BIOL 22000 Lecture Notes - Lecture 1: Methionine, Leptospira Interrogans, Vitamin K
8 Jun 2018
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Chapter 1 The Cell
1.1 Cell Theory
1.2 Eukaryotic Cells
• Eukaryotic Cells contain a true nucleus
o Membrane bound organelle are found in the cytoplasm
• Prokaryotic Cells do not contain a nucleus
Membrane-Bound Organelles
• Membrane encloses semifluid cytosol where organelles are suspended
• Cytosol allows for the diffusion of molecules throughout the cell
• Within the nucleus, genetic info is coded in DNA, which is organized into chromosomes
• Eukaryotic cells reproduce by mitosis
The Nucleus
• Nucleus is surrounded by nuclear membrane or envelope
o To separate nuclear environment from cytoplasm
• Nuclear Pores in the nuclear membrane allow for selective two-way exchange
• A subsection of nucleus is nucleolus, which synthesizes rRNA
Mitochondria
• The outer membrane serves as a barrier between cytosol and inner environment
• The inner membrane has numerous infoldings called cristae
o It contains the enzyme necessary for electron transport chain
o Highly convoluted to increase surface area available for enzymes
• The space between inner and outer membrane is called the intermembrane space
• The space inside the inner membrane is
called the mitochondrial matrix
o The pumping of protons from matrix
to the intermembrane space
establishes proton-motive force
o The proton flow through ATP
synthesis to generate ATP
• Mitochondria contain and replicate their own
genes via binary fission
• Mitochondria can kill the cell by releasing
enzymes from the ETC
o Know as apoptosis, or programmed
cell death
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2
Lysosomes
• Lysosomes are membrane bound structures containing hydrolytic enzymes that can break
down substrates
o Include substances digested by endocytosis and cellular waste products
• Lysosomal membrane hides these enzymes to prevent damage to the cells
• Release of these enzyme can autolysis
o Release of enzyme cause degradation of cellular components
Endoplasmic Reticulum
• Endoplasmic Reticulum (ER) is a series of interconnected membranes that are
contiguous with the nuclear envelope
• The single membrane of ER is folded into numerous invagination, creating a complex
structure with a central lumen
o Lumen is the compartment inside the ER
• There are two varieties of ER:
o Rough ER is stubbed with ribosomes, it is for the translation of protein destined
for secretion into its lumen
o Smooth ER lacks ribosomes, it is for lipid synthesis and detoxification of certain
drugs and poisons
▪ Also transport proteins from rough ER to Golgi apparatus
Golgi Apparatus
• Golgi Apparatus consists of stacked membrane-bound sacs
• Materials from the ER are transferred to GA in vesicles
• Once inside the GA, the cellular product may be modified by the addition of various
groups
• Can also modify it by adding signal sequences, which direct the delivery of the product to
a specific cellular location
• After modification, the products are repackaged in vesicles, and transferred to the correct
cellular location
• If the product is destined for secretion, the vesicle merges with the cell membrane and the
contents are released via exocytosis
Key Concept
• Not all cells have the same distribution of organelles
• Cells that require lots of energy for locomotion like sperm cells have high concentration
of mitochondria
• Cells involved in secretion have high concentration of RER and Golgi apparatus
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3
Peroxisomes
• Peroxisomes contain hydrogen peroxide
• Primary function is to break down very long chain fatty acids through beta-oxidation
• Participate in phospholipid synthesis
• Contain some of the enzymes involved in the pentose phosphate pathway
The Cytoskeleton
• Cytoskeleton provides structure to the cell and helps it maintain its shape
o Also provide a “road” for transport of materials around the cell
Microfilament
• Microfilaments are made up of solid polymerized rods of actin
• Actin filaments are organized into bundles and network
o Resistance to compression and fracture, and provide protection for the cell
• Actin filaments can use ATP to generate movement by interacting with myosin
o Such as muscle contraction
• Microfilaments also play a role in cytokinesis, the division of materials between daughter
cells
• Cleavage Furrow is formed from microfilaments, which organize as a ring between two
daughter cells
o The actin filament within this ring contract and become smaller, and eventually
pinch off the connection between the two cells
Microtubules
• Microtubules are hollow polymers of tubulin proteins
• Microtubules spreads throughout the cell providing pathway for motor proteins like
kinesin and dynein carry vesicles
• Cilia and flagella are motile structure composed of microtubules
o Cilia are projections from a cell that primarily involved in movement of materials
along the surface of the cell
▪ Ex: cilia line the respiratory tract and move the mucus
o Flagella are structures involved in movement of cell itself
▪ Ex: movement of sperm through the reproductive tract
• Cilla and flagella share the same structure, composed of nine pairs of microtubules
forming an outer ring, and two microtubules in the center
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Document Summary
Chapter 1 the cell: eukaryotic cells contain a true nucleus, membrane bound organelle are found in the cytoplasm, prokaryotic cells do not contain a nucleus. The nucleus: nucleus is surrounded by nuclear membrane or envelope, to separate nuclear environment from cytoplasm, nuclear pores in the nuclear membrane allow for selective two-way exchange, a subsection of nucleus is nucleolus, which synthesizes rrna. If the product is destined for secretion, the vesicle merges with the cell membrane and the contents are released via exocytosis. Peroxisomes: peroxisomes contain hydrogen peroxide, primary function is to break down very long chain fatty acids through beta-oxidation, participate in phospholipid synthesis, contain some of the enzymes involved in the pentose phosphate pathway. The cytoskeleton: cytoskeleton provides structure to the cell and helps it maintain its shape, also provide a road for transport of materials around the cell. Intermediate filaments: intermediate filaments are diverse group of filamentous proteins, including keratin and desmine.
