1. Ch. 4 Cell Processes
Materials enter and leave the cell by one of three methods.
1. Diffusion – process by which molecules of a substance move from areas of higher concentration to areas of lower concentration
The cell membrane is selectively permeable.

2. This means it permits only certain substances, mainly oxygen, water, and food molecules, to diffuse into the cell.
Waste products such as carbon dioxide are allowed to diffuse out.

3. 2. Osmosis – The diffusion of water into or out of the cell.
Water molecules move from a place of higher concentration to lower concentration.

4. Diffusion and osmosis just happen whenever there are unequal concentrations inside and outside the cell.
Neither of these processes use up any energy reserves.( No energy required)

5. 3. Active transport – special transport molecules in the cell membrane actually pick up the substance outside the cell and pull it through the cell membrane.
Active transport requires the cell to use some of its energy reserves.

6. 2 types of Active Transport
Endocytosis – brings something into the cell
Exocytosis – releases something from the cell
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7. The Cell Cycle
1. Interphase – the time when a cell spends most of its time growing and carrying out all of its normal activities.

8. 3 parts to Interphase G = Growth S = Synthesis
G 1 – the cell increases in size and organelles
S – when chromatin replicate
G 2 – the cell gets ready to divide; it is known at this stage as a parent cell

9. 2. Mitosis – It has four phases
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase

10. Prophase
Centrioles split and move to opposite ends of the cell called poles
Chromosomes appear
The nuclear membrane and nucleolus disappear
Spindle fibers form between the centrioles

11. Metaphase
Chromosomes attach to the spindle fibers and line up in the middle of the cell

12. Anaphase
The chromosomes separate and the daughter chromosomes start moving toward the poles

13. Telophase Begins when the chromosomes reach the poles
The spindle fibers disappear
Two nuclear membranes and nucleoli reform around the groups of chromosomes
The chromosomes uncoil to return to chromatin

14. Cytokinesis
The cell divides the cytoplasm to form two new daughter cells
Animal Cells – the cytoplasm divides by constricting in the middle until the membrane separates
Plant Cells – a cell plate grows in the middle toward the cell wall until division is complete

15. Key Definitions Parent Cell – the cell before it divides
Daughter Cell – reference to the newly created cell
Chromatin – thread-like materials that are located in the nucleus during interphase and is composed of DNA and protein
Centriole – the cell organelle that controls the movement of chromosomes during mitosis

16. Synthesis – to create or make
Replicate – to make an exact copy
Chromosomes – do not appear until mitosis; it is a super coil of DNA and protein; they are located in the nucleus
Chromatid – two single chromosomes that are attached at a point called the centromere
Centromere – the point of attachment within two chromosomes

17. Poles – the directed ends of a cell