one negative. This gives water an ability to adhere to other
water molecules and for other materials that have slight charges to dissolve into water.
4. How are carbohydrates and lipids similar? How are they different?
Both contain carbon, oxygen and hydrogen and provide energy and structure to cells. Lipids do not dissolve in
water, carbohydrates do.
5. What do the major types of molecules that make up living things have in common?
Organic molecules all contain Carbon atoms.
6. Some people have compared the nucleic acids DNA and RNA to a blueprint for life. How are DNA and RNA
like blueprints? How are they different?
Blueprints are plans for constructing something, such as a building. RNA and DNA are like a plan for
constructing living things. Blueprints created by people are made through consciousness and communication;
DNA and RNA blueprints are produced by cells.
2.2 (p. 54)
1. Which form of energy is especially important for living things? Why?
Glucose (C6H12O6) is especially important for life because most cells store energy as glucose.
2. How is photosynthesis important to life on earth?
Photosynthesis is the basis for life, making food that supports most other organisms. It is the so-called ‘autotrophs’ (self-feeders) that make glucose from
3. What starting materials do cells need for respiration?
Glucose and oxygen
4. How are photosynthesis and cellular respiration similar? How are they different?
Cellular respiration and photosynthesis both produce energy, but the starting materials and products are
reversed in the two processes. Photosynthesis converts CO2 and H2O into C6H2O6 with a byproduct of O2.
Respiration uses glucose and oxygen to generate energy with byproducts of carbon dioxide and water.
5. Suppose that in a lab you could remove all the oxygen from a terrarium. What would happen to the plants?
Why?
They would eventually die because even though they produce oxygen gas as a byproduct of photosynthesis,
this only occurs when there’s light. At night, when its dark, plant cells respire just like any other cell and
therefore need O2 gas.
6. How is breathing related to cellular respiration?
Cellular respiration is like breathing because when you exhale, CO2 and H2O leave your body and when you
inhale, O2 enters your body. Photosynthesis and respiration form a reciprocal dance.
2.3 (p. 63)
1. How are the processes of diffusion and osmosis alike?
They are both the spreading and evening out of molecules from concentrated to dispersed. Diffusion refers to
solvents dissolved in a solution, such as salt in salt water. Osmosis is a special kind of diffusion and refers to
the movement of water itself, through a (cell) membrane – it is how cells maintain a water balance between
inside and outside. Both happen without an input of energy; in other words, diffusion and osmosis are activated
by concentration gradients.
2. What is the difference between passive and active transport?
Both passive and active transport describe the movement of chemicals and materials into and out of cells.
Passive transport relies on concentration gradients (e.g., diffusion) and therefore requires no energy; active
transport requires additional energy to move chemicals and materials that cannot be moved based only on
concentration differences.
3. How does the surface area of a cell limit the growth of the cell?
The surface area determines the amount of interface and connection a cell has with its surrounding
environment, and since the transport of chemicals and materials into and out of cells happens through the cell
membrane, the smaller the surface area, the less contact surface there is to facilitate diffusion, osmosis and
active transport.
4. If you put a bouquet of carnations in water, through what process does the water enter the stem?
Osmosis
5. If a marine iquana were to spend a few days in a freshwater tank, would it continue to blow salt droplets
from its nostril?
No, because it would no longer be taking in excess salt from its environment, so an internal salt balance with
its freshwater environment would be lower and easier to maintain.
6. Freshwater protozoa, which are unicellular organisms, have a greater concentration of salt inside them than
does the surrounding water. Does water diffuse into or out of the protozoa?
Water must diffuse into the protozoa, to continually adjust the imbalance of salt concentration by diluting the
salt content inside the organism toward the concentration in its less salty environment.
Reviewing Key Concepts (p. 67)
18. Why is water needed by cells?
All chemical reactions in cells take place in water and water facilitates all (passive and active) transport of
materials into and out of cells through water permeable membranes.
19. Describe the main function of nucleic acids.
They form the basis of DNA and RNA that map out how to make new cells.
20. What is the role of chlorophyll in a plant’s leaves?
It captures energy from the sun used to convert carbon dioxide and water into glucose.
21. Explain why a carrot feels spongy after being soaked in salt water.
Through diffusion, the carrot loses some of its fresh (less salty) water to the salt water its soaked in.
22. Explain how the ways in which plants and animals get their energy differ.
Plants get their energy from sun and the photosynthetic conversion of CO2 and water into glucose. Animals
get their energy from the food they eat. Another why to look at it is, animals’ foods are biotic (from molecules of
living or once living things) while plants’ food are abiotic (from non-living molecules from the air). Of course,
plants need other nutrition in addition to carbon dioxide and water, and those nutrients are derived from soil
and taken up by roots that are not photosynthetic, but the principal energy conversion happens through
photosynthesis, which is unique only to cells containing chloroplasts, which animals don’t have.
Thinking Critically (p. 68)
23. Explain why chemical reactions are essential to living creatures.
Most cellular activity requires chemical reactions; very little is directly physical; and everything takes place in
aqueous solutions.
24. How does a glass filled with water and oil illustrate the properties of a cell membrane?
Cell membranes are made of lipids which are oil based molecules that repel water and therefore form an
effective but permeable boundary between the inside of a cell and its surrounding environment.
25. What are the starting materials of photosynthesis? What are the starting materials of cellular respiration?
CO2 + H2O  C6H12O6 + O2
26. What are the products of photosynthesis? What are the products of cellular respiration?
Photosynthesis makes glucose and a byproduct of oxygen gas. Cellular respiration generates energy for the
cell by breaking down glucose forming byproducts of carbon dioxide and water.
27. What are the connections between photosynthesis and respiration?
One can’t happen without the other. The two cellular processes each require the other’s byproducts and each
supplies the other with starting materials. The chemical equations are mirrors of each other. Chloroplasts and
mitochondria are symbionts, each needing the other.
28. Compare and contrast passive and active transport.
Diffusion and osmosis are forms of passive transport that move materials from higher to lower concentration
and do not require energy; active transport describe processes that are not activated by concentration
gradients and therefore require additional energy to make them happen.
29. Louis Pasteur mixed yeast and grape juice to produce alcohol. Explain what happened.
Because there was no oxygen, fermentation happened where the live yeast consumed the sugars it found in
the grape juice. This is respiration in anoxic or oxygen deprived conditions. (remember that respiration requires
oxygen…)
30. Why would it be harmful to drink seawater?
By adding salt and increasing the salt concentration in your body above its normal level, your body would
attempt to transport or purge the excess the salt from its cells thereby dehydrating them, especially if no
additional freshwater was drank to counter the seawater. There have been many occasions where people
stuck on lifeboats drank seawater in desperation and ended up dead or with brain damage due to immediate
and severe dehydration.