Introduction to BiologyChapter 3 Notes: Cell Structure and Function

Mr. Grivensky/Mr. Rutkoski

3-1 Early Microscopes

In the 1600s, a Dutch glassmaker named Anton van Leeuwenhoek discovered that if he placed several magnifying lenses at the proper distances from each other he could greatly magnify small objects.

van Leeuwenhoek is given credit for creating the first microscopes

“Cell Theory Scientists” Robert Hooke, an English physicist, at about the same time

as Leeuwenhoek, was using a microscope to observe flowers, insects, and slices of cork.

In 1665, Hooke published a book of his drawings and named the chambers he observed in plant samples, “cells”. He chose this name because they reminded him of the tiny rooms in a monastery, which are also called cells.

Hooke believed that only plants were made up of cells, as did most scientists of his time and nearly 200 years later.

In 1839, a German biologist, Theodor Schwann found that animal tissues also had cell-like structures which lead him to the conclusion that animals were made up of cells also.

..more “Cell Theory Scientists” Around the same time as Schwann made his

discovery, Robert Brown, a Scottish biologist had found that cells had a structure near the center. We now call this structure the nucleus.

German biologist, Matthias Schleiden, suggested that the nucleus played a role in cell reproduction.

In 1855, German physicist, Rudolf Virchow, studied cell reproduction further and proposed that animal and plant cells were produced by the division of existing cells.

Cell Theory The discoveries of these scientists are

summarized in the cell theory.

Cell Theory states that:

A. All living things are composed of cells B. Cells are the smallest working units of

living things

C. All cells come from preexisting cells by cell division

Modern Microscopes Compound light microscope Uses more than one lens to

magnify objects Can magnify an image up to

1000 times These are what we use at

Wyoming Area Cells and organisms can be

studied while they are still alive

Electron Microscopes: TEM Use magnets to focus a beam of electrons,

much like a television The beam of electrons can be used to

examine a sample Electron microscopes can magnify 1000x

larger than a light microscope (100,000 times)

Transmission Electron Microscope (TEM) Shines a beam of electrons through a

sample, and then projects the image onto a fluorescent screen

Electron Microscopes: SEM

Scanning Electron Microscope (SEM) Uses a beam of electrons to scan the

surface of a sample. The SEM collects the electrons that bounce off the sample, and forms an image on a television screen

Both, TEMs and SEMs can only observe nonliving specimens. These specimens

must be sliced very thin for use in a TEM, and the SEM only shows the outer surface of the specimen

SEM & TEM Photos

SEMTEM

Scanning Probe Microscope

In the early 1980s, the scanning probe microscope was invented

It does not use any lenses, and instead traces the surface of an object with a probe

These microscopes have been used to photograph molecules and atoms.

3-2 Cell Boundaries

Every cell has a cell membrane along its boundary.

The principal role of the cell membrane is to separate and protect the cell from its surroundings.

The cell membrane is said to be selectively permeable

Selectively Permeable

Selectively Permeable means that the cell membrane allows some substances through but denies passage to other substances

Lipid Bilayer

The cell membrane is composed of a phospholipid bilayer. A phospholipid has a polar end called the head and a nonpolar end called the tail. The polar heads group together on the outside of the lipid bilayer. The nonpolar heads group together on the inside of the bilayer because they avoid water.

The lipid bilayer provides the cell membrane with a tough, flexible barrier that protects the cell from substances.

Cell Membrane

Cell Wall

Found in plants, algae, and bacteria. Located outside the cell membrane. Helps to support and protect the cell. Made up of carbohydrates and

protein. The principle carbohydrate is cellulose.

Cellulose provide the cell with rigidity and strength.

Cell Wall

Passive Transport

Substances cross the cell membrane without the cell expending energy

Examples-1. Diffusion2. Facilitated Diffusion3. Osmosis

Diffusion

Diffusion is the process by which substances spread throughout a liquid or gas.

