A Tour of the Cell (Chapter 6 Lesson)

The Cell

Cell Theory

1. All living things are made up of cells

2. Cells are the basic units of structure and function of all living things

3. All cells come from preexisting cells

Classes of Cells

1. Prokaryotic (no nucleus)

1. Bacteria and archaea

2. Smaller and simpler

3. 1-10 micrometers

2. Eukaryotic (true nucleus)

1. Protists, fungi, plants, and animals

2. Larger and more complex

3. 10-100 micrometers

Overview of the Cell

1. Cell parts are called organelles (mini-organs)

2. General Functions

1. Manufacture

2. Breakdown

3. Energy processing

4. Support and Movement

Manufacture and Breakdown

The Nucleus

1. Nucleus- Control Center

1. Surrounded by a nuclear envelope

2. Contains DNA (chromatin) which directs the cell’s activities

3. Shaped by nuclear matrix

2. Nucleolus- makes ribosomes

Endoplasmic Reticulum

1. Endoplasmic reticulum- a network of passageways

1. Rough ER (dotted with ribosomes) produces proteins for export

2. Smooth ER builds lipids and detoxifies cell

2. Ribosomes assemble proteins

Golgi Body

1. Golgi body packages products in membrane-bound vesicles

1. Modifies, stores, and transports

Vacuoles and Lysosomes

1. Vacuole- large membrane-bound sacs that store:

1. Undigested food and water

2. Color pigments and poisons

2. Lysosome- a vacuole that contains digestive enzymes

1. Breaks down nutrients, bacteria, and old, organelles

2. Aids on body development

Energy, support, and movement

Chloroplasts

1. Chloroplasts convert energy from the sun into sugars

1. Site of photosynthesis

2. Found in plants and algae

Mitochondria

1. The mitochondria release energy from sugar

1. Site of cellular respiration

2. Found in plant AND animal cells

3. Called “the powerhouse”

4. Cristae- folds in inner membrane increasing surface area

Cytoskeleton

1. The cytoskeleton is a network of fibers extending throughout the cytoplasm

1. Microtubules give shape rigidity, & organization

2. Microfilaments enable movement & shape change

2. Centrosome- (microtubules)

1. Aids in mitosis

2. Contains 2 centrioles in animals

Cilia and Flagella

1. Some cells have projections that enable the cell to move

1. Cilia- short and numerous move back-and-forth

2. Flagella- long thin whip-like, move with a “S-shaped” movement

Cell Wall

1. Found in Plant cells, but not animal

2. Contains pore to allow materials to pass through

3. Adjacent primary cell walls glued together by “middle lamella”

4. (Different cell walls found in bacteria, archaea, fungi, & some algae)

Membranes: structure/function

Membrane Structure

1. The cell membrane separates the interior of a cell from its surroundings

1. The membrane acts like a layer of skin

2. Each membrane is composed of proteins & phospholipids (animals contain cholesterol)

1. Forms a phospholipid bilayer that is fluid-like

2. Proteins scattered throughout float like icebergs

3. Carbohydrates are also present

3. Membranes are selectively permeable (control what passes across)

1. small/uncharged molecules can pass (O2 , CO2 , H2O)

2. large/ charged molecules cannot pass (proteins. Sugars and ions)

4. Other functions include:

1. Enzyme activity

2. Cell-to-cell recognition

3. Cell signaling

4. Transport of materials

Types of Transport

1. Passive transport- diffusion across a membrane

1. Diffusion between phospholipids

2. Facilitated diffusion through protein channels

2. Active transport- the use of energy to move molecules

1. Pumps in the opposite direction of diffusion

2. Sodium- potassium pump

3. Bulk transport- the use of membrane vesicles to move large particles across the membrane

1. Exocytosis- spills contents outside the cell

2. Endocytosis- takes materials into cell

3. Phagocytosis- solid

4. Pinocytosis- liquid

Diffusion and Osmosis

Diffusion

1. Particles move from areas of high concentration to areas of low concentration by diffusion

2. Equilibrium is reached when particles are evenly spread out

Osmosis

1. The diffusion of water is called osmosis

1. Hypertonic- high solute ( low water )

2. Hypotonic- low solute ( high water )

3. Isotonic- equal solute and water

2. Osmosis affects the water balance of cells

1. Animals- prefer isotonic

2. Plants- prefer hypotonic environments (turgor pressure)

Membranes: structure/function

Diffusion and osmosis

Manufacture and Breakdown

Energy, support, and movement