Chapter 3 cells: section 1

Plasma membrane is composed of:

1. A bilayer of phospholipids. 2. Other components (Glycocalyx, membrane proteins)

Ribosomes

1. Are responsible for protein synthesis 2. Composed of 2 subunits of proteins and ribosomal RNA (rRNA) 3. May be scattered in cytoplasm = free ribosomes - floating in the cytosol 4. May be associated with the endoplasmic reticulum (ER) - fixed ribosomes - attached to the rough ER. Proteins manufactured by fixed ribosomes enter the cisternae of the RER.

Intermediate filament

1. Are the strongest and most durable parts of the cytoskeleton - act like a highway 2. Give strength and support, move materials through cytoplasm.

Cell Theory

1. Cells are the building blocks of all living things. 2. All cells come from the division of preexisting cells. 3. Cells are the smallest units that perform vital functions.

Cytoskeleton functions:

1. Giving the cell an internal framework 2. Giving strength and flexibility to the cytoplasm 3. Intracellular movement of organelles (network of highways).

Microtubules

1. Largest components of cytoskeleton 2. Provide strength and move organelles

Rough endoplasmic reticulum

1. Outer surface is studded with ribosomes 2. Functions in alteration and packaging of proteins synthesized by its attached ribosomes - (liver cell) 3. Cisternae are flattened. Functions as a combination workshop and shipping depot. It is where many newly synthesized proteins are chemically modified and packaged for export to the Golgi Apparatus.

Microfilaments

1. Provide strength and support for the cell. 2. Are composed of the protein actin (important in muscle contraction). 3. Help stiffen microvilli, which are finger-shaped extensions of the plasma membrane. 4. The terminal web is a layer of microfilaments just inside the plasma membrane.

Golgi apparatus function

1. Renewing or modifying the plasma membrane 2. Modifies and packages molecules that will be secreted 3. Packages enzymes within vesicles that will be used in the cell - sends to destination

Cells are composed of:

1. The plasma membrane separates the cell contents, or cytoplasm, from the extracellular fluid. 2. Cytoplasm is a general term for the material between the plasma membrane and the membrane surrounding the nucleus. A colloid with a consistency that varies between that of thin maple syrup and almost-set gelatin, cytoplasm contains many more proteins than extracellular fluid. 3. Cytosol is the fluid component of cytoplasm. Also called intracellular fluid; may contain inclusions of insoluble materials. 4. Organelles intracellular structures with specific functions.

Plasma membrane

A physical barrier that separates the inside of the cell from the surrounding extracellular fluid.

Membranous organelles

Are isolated from the cytosol by phospholipid membranes, just as the plasma membrane isolates the cytosool from the extracellular fluid. Include: Mitochondria, nucleus, endoplasmic reticulum, Golgi apparatus, Lysosomes, and peroxisomes.

Non-membranous organelles

Are not completely enclosed by membranes, and all of their components are in direct contact with the cytosol. Include: Cytoskeleton, microvilli, centrioles, cilia, and ribosomes.

Chromosomes

At the beginning of cell division, DNA coiling becomes tighter and more complex, finally resulting in the formation of distinct structures.

Functional class of proteins: ANCHORING PROTEIN

Attach the plasma membrane to other structures and stabilize its position. Inside the cell, membrane proteins are bound to the cytoskeleton.

Functional class of proteins: CARRIER PROTEINS

Bind solutes and transport them across the plasma membrane.

Functional class of proteins: RECEPTOR PROTEINS

Bind to specific extracellular molecules called ligands. A ligand can be anything from a small ion like calcium, to a relatively large and complex hormone.

Functional class of proteins: CHOLESTEROL

Cholesterol prevents cell from being too hot or too cold; too liquid or too solid. Cholesterol keeps consistency of membrane constant.

Functional class of proteins: RECOGNITION PROTEINS

Detected by cells of the immune system. Enzymes in plasma membranes may be integral or peripheral proteins.

Cisternae

Formed by the endoplasmic reticulum (folded ribbon)

Nucleosome

Formed when DNA coils TIGHTLY around histones forming small complexes.

A gamete (sex cell)

Has 23 chromosomes

Human somatic cells (body cell)

Have 23 PAIRS of chromosomes, or, 46 total

Cilia

In lining of respiratory and reproductive tract 1. Long slender projections of the plasma membrane 2. Commonly found on cells in the lining of the respiratory & reproductive tracts. 3. Help move fluids across the surface of cells. Supportive, protective, movement

Membrane proteins

Integral (embedded in membrane) Peripheral (bound to outer surface)

Functional class of proteins: CHANNELS

Integral proteins containing a central pore (channel) that forms a passageway completely across the plasma membrane. The channel permits the passage of water and small solutes that cannot otherwise cross the lipid bilayer of the plasma membrane.

