Ch. 4 Cell Processes

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 • P. 89

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