A Tour of the Cell
CHAPTER 7
A TOUR OF THE CELL
OUTLINE
I. How We Study Cells
A. Microscopes provide windows to the world of the cell
II. A Panoramic View of the Cell
A. Prokaryotic and eukaryotic cells differ in size and complexity
B. Internal membranes compartmentalize the functions of a eukaryotic cell
III. The Nucleus and Ribosomes
A. The nucleus contains a eukaryotic cell’s genetic library
B. Ribosomes build a cell’s proteins
IV. The Endomembrane System
A. The endoplasmic reticulum manufactures membranes and performs many other
biosynthetic functions
B. The Golgi apparatus finishes, sorts, and ships cell products
C. Lysosomes are digestive compartments
D. Vacuoles have diverse functions in cell maintenance
V. Other Membranous Organelles
A. Peroxisomes consume oxygen in various metabolic functions
B. Mitochondria and chloroplasts are the main energy transformers of cells
VI. The Cytoskeleton
A. Provides structural support to cells for cell motility and regulation
VII. Cell Surfaces and Junctions
A. Plant cells are encased by cell walls
B. The extracellular matrix (ECM) of animal cells functions in support, adhesion,
movement and development
C. Intercellular junctions help integrate cells into higher levels of structure and
Function
OBJECTIVES
- Distinguish between prokaryotic and eukaryotic cells.
Prokaryotic cells are those without nuclei or other membrane enclosed organelles. Ex. Bacteria and archaebacteria.
Prokaryotic Cell
Eukaryotic cells are those with membrane enclosed nuclei and other specialized organelles in their cytoplasm. In addition, there are two main types of eukaryotic cells: The Animal cell and the Plant cell.
Animal Cell plant cell
4. Describe the structure and function of the nucleus, and briefly explain how the nucleus
controls protein synthesis in the cytoplasm.
The nucleus contains most of the genes that control the cell. The nuclear envelope encloses the nucleus, separating its contents from the cytoplasm.
5. Describe the structure and function of a eukaryotic ribosome.
Ribosomes are the sites where the cell assembles proteins. Cells that have high rates of protein synthesis have a particularly great number of ribosomes, another example of cell structure fitting function.
6. List the components of the endomembrane system, describe their structures and
functions and summarize the relationships among them.
The endomembrane system consists of the collection of membranes inside and around a eukariotic cell, related either through direct physical contact or by the transfer of membranous vesicles.
THE ENDOPLASMIC RETICULUM MANUFACTURES MEMBRANES AND PERFORMS MANY OTHER BIOSYNTHETIC FUNCTIONS
• CONTINOUS WITH THE NUCLEAR ENVELOPE, THE ENDOPLASMIC RETICULUM (ER) IS A NETWORK OF CISTERNAE.
• CISTERNAE: MEMBRANE ENCLOSED COMPARTMENTS.
• TRANSPORT VESSICLE: DISTRIBUTES ER’S PRODUCTS
• TYPES OF ENDOPLASMIC RETICULUM
SMOOTH ER: LACKS RIBOSOMES; SYNTHESIZES STEROIDS, METABOLIZES CARBS.
ROUGH ER: HAS BOUND RIBOSOMES; PRODUCES PROTEINS
7. Describe the vacuole & list types of vacuoles
Vacuoles are fluid membrane-bound bodies.
Different types of vacuoles:
- Food vacuoles are temporary receptacles of nutrients. Food vacuoles often merge with lysosomes, whose digestive enzymes break down the food.
- Storage vacuoles in plants store starch, pigments, and toxic substances (nicotine, for example).
- Central vacuoles are the large bodies occupying mast of the interior of certain plant cells. When fully filled, they exert turgor, or pressure, on the cell walls, thus maintaining rigidity in the cell. They also store nutrients and carry out functions otherwise assumed by lysosomes in animal cells.
- Contractile vacuoles are specialized organelles in single-celled organisms that collect and pump excess water out of the cell.
8. Explain the role of peroxisomes in eukaryotic cells.
Perixisomes are common in liver and kidney cells where they break down toxic substancesand in photosynthesizingplant cells.
9. Describe the structure & function of a mitochondrion
A mitochondria is the outer membrane and inner membrane folded into cristae, this is the site of the cellular respiration in eukaryotes.
