Cells and Their Amazing Organelles

Cells can be …

Prokaryotic -no membrane bound

organelles

Eukaryotic - membrane bound organelles

Eukaryotic cells include …

Plant Cell Animal Cell

Why are cells so small?• As cell size increases

the volume increases much faster than the surface area.

• Cells obtain nutrients, gain information and rid waste through their plasma membrane.

As cell size increases, it’s ability to exchange materials with its

environment becomes limited by the amount of membrane area that is available for exchange.

Ratio of Surface Area:Volume

Cell Membrane

• Outer boundary of all cells .

• Described as being a fluid mosaic.

• Semi-permeable: controls what enters and leaves the cell.

Fluid-mosaic model of membrane structure

How molecules cross the plasma membrane

Vesicles• Membranous structures

that derive from other membranous cellular parts.

• Carry substances from one part of the cell to another.

• Bind to the correct region if protein receptors are compatible.

Cytoplasm

• Consists of the cytosol (liquid) and all of the organelles within cell .

The Nucleus

• Controls most activities in the cell by controlling protein production.

• Contains all genetic information in the form of DNA.

• Nucleus is surrounded by the nuclear envelope - a double

membrane

• The nuclear envelope has nuclear pores that control entry and exit of materials

The Nucleolus

• A darkened region where ribosomes (ribosomal RNA) is synthesized

Ribosomes• Composed of a large and

small sub-unit of RNA

• Make proteins in the cell.

• May be free-floating in cytoplasm or attached to endoplasmic reticulum.

Free Floating Ribosomes Ribosomes

on ER

Endoplasmic Reticulum• Series of folded

membranes that form sacs or tubes.

• Rough ER has ribosomes attached.

• Smooth ER doesn’t have ribosomes.

Smooth Endoplasmic Reticulum

• The site for:

- synthesis of steroids and other lipids,

- Ca++ storage in muscle cells,

- detoxification of drugs, toxins, alcohol (especially in liver cells)

Rough Endoplasmic Reticulum

• The site where proteins are made to be used inside or outside of cell.

• Once proteins are made they are packaged into vesicles to be “shipped” to Golgi apparatus.

Golgi Apparatus

• Saclike membranes used for storing, modifying and packaging of proteins and other chemicals.

Endomembrane System

Proteins made by Rough

ER are shipped to Golgi

Apparatus in vesicles

where they are modified.

From here they move to

the cell membrane in

secretory vesicles which

release them externally.

Golgi apparatus

ribosomes

vesicle

smooth ERrough ER

nucleolusnucleus

vesiclecell membrane

lipids

Lysosomes

• Formed in Golgi bodies

• Contain hydrolytic (digestive) enzymes to break down unwanted particles

• Help white blood cells to destroy bacteria

Mitochondria

• Produce ATP through cellular respiration

• Mitochondria replicate by binary fission - similar to prokaryotic

cell division

Mitochondrial Structure- have double membrane structure

- inner membrane folded into inward projections called cristae

- two spaces within the mitochondrion - the matrix and the intermembrane space

Chloroplasts

• sites of photosynthesis in nearly all plants and some protists.

• trap light energy and convert it into chemical energy

Chloroplast Structure- have double membrane structure

-Within the stroma (fluid) are a series of stacks of flattened

-membranous structures called thylakoids (stacks of these are called grana)

Cytoskeleton• Composed of proteins that

maintain the cell’s structure, transport materials, and position and move organelles.

• 3 cytoskeletal components:

microtubules

actin filaments

intermediate filaments

Actin Filaments• involved in cellular and

organelle movement.• smallest components of

the cytoskeleton.• “Motor” molecules

Intermediate Filaments• involved in anchoring organelles in place and •holding cells together .

Microtubules- hollow tubes made of proteins called tubulin dimers.

-These are responsible for cell movement by changing in length by adding/taking away tubulin dimers polymerization/ depolymerization

-Work with actin in the movement of organelles.

- These are the largest components of the cytoskeleton.

Cellular Work- Microtubules work with actin (and other motor molecules) in the movement of organelles and other cellular structures.

- These are the largest components of the cytoskeleton.

Cilia/Flagella Movement• A flagellum has pairs of

microtubules in a 9+2 pattern each pair of tubules has short arms of dynein (a motor molecule) that pulls on neighboring tubules causing the structure to twist throughout.

Back to Plant Cells

Contain:• chloroplasts • A cell wall• A large central

vacuole• No centrioles

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