In diffusion, substances move from regions of high concentration to regions of low concentration

Diffusion

Facilitated Diffusion

Substances diffuse across the cell membrane through special channels in protein

Example is glucose

Osmosis

The diffusion of water through a selectively permeable membrane

Hypertonic Solution

Hypertonic Solution: Solute concentration of solution higher than cell More dissolved particles outside of cell

than inside of cell Hyper = more (think hyperactive); Tonic

= dissolved particles Water moves out of cell into solution Cell shrinks

Hypertonic Solution

Hyoptonic Solution

Hypotonic Solution: Solute concentration of solution lower than cell Less dissolved particles outside of cell

than inside of cell Hypo = less, under (think hypodermic,

hypothermia); Tonic = dissolved particles Water moves into cell from solution Cell expands (and may burst)

Hypotonic Solution

Isotonic Solution

Isotonic Solution: Solute concentration of solution equal to that of cell No net water movement

Isotonic Solution

Active Transport

Requires energy The movement of substances against

a concentration gradient Similar to a pump. Examples

1. Endocytosis2. Phagocytosis3. Exocytosis

3-3 Inside the Cell

There are two categories of organisms: prokaryotes and eukaryotes

Prokaryotes- organisms that do not contain nuclei and membrane bound organelles (ex.bacteria)

Eukaryotes- organisms that contain a nucleus and organelles

Nucleus

Control center of the cell Large and dense Contains nearly all of the cell’s DNA

DNA

Contains coded instructions for making proteins

DNA wrapped around special proteins(histones) is known as chromatin

Chromatin condenses to form chromosomes

Chromatin/Chromosomes

Structures in the Nucleus

Nucleolus- small, dense region found in the nucleus; ribosomes are assembled here

Nuclear envelope- two distinct membranes that contain many holes called nuclear pores

Structures of the Nucleus

Cytoplasm

Portion of the cell outside of the nucleus

Fluid like material that contains organelles

Organelles-small structure that performs a specialized function within the cell

Organelles

Ribosomes Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Golgi Apparatus Lysosomes Cytoskeleton

1. Microtubules2. Microfilaments

Organelles- continued

Cilia Flagella Vacuoles Centrioles Plastids Mitochondria Chloroplast

Ribosomes

RibosomesProtein and RNA complex responsible for protein synthesis

Rough Endoplasmic Reticulum

Rough endoplasmic reticulum (RER)A network of interconnected membranes forming channels within the cell. Covered with ribosomes (causing the "rough" appearance) which are in the process of synthesizing proteins.

Smooth Endoplasmic Reticulum

Smooth endoplasmic reticulum (SER)A network of interconnected membranes forming channels within the cell. A site for synthesis and metabolism of lipids.

Golgi Apparatus

Golgi apparatusA series of stacked membranes. Vesicles (small membrane surrounded bags) carry materials from the RER to the Golgi apparatus. Vesicles move between the stacks while the proteins are "processed" to a mature form.

Lysosomes

LysosymesA membrane bound organelle that is responsible for degrading proteins and membranes in the cell, and also helps degrade materials ingested by the cell.

Cytoskeleton

The cytoskeleton extends through out the cytoplasm.  Composed of protein fibers called intermediate filaments, microtubules and microfilaments, the cytoskeleton maintains cell shape, allows the cell to move, and moves structures within the cell. 

Cilia and Flagella

Plant cells do not have cilia and flagella.  Both are anchored in the cytoplasm by centrioles and extend from the outside surface of the plasma membrane.  Flagella are used to propel the cell.  Cilia can be used to propel the cell, or move fluids past the cell.

Cilia and Flagella

Vacuole

VacuolesMembrane surrounded "bags" that contain water and storage materials in plants.

Centrioles

A centriole is a short, barrel shaped ring composed of nine microtubules around an empty center.  Centrioles are found only in animal cells.  They are arranged in pairs that sit perpendicular to one another.

Plastids

Plastids are a storage organelle unique to plant cells and some photosynthetic protists.  They are not found in animal cells.  Located in the cytoplasm, the plastids are used to store substances such as pigments and starches.

Mitochrondria

MitochondriaSurrounded by a double membrane with a series of folds called cristae. Functions in energy production through metabolism. Contains its own DNA.

Chloroplast

Chloroplasts (plastids)Surrounded by a double membrane, containing stacked thylacoid membranes. Responsible for photosynthesis, the trapping of light energy for the synthesis of sugars.

Animal Cell

Plant Cell