Unit 2 Chapters 3 & 4 The Cell

Essential Questions 1.What are cells? 2.How do we observe cells? 3.What are the parts of cells and what are their functions? 4.How do things move across the cell membrane?

3-1 Cells  cell: the basic unit of life  Has all characteristics of life

Microscopes as Windows to Cells  The first light microscope was developed around  Robert Hooke – 1665  Observed“compartments,” cells, in a thin slice of cork  Anton van Leeuwenhoek  1700 developed simple light microscopes with high-quality lenses to observe tiny living organisms “animalcules”

Cell Theory 1.All living things are made up of one or more cells 2.Cells are the basic unit of structure and function in living things 3.Cells only come from other cells

Microscopes  Light microscopes (LM) magnify objects up to 1000 times, bacteria or larger  Electron microscopes (1950’s) use a beam of electrons and can magnify up to 1 million times  Cells must be killed and preserved  Scanning Electron Microscope (SEM) to study the surface structures of cells  Transmission Electron Microscope (TEM) to explore their internal structure  micrograph: a photograph of the view through a microscope

Eukaryotic Cell  eukaryotic cell: has a nucleus surrounded by its own membrane  Protists, fungi, plants, and animals  Much larger than a prokaryotic cell ~ 10 to 100 micrometers

Prokaryotic Cell  prokaryotic cell: lacks a nucleus and most other organelles  Bacteria and archaea; found in earliest fossil record  Much simpler in structure than a eukaryotic cell ~1 to 10 micrometers  The DNA is concentrated in the nucleoid region which is not separated by a membrane

3-2 The Cell Membrane  Structure  Membranes regulate the transport of substances across the boundary  Composed mostly of proteins and phospholipids

Phospholipids  Two fatty acids at one end  hydrophobic  Phosphate group(PO 4 3- ) at the other  Negatively charged and hydrophilic

Phospholipid Bilayer  phospholipid bilayer: the phospholipids form a two-layer “sandwich” of molecules that surrounds the organelle or cell  Phosphate ends face the outside  Fatty acids inside  Fluid mosaic  Proteins drift freely within the membrane

Nucleus  nucleus: houses the cell’s genetic material in the form of DNA, largest organelle  chromosomes: wound up DNA  nucleolus: center of the nucleus; makes ribosomes

Cytoplasm  cytoplasm: the entire region of the cell between the nucleus and the plasma membrane, which consists of organelles and fluid  cytoskeleton: provides structure for a cell

Organelles  organelle: each part of a cell with a specific job to do, “mini-organ”  many are enclosed by their own membranes to help maintain the chemical environment inside that is different then the rest of the cell

Endoplasmic Reticulum(ER)  Works as a highway to move substances through the cell

Ribosomes  Help make proteins

Mitochondria  Powerhouse of the cell  Produces energy  More active cells have more mitochondria  Folded membrane gives more surface are for more energy production

Golgi Body  Like a post office  Packages proteins and lipids to send to other places in the cell or to different cells

Centrioles  Only in Animal Cells  Used during cellular reproduction  Small, rod shaped; located near nucleus

Additions for Plant Cells  chloroplasts: organelle where photosynthesis occurs  cell wall: protects the plant cell and maintains its shape; consists of cellulose and is found outside the plasma membrane  vacuoles: large membrane bound sacs for storage  Main water storage in plants

4-1 Cells and Their Environment  concentration: how crowded particles are  concentrate: a strong form of a juice  Most of the water is taken out

Diffusion  diffusion: the net movement of particles of a substance from where they are more concentrated to where they are less concentrated.  Permeable membrane: a membrane that allows molecules to pass through freely equilibrium: a system is in balance; the number of molecules going one direction is equal to the number in the other direction.

4-2 Osmosis  osmosis: the passive transport of water across a selectively permeable membrane

Water Balance  Water balance in animal cells  if there is too much water moving in the cell may burst  too much moving out it may shrivel and die  animals in aquatic environments depend on isotonic conditions  Water balance in plant cells  a plant cell is healthiest in hypotonic(more water) environments because it remains firm but will not burst. The cell wall is too strong.  in an isotonic situation, there is no net movement of water so it will wilt.

Passive Transport  passive transport: diffusion across a membrane that expends no energy  Diffusion and Osmosis

4-3 Active Transport  active transport: a cell uses energy to move molecules or ions across a membrane  maintains the cell’s chemical environment usually from low to high concentration  Ex. in animal cells, K and Na pump; K pumps in, Na out.

Transport of Large Molecules  vesicles: small membrane sacs that specialize in moving products into, out of, and within a cell  exocytosis: vesicle fuses with the plasma membrane and spills contents outside the cell  endocytosis: reverse; takes material into the cell within vesicles that bud inward