Cell Growth and ReproductionCell Growth and Reproduction

Chapter 9

Chapter Objective

Describe the processes of cell growth and cell reproduction (SPI 3210.1.6.)

Section 9.1

The cell cycle multiplies cells

Section Objectives

1. Describe the structure and function of a chromosome.

2. Given a diagram or picture of a cell, identify whether the cell is in the interphase or mitotic phase of the cell cycle and explain what happens during each phase.

Key Terms

• chromatin• chromosome• sister chromatid• centromere• cell cycle

• interphase• mitotic phase• mitosis• cytokinesis

Large Cells Can Have Problems!

As cells grow, their volume increases much more rapidly than their surface area!

Large cells may have difficulty supplying nutrients and expelling enough waste products.

Why is size a problem?

Transport of Substances

Substances move by diffusion or by motor proteins.

Diffusion over large distances is slow and inefficient.

Small cells maintain more efficient transport systems.

Cellular Communications

The need for signaling proteins to move throughout the cell also limits cell size.

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

• How often a cell divides depends on the type of cell (its functionfunction).

• Eukaryotic cells that do divide undergo an orderly sequence of events known as the cell cycle.

Cells Divide at Different Rates

The Cell Cycle

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.

Cells reproduce by a cycle of growing and dividing called the cell cycle.

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

Mitosis - the cell’s nucleus and nuclear material divide.

Cytokinesis - a cell’s cytoplasm divides.

The Cell CycleThe Cell Cycle

Phases of The Cell CyclePhases of The Cell Cycle

• Interphase–G1 (Gap1)–S (DNA Synthesis)–G2 (Gap2)

• Mitotic (M) Phase• Cytokinesis

The Cell Cycle

The Stages of Interphase

1st stage - G1

The cell is growing, carrying out normal cell functions, and preparing to replicate DNA.

2nd Stage – S The cell copies its DNA in preparation for

cell division.

The Stages of Interphase

S phaseGenetic material (chromosomes) duplicate)

3rd Stage - G2

Cell prepares for division of nucleus (mitosis).

The Stages of Interphase

Mitosis and CytokinesisMitosis and Cytokinesis

Concept 9.2

Cells divide during the mitotic phaseCells divide during the mitotic phase

Section Objectives

Given diagrams or pictures of cells in various stages of the mitotic phase of the cell cycle, identify and name the stages and explain what happens during each stage.

Key TermsKey Terms

• prophaseprophase• sister chromatidsister chromatid• centromerecentromere• spindle apparatusspindle apparatus

• metaphasemetaphase• anaphaseanaphase• telophase telophase

Mitotic PhaseMitotic Phase

• Unique to eukaryotes• Very accurate (error rate 1/100,000

cell divisions)

CentromereCentromere

Chromosomeduplication

Sister chromatidsSister chromatids

Chromosome distributionto daughter cells

ChromosomePrior to S phase

Mitosis Duplicates the Nucleus (Chromosomes)

The Mitotic Phase

Stages of Mitosis

Prison (Prophase)

Men (Metaphase)

Are (Anaphase)

Thin (Telophase)

Prophase

The cell’s chromatin tightens.

Sister chromatids are attached at the centromere.

Spindle fibers form in the cytoplasm.

The nuclear envelope seems to disappear.

Spindle fibers attach to the sister chromatids.

Metaphase

Sister chromatids line up in the middle of the cell.

Anaphase

Microtubules of the spindle apparatus begin to shorten.

Sister chromatids separate.

Chromosomes move toward the poles of the cell.

Telophase

The chromosomes arrive at the poles and begin to relax.

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

The spindle apparatus disassembles.

Process by which the cytoplasm of a Process by which the cytoplasm of a cell is divided in two; usually follows cell is divided in two; usually follows mitosis and meiosis.mitosis and meiosis.

CytokinesisCytokinesis

Microfilaments constrict, or pinch, the cytoplasm to create a cleavage furrow

Cytokinesis in Animal Cells

Cell wall too rigid for microfilaments to constrict cell.

Cell plate created.

Cytokinesis in Plant Cells

How Cytokinesis Differs in PlantsHow Cytokinesis Differs in Plants

Section 9.3

Cell Cycle Regulation

Terms to knowTerms to know

• cyclincyclin• cyclin-dependent kinasecyclin-dependent kinase• cancercancer• carcinogencarcinogen• apoptosisapoptosis• stem cellstem cell• benign tumorbenign tumor• malignant tumormalignant tumor• metastasismetastasis

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

Checkpoints in the cell cycle can stop the cycle if something goes wrong.

Apoptosis

Programmed cell death

Cells going through apoptosis actually shrink and shrivel in a controlled process.

Signals from the checkpoints can start apoptosis.

A disease caused by severe A disease caused by severe disruption of the mechanisms disruption of the mechanisms that normally control the cell that normally control the cell cycle.cycle.

Cancer

Abnormal Cell Cycle: Cancer

Cancer is the uncontrolled growth and division of cells.

Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.

Cancerous cells reproduce at an abnormally fast rate!

Benign:Benign: An abnormal mass of normal An abnormal mass of normal cells.cells.

Types of Tumors

Malignant: A mass of abnormal cells resulting from uncontrolled cell division.

The spread of cancer cells The spread of cancer cells beyond their original site beyond their original site

Metastasis

Causes of cancerCauses of cancer

• Genetic mutationsGenetic mutations• FoodFood• HormonesHormones• RadiationRadiation• TobaccoTobacco• Weight & physical activityWeight & physical activity• Workplace environmentWorkplace environment

Cancer TreatmentsCancer Treatments

• SurgerySurgery• Radiation therapyRadiation therapy• ChemotherapyChemotherapy• A mix of the threeA mix of the three

Stem Cells

Unspecialized cells that can develop into specialized cells when under the right conditions

Embryonic 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

chromatin: combination of DNA and protein molecules, in the form of long, thin fibers, making up the genetic material in the nucleus of a eukaryotic cell.

chromosome: condensed threads of genetic material formed from chromatin as a cell prepares to divide.

sister chromatid: one of a pair of identical chromosomes created during the S phase before a cell actually divides.

Vocabulary Review

centromere: region where two sister chromatids are joined tightly together.

Vocabulary Review (contd’)

cell cycle: sequence of events from the production of a eukaryotic cell to the time the cell itself reproduces.

interphase: stage of the cell cycle during which a cell carries out its metabolic processes and performs its functions in the body.

mitotic phase: stage of the cell cycle when a cell is actively dividing.

mitosis: process by which the nucleus and duplicated chromosomes of a cell divide and are evenly distributed, forming two daughter nuclei.

cytokinesis: process by which the cytoplasm of a cell is divided in two; usually follows mitosis and meiosis.

Vocabulary Review (contd’)