A Tour of the Cell

Overview: The Cell Cell: the basic unit of all living organisms Cell: the basic unit of all living organisms 2 types: 2 types: Prokaryotic Prokaryotic Eukaryotic Eukaryotic

All cells have several basic features All cells have several basic features A plasma membrane A plasma membrane Contain cytosol: jellylike substance where organelles & other components are found Contain cytosol: jellylike substance where organelles & other components are found Contain chromosomes Contain chromosomes Have ribosomes Have ribosomes

Major difference: location of DNA Major difference: location of DNA Eukaryotic: membrane enclosed (nucleus) Eukaryotic: membrane enclosed (nucleus) Prokaryotic: not membrane enclosed Prokaryotic: not membrane enclosed Region called nucleoid Region called nucleoid

Other differences: Other differences: Eukaryotes have organelles Eukaryotes have organelles Eukaryotes are generally larger Eukaryotes are generally larger

The Eukaryotic Cell

The Nucleus

Contains genes of the cell Contains genes of the cell Enclosed by nuclear envelope Enclosed by nuclear envelope Double membrane Double membrane Perforated by pores Perforated by pores DNA is organized into chromosomes inside nucleus DNA is organized into chromosomes inside nucleus Nucleolus: makes ribosomes Nucleolus: makes ribosomes

Ribosomes

Made of rRNA & proteins Made of rRNA & proteins Carry out protein synthesis Carry out protein synthesis Cells with high rate of protein synthesis have high number’s of ribosomes Cells with high rate of protein synthesis have high number’s of ribosomes Human pancreas cells have a few million ribosomes Human pancreas cells have a few million ribosomes Can be free or attached Can be free or attached

The Endoplasmic Reticulum

Network of membranes Network of membranes 2 types: 2 types: Smooth ER: lacks ribosomes Smooth ER: lacks ribosomes Rough ER: contains ribosomes on outer surface Rough ER: contains ribosomes on outer surface

Functions of Smooth ER Diverse metabolic processes Diverse metabolic processes Synthesis of lipids Synthesis of lipids Metabolism of carbohydrates Metabolism of carbohydrates Detoxification of drugs & poisons Detoxification of drugs & poisons Cells that synthesize steroids and/or hormones are rich in smooth ER Cells that synthesize steroids and/or hormones are rich in smooth ER

Liver cells help detoxify drugs & poisons Liver cells help detoxify drugs & poisons Adds hydroxyl group to drug/poison Adds hydroxyl group to drug/poison Makes molecules more soluble Makes molecules more soluble Alcohol creates this type of response Alcohol creates this type of response Induces smooth ER to work quickly Induces smooth ER to work quickly Increases rate of detoxification Increases rate of detoxification As a result: increases tolerance As a result: increases tolerance

Functions of Rough ER Make proteins that are secreted by the cell Make proteins that are secreted by the cell Ex. Pancreatic cells secrete insulin Ex. Pancreatic cells secrete insulin Proteins get separated from proteins that remain in cell Proteins get separated from proteins that remain in cell Place in transport vesicles Place in transport vesicles Also makes phospholipids Also makes phospholipids

The Golgi Apparatus

After leaving ER, many transport vesicles head here After leaving ER, many transport vesicles head here The center of manufacturing, warehousing, sorting, & shipping The center of manufacturing, warehousing, sorting, & shipping Products of ER get modified, stored & sent to their destinations Products of ER get modified, stored & sent to their destinations Made of flattened membrane sacs called cisterae Made of flattened membrane sacs called cisterae

Has a distinct polarity Has a distinct polarity Cis face  receiving Cis face  receiving Trans face  shipping Trans face  shipping Cis face is usually near ER Cis face is usually near ER

Lysosomes

A membranous sac of hydrolytic enzymes A membranous sac of hydrolytic enzymes These enzymes work best in acidic pH These enzymes work best in acidic pH Hydrolytic enzymes & membrane are made by rough ER Hydrolytic enzymes & membrane are made by rough ER Some actually bud off trans face of Golgi apparatus Some actually bud off trans face of Golgi apparatus Carry out intracellular digestion Carry out intracellular digestion Ex. Assist in phagocytosis Ex. Assist in phagocytosis Ex. Recycle cell’s organic material Ex. Recycle cell’s organic material

Vacuoles

Membrane bound vesicles with many functions Membrane bound vesicles with many functions Store food Store food Contractile vacuole  pumps water out of cell Contractile vacuole  pumps water out of cell In plants & fungi  hydrolysis In plants & fungi  hydrolysis Central vacuole  stores a variety of compounds Central vacuole  stores a variety of compounds

Mitochondria

Found in nearly all eukaryotes Found in nearly all eukaryotes Some have single, large mitochondrion Some have single, large mitochondrion Most have hundreds or thousands Most have hundreds or thousands Number correlates with level of metabolic activity Number correlates with level of metabolic activity Enclosed by 2 membranes Enclosed by 2 membranes Outer  smooth Outer  smooth Inner  folded into cristae Inner  folded into cristae Has its own DNA Has its own DNA Serves as site of cellular respiration Serves as site of cellular respiration

Chloroplasts

Site of photosynthesis Site of photosynthesis Specialized plastid – group of closely related plant organelles Specialized plastid – group of closely related plant organelles Leucoplast: colorless; stores starch, lipids, & proteins Leucoplast: colorless; stores starch, lipids, & proteins Chromoplasts: have pigments that give fruits & flowers a yellow or orange hue Chromoplasts: have pigments that give fruits & flowers a yellow or orange hue Chloroplasts: have green pigments Chloroplasts: have green pigments Enclosed by 2 membranes Enclosed by 2 membranes Has its own DNA Has its own DNA

Peroxisomes

Specialized metabolic compartment bound by a single membrane Specialized metabolic compartment bound by a single membrane Transfers hydrogen to O 2 to form H 2 O 2 Transfers hydrogen to O 2 to form H 2 O 2 H 2 O 2 is toxic H 2 O 2 is toxic Also has enzymes that convert it to H 2 O Also has enzymes that convert it to H 2 O

Cell-to-Cell Connections Tight junctions: connect cells by tightly pressing them together Tight junctions: connect cells by tightly pressing them together held in place by special proteins held in place by special proteins Prevents extracellular fluid from leaking Prevents extracellular fluid from leaking

Desmosomes: fasten cells together into strong sheets Desmosomes: fasten cells together into strong sheets Ex. Muscle cells Ex. Muscle cells

Gap junctions: cytoplasmic channels from one cell to another Gap junctions: cytoplasmic channels from one cell to another Necessary for communication Necessary for communication