Cells

Cell Theory 1665, Robert Hooke was the first to uswe a microscope to observe “cells” small compartments in a plant By the 1800s, cells had been found in every organism Developed the cell theory: –All living things are composed of cells –Cells are the basic unit of structure and function in living things –Cells come from other cells

Microscopes Light microscopes are useful for magnifying objects up to about 1000 times their actual size –works for viewing objects about the size of a bacterium or larger. –But much of a cell's structure is so small that even magnifying it 1000 times is not enough to see it

Microscopy oscope/ oscope/ magnifying/index.htmlhttp://micro.magnet.fsu.edu/primer/virtual/ magnifying/index.html Light is only good for seeing relatively large objects (the size of a bacterium) –smaller than that you need an electron microscope

Cell Size Restricted by metabolic requirements Surface area-to- volume ratio decreases w/ increased size

Prokaryotic vs Eukaryotic lacks a nucleus and most other organelles bacteria appear earliest in Earth's fossil record Small (1-10  m) has a nucleus surrounded by its own membrane has other internal organelles bounded by membranes Protists, fungi, plants, and animals consist of eukaryotic cells appeared later in Earth's history Larger (  m)

Plant vs. Animal Cells

Organelles Means “mini- organs” 1.Cytoplasm 2.Nucleus 3.Ribosome 4.Endoplasmic reticulum 5.Golgi 6.Vacuoles 7.Lysosomes 8.Chloroplast : plants only 9.Mitochondria 10.Cytoskeleton 11.Plasma membrane

Cytoplasm The space between the nucleus and the plasma membrane Where the organelles are suspended in a thick “jello – like” fluid

Nucleus Only found in eukaryotic cells Contains DNA, which is wrapped around proteins to form chromatin Contains the nucleolus (structure that creates ribosomes – see next slide) Surrounded by nuclear envelope (a membrane that separates it fro the rest of the cell

Ribosome Create proteins Made from RNA and protein Can be found in the cytoplasm or attached to the endoplasmic reticulum (see next slide)

Endoplasmic Reticulum (ER) The highway Huge membrane network that crisscrosses the entire cell Rough ER has ribosomes attached –Secretes proteins Smooth ER has no ribosomes attached –Manufactures lipids an steroids –Detoxifies many chemicals

Golgi Receives proteins from the RER and packages them so they are sent to the proper location Modifies proteins

Vacuoles Food storage Salt storage Contractile vacuoles in protozoa pumps out excess water

Lysosomes Contain digestive enzymes Recycle damaged organelles and proteins Destroy bacteria

Chloroplast Found only in plant cells Turn light into glucose (photosynthesis)

Mitochondria Where cellular respiration occurs (energy is produced) from glucose

Cytoskeleton The architecture that gives the cell shape and allows things to move Made of microtubules and microfilaments

Self- quiz htmlhttp://darwin.nmsu.edu/~molbio/cellgame/cellpin. html mePlant.htmlhttp://darwin.nmsu.edu/~molbio/cellgame/CellGa mePlant.html intro.htmlhttp://w3.dwm.ks.edu.tw/bio/activelearner/04/ch4 intro.html Review – mal.htmlhttp:// mal.html

Plasma Membranes

Cell membrane is composed mainly from phospholipids, but contains proteins and some carbohydrates as well Described as a phospholipid bilayer, it is both hydrophobic and hydrophilic Functions as a selective barrier: Selectively permeable Fluid: the various components can “float”; they are not tightly held in place

What type of molecules could pass through the phospholipids? Small Non-polar What about all the other molecules? They must be brought in through “doors” The “doors” are the proteins

The proteins act as gatekeepers, only allowing certain substances into the cell No Entrance! Come on in!

What do all those proteins do? (with the help of carbohydrates) (Keeps the cells in place)

1. Describe the arrangement of the phospholipid bilayer. The hydrophilic heads face the watery inside and the watery outside of the cell, while the hydrophobic tails are sandwiched in the middle. 2. Name some parts, other than phospholipids, that make up the plasma membrane. Sample answers: proteins, transport proteins, enzymes, carbohydrate chains

Transport Basics Passive transport –Substances move along the concentration gradient –no energy required Active transport –Substances move against the concentration gradient –requires energy

Passive Transport 1. Diffusion Things move from an area of high concentration to an area of low concentration. online.com/objects/index_tj.asp?objid=AP 1903http:// online.com/objects/index_tj.asp?objid=AP ogy1111/animations/passive1.swfhttp:// ogy1111/animations/passive1.swf

Passive Transport 2. Osmosis Refers specifically to the movement of water Hypertonic refers to a HIGH solute concentration Hypotonic refers to a LOW solute concentration Isotonic means both sides are equal 11/animations/passive1.swfhttp:// 11/animations/passive1.swf m1.htmlhttp://science.nhmccd.edu/biol/membrane/osfra m1.html

If the solution is isotonic relative to the cell, then the solute concentrations are the same on both sides of the membrane and water moves equally in both directions A hypertonic solution has increased solute, and a net movement of water outside causing the cell to shrink. (plasmolysis) A hypotonic solution has decreased solute concentration, and a net movement of water inside the cell, causing swelling or breakage. (cytolysis)

Plasmolysis = cells shrinking due to exit of water

Cytolysis = cells exploding due to entrance of water

Passive Transport 3. Facilitated Diffusion The substance needs a “door” to get through the membrane

Active Transport Moves substances against the concentration gradient Requires energy ogy/Biology1111/animations/active 1.swfhttp:// ogy/Biology1111/animations/active 1.swf

Endocytosis is a type of Active Transport Endocytosis brings large things into the cell logy/Biology1111/animations/activ e1.swfhttp:// logy/Biology1111/animations/activ e1.swf Phagocytosis is specifically bringing food into the cell

Endocytosis brings things into the cell. Exocytosis gets things out of the cell.

1. Describe the direction of solute movement in passive transport and active transport. Passive transport: solute moves from an area of high concentration to an area of low concentration; active transport: solute moves from an area of low concentration to an area of high concentration.

2. What is the difference in energy expenditure between passive and active transport? Passive transport does not require energy; active transport always requires energy.