Chapter 6 Biology – Campbell • Reece A Tour of the Cell Chapter 6 Biology – Campbell • Reece

How We Study Cells… Microscopes Magnification Resolving Power or resolution 3 types of microscopes: Light Microscopes – a beam of light passes through the object, magnify up to 1000x, resolution of 0.2µm Transmission Electron Microscope (TEM) – passes a beam of electrons through the object, greater magnification, resolution of 2nm Scanning Electron Microscope (SEM) – passes a beam of electrons over the surface of the object, creates a 3-D image

Compound Light Microscope

Transmission Electron Microscope

Scanning Electron Microscope

Isolating Organelles Cell fractionation – take cells apart and separate the major organelles Homogenization – the disruption of cells Centrifuge at low speed – separates the “soup” into a pellet and a supernatant The supernatant is then centrifuged at higher speed The process is repeated multiple times at higher speeds

Cell Fractionation

Prokaryotic vs. Eukaryotic All cells have: plasma membrane, cytosol, chromosomes, and ribosomes Prokaryotic cells No membrane-bound nucleus Ex. bacteria Eukaryotic cells Have a membrane-bound nucleus Usually larger than prokaryotic cells Ex. Human skin cell

Surface Area vs. Volume Larger organisms do not generally have larger cells, they have more cells

REMINDER: You are responsible for the information cell parts & organelles (pages 100-119) Questions on the test may come from these pages!!!

Extracellular Matrix Although they do not have a cell wall, animal cells do have an extracellular matrix made up of collagen, proteoglycans, fibronectins, and integrins

Intercellular Junctions Plasmodesmata – channels in cell walls (connects one plant cell to another)

Intercellular Junctions 3 types in animal cells Tight junctions – membranes of neighboring cells are fused Ex. between skin cells Desmosomes (anchoring junction) – cells held together by filaments Ex. attach muscle cells to each other Gap junctions – cytoplasmic channels between adjacent animal cells (similar to plasmodesmata)

Intercellular Junctions (in animal cells)