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Book C

Chapter 2

Cell Processes and Energy

I. Photosynthesis

-the process of making food from light energy

-plants use energy from the sun

to change water and carbon dioxide into

oxygen and glucose (sugar)

- takes place in the chloroplasts of plant cells.

- chloroplasts contain the pigment chlorophyll which helps to

start the process of photosynthesis.

Photosynthesis equation:

CO₂ + H₂O + light energy ---------------> O₂ + C₆H₁₂O₆ (glucose)

II. Respiration:

-the process that cells use to break down simple food (glucose)

and release energy

Respiration Equation:

O₂ + C₆H₁₂O₆ (glucose) ---------------> CO₂+ H₂O + chemical energy

compare photosynthesis and respiration:

photosynthesis uses carbon dioxide and water and light energy

respiration releases carbon dioxide and water and chemical energy

photosynthesis releases oxygen and glucose

respiration uses oxygen and glucose

They are opposites.

III. Cell division

The Cell cycle -- the steps a cell goes through as it grows and develops

Stage 1: Interphase

- the cell grows, makes a copy of its

genetic material (DNA), and

prepares to divide into two cells

Stage 2: Mitosis

- the stage in which a cell's nucleus divides into two nuclei

Four parts of mitosis

1. prophase -- chromatin in the nucleus form chromosomes and the nuclear membrane disappears

2. metaphase-- chromosomes line up in the center of the cell. Spindle fibers attach to chromosomes

3. anaphase -- chromosomes (chromatids) move to opposite sides of the cell.

4. Telophase -- the nuclear membrane reappears

Stage 3: Cytokinesis

- the cytoplasm divides, forming the two new cells

Diagrams of the cell cycle:

Nucleic acids:

-- very large organic molecules made of carbon, hydrogen, oxygen, nitrogen and phosphorus.

-- contain the instructions a cell needs to carry out life functions

-- one kind is DNA (deoxyribonucleic acid)

DNA structure:

-- shaped like a twisted ladder

-- sides of the ladder are made up of sugar molecules called deoxyribose and phosphate molecules (which contain the element phosphorous)

-- rungs of the ladder are made of a pair of molecules called nitrogen bases

pairs of nitrogen bases

adenine (A) only pairs with

thymine (T)

cytosine (C) only pairs with

guanine (G)

This pairing is the key to understanding how DNA replication or duplication occurs. In replication the two sides of the DNA molecule unwind and separate like a zipper separating. Then the nitrogen bases (A,T,G,C) which are floating in the nucleus pair up with bases on each half of the molecule. The order of the bases in the two new DNA molecules will exactly match the order of the bases in the original DNA molecule.

IV. Cancer

- a disease in which cells grow and divide uncontrollably

- usually begins when some of the DNA in a chromosome is damaged

The damage causes a change in the DNA called a mutation

one cell mutating

Cancer begins when mutations disrupt the normal cell cycle

causing the cells to divide in an uncontrolled way. These cells

become a mass of abnormal cells called a tumor

the cell divides uncontrolably

Tumor cells break off and enter the bloodstream.

Cancer is treated using one or more of these methods:

1.surgery to remove the tumor

2.radiation - beams of energy waves to

destroy the tumor

3. Chemotherapy - drugs to kill cancer cells