Post on 06-May-2015
Inside the Cell:Part 1
Dr. Corl
BIOL 105
September 9, 2013
Inside the Cell:
Introduction
• The Cell Theory:– All organisms are composed of cells– All cells are derived from preexisting cells
• All cells have:– Nucleic acids (to store genetic information)– Proteins (e.g. enzymes which speed up reactions)– Carbohydrates (provide chemical energy)– Plasma membrane (aka cell membrane)
Prokaryotes vs. Eukaryotes
• Two broad groupings of life, based on cell structure:
– Prokaryotes (e.g. bacteria)• Lack a membrane-bound nucleus.
– Eukaryotes (e.g. plants and animals)• Have a membrane-bound nucleus (nuclear
envelope)
Prokaryotic Cells
• Plasma membrane:– Encased by a cell wall:
• Helps protect the cell inside.
– Surrounds the cytoplasm:• Interior contents of the cell.
• Flagellum:– Spins to help cell move.
• Fimbriae:– Numerous needlelike
projections.– Help cell to adhere to other
cells or surfaces.
Prokaryotic DNA
• Most genes are contained within a single, circular, DNA-containing chromosome.
• NO nuclear membrane.• Prokaryotes may also have a few other genes contained within small,
circular plasmids.
Prokaryotic Ribosomes
• Ribosomes:– Made up of RNA and protein molecules.– Important for manufacturing proteins.
Differences Between Prokaryotes and Eukaryotes
• Eukaryotic cells:– House DNA in a membrane-bound nucleus.– Are usually much larger than prokaryotic cells.– Contain extensive internal membranes.– Have a diverse and dynamic cytoskeleton.
Membranearound nucleus
No nucleus
Compartmentalization into Organelles
• Due to large size of eukaryotic cells:
– Volume is compartmentalized into many smaller membrane-bound organelles.
– Different organelles perform different functions. For example:
• Chloroplasts: conduct photosynthesis• Lysosomes: contain digestive enzymes
Typical Animal Cell
Typical Plant Cell
Nucleus
• Contains a cell’s genetic information:– Stored in the DNA sequences of chromosomes.
Nucleus
• Bounded by double membrane: nuclear envelope.• Contains a nucleolus: where ribosomal RNA is synthesized.
• Composed of proteins and RNA.• Found scattered in the cytosol (the fluid portion of the cytoplasm).• Involved in protein synthesis.
Ribosomes
Rough Endoplasmic
Reticulum (ER)
• Network of membrane-bound sacs and tubules, lined with ribosomes.
• Many proteins are synthesized here.
Golgi Apparatus
• Consists of flattened membranous sacs (cisternae).• Receives products from rough ER and processes them.• Sends finished products to cell surface (and other locations).
Smooth Endoplasmic
Reticulum
• Lacks ribosomes.• Site of lipid biosynthesis. May store Ca2+ ions.
Endomembrane System
• Primary center for protein and lipid synthesis in the cell.
• Consists of:– Rough endoplasmic reticulum.– Smooth endoplasmic reticulum.– Golgi apparatus.– Lysosomes.
Lysosomes
• Have a relatively acidic lumen (interior: pH = 5).• Contain many digestive enzymes (acid hydrolases):
– Involved in digesting various molecules into monomers.
Delivering Materialto Lysosomes
Receptor-mediated
Endocytosis
EndocytosisEndocytosis:
– Any pinching off of the plasma membrane that results in uptake of material from outside the cell.
– 3 types of endocytosis:
• 1.) Phagocytosis• 2.) Pinocytosis
– Cell “drinks” in small droplets of extracellular fluid when cell membrane folds inwards and pinches off.
• 3.) Receptor-mediated
endocytosis
Vacuoles
• Plant and fungi have large vacuoles.
• Store water, ions, and nutrients.
Peroxisomes
• Perform oxidative reactions:– Reactions that remove
electrons from molecules.
• Peroxisomal enzymes:– Help metabolize fatty
acids into smaller molecules.
– Help detoxify many toxins, including alcohol.
– Include catalase, which breaks down H2O2.
Mitochondria
• Have two membranes, their own DNA and their own ribosomes.
• Involved in producing ATP, the cell’s energy currency.
Chloroplasts
• Found in plant and algal cells.• Have two membranes and their own DNA.• Involved in photosynthesis:
– Converting light energy into chemical energy.
Chloroplasts
• Interior dominated by thylakoid membranes:– Stacks of thylakoids: grana.– Interior of thylakoids: lumen.
• Stroma: fluid surrounding thylakoids.
Cytoskeleton and Cell Wall
• Cytoskeleton:– Fibers which gives the cell shape and structural stability.
• Cell Wall:– Protects the cell. – Found in fungi, algae, and plants.
Cell Structure and Function
• A cell’s structure correlates with its function.– Testis cell:
• Lipid exporting cell - has lots of smooth ER.
– Plant leaf cell:• Sugar manufacturing cell - has lots of chloroplasts.
Summary Table
Summary Table
Typical Animal Cell
Typical Plant Cell
Review Questions
• How do prokaryotic cells differ from eukaryotic cells?
• Describe the components of the endomembrane system.
• What cellular components are found in the nucleus?
• Contrast the function of the mitochondrion versus the chloroplast.