Cells

Cells

Cytoskeleton

• The cytoskeleton is a network of fibers extending throughout the cytoplasm and it helps to hold the cells shape together.
• They are the "muscles" for movement.
• The three types are microfilaments, intermediate filaments, and microtubules.

Microfilaments

• Helical rods made out of a globular protein called actin.
• These help the cell move and change their shape.
• Actin and other fibers work together to make muscles contract.

Intermediate Filaments

• These are ropelike fiberous proteins.
• They have reinforced rods to bear tension and they anchor organelles.

Microtubules

• Straight, hollow tubes that are made of globular proteins. They are called tubulins.
• Globular molecules are like small marbles.
• They make themselves longer by adding tubulin subunits to one end.
• Their functions are providing shape, tracks for organelles to move within teh cytoplasm, they guide the movement of chromosomes during cell division, and move the cilia and flagella.

Cilia

• Shorter than flagella and they are more numerous.
• Propel protists; single celled organisms.
• Can be damaged by smoking and line the respiratory tract.
• The cilia push debri up and out of the body.

Flagella

• A type of transport.
• Propel sperm, other animals, and protists.

Microtubule Structure

• Microtubules form a 9 + 2 arrangement which means that there are 9 doubles of microtubules forming a ring around one double.
• These make up one cilia or one flagella
• To move the cilia or flagella, a motor protein called dyneins is needed. It grabs ontioo an adjacent microtubule doublet.
• These structures are flexible.
• Basal bodies and centrioles have identical structures.
• Basal bodies are anchor cilia or flagella in the cytoplasm.

Plasma Membrane

Membranes of the Cell

• Plasma Membrane - cell's outer membrane (Cell Membrane)
• Endomembranes - smooth and rough endoplasmic reticulum, golgi, vacuole, and lysosome (only these internal oragnelles can break apart)
• Membranous envelopes - nucleus, chloroplast, and mitochodria (have 2 membranes)

Membrane Features

• Semi-permeable - allow some substances to pass through, but blocks the passage of other substances. (only small things can go through)
• Membranes enclose and maintain the specific chemical environment.
• Every membrane carries out its specific functions.

Membrane Structure

• Two layer membrane called phospholipid bilayer.
• Made of proteins and lipids
• Contains two fatty acids instead of three (hydrophobic)
• Contains a phosphate group in the place of the third fatty acid (hydrophilic)

Membranes and Proteins

• Specific proteins are inserted into the phosolipid bilayer to:

1. Attach to the cytoskeleton
2. Talk to other cells
3. Enzyme Activity
4. Transporting passively and actively
5. Two cells holding each other, intercellular joining
6. Cell-cell recognition

Flexibility

• Membranes are not rigid.
• Protiens move freely on the membrane and do not just stay in one spot.
• This is called the fluid mosaic model.

Diffusion and Osmosis

• In diffusion, the molecules move.
• In osmosis, the water moves.
• Diffusion: the tendency of molecules to move from a high concentration to a low concentration until equilibrium is reached.
• Equilibrium is when the conecentration of either side it equal.

Passive Transport

• Diffusion across a membrane.
• Cell does not use any energy for diffusion.
• Selectively permeable membrane.
• Water, O2, and CO2 go through the membrane because they are small.

Osmosis

• Osmosis: passive transport of water across a semi-permeable membrane.
• Solute = what is dissolved.
• Solvent = what the solute is dissolved in.
• Water moves across the membrane, not the solute.

Hypertonic

• High concentration of solute and lower for solvent.
• Hyper = above.
• Plasmolysis = losing water.
• Cells will shrivel up if there is not enough water.

Hypotonic

• High concentration of solvent and lower for solute.
• Hypo = below.
• Lysing = bursting of a cell.
• Good for plant cells.

Isotomic

• Everything is equal.
• Isos = equal.
• Animal cells like this, but plant cells do not.

Effect on living animal cells

• Osmoregulation - control of water balance.
• Animals must use this to survive.
• Blood cells love this.

Effect on living plant cells

• Most plants thrive in a hypotonic environment when the vacuole is full.
• Plants become wilted in a isotonic environment.

Posted on 10/4/2010

Next Scribe: Katie B.