Chapter 4 – A Tour of the Cell And comparison to viruses

Intro

Intro

Intro

Intro

Intro

State Standards Standard 1.c. – Prokaryotic cells, eukaryotic cells (including those from plant and animals), and viruses differ in complexity and general structure Standard 1.e. – The endoplasmic reticulum and Golgi apparatus play a role in the secretion of proteins

The Microscopic World of Cells Organisms are either: Single-celled, such as most bacteria and protists Multicelled, such as plants, animals, and most fungi

The Microscopic World of Cells The human body is made up of trillions of cells many of which are specialized Muscle cells, Nerve cells, & blood cells…

The Cell Theory Cells were first discovered in 1665 by Robert Hooke. The accumulation of scientific evidence led to the cell theory - All living things are composed of one or more cells - All cells are formed from previously existing cells

Microscopes provide windows to the world of the cell The Light Microscope Light passes through the specimen Lenses enlarge, or magnify, the image Magnification – the increase in the specimen’s apparent size Resolving power – the ability to show 2 objects as being separate

Microscopes provide windows to the world of the cell The Electron Microscope Uses a beam of electrons Resolving power is higher than the light microscope Can magnify up to 100,000X

Microscopes provide windows to the world of the cell Scanning Electron Microscope (SEM) Used to study the details of the surface of the cell Produces a 3D image Used to study cell and organelle surfaces

Microscopes provide windows to the world of the cell Transmission Electron Microscope (TEM) An electron beam is aimed through a thin section Used to explore the internal structures of the cell

The Two Major Categories of Cells

The Two Major Categories of Cells There are 2 major categories of cells - Prokaryotic cells - Eukaryotic cells Both cells - Are surrounded by a plasma membrane - Consist of cytoplasm and organelles and contain DNA Prokaryotic and eukaryotic cells differ in several ways

The Size of Cells Most cells are 10-100 micrometers in size Cell size and shape are related to their function Ex: red blood cells, nerve cells, eggs

The Size of Cells The lower limit of cell size is determined by the fact that a cell must be large enough to house the parts (DNA, organelles) it needs to survive and reproduce. The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of wastes.

Prokaryotic Cells Smaller than eukaryotic cells (2-8 um) Enclosed by a plasma membrane that is usually surrounded by a rigid cell wall The cell wall may be covered by a sticky capsule DNA is found inside the cell but it is not housed in a nucleus Ribosomes (70S) are present Internal structures surrounded by membranes are not present

Structures of the Prokaryotic Cell Nucleoid region – area where DNA is coiled in the cytoplasm. DNA is in direct contact with the rest of the cell Plasmid – smaller circular DNA molecules Ribosomes – where proteins are made Plasma membrane – encloses the cytoplasm of the prokaryotic cell

Structures of the Prokaryotic Cell Cell wall – rigid, composed of lipids, carbohydrates and protein. Protects the cell and maintains its shape Cell Wall components determine if bacteria is classified as gram positive (+) or gram negative (-)..In general more toxic and resistant to antibiotics http://www.bio.upenn.edu/computing/media/Instructional.Stain.Gram.php

Structures of the Prokaryotic Cell Capsule – sticky outer coat that surrounds some prokaryotes. Protects the cell surface. Helps bacteria attach to surfaces Pili – short surface projections found in some prokaryotes. Helps attach bacteria to surfaces Flagella – long whiplike extensions found in some prokaryotes. Propel cell through liquid environments

The Role of Bacteria in the Nitrogen Cycle

Eukaryotic Cells Larger than prokaryotic cells (10-100 um) More complex in structure DNA housed in the nucleus Ribosomes (80S) Membrane bound organelles

Comparing Animal and Plant Cells Animal cells contain centrioles, lysosomes, flagella Plant cells contain a central vacuole, cell wall, chloroplasts

Comparing Eukaryotic and Prokaryotic Cells- Prokaryotes Eukaryotes Differences Commonalities

Comparing Eukaryotic and Prokaryotic Cells- Differences in parallel statements Date back at least 3.5 BYA Ex include: Bacteria & Archaeabacteria Simpler Structure (all single celled organisms) Naked DNA (not wrapped around histone proteins) Circular Chromosomes DNA in cytoplasm (nucleoid region) 70S ribosomes No internal membrane compartments (no membrane bound organelles)-ex: no mitochondria, no Rough ER Eukaryotic Cells Descended from ancient prokaryotes 2.1 BYA Ex organisms: plants, animals, fungi, protists More Complex Structure (mostly multicellular organisms but some single celled organism) DNA associated with histone proteins Chromosomes linear DNA separated from cytoplasm (in nucleus) 80S ribosomes Internal membrane compartments (membrane bound organelles) –ex: yup mitochondria and Rough ER

Comparing Eukaryotic and Prokaryotic Cells- Commonalities: Prokaryotes & Eukaryotes Smallest units of Life (therefore has the characteristics of life Chapter 1!) Requires energy (to run metabolic reactions of life) Grows and develops Independently reproduce DNA stores genetic information Can evolve over generations Order: internal organization Responds to environmental stimuli Ribosomes build proteins for the cells Contains plasma membrane to regulate what enters and leaves the cell Filled with cytosol (fluid)