chapter 5: homeostasis and transport
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Chapter 5: Homeostasis and Transport. Lesson 1: Cell Structures Involved in Cell Transport. Lesson Objectives. Describe the structure and function of the plasma membrane in relation to cell transport. Identify the types of membrane proteins involved in cell transport. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 5: Homeostasis and TransportLesson 1: Cell Structures Involved in Cell Transport
Describe the structure and function of the plasma membrane in relation to cell transport.
Identify the types of membrane proteins involved in cell transport.
Identify the roles of the cytoplasm and cytoskeleton in cell transport.
Identify the role of the endomembrane system in eukaryotic organisms in cell transport.
Discuss special transport structure of plant cells.
Outline the role of cell transport in homeostasis.
Lesson Objectives
Barrier between cytoplasm inside and environment outside the cell Protects, supports the cell Controls what goes in and what goes out
◦ Selective permeability allows only certain substances to pass through Water most important substance; most essential
molecules for life are soluble Inorganic ions: sodium (Na+), potassium (K+), calcium
(Ca2+), and chlorine (Cl-) Gases: oxygen helps release energy that powers cellular
reactions Hormones: transmit messages
FROM OUTSIDE TO INSIDEThe Plasma Membrane
Consists of two layers of phospholipids◦ hydrophobic, or water-hating, interior (tails)◦ hydrophilic, or water-loving, exterior (heads)
Proteins embedded within have a variety of functions
Hydrophobic molecules are nonpolar, easily cross; if small enough
Hydrophilic molecules are polar, need help to cross; usually through embedded proteins
The Phospholipid Bilayer
NOT INVOLVED IN TRANSPORT◦ Peripheral proteins loosely bound to membrane
surface or to part of a integral protein INVOLVED IN TRANSPORT
◦ Integral proteins transmembrane protein; extend into and usually span interior of membrane
Proteins Embedded in the Plasma Membrane
Transport proteins ions, polar molecules Types of transport proteins:
◦ Channel proteins hydrophilic channel Water passes through aquaporin channel proteins Ions pass through ion channels Other ions pass through gated channels; open and
close in response to a stimulus◦ Carrier proteins hold molecules and change shape
as they pass them through Sodium-potassium pump
Integral proteins types…
Contains enzymes, salts, organelles, and a variety of organic molecules◦ Enzymes help dissolve cellular waste for export◦ Salts are conductors of electricity
Movement generated through churning of cytoplasmic streaming speeds up distribution of nutrients, proteins, and organelles within cell
http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_-_cytoplasmic_streaming.html
Cytoplasm’s Role in Intracellular Transport
Consists of three different threadlike structures: microfilaments, intermediate filaments, microtubules◦ Microfilaments and microtubules both components of
intracellular transport Microfilaments composed of protein called actin; act like
tracks within cells for myosin molecules Microtubules tracks for vesicle intracellular transport
Role of Cytoskeleton in the Cytoplasm
Separates and compartmentalizes interrelated functions of variety of organelles◦ Equates to a division of labor
Organelles involved:◦ Nuclear envelope, smooth endoplasmic reticulum,
rough ER, Golgi, lysosomes, endosomes, vesicles, vacuoles, and plasma membrane
Some through direct connection; others through vesicular transport◦ Vesicles bud off of sending organelles; fuse with
receiving organelles
The Endomembrane System in Eukaryotic Cells
Helps make and transport proteins and lipids Connected to the pores of the nuclear envelope Two types of endoplasmic reticulum:
◦ Rough endoplasmic reticulum (RER)◦ Smooth endoplasmic reticulum (SER).
Rough Endoplasmic Reticulum (RER)◦ Studded with ribosomes; involved in protein synthesis, the production and
transport of new membrane, and the modification and transport of newly formed proteins within the cell
◦ Proteins synthesized on the RER are transported to other locations through vesicles formed in the SER.
Smooth Endoplasmic Reticulum (SER)◦ Not studded with ribosomes◦ Contains enzymes for lipid biosynthesis (change to phospholipids and steroids)◦ Forms transition vesicles that travel along microtubular tracks in the cytoplasm
Transport molecules made in the RER to the Golgi apparatus
The Endoplasmic Reticulum (ER)
Processes proteins and prepares them for use both inside and outside the cell
Receives proteins from the ER that have been transported in vesicles, packages and labels them
Sends them on to their next destinations in another set of vesicles
Also involved in the transport of lipids around the cell
http://www.johnkyrk.com/golgiAlone.html
The Golgi Apparatus
Sac-like organelles Store and transport large molecules Pinch off ER and Golgi
◦ Transport to plasma membrane; fuse with it◦ Going out = exocytosis
Pinch inward at plasma membrane◦ Transport to destinations inside the cell◦ Going in = endocytosis
Vesicles
Lysosomes bud off of the Golgi apparatus; infused with hydrolytic enzymes◦ Digestive vesicles of the cell; contain enzymes called hydrolases
Digest proteins, nucleic acids, lipids, and complex sugars. ◦ Vesicles enter the cell through endocytosis; sent to lysosomes contents
processed Break down and disarm many potentially pathogenic and foreign materials; expel
them outside the cell through exocytosis Endosomes formed during endocytosis allow materials from outside
the cell to enter the cell◦ Formed when the cell’s plasma membrane folds inward to surround
macromolecules, encircles them, brings them into the cell by pinching off the membrane at their point of entry
Vesicles larger than 100 nanometers in size are referred to as vacuoles.
Lysosomes and Endosomes
Structure not found in animal cells, cell wall◦ Rigid layer that surrounds the plasma membrane◦ Supports and protects the cell
Tiny holes, or pores, in the cell wall called plasmodesmata (singular, plasmodesma) ◦ Form open channels through which strands of cytosol
connect between adjacent cells◦ Allow water, nutrients, and other substances to move
into and out of the cells
Special Transport Structure in Plant Cells
Cell to function normally=> stable state must be maintained inside the cell◦ Example: concentration of salts, nutrients, and other substances
must be kept within a certain range Process of maintaining stable conditions inside a cell (or an
entire organism) is homeostasis◦ Homeostasis requires constant adjustments, because conditions are
always changing both inside and outside the cell◦ Structures and processes described in this lesson and the next
lesson play important roles in homeostasis and are consider homeostatic mechanisms
◦ By moving substances into and out of cells, they keep conditions within normal ranges and maintain homeostatic regulation inside the cells and the organism as a whole
If homeostatic mechanisms fail to maintain homeostatic regulation disease or death of a cell or organism may follow.
Homeostasis and Cell Function
A major role of the plasma membrane is transporting substances into and out of the cell.
The plasma membrane is selectively permeable, allowing only certain substances to pass through.
Proteins embedded within the plasma membrane help to move hydrophilic, polar molecules into the cell.
The cytoplasm is the internal medium for cell transport. Vesicle aids in the import and export of macromolecules. Plant cells have a special transport structures that are not
found in animal cells, called plasmodesmata. Cell transport helps cells maintain homeostasis by keeping
conditions within normal ranges inside all of an organism’s cells.
If homeostatic mechanisms fail, homeostatic regulation may fluctuate and disease or death of a cell or organism can follow.
Lesson Summary