Biology Chapter 9 Notes

Biology – Ratcliff - Ferrell

CHAPTER 9 NOTES

Cellular Growth:

·      As the cell grows, its volume (size) increases (gets bigger) much faster than the surface area.

·      The cell might have difficulty supplying nutrients and expelling enough waste products.

Transport of Substance:

·      Substances move by diffusion or by motor proteins

·      Diffusion over large distances is slow and inefficient

·      Small cells maintain better transport systems

Cellular Communications:

·      The need for telling proteins to move throughout the cell also limits cell size

·      Cell size affects the ability of the cell to communicate instructions for cellular functions

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The CELL CYCLE

Is when cells reproduce by a cycle of growing & dividing

·      Cell division prevents the cell from becoming too large

·      It also is the way the cell reproduces so that you grow and heal certain injuries

THE STAGES of the CELL CYCLE:

1.   Interphase: the cell grows, carries out cellular functions, and replicates.

2.   Mitosis: when the cell’s nucleus (middle) and nuclear material divide

3.   Cytokinesis: when the cell’s cytoplasm divides, creating a new cell

THE CELL CYCLE:

1. Interphase: the cell grows, carries out cellular functions, and replicates.

Interphase Stages:

1.   G1: the cell is growing, carrying out normal cell jobs & preparing to copy DNA

2.   S: the cell copies its DNA getting ready for cell division

3.   G2: the cell prepares for the division of its nucleus

2. Mitosis: when the cell’s nucleus (middle) and nuclear material divide

         4 Mitosis Stages:

1st)             PROPHASE:

1.   The cell’s chromatin tightens

2.   Sister chromatids are attached at the centromere

3.   Spindle fibers form in the cytoplasm

4.   The nuclear envelope seems to disappear

5.   Spindle fibers attach to the sister chromatids

2nd)            METAPHASE:

1.   Sister chromatids are pulled along the spindle apparatus toward the center of the cell

2.   They line up in the middle of the cell

3rd)            ANAPHASE:

1.   The microtubules of the spindle apparatus begin to shorten

2.   The sister chromatids separate

3.   The chromosomes move toward the poles of the cell

4th)            TELOPHASE:

1.   The chromosomes arrive at the poles and begin to relax

2.   Two nuclear membranes begin to form and the nucleoli reappear

3.   The spindle apparatus disassembles

3. Cytokinesis: when the cell’s cytoplasm divides, creating a new cell

·      In animal cells, microfilaments constrict (tighten), or pinch the cytoplasm

·      In plant cells, a new structure, called a cell plate, forms

CELL CYCLE REGULATION:

NORMAL Cell Cycle:

Different cyclin/CDK combinations signal other activities, including DNA replication, protein synthesis, and nuclear division throughout the cell cycle.

Quality Control Checkpoints

·      The cell cycle has built-in checkpoints that monitor (watch) the cycle and can stop it if something is wrong

·      Spindle checkpoints also have been identified in mitosis

ABNORMAL Cell Cycle: CANCER

Is the uncontrolled growth & division of cells. Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function

Causes of CANCER:

·      Mutations in the cell

·      Various environmental factors (reasons)

APOPTOSIS Is programmed cell death

Cells going through apoptosis actually shrink (become smaller) & shrivel in a controlled process

STEM CELLS Are unspecialized cells that can develop into specialized cells when under the right conditions.

EMBYRONIC STEM CELLS After fertilization, the resulting mass of cells divides repeatedly until there are about 100-150 cells. These cells have not become specialized.

ADULT STEM CELLS Found in various tissues in the body and might be used to maintain and repair the same kind of tissue

·      Less controversial because the adult stem cells can be obtained with the consent of their donor.