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KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

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KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions. - PowerPoint PPT Presentation


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KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions. The cell cycle represents the life cycle of a cell. The cell cycle has three main stages:. (1) INTERPHASE (a) G 1 : cell grows, organelles double in number; cell does its job.

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KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

the cell cycle represents the life cycle of a cell
The cell cycle represents the life cycle of a cell.
  • The cell cycle has three main stages:
  • (1) INTERPHASE
  • (a) G1: cell grows, organelles double in number; cell does its job
  • (b) S (DNA synthesis) DNA is copied
  • (c) G2 : More growth;
  • (2)Mitosis: division of the cell’s DNA
  • (3) Cytokineses (cell divides into 2 cells)
why do cells divide
Why do cells divide?
  • They become too large
    • The volume of the cell increases faster than the surface area
    • Cells need large surface area (cell membranes) to move things in and out
why do cells divide1
Why do cells divide?
  • 2. To make more cells so the organism can grow
    • Example: a growing baby needs more skin cells!
  • 3. To replace old, worn out cells
  • Cells reproduce at different times depending on their jobs.
some cells do not divide in adults
Some cells do not divide in adults:
  • Brain cells
  • Nerve cells
  • Muscle cells

Stem Cells are the focus of much research to find ways to create new cells of these types.

before mitosis starts chromosomes must be made to package the dna
Before Mitosis starts, chromosomes must be made to “package” the DNA

(2) DNA coils around proteins called histones.

(1) DNA is copied in S period of Interphase.

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(3) Anaphase

  • Sister chromatids divide.
  • Chromosomes are pulled to the poles.
chromosome vocabulary

Sister chromatids

telomere

centromere

telomere

Duplicated chromosome

Chromosome vocabulary
  • Chromosome = Coiled DNA
  • Sister Chromatids: Two identical chromosomes held together
mitosis occurs in 4 steps
Mitosis occurs in 4 steps:
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • Cytokinesis: the process of dividing the cell’s cytoplasm follows immediately after mitosis
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(1) Prophase

  • Early Prophase:
  • Chromosomes are made; sister chromatids are formed
  • Nuclear membrane breaks down
  • Middle/Late Prophase:
  • Spindle fibers form
    • polar fibers
    • kinetochore fibers
    • asters form (only in animal cells)
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(2) Metaphase

  • Kinetochore fibers move sister chromatids to the equator of the cell and line them up.
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(3) Anaphase

  • Sister chromatids divide.
  • Chromosomes are pulled to the poles.
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(4) Telophase

  • Chromosomes unwind.
  • Nuclear membranes reform.
  • Spindle fibers break apart.
cytokinesis
Cytokinesis
  • Cytokinesis differs in plant and animal cells:
  • In animal cells, the membrane pinches in.
  • In plant cells, a cell plate grows down middle.
in cancer mitosis is uncontrolled

normal cell

cancer cell

bloodstream

In cancer, mitosis is uncontrolled.
  • Cancer cells divide constantly and form clumps called tumors.
  • Benign tumors: remain clumped; can be removed.
  • Malignant tumors: break apart (metastasize) and can form tumors in other parts of the body.
cancer cells
Cancer Cells

Why are cancer cells a problem?

They do not do their jobs!

  • How do cells become cancerous?
  • Cancerous cells come from normal cells with damage to DNA.
  • Damage could be genetic or caused by carcinogens
  • Carcinogens are substances known to promote cancer.
    • Examples:
cancer cells1
Cancer Cells
  • How do we treat cancer?
  • Radiation – using lasers to kill cancerous cells
  • Chemotherapy– using poisons to kill cancerous cells
  • Both treatments kill both cancerous and healthy cells.
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Cell OrganizationCells are organized to carry out complex functions

Organ

Systems

Organs

Tissue

Cells

multicellular organisms depend on interactions among different cell types

SYSTEMS

leaf

shoot system

stem

vascular

tissue

CELL

TISSUE

ORGAN

root system

lateral

roots

primary

root

Multicellular organisms depend on interactions among different cell types.
  • Tissues: groups of cells with same job
  • Organs: groups of tissues with same job
  • Organ systems : groups of organs
specialized cells perform specific functions

Inner: intestines

Outer: skin cells

Middle: bone cells

Specialized cells perform specific functions.
  • Cell differentiation: when a cell “gets its job”
  • Cells differ because different DNA is read.
  • A cell’s location in an embryo helps determine what type of cell it will become
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Before a cell differentiates (gets its job), it’s a stem cell.

There are three types of stem cells:

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First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.

  • Pros for Adult stem cells:
  • may prevent transplant rejection.
  • Cons for Adult stem cells:
  • can be hard to find and grow.
  • Pro for Embryonic stem cells:
  • are pluripotent and can be grown easily
  • Con for embryonic stem cells
  • raises ethical issues
  • Stem cells come from adults and embryos.
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May cure disease

  • May replace damaged organs.
  • Potential Benefits to using Stem Cells:
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