Thick filament

Interact with actin to produce muscle contraction - create movement

Smooth endoplasmic reticulum

Lipid synthesis 1. Not associated with ribosomes 2. Cisternae are tubular 3. Functions in lipid and carbohydrate metabolism -- Synthesizes phospholipids & cholesterol needed for maintenance and growth of the plasma membrane, ER, nuclear envelope, and Golgi apparatus -- Synthesizes steroid hormones in reproductive organs such as androgens and estrogens (the dominant sex hormones in males and in females, respectively). -- Synthesizes triglycerides for storage in liver and fat cells --- carbohydrate storage in liver and muscles -- Synthesizes glycogen for storage in skeletal muscles & liver cells

Mitochondria

Makes ATP for the cell. Responsible for the production of energy (ATP) -- For ATP you need oxygen and glucose - primary fuel for the process of aerobic metabolism or cellular respiration. Numbers vary between cells with different energy demands (Muscle cells have a lot because they do a lot of activity). -- Have a double membrane

Components of cytoskeleton

Microfilaments Intermediate filaments Thick filaments Microtubules Centrioles Cilia

Centrioles

Organize microtubules during cell division to help move chromosomes. Helps with mitosis by moving chromosomes around during cell division If no centrioles are in a cell the cell cannot divide.

Membrane flow

Other than mitochondria all membranous organelles in the cell are either interconnected or in communication through the movement of vesicles.

Differentiation

Process of gradual specialization that produces different types of cells: A. Cells have a metabolism. They break molecules down and build molecules up. 1. Zygote: At fertilization, the fertilized ovum -- which is very large -- contains the genetic potential to become any cell in the body. 2. As divisions occur, the cytoplasm is subdivided into smaller parcels. These parcels differ from one another because there were regional differences in the composition of the cytoplasm at fertilization. 3. The cytoplasmic differences affect the DNA of the cells, turning specific genes on or off. The daughter cells begin to develop specialized structural and functional characteristics. This process of gradual specialization is called DIFFERENTIATION. 4. DIFFERENTIATION produces the specialized cells that form the tissues responsible for all body functions.

Structure of the nucleus: Nucleoplasm

Refers to the fluid contents of the nucleus. Contains ions, enzymes, RNA and DNA nucleotides, small amounts of RNA, and DNA

Proteins

Responsible for making amino acids and linking them together in a long chain.

Lysosomes

Special vesicles that provide an isolated environment for potentially dangerous chemical reactions. These vesicles contain digestive enzymes (break down foreign particles). Lysosome is also known as a suicide packet. Sometimes digests the whole cell - autolysis

Nucleus

Stores genetic information

Contents of the nucleus: DNA

Stores instructions for protein synthesis.

Glycocalyx

Superficial membrane carbohydrates form a layer known as the glycocalyx. Carbohydrates account for roughly 3 percent of the weight of a plasma membrane; they are components of complex molecules such as proteoglycans (carbohydrate with some protein attached), glycoproteins (protein with some carbohydrates attached, and glycolipids (lipids with carbohydrates attached). THE GLYCOCALYX IS IMPORTANT IN CELL RECOGNITION, BINDING TO EXTRACELLULAR STRUCTURES, AND LUBRICATION OF THE CELL SURFACE.

Structure of the nucleus: Nuclear envelope

Surrounds the nucleus in a double layered membrane

Ribosomal protein

The more proteins a cell synthesizes,the more ribosomes it has. Liver cells have many, fat cells have few.

Phospholipid bilayer

The phospholipid molecules form 2 layers. In each half of the bilayer the phospholipids lie with their hydrophilic heads at the membrane surface and their hydrophobic tails on the inside, just as in a micelle.

Chromatin

The term for the filaments formed by DNA wrapping LOOSLY around histone proteins.

Structure of the nucleus: Nucleoli

Transient nuclear organelles that synthesize ribosomal RNA. Nucleoli are compsed of RNA, enzymes and proteins called HISTONES.

Structure of the nucleus: Nuclear pores

passageways that permit chemical communication between the nucleus and the cytosol. -- choses what goes in and out -- semipermeable

Nuclear genetic information

used to direct the synthesis of proteins in every body cell