Cell Walls and Membranes

Borders are important…2 types in cells: walls & membranes

Cell WallWhat it’s for…SupportProtection

What organisms have cell walls?Found in…

PlantsFungiAlgaeBacteria (prokaryotes)

What’s the cell wall made of? Fibers of carbs and proteins made in the cell In Plant cells: Composed of cellulose This is what makes wood and paper

Cell membranes (also called plasma membranes)…Surround all cellsFlexible barrier that separates the inside

and outside of the cellOften referred to as a “mosaic”

Cell Membrane

• Has 2 layers

• Has openings for substances to enter and leave the cell

What is the cell membrane made of?

• Looks like a sandwich

• Outside layers –Made of phosphate molecules

–Are Polar – mix with water –Hydrophilic (“water-loving”)

–Form two layers like two pieces of bread

• Inside layer –Made of lipids (fat)–Water resistant

• Non polar, don’t mix with water• Hydrophobic (“water-fearing”)

• Has small “doorways” or openings that are called transport proteins

What’s another name for the cell membrane?

• Phospholipid Bilayer

Drawing of Cell Membrane

• Phospholipid sandwich:

Function of cell membrane

• Selective permeability• Selective = only some things allowed in or out

• Permeability= has small holes in it

• Without selective permeability the cell would have no control of what comes in and out and would die

• Membrane is a “fluid mosaic”

• Fluid = it moves and is flexible

Mosaic = proteins, carbs & cholesterol make a pattern on the surface of the membrane

Cell membrane’s functionProvides protection

and supportAnchors the

cytoskeleton

Phospholipid bilayerTwo layers of lipidsSprinkled with : glycolipids, carbohydrates,

cholesterol and Transport Proteins Flexible yet strong

The Wonderful World of Cells

Prokaryotic Cells

• No true nucleus• No membrane

bound organelles• DNA is small and a

ring• Has free ribosomes• Most primitive of life

forms, but also the most sucessful!!!

Eukaryotic Cells• “True” cells• Membrane bound

nucleus• Membrane bound

organelles• Complex organization• Make up all life except

Bacteria

The Eukaryotic Organelles

• In the following slides, you will get the low down on the organelles found in animal and plant cells.

• You will be responsible for knowing each organelle, knowing what its job is, and being able to identify it on a diagram!

Cell Wall

• Only in plant, bacteria & fungi cells• Outside of the membrane• Is stiff gives shape and support

Cell WallRigid Cell Boundary

• NOT IN ANIMAL CELLS!

• Made of cellulose,chitin, or peptidoglycans

• Retains shape and withstands internal and external pressure

Cell wall

Nucleus

• Brain of the cell• Contains Chromosomes made of

DNA

Nucleus The “Brain” of the Cell

• It directs the manufacture of proteins and other important chemicals

• Contains the nucleolus is key in the production of RNA

• It is surrounded by a semi-permeable membrane

Nuclear envelope

Chromatin

nucleolus

Cytoplasm

• Clear jelly-like fluid inside the cell

• Cell parts float in it

Endoplasmic Reticulum*The cell’s internal Transport

Highway• A membrane encased

transport and manufacture system

• Rough ER has ribosomes and manufactures proteins

• Smooth ER manufactures lipids for membranes

Ribosomes

• Small and round

• Make Proteins

Ribosomes*Protein Assembly Sites

• Small 2-part structures made of rRNA

• Site of Protein synthesis (building) using blueprint from the DNA

• Can be free, or attached to the ER (Endoplasmic Reticulum)

Golgi Apparatus

• Flat stacks of small containers

• Sort and package proteins

The Golgi Apparatus*Postal Service of the Cell

• Receives unfinished products from the ER

• Refines them to final form

• Packages them and tags them for proper delivery

• Ships them out of the cell

Vacuole*The Storage Closet of the Cell

• Storage for chemicals made by the cell

• Storage of food particles brought into the cell

• Water storage• Water level control

(Plants and Protists in particular)

Lysosome*Clean-up/ Digestive crew

• Small organelles filled with enzymes

• Digestion of lipids, carbs, and proteins

• Breakdown of worn out cell parts

• Removal of toxic chemicals

Mitochondria

• Mighty mitochondria!

• Help the cell change food to energy

• Look like sausages

Mitochondria*Power Plant of the Cell

• Convert chemical energy from food into ATP (Energy for the cell)

• Have their own ribosomes

• Have their own DNA

Choloroplasts

• Only in plant cells• Change light energy into food

Chloroplasts*Solar Generator Supreme

• Convert solar wave energy to the chemical energy of sugar

• Have their own ribosomes

• Have their own DNA

Cytoskeleton

• A network of protein filaments that give shape to the cell

• Base for movement in cells

• An internal monorail system to move things within a cell

• Base for the centrioles used in cell division

Centrioles

• Made of microtubules• Important during cell division• Located in the cytoplasm near the nucleus

Animal vs. Plant cell

You will be required to label a diagram, and identify the differences between plant and animal cells. See p. 192 of your textbook