Unit 3: Cells - The living units

Cells - Basis of Life ●Highly organized ●Made of four primary elements – N, O, C, H ●About 60% water ●Bathed in a dilute saltwater solution (something like seawater) called interstitial fluid ●Vary in shape and function

Structure of a Generalized Cell

Anatomy of a Cell Cells are not all the same All cells share general structures Cells are organized into three main regions: Nucleus Cytoplasm Plasma membrane

The Nucleus Control center of the cell Contains genetic material (DNA) Three regions: Nuc lear membrane Nucleolus Chromatin

Nuclear Membrane Double-layered barrier of nucleus Contain nuclear pores that allow for exchange of material with the rest of the cell

Nucleolus Sites of ribosome production Ribosomes then migrate to the cytoplasm through nuclear pores Nucleus contains one or more nucleoli

Chromatin Genetic information Composed of DNA and protein Scattered throughout the nucleus Chromatin condenses to form chromosomes when the cell divides

Cytoplasm Material outside the nucleus and inside the plasma membrane Cytosol Fluid that suspends other structures Organelles Metabolic machinery of the cell Inclusions Non-functioning units; stored nutrients or cell products (i.e. fat droplets, pigments, glycogen, mucus)

Cytoplasmic Organelles

Ribosomes Sites of protein synthesis Made of protein and RNA Found in two locations Free in the cytoplasm Attached to rough endoplasmic reticulum ‘Factory Worker’

Endoplasmic Reticulum Fluid-filled tubules for carrying substances Two types of ER Rough ER: Site where proteins are folded and transported Studded with ribosomes (makes it look ‘rough’) ‘Factory that houses the factory workers’ Smooth ER: Functions in cholesterol synthesis and breakdown, fat metabolism, and detoxification of drugs No ribosomes

Golgi Apparatus Modifies and packages proteins Produces different types of packages Secretory vesicles Cell membrane components Lysosomes ‘Stack of flattened sacs’ ‘FedEx Shipping Plant’

Lysosomes and Peroxisomes Lysosomes Contain enzymes that digest materials within the cell Used in programmed cell death Peroxisomes Detoxify harmful substances Break down free radicals (highly reactive, dangerous chemicals) to H2O2 Membranous sacs of special enzymes (like catalase) Replicate by pinching in half

Mitochondria Carry out reactions where oxygen is used to break down food Provides ATP for cellular energy Change shape continuously ‘Mighty Mitochondria’ ‘Powerhouse of the cell’

Cytoskeleton Provides the cell with an internal framework Network of protein structures that extend throughout the cytoplasm ‘Scaffold of the cell’

Cytoskeleton Three different types: Microfilaments-cell motility and change in shape- actin and myosin Intermediate filaments-form desmosomes and internal guy wires-fibrous subunits Microtubules-determine shape of cell-tubulin subunits

Centrioles Site for formation of mitotic spindle during cell division Able to form cilia and flagella in special cells Rod-shaped bodies made of microtubules Arranged in a 9+3 formation

Cell Diversity 75 to 100 trillion cells in human body 200 different cell types 1. Connect body parts Fibroblast Erythrocyte (RBCs)

Cell Diversity 2. Cover and line body organs Epithelial Cell

Cell Diversity 3. Move organs and body parts Skeletal muscle Smooth muscle

Cell Diversity 4. Stores nutrients Fat cell

Cell Diversity 5. Fight disease Macrophage cell

Cell Diversity 6. Gathers information and controls body functions Nerve cell

Cell Diversity 7. Reproduction Ovum (egg) Sperm