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!! 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

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

Plasma Membrane and Cytoplasm  All cells surrounded by a plasma membrane Phospholipid bilayer  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

Cell Walls  Plant cells Permeable Protective In addition to a plasma membrane

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……

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

Cytoskeleton: Cilia and Flagella - Movement  Hairlike projections  Help in the movement of cells  Some examples….  Why would we need them?

Vacuoles  Membranous sacs contractile vacuoles of protists central vacuoles of plants

Prokaryotes Archae Bacteria

“Micro”organisms

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

Prokaryotic Cells  Cell Wall  Capsule  Flagellum  Plasma membrane  Nucleoid  Plasmids  Ribosomes

Microbiology  The study of of organisms (microorganisms or microbes) too small to be seen without magnification  This includes: 1. Bacteria 2. Viruses 3. Fungi 4. Protozoa 5. Helminths (worms) 6. Algae

The Microbes 1. Bacteria –Single-celled organisms –Various shapes Spherical Rod Spiral shapes –Cellular –Lack membrane- enclosed cellular structures –Widely distributed in nature Klebsiella pneumoniae, bacteria that causes pneumonia in humans

The Microbes 2. Viruses –Acellular –Composed of nucleic acid and a few proteins –Replicate themselves to display other properties of living organisms when they invade living cells

The Microbes 3. Fungi –Yeasts and molds Single-celled, microscopic –Mushrooms Multicellular, macroscopic –Cell nucleus and other cellular structures –Absorb nutrients from their environment –Widely distributed in water and soil –Act as decomposers of dead organisms

The Microbes 4. Protozoa –Single-celled, microscopic organisms –Have at least one nucleus and many cellular structures –Obtain food by engulfing or ingesting smaller organisms –Most can move –Found in many different environments Amoeba

The Microbes 5. Helminths –Large, multicellular –Parasitize host tissues –Organs for reproduction, digestion, movement, protection –Mouthparts –Ingestion of larvae or eggs in food Tapeworm Head

The Microbes 6. Algae –Single-celled microscopic organisms –Have a nucleus and many membrane- enclosed cellular structures –Photosynthesize their own food –Widely distributed in fresh and salt water –Important source of food for other organisms Micrasterias, a green algae living in fresh water