chapter 9 cellular reproduction. main idea – cells grow until they reach their size limit, then...

42
Chapter 9 Cellular Reproduction

Upload: cynthia-randall

Post on 19-Jan-2016

219 views

Category:

Documents


3 download

TRANSCRIPT

Page 1: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Chapter 9 Cellular

Reproduction

Page 2: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide.

Most cells are smaller than the . at the end of a sentence in your textbook.

Why are cells so small?What are the primary stages of the cell cycle?What is interphase?What are the stages of interphase?

Page 3: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Section 9.1 Cellular GrowthCell Size LimitationsThe key factor that limits cell size is the ratio

of its surface area to its volume.

The surface area of a cell is the area covered by the plasma membrane.

Remember the plasma membrane is the structure that all nutrients and wastes must pass through.

Page 4: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

The volume is the space made up of the inner contents of the cell, including all organelles and cytoplasm.

Page 5: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Which cell would be able to distribute nutrients and wastes to all parts of the cell more efficiently?

Page 6: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Calculating Cell SizeTo calculate surface area use the formula:Length x Width x Number of Sides = surface areaSmall cube = 1µm x 1µm x 6 sides = 6µm2

To calculate volume use the formula:Length x Width x Height = volumeSmall cube = 1µm x 1µm x 1µm = 1µm3

The ratio of surface area to volume is 6:1

Page 7: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Medium cubeSurface area = 2µm x 2µm x 6 = 24µm2

Volume = 2µm x 2µm x 2µm = 8µm3

Medium cube ratio = 3:1

This is a smaller ratio of surface area to volume.

This means the cell might have a harder time supplying nutrients and expelling wastes products.

Page 8: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

What is your prediction for the largest cube?Large cubeYour turn

Surface area = ?Volume = ?Ratio = ?

Page 9: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Large cube calculationsSurface area = 4µm x 4µm x 6 = 96µm2

Volume = 4µm x 4µm x 4µm = 64µm3

Ratio = 1.5:1

Does the nucleusseem to change size?

Would the otherorganelles change size?

Which cell above would be the most efficient?

Page 10: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Another reason cells stay small is to transport substances more efficiently.-Substances move bydiffusion or by motor proteins.

-Diffusion over largedistances is slow andinefficient.

-Small cells maintain more

efficient transport systems.

Page 11: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Another reason cells stay small is to communicate more efficiently. Cell size affects the cell’s ability to communicate

instructions for cellular functions.

If a cell becomes too large, it becomes almost impossible for cellular communications.

Example: The signal to trigger protein synthesis might not reach the ribosome fast enough in large cells to make protein to keep the cell alive.

Page 12: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

The Cell Cycle - Once a cell reaches its size limit it will stop growing or divide.Cells reproduce by a cycle of growing and dividing

called the cell cycle.

Most cells will divide.

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.

Page 13: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

3 Main stages of the cell cycle

Stage 1 – InterphaseInterphase is divided upinto 3 substages.G1, S, G2

- cell grows (G1)

- carries out cell functions (S)- replicates (G2)

(makes copies of its DNA)

Page 14: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

The 3 Stages of interphase

G1 (stage 1)

- the cell is growing, - carrying out normal cell functions- preparing to duplicate

DNA

Page 15: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

S (stage 2)

- Cell copies its DNA- Prepares for cell division

The 3 Stages of interphase

Page 16: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Genetic material is replicated (S)

Chromatin is the relaxed

form of DNA in a cell’snucleus.

Chomosomes arestructures that containthe genetic material thatis passed from

generationto generation.

Page 17: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Sister chromatids Chromosomes

Shape:- Chromatin coil around histones- 2 identical halves = sister chromatids- Held together with a centromere.

Page 18: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

The 3 Stages of interphase

G2 (stage 3)

- Cell prepares for the division of its nucleus.

- The cell checks to make sure everything is ready to go on to mitosis.

Page 19: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Stage 2 - MitosisDuring mitosis the cell’snucleus and nuclear materialdivide.

Mitosis is divided up into 4 substages.

Page 20: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Stage 3 - Cytokinesis

During cytokinesis a cell’scytoplasm divides,creating a new cell.

Some cells complete thecycle as fast as 8 minutes.

Some cells take a year tocomplete the cycle.

Most animal cells take 24hours to complete the cellcycle.

Page 21: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Section 9.2 Mitosis and Cytokinesis

Main Idea: Eukaryotic cellsreproduce by mitosis,the process of nucleardivision, and cytokinesisof cytoplasm division.

Page 22: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Mitosis – Why is it important?The key activity of mitosis is to accuratelyseparate the cell’s duplicated DNA.Why?1. Genetic information is passed into new cells.2. genetically identical daughter cells are made. (same

DNA, cytoplasm and organelles as parent cell)3. Increases the number of cells so young organisms can

grow to its adult size.-4. Organisms can replace damaged cells.

