The Cell Chapter 4

Cells Marks the boundary between the “living and the dead” Structural and functional unit of an organism Smallest structure capable of performing all of the functions necessary for life

What is a cell? Why do we care? We have TRILLIONS of them!! (@65) Every organism is composed of one or more cells Basic unit of structure and function in organisms All come from pre-existing cells Cell Theory

Why are Cells so Small???? Large cells have far less surface for each unit of volume than do small cells

All cells……. Have an outer plasma membrane Contain DNA Enclosed within the cell somewhere Contain cytoplasm

Plasma Membrane All cells surrounded by a plasma membrane Phospholipid bilayer forms spontaneously whenever a collection of phospholipids is placed in water

Cytoplasm material inside a cell is the cytoplasm Everything between the plasma membrane and the region of DNA Gives cells their shape Assist in movement of cell and organelles

Microscopes Compound light microscope Multiple lenses increase magnifying power

Two basic kinds of cells Prokaryotic Nothing separates the DNA from internal cell parts Eukaryotic Contain organelle sacs Nucleus – contains the DNA

Eukaryotic Cells

Examples of Eukaryotic Cells: Animal Plant Fungi Protozoa

Organelles Organelles act as their own separate “organs” They physically isolate chemical reactions inside cells Animals and plants will differ in their organelles

Nucleus Encloses the DNA of a eukaryotic cell Contains chromosomes Functions: Prevents DNA from getting entangled with structures in the cytoplasm Outer membranes act as a boundary

Components of the nucleus Nuclear pores Nuclear envelope Nucleolus Nucleoplasm DNA Chromosomes Chromatin

Nuclear envelope Double-membrane system composed of lipid bilayer (with pores) Bilayers surround the fluid part of nucleus (nucleoplasm) Continuous with the endoplasmic reticulum

Nucleolus Dense mass located within the nucleus Produces ribosomes

Ribosomes Site of protein synthesis Occurs in the cytoplasm Attached to the endoplasmic reticulum Differ between prokaryotes and eukaryotes Why is this important from a health aspect?

Endomembrane System Helps modify proteins into final form Lipids are assembled Compartmentalizes the cell Main components: 1. Nuclear envelope 2. Endoplasmic reticulum (ER) 3. Golgi body 4. Various vesicles (transport)

1. Nuclear envelope Merges with the membrane of the ER Consists of membranous channels and saccules

2. Endoplasmic Reticulum Channel that snakes through the cytoplasm Lipids assembled and polypeptide chains modified into final proteins Can be rough or smooth Dependant on the attachments of ribosomes Rough ER Processing and modification of proteins Smooth ER Synthesizes phospholipids

3. Golgi Body (Apparatus) Series of flattened sacs Collects, sorts, packages, and distributes materials such as proteins and lipids Contain enzymes that put the finishing touches on proteins and lipids

4. Vesicles Enzymes from golgi apparatus sort and package the molecules into vesicles Tiny sac that moves through cytoplasm Function in transport, storage, or digestion of substances Two main types: Lysosomes Peroxisomes

Lysosome A lysosome is a membrane-enclosed sac contains digestive enzymes to break down: Macromolecules damaged organelles

Put it all together……

Organelles That Contain DNA Eukaryotic cells contain cell-like organelles that, besides the nucleus, also contain DNA these organelles appear to have been derived from ancient bacteria that were then assimilated by the eukaryotic cell they include the following organelles: Mitochondria Chloroplasts

Energy-Related Organelles organelles specialize in converting energy to a form that can be used by the cell Requires solar energy Dissipates as heat Chloroplasts Use solar energy to synthesize carbohydrates Carbohydrates then broken down in the….. Mitochondria Produce ATP molecules

Energy-Related Organelles Photosynthesis Cellular Respiration The chemical energy of carbohydrates is converted at ATP

DNA in mitochondria?? mtDNA Inherited solely from mother First set of DNA to be sequenced Endosymbiotic theory Helps in evolutionary inheritance

Organelles That Contain DNA The theory of “endosymbiosis” states that some organelles evolved from a symbiosis one cell of a prokaryotic species was engulfed by and lived inside of a cell of another species of prokaryote

Organelles That Contain DNA Other evidence supporting endosymbiotic theory: Mitochondria are about the same size as modern bacteria The cristae in mitochondria resemble folded membranes in modern bacteria Mitochondrial ribosomes are similar to modern, bacterial ribosomes in size and structure Mitochondria divide by fission, just like modern bacteria

Cytoskeleton – Cytoplasm System of interconnected fibers, threads, and lattices in the cytosol Extend from nucleus to the plasma membrane Gives cells their shape Assists in movement of cell and organelles Assemble and disassemble as needed

The three protein fibers of the cytoskeleton

The Cytoskeleton: Interior Framework of the Cell Centrioles complex structures that assemble microtubules in animal cells and the cells of most protists anchor locomotory structures such as flagella or cilia

The Cytoskeleton: Interior Framework of the Cell vacuoles membrane-bound storage centers central vacuole filled with water and dissolved substances

Outside the Plasma Membrane Cell walls found in plants, fungi, and many protists comprised of different components than prokaryotic cell walls function in providing protection, maintaining cell shape, and preventing excessive water loss/uptake

Outside the Plasma Membrane Extracellular matrix (ECM) takes the place of the cell wall in animal cells and is comprised by a mixture of proteins secreted by the cell collagen and elastin proteins Form a protective layer over the cell surface fibronectin protein Connects the ECM to the plasma membrane integrins Connected to fibronectin Proteins that extend into the cytoplasm of the cell

Plant Cells Cell wall Central vacuole Chloroplasts

Fungal Cells Mold or yeast Spores Cell wall Unicellular or multicellular

Protozoa Cells No cell wall Unicellular Motility

Prokaryotes Archae Bacteria

“Micro”organisms

Characteristics of Cells Prokaryotic cells ~1.0 µm in diameter All are microorganisms Unicellular Bacteria and Archaea no nucleus no membrane-bound organelles

Prokaryotes – General cell structure Nucleoid Pili Fimbriae Flagella Cell wall Glycocalyx Ribosomes