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Chapter 3 Sec. 2: Cell Features - PowerPoint PPT Presentation

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Chapter 3 Sec. 2: Cell Features. Cell Theory. All living organisms are made of one or more cells. Cells are the basic unit for both structure and function . Cells come from preexisting cells.

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Chapter 3 Sec. 2: Cell Features

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Chapter 3 Sec. 2:Cell Features

Cell Theory

  • All living organisms are made of one or more cells.

  • Cells are the basic unit for both structure and function.

  • Cells come from preexisting cells.

    - not by spontaneous generation (mice from rags, worms from horse hairs) we believe in biogenesis

Robert Hooke

  • Englishman

  • Looked at cork

  • Saw cubicals

  • 1st person to see cells – but they were dead cells.

Scientists involved in cell theory

  • Schleiden – All plants are made of cells

  • Schwann – All animals are made of cells

  • Virchow – All cells come from other cells

Differences in Cells

  • Size –

    • biggest cell is ostrich egg

    • smallest is bacteria .002 mm

    • most are from 5 to 20 µm in diameter

Differences in Cells

  • The size of the cell is limited by the surface area to volume ratio.

    Surface area= amount of cell membrane available

    Volume= amount of material inside the cell

Surface Area to Volume Ratio Calculation Activity

  • Using 1 cm cubes, build a 2 cm x 2 cm x 2 cm block to symbolize a small cell.

  • Calculate the surface area by using the formula: (l x w x number of sides)

  • Calculate the volume by using the formula: (l x w x h)

  • Calculate the ratio by dividing the surface area by the volume.

  • Repeat using a 3 x 3 x 3 cell.

  • Repeat using a 4 x 4 x 4 cell.

What happens when the surface area to volume ratio gets too small?

Cell division occurs!

Cells can be different by…

  • Internal organization (does it have a nucleus or not????)

Cell Internal Organization…

Prokaryotes: Organisms without a nucleus or any membrane bound organelles (ex. Bacteria & simple algae)

Eukaryotes: Have nuclei & membrane bound organelles

(ex. Humans, fish, trees, sponges)

Prokaryote Characteristics:

  • First life forms on Earth (3.5 billion years ago)

  • May or may not need oxygen

  • Cytoplasm holds everything – enzymes, ribosomes, DNA, etc.

  • Have a cell wall surrounding cell membrane

  • Many have flagella for movement


  • All have a nucleus containing DNA

  • Have organelles outside the nucleus – internal compartments with specific functions to perform

  • Most organisms ARE eukaryotes!

Common Features of Cells…

  • Cell Membrane

  • Cytoplasm

  • Cytoskeleton

  • Ribosomes

  • DNA

Common Features of Cells…

  • Cell Membrane

    - gatekeeper of the cell

    - is selectively permeable

    (allows only certain substances to pass in or out)

Parts of a cell…

  • Structure of the Cell Membrane

    - made of lipids and proteins (mostly lipids)

    - two layers thick

    (phospholipid bilayer)

  • Model of the cell membrane is called the Fluid Mosaic Model

The Cytoskeleton:

  • Is the internal framework or support

  • Is composed of a protein fiber network

  • 3 different kinds of cytoskeleton fibers:

    • Microfilaments (fibers made of protein actin)

    • Microtubules (hollow – made of protein tubulin)

    • Intermediate fibers (thick protein ropes)

Section 3:Cell Organelles

Cell Parts-The Nucleus…

  • Is the Control Centerfor the cell

  • Contains DNA and RNA

  • Is filled with nucleoplasm and chromatin (dark grainy material that changes into chromosomes during cell division)

Cell Parts-The Nucleus…

  • Nucleus is contained by a nuclear membrane made of 2 layers

  • Nuclear membrane has pores to allow materials to leave nucleus

Cell Parts-The Nucleus…

  • Has a nucleolus (small dark oval inside)

  • Nucleolus produces ribosomes

Parts of the cell…

  • Endoplasmic Reticulum (E.R.)

    The cell’s subway system

Endoplasmic Reticulum

  • Materials (especially proteins) are transported from one area to another.

  • 2 kinds of ER – smooth and rough

  • Smooth has no ribosomes attached.

  • Rough has lots of ribosomes attached.

  • Vesicles form when ends of ER pinch off as a membrane sac

Parts of the cell…

  • Ribosomes

  • Are produced in the nucleolus

  • They produceproteins

  • Are located on the surface of endoplasmic reticulum and also free floating in the cytoplasm.

  • Are made of ribosomal-RNA

Parts of the cell…

  • Golgi Apparatus


Golgi Apparatus

  • Proteins packaged in vesicles move to Golgi apparatus - also called Golgi bodies or golgi complex

  • GA looks like stacks of flattened pancakes

  • GA areproteinprocessing centers – refined, processed & packaged.


  • Are small spherical structures that contain digestive enzymes that allow cells to recycle its materials.

  • Lysosomes act as the “recycling center” for the cell.

Protein Packaging & Distribution

  • Made at ribosomes on ER & packaged into vesicles

  • Travel from ER to Golgi Apparatus

  • Get processed & repackaged at GA

  • Move from GA to cell membrane for export

Mitochondria: (mighty mitochondria)

  • produce ATP energy by breaking down glucose

  • have double membranes

  • have in and out folds called Cristae

  • Have ring of DNA


Parts of the cell…

  • Which cells have the most mitochondria?

    High energy requiring

    cells like muscles!

Parts of the cell…

  • Cilia & Flagella

  • Used for movement of the cell

  • Cilia are short and numerous

  • Flagella are usually 1-2 in number and very long like a whip

  • Made of sets of microtubules

Structures of Plant Cells

Plant Cells

  • All plant cells have a Cell Wall

    - on the outside of cell membrane

    - provides cell support & strength

    - made of cellulose - a carbohydrate

Plant Cells…

  • Central Vacuole

    - are storage spots in cytoplasm

    - very large

    - may store water, enzymes, waste products, or even toxins

Plant Cells…

  • Contain Plastids

    - are membrane bound structures

    - have their own type of DNA

    3 kinds:

    • Chloroplasts

    • Leucoplasts

    • Chromoplasts

Plant Cells…

  • Have Chloroplasts:

    - green

    - membrane bound structures

    - store chlorophyll (green pigment needed for photosynthesis) so…

    - chloroplasts are the sites of photosynthesis.

Plant Cells…

  • Leucoplasts:

    - are white structures inside cells

    - are storage areas for produced food.

    - Ex: Potato grains stained in lab.

    - may be other starchy materials like corn, wheat

Plant Cells…

  • Chromoplasts –

    are the colored pigments seen in petals of flowers or in leaves in fall.

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