all organisms are made of cells

most cells are too small to be seen with the naked eye

viruses “sabotage” cells

three most important parameters of microscopy

1. magnification : the ratio of an object’s image size to its real size

2. resolution : the measure of the clarity of the image or minimum distance between two distinguishable points

3. contrast : visible differences in parts of the sample

• viruses are NOT cells but we can see them with a electron microscope

• in a light microscope: visible light is passed through a specimen and then through glass lenses

• lenses refract (bend) the light, so that the image is magnified

basic features of ALL CELLS

1. plasma membrane (boarder)

2. cytosol (semifluid substance in plasma membrane)

3. chromosomes (carry genes)

4. ribosomes (make proteins)

   

   • two types of cells

     • eukaryotic cells : most of the DNA is in the nucleus (organelle); organelles are bound by a membrane

     • prokaryotic cells (bacteria) : do NOT have a nucleus ; no membrane-bound organelles

       • Cell wall: protective layer of extracellular matrix that surrounds the plasma membrane of some cells, just outside the cell membrane

     • both types contain a cytoplasm bound by the plasma membrane

• plasma membrane : selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of very cell; membrane that encloses a cell and separates it from the external environment.

  • the general structure of a biological membrane is made of a double layer of phospholipids

• cytosol : jellylike mixture of water, sugars, ions, and proteins and solutes enclosed by a cell’s plasma membrane

  • major part of a cell’s metabolism occurs in cytosol, and the cell’s other internal components, including organelles, are suspended in it

• Organelles : structures that carry out special functions inside a cell

  • virus is smaller than most organelles

  • nuclear envelope: covers nucleus

  • endoplasmic reticulum: has ribosomes on surface

  • Golgi apparatus: modifies proteins

  • lysosomes: digest waste and harmful pathogens; can digest some bacteria, viruses, and worn out parts of the cell

  • vacuoles: contain water (plants)

  • plasma membrane: covers cell

• cytoplasm : in a eukaryotic cell, collective term for everything between the cell’s plasma membrane and its nucleus. In a prokaryotic cell, everything enclosed by the plasma membrane.

function of the cell is dependent on the nucleus that includes DNA, the DNA includes the GENES that tell the proteins what to do

• nuclear membrane: a double membrane where each membrane consists of a lipid bilayer that surrounds the nucleus

• nucleus: contains DNA → organized into discrete units called CHROMOSOMES;

  • nucleotide : basic subunit of DNA

    • 4 nucleotides are A, T, C, G

• each chromosome is one long DNA molecule associated with proteins

  • DNA and proteins of chromosomes together are called chromatin

  • DNA is not “naked” but covered with proteins; and all DNA throughout the body are the same

• ribosomes: organelle that uses the information from the DNA to MAKE proteins

  • can either be “free” or attached to the endoplasmic reticulum

    • “rough” E.R. has ribosomes

      • ribosomes then go through the Golgi apparatus to be modified; then goes to transport vesicle to be transported throughout the cell

    • “smooth” E.R. makes fats, carbs, and detox from drugs and poisons

• cytoskeleton: network of fibers extending throughout the cytoplasm; gives cell its structure/frame that is like a highway that allows things to move from one organelle to the next

  • travels through vesicles (package truck)

differences

animal cell

• has cell membrane, no cell wall

plant cell

• has cell wall that surrounds membrane

• vacuole: stores water

• chloroplast: site of photosynthesis; contains chlorophyll and enzymes; plants photosynthesize and release oxygen network

mitochondria : powerhouse of the cell ; double-membraned organelle that produces ATP (protein) by aerobic respiration in eukaryotes

Cilia: moves in our windpipe and bronchi of our lungs → traps in debris from getting into our lungs

bacterial cells: some cells have flagellum and pilus that help with movement and interact with other cells ; no nuclear membrane

• Cell membrane and cytoplasm: The cell is completely covered by a cell membrane that acts like a “security gate.” Only certain molecules are allowed to pass into or out of the cell. The inside of the cell (the cytoplasm) is filled with liquid (cytosol) and various organelles that do specific jobs for the cell.

• Nucleus: The largest organelle in the cell is the nucleus. The nucleus acts as the “control center” or main office of the factory. Inside the nucleus, DNA is the “boss.” DNA molecules contain the plans for every protein the cell can manufacture. As the boss, DNA never leaves the office. Instead, a messenger molecule (messenger RNA) carries written instructions for building a protein to the rest of the factory.

• Ribosomes are “workbenches” that work only on proteins. Ribosomes read the instructions from messenger RNA and assemble materials into a polypeptide.

• Endoplasmic reticulum is part of the factory’s “assembly line.” There are two types of endoplasmic reticulum. Rough endoplasmic reticulum (RER) works only on proteins. Smooth endoplasmic reticulum (SER) builds lipids.

• Golgi complex: The Golgi complex is the “distribution center.” It modifies, sorts, tags, packages, and distributes the proteins and lipids.

• Transport vesicles are tiny spheres of membrane that surround and carry proteins or lipids to their destination. That destination may be inside the cell, or vesicles may eject their contents out of the cell (exocytosis).

• Cytoskeleton is the “skeleton” or structural components of the factory. This includes structures that act like monorails to move transport vesicles containing proteins or lipids to their destinations.

• Mitochondria: All this work requires energy. The mitochondrion is an energy-generating organelle that takes in fuel (food) and mass produces the energy molecule ATP.

• Lysosomes and peroxisomes are the factory’s “cleaning crew.” Lysosomes are vesicles filled with strong enzymes that digest large molecules and worn-out organelles. Similar to lysosomes, peroxisomes have enzymes that break down smaller molecules and detoxify poisons.

What structure allows only certain molecules to pass into or out of the cell?

• cell membrane

What cellular structure contains most of the DNA?

• nucleus

Which of the following are the only molecules built by ribosomes and rough endoplasmic reticulum (RER)?

• proteins

Which of the following types of biological molecules are synthesized at the endoplasmic reticulum?

• proteins

• lipids

_____ & ____ are responsible for breaking down cellular components and molecules.

• lysosomes

• peroxisomes

On average, eukaryotic cells are approximately _____ prokaryotic cells.

• 10 times larger than

Which of the following characteristics is specific to prokaryotic cells?

• plasmids
  

Mitochondria are an example of _____.

• organelles found within eukaryotic cells
  

Which of the following structures are found only in eukaryotic cells? Select all that apply.

• rough e.r.

• nuclei

• the Golgi complex
  

Which of the following are parts of both prokaryotic and eukaryotic cells? Select all that apply.

• plasma membrane

• cytosol

• DNA

In prokaryotic cells, the DNA is located in the _____ while in eukaryotic cells, DNA is located in the ______.

1. nucleoid

2. nucleus
   

What part of a phospholipid faces the cytosol inside a cell?

• hydrophilic head
  

Ions and polar molecules can cross the plasma membrane in regions where the membrane has incorporated _____.

• transport proteins

The plasma membrane is considered a fluid mosaic because it permits incorporated molecules such as receptors and transport proteins to _____.

• move around laterally within the membrane
  

The word bilayer in the term phospholipid bilayer refers to which of the following?

• The two layers of phospholipids that make up the membrane

The cell membrane is _______ because some molecules can travel across the membrane while others cannot.

• semipermeable

Which small molecule decreases the fluidity of the plasma membrane?

• cholesterol