Lec4notescomplete

Lec4notescomplete - Bio1A Dr. McCray Chapter 6 A Tour of...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Bio1A Dr. McCray Lec 4 Complete Notes 1 Chapter 6 A Tour of the Cell Importance of Cells All organisms are made of cells The cell is the simplest collection of matter that displays the properties of life Cell structure is correlated to cellular function All cells are related by their descent from earlier cells Light Microscopes In a light microscope (LM), visible light passes through a specimen and then through glass lenses, which magnify the image The minimum resolution of an LM is about 200 nanometers (nm), the size of a small bacterium LMs can magnify effectively to about 1,000 times the size of the actual specimen Various techniques enhance contrast and enable cell components to be stained or labeled Most subcellular structures, or organelles , are too small to be resolved by a LM Fig 6-2, Fig 6-3a, Fig 6-3b Electron Microscopes Two basic types of electron microscopes (EMs) are used to study subcellular structures Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3D Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen TEMs are used mainly to study the internal ultrastructure of cells Fig 6-4 Isolating Organelles by Cell Fractionation Cell fractionation takes cells apart and separates the major organelles from one another Ultracentrifuges fractionate cells into their component parts Fig 6-5b Eukaryotes The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells Protists , fungi , animals , and plants all consist of eukaryotic cells All Cells Basic features of all cells: Plasma membrane Semifluid substance called the cytosol
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Bio1A Dr. McCray Lec 4 Complete Notes 2 Chromosomes (carry genes) Ribosomes (make proteins) Prokaryotes Prokaryotic cells have no nucleus In a prokaryotic cell, DNA is in an unbound region called the nucleoid Prokaryotic cells lack membrane-bound organelles Fig 6-6 Eukaryotes Eukaryotic cells have DNA in a nucleus that is bounded by a membranous nuclear envelope Eukaryotic cells have membrane-bound organelles Eukaryotic cells are generally much larger than prokaryotic cells The logistics of carrying out cellular metabolism sets limits on the size of cells Fig 6-7 Membranes The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of the cell The general structure of a biological membrane is a double layer of phospholipids Fig 6-8, Fig 6-9a, Fig 6-9b Nucleus The nucleus contains most of the DNA in a eukaryotic cell The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle The nuclear envelope encloses the nucleus, separating it from the cytoplasm Fig 6-10
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 7

Lec4notescomplete - Bio1A Dr. McCray Chapter 6 A Tour of...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online