Ratio of Surface Area to Volume As the cell grows, its volume increases much more rapidly than the...

Ratio of Surface Area to Volume

As the cell grows, its volume increases much more rapidly than the surface area.

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

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.

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

The Cell CycleThe 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

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

Quality Control Checkpoints

The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.

Spindle checkpoints also have been identified in mitosis.

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

Causes of Cancer

The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations.

Various environmental factors can affect the occurrence of cancer cells.

Causes of cancerCauses of cancer

• FoodFood

• Genetic mutationsGenetic mutations

• HormonesHormones

• RadiationRadiation

• TobaccoTobacco

• Weight & physical activityWeight & physical activity

• Workplace environmentWorkplace environment

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

Types of Tumors

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

A mass of abnormal cells A mass of abnormal cells resulting from uncontrolled cell resulting from uncontrolled cell division division

Malignant Tumor

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

Metastasis

Cancerous cells reproduce at an abnormally fast rate!

Cancer TreatmentCancer Treatment

• SurgerySurgery

• Radiation therapyRadiation therapy

• ChemotherapyChemotherapy

• A mix of the threeA mix of the three

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.

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

Producing offspring that are clones of the parent No Diversity with asexual reproduction

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Process in which a single cell or set of cells produces offspring that inherit all their genetic material from one parent.

Offspring are not diverse.

Asexual reproduction

1. Binary Fission

2. Budding

3. Parthenogenesis

4. Regeneration

Types of Asexual Reproduction

Binary Fission

A type of asexual reproduction in which a prokaryoteprokaryote replicates DNA, and divides in half, producing two identical daughter cells.

Offspring grows out of body of Offspring grows out of body of parent.parent.

Budding

Yeast(Unicellular fungi)

Hydra(Multicellular cnidarian)

In this form, if a piece of a parent is In this form, if a piece of a parent is detached, it can grow and develop detached, it can grow and develop into a completely new individual.into a completely new individual.

Echinoderms exhibit this type of Echinoderms exhibit this type of reproduction.reproduction.

Regeneration

Genetic material from two parents combines to produce offspring that are genetically different from the parents

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The egg from a female & the sperm from the male combine through fertilization to form a zygote

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Egg and sperm are called Gametes (sex cells)

Two Methods of ReproductionTwo Methods of Reproduction

AsexualAsexual– Offspring identical to the original cell or Offspring identical to the original cell or

organismorganism– Involves inheritance of Involves inheritance of allall genes from genes from

one parentone parentSexualSexual

– Offspring similar to parents, but show Offspring similar to parents, but show variations in traitsvariations in traits

– Involves inheritance of Involves inheritance of uniqueunique sets of sets of genes from two parentsgenes from two parents

Process in which genetic material from two parents combines and produces offspring that differ genetically from either parent.

Leads to diversity in offspring.

Sexual reproduction

Sperm, Eggs, & FertilizationSperm, Eggs, & Fertilization

TestesTestes - male organ that - male organ that produces spermproduces sperm

OvariesOvaries - female organ that - female organ that produces eggs.produces eggs.

MeiosisMeiosis

A type of cell division that produces four cells, A type of cell division that produces four cells, each with half the # of chromosomes (haploid each with half the # of chromosomes (haploid #) as the parent cell.#) as the parent cell.

Parent CellParent Cell4646

chromosomeschromosomes

23

23

23

23

In meoisis, the final cells have In meoisis, the final cells have halfhalf the number the number of chromosomes as the parent cell.of chromosomes as the parent cell.

• 1 chromosome of each pair is from your mother 1 chromosome of each pair is from your mother and 1 from your dad.and 1 from your dad.

• 22 are alike, whether male or female (autosomes)22 are alike, whether male or female (autosomes)

• The 23rd chromosome is called the Sex The 23rd chromosome is called the Sex Chromosome. It occurs as either X or Y. Chromosome. It occurs as either X or Y.

XY = maleXY = male

XX = femaleXX = female

Humans have 46 ChromosomesHumans have 46 Chromosomes(23 homologous pairs)(23 homologous pairs)

Karyotype

A display of the chromosomes of A display of the chromosomes of an individual. an individual.

Male KaryotypeMale Karyotype

Female KaryotypeFemale Karyotype

Homologous ChromosomesHomologous Chromosomes

Two chromosomes in a matching pair.Two chromosomes in a matching pair.

Homologous Chromosomes

1.1. Each has the Each has the same sequencesame sequence of genes. If of genes. If one has gene for eye color, the other will one has gene for eye color, the other will too - at the same location.too - at the same location.

2.2. However, the genes However, the genes might be slightly might be slightly different versions.different versions.

Mitosis & Meiosis Mitosis & Meiosis DifferenceDifference

MeiosisMeiosis – 4 daughter cells with ½ the – 4 daughter cells with ½ the number (haploid number) of original number (haploid number) of original chromosomes.chromosomes.

MitosisMitosis – 2 daughter cells with the – 2 daughter cells with the same number of original chromosomes.same number of original chromosomes.

Comparison of Meiosis & MitosisComparison of Meiosis & Mitosis

Meiosis Mitosis

DNA Replication 1 time 1 time

Nuclear divisions 2 1

Number of daughter cells 4 2

Daughter cell chromosome number Haploid (n) Diploid (2n)

Daughter cells identical to parent No Yes

Meiosis increases genetic variation

Crossing-overCrossing-over

FertilizationFertilization

In humans, (2In humans, (22323))22 different possible different possible zygotes – over 70.3 trillion!zygotes – over 70.3 trillion!

If crossover occurs only once, then If crossover occurs only once, then (4(42323))22 4 octillion possible combinations. 4 octillion possible combinations. (27 0’s)(27 0’s)