Cell Growth and Reproduction

Cell Size Limitations

How does a cell receive materials and expel its wastes?

Through the plasma membrane This means that no part of the cell

can be too far away Mitochondria of a cell 20 cm wide

would have to wait months

Surface Area to Volume Ratio The more volume = more

cytoplasm = more energy requirements Volume increases much

greater than surface area If a cell a cell were to double;

it would require 8X as much nutrients

Cell Reproduction

Recall cell theory One cell becomes two Chromosomes – structures

which contain DNA and are carriers of genetic material that is copied and passed from generation to generation

Cell Reproduction cont…

Most of time as chromatin Chromatin – long strands of

DNA wrapped around proteins Condenses before cell division Cell division follows a pattern

or cycle

Chromosomes

The Cell Cycle

Events that occur in the life of a cell

Includes 3 major stages: Interphase Mitosis Cytokinesis

Interphase

Most of the cell cycle is in what stage?

3 parts G1- rapid growth and metabolic

activity S – DNA synthesis and replication G2 – Cell prepares for division

Mitosis

Cells undergo division when they get to a certain size

Continuous process Stages are named for ease of

identification

Steps of Mitosis

Prophase Metaphase Anaphase Telophase Cytokinesis

Prophase

Chromatin condenses into chromosomes

Two halves called sister chromatids are held together by contromere

Nucleus disentegrates Centrioles go to poles Spindle forms

Prophase

Metaphase

Chromosomes pulled by spindle fibers at the centromeres

Sister chromatids lined up in the middle

Single file

Metaphase

Anaphase

Centromeres split Sister chromatids pulled apart

by spindle fibers Pulled to opposite sides

Anaphase

Telophase

Chromatids reach opposite poles

Chromosomes unwind Spindle breaks down Nuclear membrane and

nucleolus reappear

Telophase

Cytokinesis

Dividing the cytoplasm between the two new daughter cells

Cleavage furrow in animal cells

Cell plate in plant cells

Cytokinesis in Animals

Cytokinesis in Plants

Mitosis in Onion Cell

Mitosis in Whitefish

In mitosis, the two double copies of the DNA attached to the spindle fibers are known as __________. a.  centromeres   b.  chromatids   c.  centrioles   d.  nucleoli

During which phase do most cells spend the most time?

a.  prophase   b.  metaphase   c.  anaphase   d.  interphase 

If a cell has 20 chromosomes, how many chromosomes will be present in the daughter cells?

a.  5   b.  20   c.  10   d.  30 

List the stages of the Cell Cycle in order

Name one stage of Interphase