The mitochondrion
11. Identify the three functional compartments of a chloroplast. Describe probable functions of the cytoskeleton.
The chloroplast
The cytoskeleton gives the cell shape, anchors some organelles and directs the movement of others, and may enable the entire cell to change shape or move.
13. Describe the structure, monomers and functions of microtubules, microfilaments and
intermediate filaments.
Microtubules: hallow cylinders; shape the cell, guide movement of organelles, aid chromosome separation in dividing cells.
Microfilaments: thin rods built from the protein actin; function in muscle contraction.
Intermediate filaments: support cell shape and organelles in place.
14. Explain how the ultrastructure of cilia and flagella relates to their function.
Flagella and cillia are structures the protude the cell membrane and make wavelike movements. Flagella and cilia are classified by their lenghts and by their numbers per cell: flagella are long and few; cilia are short and many.
17. Describe the structure of intercellular junctions found in plant and animal cells, and
relate their structure to function.
The many cells of an animal or plant are integrated into one functional organism. Neighboring cells often adhere, interact, and communicate through special patches of direct physical contact.
Chapter 8
MEMBRANE STRUCTURE AND FUNCTION
OUTLINE
I. Membrane Structure
A. Membrane models have evolved to fit new data: science as a process
B. A membrane is a fluid mosaic of lipids, proteins, and carbohydrates
II. Traffic Across Membranes
A. A membrane’s molecular organization results in selective permeability
B. Passive transport is diffusion across a membrane
C. Osmosis is the passive transport of water
D. Cell survival depends on balancing water uptake and loss
E. Specific proteins facilitate the passive transport of selected solutes
F. Active transport is the pumping of solutes against their gradients
G. Some ion pumps generate voltage across membranes
H. In cotransport, a membrane protein couples the transport of one solute to another
I. Exocytosis and endocytosis transport large molecules
OBJECTIVES
- Describe the function of the plasma membrane.
The function of the Plasma Membrane is to regulate the movement of materials in and out of the cell.
5. Describe the fluid properties of the cell membrane and explain how membrane fluidity
is influenced by membrane composition.
(a) Lipids move laterally in a membrane, but flip-flopping across the membrane is rare
(b) Unsaturated hydrocarbon tails of phospholipids have kinks that keep the molecules from packing together, enhancing membrane fluidity.
(c) cholesterol reduces membrane solidification at cold temperatures.
6. Explain how hydrophobic interactions determine membrane structure and function.
Membranes are not static sheets of molecules locked rigidly in place. A membrane is held together primarily by hydrophobic interactions, which are much weaker than covalent bonds.
7. Describe how proteins are spatially arranged in the cell membrane and how they
contribute to membrane function.
- integral proteins are embedded in the lipid bilayer
- peripheral proteins are attached to the surface
- the inside and outside membrane faces differ in composition
- carbohydrates linked to proteins and lipids in the plasma membrane are important for cel-cell recognition
8. Describe factors that affect selective permeability of membranes.
9. Define diffusion; explain what causes it and why it is a spontaneous process.
Diffusion: the spontaneous movements of a substance down its concentration gradient.
10. Explain what regulates the rate of passive transport.
Specific proteins facilitate passive transport of selective solutes
-IN FACILITATED DIFFUSION, A TRANSPORT PROTEIN SPEEDS MOVEMENT OF A SOLUTE ACROSS A MEMBRANE DOWN ITS CONCENTRATION GRADIENT
11. Explain why a concentration gradient across a membrane represents potential energy.
12. Define osmosis and predict the direction of water movement based upon differences in
solute concentration.
Osmosis is the passive transport of water
-water flows across a membrane from the side where solute is less concentrated (hypotynic)to the side where solutes is more concentrated (hypertonic).
14. Describe how living cells with and without walls regulate water balance.
Cell survival depends on balancing water uptake and loss
15. Explain how transport proteins are similar to enzymes.
16. Describe one model for facilitated diffusion.
The transport protein alternates between two conformations, moving a solute across the membrane as the shape of the protein changes. The protein can transport the solute in either direction, with the net movement being down the concentration gradient of the solute.
17. Explain how active transport differs from diffusion.
20. Explain how large molecules are transported across the cell membrane.
They are shaped in order to fit through.
21. Give an example of receptor-mediated endocytosis.
Phagocytosis