Page 23: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Four Stages of Mitosis

1. Prophase - 3 phases early-nucleoi break down

middle nuclear membrane break down

late centrioles on opposite sides

2. Metaphase

3. Anaphase

4. Telophase

Page 24: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Prophase – The 1st stage

-Longest stage of mitosis-Chromatin tightens into chromosomes-Chromosome contains genetic material-Each half of the X is a Sister Chromatid -Sister Chromatids are

structures that contain identical copies DNA.

-Centromere is where sister chromatids are attached at the center.

Page 25: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Spindle Apparatus isimportant for moving andorganizing chromsomes beforecell division. 1. Nucleolus seems to disappear2. Spindle fibers form in

cytoplasm (microtubules)3. Centrioles migrate to the

ends or poles of the cell.4. Aster fibers appear at the

centrioles

During middle prophase….

Page 26: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Near the end of prophase…

- Nuclear envelope seems to disappear

- Spindle fibers attach toeach side of sister chromatids- Spindle fibers attach at

each pole of the cell.If the cell were to divide now,

where do you predict it would split?

Page 27: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Metaphase is the 2nd stage of mitosis

One of the shortest stages1. Sister chromatids are pulled bymotor proteins toward the centerof the cell2. Chromatids line up in the middle or equator of the cell.

Page 28: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Anaphase – the 3rd stage of mitosis

Chromatids are pulled apartduring anaphase.1. Microtubules shorten and

pull apart at the centomere2. Sister chromatids separate into 2 identical chromosomes3. Chromosomes move towards

the poles of the cell.

Page 29: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Telophase – 4th stage of mitosis

The stage when chromosomesarrive at the poles of the cell.1. Chromosomes relax back into

chromatin2. Two new nuclear membranes

start to form3. nucleoli reappear4. spindle apparatus disassembles

Page 30: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Cytokinesis…the division of cytoplasm

In animals1. Microfilaments will constrict

to pinch off cytoplasm to form a groove.

2. will result in 2 cells with identical nuclei

In plants1. a cell plate forms between

the 2 daughter nuclei2. cell wall then forms3. two genetically identical

cells are formed

Page 31: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Cells alive www.cellsalive.com

Page 32: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Section 9.3 Cell Cycle RegulationMain Idea: Normal Cell CycleThe timing and rate of cell division is

important to healthy cells.

The rate of cell division depends on the type of cell.

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

Page 33: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Types of cells

All somatic (body cells) have the same number of chromosomes. (46) 2n

Body cells are called diploid as they have 2 copies of each chromosome. (di = 2)

All gametes (sex cells) have half the number of chromosomes (23) n

Sex Cells are called haploid as they have half the number of chromosomes.

Page 34: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Apoptosis – programmed cell death

Not all cells are destined to survive.

Example: Human development-Hands and Feet of embryo

Cells between fingers and toesundergo apoptosis.When it is time to separatefingers and toes in theorganism.Cells shrivel and shrink to bedisposed of by the cell.

Page 35: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Example of Problem with Apoptosis: Web Fingers

Page 36: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Protecting normal cell growth

Apoptosis also occurs when…-Cells have been damaged beyond repair-DNA has been damaged that could lead to

cancer-In plants apoptosis is what causes leaves to

fall from the trees.

Page 37: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Cancer.. uncontrolled cell growth and division of cells

When the normal controlmechanisms in a cell fails,cancer can result.

Cancer cells can be identifiedbecause they have anabnormal shape compared tothe normal cell.

Left unchecked, a canceroustumor can destroy its hostorganism.

Page 38: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

More about CancerCancer occurs due to mutations or changes

in the segments of DNA that controls the production of proteins.

Often the genetic change or damage is repaired by the cell’s repair system.

Environmental Factors can affect cells.Carcinogens are substances that are

known to cause cancer.Avoiding carcinogens can help reduce the

risk of cancer.

Page 39: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Carcinogens are substances that are known to cause cancer.

Avoiding carcinogenscan help reduce the riskof cancer.

Lung cancer can resultfrom 1 and 2 at theright.

Is lung cancer passed onin cells by geneticmaterial?

Known Carcinogens1)Tobacco products:-first hand smoke

(smoking)-second hand smoke-smokeless tobacco2) Asbestos Ultraviolet radiation (sun)X-ray radiationHarmful chemicals

Page 40: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Cancer geneticsMore than one change in DNA is needed in a

normal cell to cause cancer.Over time, there might be many changes in

DNAThis might explain why the risk of cancer

increases with age.An offspring that inherits one or more changes

from a parent may be at a higher risk for developing cancer.

Page 41: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Stem Cells are unspecialized cellsthat can develop intospecialized cells underthe right conditions.

Because stem cells arenot locked intobecoming a certain cell,they might be the key tocuring many medicalconditions and geneticdefects.

Page 42: Chapter 9 Cellular Reproduction. Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide. Most cells are smaller

Prokaryotic Cells divide by Binary Fission