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The Cell

Chapter 5

 

 

5.1
What is a Cell ?

Microscopic

All living things

One celled

Many celled

The Cell Theory

mid 1600’s microscopes were used by Robert Hooke

Slices of cork

1693, Anton van Leeuwenhoek

single lense

pond water

bacteria

1824, Henry Dutrochet – living things made of cells

1831, Robert Brown noticed the nucleus

1838, Matthias Schleiden, theory all plants made of cells

1839, Theodor Schwann, proposed that all animals were made of cells

1839, Johannes Purkinje, used the term protoplasm

1855, Rudolf Virchow, all cells rise from pre-existing cells.

1861, Max Schultze, define protoplasm

1861, Felix Dujardin, recognized the existence of one-celled organisms

Ideas that make up the
Cell Theory

All organisms are made of one or more cells and the products of those cells. An organism may be a single cell, such as a bacterium, or many cells organized to function together, as in an animal or plant. In many-celled organisms, there may be intercellular material made by the cells.

All cells carry on life activities. The life activities of a many-celled organism are the combined results of the activities of its individual cells.

New cells arise only from other living cells by the process of cell division.

The Two Basic Cell Types

Fundamentally alike, but

Prokaryotic cells – without nucleus

Lacks any kind of organelle

Eukaryotic cells – true nucleus

Does contain many membrane-bound organelles

Nucleus, very important part of cell.

DNA located

Cell Size

Prokaryotic – 1 and 10 micrometers

Eukaryotic – 10 times larger than prokaryotic, 10 – 100 micrometers

5.2 Cell Structure

Organelles – specialized internal structures of the cell.

Some enclosed within own membrane, some are not.

Specific functions

Figure 5-5, p. 83

 

 

Cell Walls

Cells are enclosed by a rigid wall

Lies just outside cell membrane

Shape and protection

Plants – composed of cellulose

Many small openings

Animal cells do not have cell walls

 

The Cell Membrane

Also called plasma membrane

Separates cell from its environment

Controls material in and out of cell

Maintains homeostasis

Structure – two layers composed of lipids, proteins, and carbohydrates

Behaves like a fluid mosaic

Protein functions

Transport, receptors, enzymes, binding the membrane to cytoplasm

Selective permeability

The Nucleus

Round control center for cell’s metabolism and reproduction

Removed – cell will die

Nuclear envelope – surrounds nucleus

Selectively permeable

Forming well define pores

Controls the substances that goes in and out

Nucleoplasma remains chemically different and mostly chromatin

Chromosomes – contains hereditary material of cell

Nucleoli dense granular bodies, made up of DNA, RNA and protein. Site of ribosome production

 

 

The Cytoplasm

Watery material between cell and cell membrane

Many chemical reactions o cell metabolism take place in cytoplasm

Location of a variety of organelles

Organelles in the cytoplasm

Endoplasmic reticulum

Ribosomes

Golgi bodies

Lysosomes

Mitochondria

Microtubules

Microfilaments

Centrioles

Cilia and Flagella

Vacuoles

Plastids

Leucoplasts

Chromoplasts

Endoplasmic Reticulum

System of fluid-filled canals enclosed by membranes, fig 5-8

Serve as paths for transport of material through cell

Divide into different compartments for various reactions to occur

Rough or smooth

Rough have ribosome lining

Smooth no ribosomes

Ribosomes

Golgi Bodies

Lysosomes

Mitochondria

Microtubules

Microfilaments

Centrioles

Cilia and Flagella

Vacuoles

Plastids

Origins of the Eukaryotic Cell

Endosymbiotic theory

Endosymbiosis

Oxygen

DNA

5.3 Maintaining a Constant Cell Environment

Homeostasis

pH

Disrupted – cell dies

Special properties of cell membrane

Selective Permeability of the cell Membrane

Passing through cell membrane with ease

Neutral molecules vs charged ions

Permeability varies from one type of cell to another, or even the same cell

Diffusion

Spread from one region of high concentration to an area of lower concentration

Coffee grains

Perfume

Molecules are in constant motion

Concentration gradient

Equilibrium

Oxygen and carbon dioxide

Facilitated Diffusion

Some substances diffuse across cell membranes more rapidly than one might expect from the chemical properties of these substances.

Specialized proteins in the cell membrane

No chemical reactions from transport proteins

Works in the direction of the concentration gradient

Higher to lower concentration – speeds up.

Glucose from your blood into cells of your body

Figure 5-16, p. 93

Osmosis – The Diffusion of Water

The diffusion of water across a selectively permeable membrane from a region of high water concentration to a region of low water concentration

Figure 5.17, p. 93

Osmotic Pressure

Increased pressure resulting from osmosis is equal to the tendency of water to enter the solution.

Effects of Osmosis

Isotonic solution – is one that has the same concentration of dissolved substances as the living cell placed in it.

Hypotonic solution – contains a lower concentration of dissolved substances than the cell.

Hypertonic solution – contains a higher concentration of dissolved substances than the cell.

Figure 5-18, p. 95

Plasmolysis – shrinking of cytoplasm by ososis.

Passive and Active Transport

Passive transport

Active transport

Endocytosis

Pincytosis

Phagocytosis

Exocytosis

5.4 Organization of Cells in Living Things

A cell exists independently is regarded as a one-celled, or unicellular, organism

Unicellular and Colonial Organisms

Able to carry out life processes

Unicellular organisms

Bacteria, protozoa, algae, some fungi

Simplest level – colonial organisms or colony

Complex colonies show some specialization

Volvox ( algae ) fig. 5-20

Multicellular Organisms

Cells specialized

Tissues

Epithelial

Connective

Muscular

Skeletal

Smooth

Involuntary

Automatic

Cardiac

Organs

Organ systems

 

The End

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