Cellular Level of Organization

Introduction Two types of cells Sex cells (haploid) Somatic cells (diploid)

Cell Membranes 4 main functions

1. Physcial Isolation Separates inside of cell from outside

2. Selectively Permeable Membrane Regulates exchange with the environment

3. Sensitivity Contains receptors

4. Structural Support The cell membrane can connect to other cells or extracellular proteins

Cell Membrane Structure Hydrophilic head Hydrophobic tails

Cell Membrane Structure Ions and water soluble compounds cannot cross the membrane

Cell Membrane Structure This separates the extracellular fluid from the cytosol which is important for homeostasis

What are in membranes? 1. Cholesterol

What are in membranes? Integral proteins

What are in membranes? Enzymes Catalyzes reactions

What are in membranes? Receptor proteins Protein – lock Ligand - key

What are in membranes? 5. Carrier Protein Transports things across the membrane

What are in membranes? Channels Allows continuous movements of ions and water soluble materials

What are outside cell membranes? Peripheral proteins Glycoproteins Glycolipids

Glycoprotiens and glycolipids Can tell if certain cells are normal or abnormal by their glycoproteins and glycolipids

Organelles Components of cells

1. Cytoskeleton Strength and flexibility Composed of 3 main structures Microfilaments ( actin ) Intermediate filaments ( collagen ) Microtubules ( tubulin )

2. Microvilli Increase surface area Finger-shaped projections of cell membranes

3. Centrioles Their involved in cell division Not found in RBC, skel. muscle cells, cardiac muscle cells, and neuron cells

4. Cilia Long slim extensions of the cell membrane Found in trachea

5. Ribosomes Synthesize proteins Composed of two subunits ( one small and one large) Free ribosomes Fixed ribosomes

6. Endoplasmic Reticulum Network within the cytoplasm attached to the nucleus

6. Endoplasmic Reticulum Two types SER RER

6. Endoplasmic Reticulum SER Detoxifies drugs or toxins Synthesizes lipids and carbs

6. Endoplasmic Reticulum RER Transports materials and synthesizes proteins

7. Golgi Apparatus Proteins come from the ER into the golgi for modification

8. Lysosome Breaks down and recycles organelles Breaks down bacteria and foreign material

9. Peroxisomes Breaks down fatty acids and organic compounds

10. Mitochondria Powerhouse of the cell Produces ATP – energy Contains two membranes (outer and inner)

11. Nucleus Chromosomes are stored here Composed of DNA

Membrane Transport Membranes are selectively permeable

Membrane Transport Passive processes do not require energy

Membrane Transport Active processes require energy

Membrane Transport 3 major ways in which materials are transported Diffusion Carrier-mediated transport Vesicular transport

Diffusion Hypotonic solution – less concentrated

1. Diffusion Hypertonic – more concentrated

1. Diffusion Isotonic solutions – equal concentration

1. Diffusion Solutes move from hypertonic solution to hypotonic solution

Ions and Water Remember ions and water must pass through channels

Lipid Soluble Substances Alcohol, fatty acids, and steroids are lipid soluble

O2 and CO2 O2 and CO2 pass easily

Glucose Glucose to big to cross cell membrane

2. Carrier-Mediated Transport Can be passive or active

2. Carrier-Mediated Transport Proteins carry substances across

2. Carrier-Mediated Transport Sometimes carries two things at once (cotransport)

2. Carrier-Mediated Transport Sometimes carries to things in opposite directions (countertrasnport)

2. Carrier-Mediated Transport Fascilitated Diffusion Active Transport Secondary Active Transport

Facilitated Diffusion Passive

Facilitated Diffusion Carries substances such as glucose and amino acids

Facilitated Diffusion Goes down conc. Gradient but limited to number of carrier proteins

Active Transport Requires energy

Active Transport Not dependent on concentration gradient

Active Transport Ion pumps use active transport

Active Transport Exchange pumps move two kinds of ions in different directions Example: Na+/K+ Pump

Na+/K+ Pump Na higher in concentration outside cell K higher in cell

Na+/K+ Pump Sometimes Na diffuses into cell and K leaves through leaky channels

Na+/K+ Pump Na+/K+ pump puts things back into order

Na+/K+ Pump Ejects on average 3Na+ and bringing in 2K+ ions

Secondary Active Transport Does not require energy

Secondary Active Transport Goes down a conc. gradient

Secondary Active Transport It uses the concentration gradient of a molecule as the driving force to move another molecule against the concentration gradient

3. Vesicular Transport Requires energy

3. Vesicular Transport Endocytosis Exocytosis

Endocytosis Imports substances into the cell

Endocytosis Receptor mediated endocytosis Pinocytosis Phagocytosis

Receptor Mediated Endocytosis Extremely selective

Receptor Mediated Endocytosis Plasma membrane proteins bind only with certain substances

Pinocytosis Cell drinking

Pinocytosis Dissolved proteins gather on the external surface of the plasma membrane, causing the membrane to invaginate and to incorporate a droplet of fluid

Phagocytosis Cell eating

Phagocytosis Parts of the plasma membrane flow around a relatively large or solid material and engulf it.

Exocytosis Expels material out of the cell