Biology 211Anatomy & Physiology I

Dr. Thompson

Cells

Recall:

SYSTEMS are composed of one or more organs, all serving a common function

ORGANELLES are composed of different types of molecules, all serving a common function

ORGANS are composed of one or more types of tissues, all serving a common function

TISSUES are composed of one or more types of cells and their products, all serving a common function

CELLS are composed of different types of organelles, all serving a common function

All cells in the human body:

- Obtain nutrients from surrounding extracellular matrix and secrete waste products into it.

- Use oxygen to metabolize fuel molecules

- Produce complex molecules from simpler precursers, either for their own use or for export AND break complex molecules back down into smaller ones

- Interact with other cells

- Reproduce themselves (this characteristic is lost in some cells and retained in others)

Cells:

- Highly organized; composed of organelles and cytoplasm

- Arise from prexisting cells Some exist as stem cells to replace more specialized ones

- In human, all eukaryotic: nuclei and other organelles surrounded by membranes

- Some = highly specialized & can perform only one function Others = relatively unspecialized with many functions

Cells:

Size: Highly variable Average = 15-30 micrometers diameter Range = 2 micrometers (sperm) 100 micrometers (oocyte)

Skeletal muscle cells may be 300 millimeters long Nerve cells may be more than a meter long

Cells:

Shape: Highly variable:

Independent Study:

Chapter 3 of your Saladintext discusses the organelles of most cells.

You should understand thebasic structure and functionof each of the following: Nucleus Ribosomes Endoplasmic reticulum Golgi complex Mitochondria Lysosomes Peroxisomes Vesicles Cytoskeleton

You will be responsible for these on exams

You should also understand the basic structure and function of cilia and flagella

Plasma Membrane:Also called "plasmalemma"May have special names in specific types of cells e.g. "sarcolemma" in muscle cells, "neurolemma" in nerve cells

- Keeps inside in and outside out while- Controlling movement of ions/molecules into and out of cell

- Interacts with other cells and with extracellular materials around cell

- Allows cell to recognize and respond to chemical signals

Plasma Membrane:

Basic structure = double layer of phospholipids with proteins and cholesterol embedded within it

Plasma Membrane:

Regulates movement of ions and molecules into and out of the cell, but highly selective

- Freely permeable to some molecules (e.g. oxygen) - Partially permeable to others (e.g. glucose) - Totally nonpermeable to some (e.g. glycogen)

Facilitates the uptake of ions/molecules needed by the cell (sugars, fatty acids, amino acids, oxygen, hormones, etc)Facilitates the release of waste products (carbon dioxide, lactic acid, etc) and secretory products (hormones, proteins, etc.)

Plasma Membrane:

This regulated movement of ions and molecules is due to:

a) Solubility of phospholipids for nonpolar molecules

b) Channels for passive movement of materials across the membrane. These channels can open and close.

c) Pumps to actively transport molecules across the membrane. These pumps turn on and off.

Plasma Membrane:

Has many types of specialized junctions for cell-to-cell attachment and/or communication. We will focus on three:

1. Tight junctions: Protein molecules in plasma membranes of two adjacent cells form bonds; hold cells strongly together and prevent materials from passing between them

Plasma Membrane:

Has many types of specialized junctions for cell-to-cell attachment and/or communication. We will focus on three:

2. Desmosomes: Protein molecules in plasma membranes of two adjacent cells form bonds in isolated spots; hold cells strongly together

Plasma Membrane:

Has many types of specialized junctions for cell-to-cell attachment and/or communication. We will focus on three:

3. Gap Junctions: Protein molecules in plasma membranes of two adjacent cells form channels between them; allow molecules to flow from cell to cell

Movement of Materials Across Plasma Membrane:

Thousands of different materials are actively crossing the plasma membranes of your cells every second of every day of your life, both into and out of the cell:e.g. Water Nutrients like amino acids, monosaccharides, fatty acids, nucleotides, vitamins Gases like oxygen, carbon dioxide Waste products like lactic acid, urea, bilirubin Ions (electrolytes) like sodium, potassium, magnesium, iron, calcium, chloride, phosphate, sulfate Hormones like insulin, estrogens, growth hormone Neurotransmitters Proteins the cell secretes Debris which phagocytic cells ingest (many others)

Movement of Materials Across Plasma Membrane:

Thousands of different materials are actively crossing the plasma membranes of your cells every second of every day of your life, both into and out of each cell:

This is not a random process! Each cell has a variety of different processes to regulate this exchange so that The right materials cross the membrane In the right concentrations At the right time In the right direction etc.

Movement of Materials Across Plasma Membrane:

More Independent Study:

Saladin text discusses various types of membrane transport.Be sure you understand, in moderate detail, how each of the following occur and what it accomplishes:

- Filtration - Simple diffusion, including osmosis - Facilitated diffusion - Active transport (including cotransport) - Pinocytosis - Receptor-mediated endocytosis - Phagocytosis

You will be responsible for these on exams

Let's move on to tissues