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

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.

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

### Eukaryotes

• 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)

### 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.

### Parts of the cell…

• Golgi Apparatus

vesicle

### 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.

### Lysosomes:

• 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

### 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.