Chapter 3 Notes, part 1

“Looking at Cells”Cells were discovered in the 17th century, when microscopes were invented….

Cells were discovered by….. Robert Hooke, in 1665 he looked at a

thin piece of cork and ‘saw a lot of little boxes’ which reminded him of the small rooms where monks live, so he called them cells

Anton von Leeuwenhoek used a microscope ten years later to view water from a pond, and he called the tiny organisms he saw ‘animalcules’

Measurement

See table 1, p. 50 Cells are measured in units of

micrometers, abbreviated μm. The symbol μ stands for the prefix ‘micro’

See figure 2, page 51, which shows the sizes of different objects

Know these words….. Magnification: the amount of times a

specimen being viewed is enlarged in order to be seen, varies with power of microscope

Resolution: the ability that the microscope has to distinguish between two different objects, ie. The nucleus vs. the endoplasmic reticulum

Contrast: ability to see detail within the specimen clearly

Types of microscopes

Light microscope Transmission and scanning electron

microscopes Scanning tunneling microscope

Compound light microscopes What we work with in

class Light rays pass through

specimen and come into focus through two glass lenses.

The eyepiece lens gives a total of 10x magnification. The objective lens varies with microscopes but can be up to 100x magnification. Total magnification is found by multiplying eyepiece lens by objective lens.

Transmission Electron Microscopes

Use electrons to pass through specimens to view detail; image projected onto screen or photographic film

Scanning electron microscopes The specimen is

first coated with a thin layer of metal and an image is produced by the electrons which bounce off of the image

Scanning tunneling microscopes New video and

computer techniques are increasing microscope resolution and magnification

This type of microscope uses a needle-like probe to measure voltages of electrons. It can track the movement of electrons and can see atoms!

Compare the images produced by different microscopes…..

See p. 52 for a light microscope image of sperm

See p. 53 for a T.E.M. image of sperm See p. 54 for an S.E.M. image of

sperm

Section 3.2: Cell Features

The cell theory: was bulit on the ideas of Hooke and Leeuwenhooek by the following: Schleiden who said that cells make up

every part of a plant Schwann who claimed that animals are

also made of cells Virchow who determined that cells come

from other cells.

The cell theory summarized…

All living things are made of one or more cells

Cells are the basic unit of structure and function in organisms

All cells arise from existing cells

Cell size and sufrace area:volume ratio Small cells function more efficiently than

larger cells If the surface area of a cell is larger than

it’s volume, then the cell can gather essential nutrients and water and they can get in fast.

If the surface area to volume ratio is close in number to the volume, it takes too long for materials to reach the interior of the cell

See table 2 p. 55

Common features of cells: Most cells have…

A cell membrane: encloses cell, separates interior

Cytoplasm: the fluid in which interior cell structures are suspended, also called cytosol

Cytoskeleton: for cellular structure Ribosomes: make proteins DNA: all cells have DNA which contains

instructions for making proteins, regulating the activities of the cell, and allowing the cell to reproduce. Red blood cells lose their DNA at a certain point in their life.

Prokaryotes

A single-celled organism that lacks a nucleus and other internal compartments

Common prokaryotes which cause infection and spoil food: Bacteria

Characteristics of Prokaryotes:

Have little internal structure Many have a capsule and flagella DNA is located near the center of the

cell and is not contained in a nucleus A cell wall surrounds the membrane

and provides structure and support Many have flagella which propel them

along

Typical prokaryote:

Eukaryotic Cells

Cells with a nucleus and other organelles

An organelle is a structure within a cell that carries out specific activities for that cell

Some eukaryotic cells have cilia which are short hairlike structures that protrude from the surface of the cells

cytoskeleton Provides the internal framework of an

animal cell, much as our skeleton provides the internal framework of our bodies

Three types of cytoskeleton fibers: Actin fibers: found just inside of the cell

membrane; helps cell membrane move Microtubules: transport information from nucleus

to different parts of the cell Intermediate fibers: keep ribosomes and

enzymes in place within cell

The cell membrane

to separate the internal from external environment of the cell

Regulates materials entering and leaving the cell.

Helps the cell, in turn the organism, maintain homeostasis

cell membrane structure Made up of a

phospholipid bilayer Phospholipid: a

molecule with a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail

Cell membrane proteins Proteins embedded in the membrane have

polar and nonpolar ends just like the membrane; this keeps them embedded inside of the membrane

These proteins have different functions: Receptor proteins recognize and bind to

substances outside the cell Enzymes assist chemical reactions in the cell Transport proteins help substances move across

the membrane

Upcoming Biology Schedule:

This weekend’s homework: worksheet packet

Monday: chapter 3 lab (read) Wednesday: go over lab/test review Friday (Happy Halloween!) TEST!!!