Download Ch.7.2 Cell Structure Notes

Notes Chapter 7.2 “Cell Structure”
Eukaryotic cells can be divided into two regions: the nucleus and the cytoplasm
 Cytoplasm: the region of the cell outside the nucleus
o Prokaryotic cells have cytoplasm but no nucleus.
 The nucleus contains nearly all the cell’s genetic information (DNA), and
therefore, the code for making proteins and other molecules that the cell
needs.
o Surrounded by a porous nuclear envelope which allows substances
to move into and out of the nucleus
o Contains chromosomes which carry DNA
o Most contain a nucleolus – responsible for the production of
ribosomes
 Organelles: “tiny organ”, specialized structures inside the cytoplasm
 Vacuoles: storage areas in a cell (for carbohydrates, waste, water, &
proteins)
o in plants the vacuole is usually singular and large (the pressure of the
water in the vacuole helps support the leaves and flowers of the plant)
o in single celled organisms (paramecium, euglena) there is a
contractile vacuole which expels excess water from the cell
o vesicles – membrane bound organelles in eukaryotic cells that moves
materials between organelles and out of the cell
 Lysosomes: “the clean-up crew” of a cell
o Filled with enzymes
o Break down old organelles, as well as carbohydrates, proteins, and
lipids into molecules that can be used by the cell
 Cytoskeleton: protein filaments that give a cell its shape and help
transport materials within a cell
o Microfilaments – made of a protein called actin
 Enable amoebas to move using pseudopods – “false feet” –
structures that enable them to “crawl” across a surface
o Microtubules – made of proteins called tubulins
 Make centrioles in animal cells, mitotic spindle, cilia, and flagella
 In cilia and flagella microtubules are arranged in a “9 + 2”
pattern that allow the cells to move through their environment
 Cilia and flagella are extensions of the cell surface
 Ribosomes: structures made of RNA and protein
o responsible for the assembly of protein molecules from DNA’s coded
instructions
 Endoplasmic Reticulum: (ER) assembly of lipids, proteins, and other
molecules within the cell
o rough ER has ribosomes on the surface that complete the assembly
of proteins
 proteins made here are released (secreted) from the cell
 proteins that are made here are membrane proteins and those
needed at the lysosomes and in other specialized structures
within the cell
o smooth ER has no ribosomes on the surface
 contain enzymes that help create lipids for membrane and
detoxify drugs
 Golgi Apparatus: take proteins made in the rough ER and modifies, sorts,
and packages them
o These proteins will be stored or released from the cell
Protein
made in the
rough ER
Protein packaged in
vesicles are
transported to Golgi
Apparatus
In Golgi apparatus
proteins are modified,
sorted, and packaged
Proteins are
transported in
vesicles to be
stored or secreted
 Chloroplasts: capture energy from the sun and converts it to food for the
organism (in the form of chemical energy)
o This process is called photosynthesis.
o Chloroplasts are surrounded by two membranes.
o Contain the pigment chlorophyll
o Has its own DNA
 Mitochondria: convert chemical energy of food into compounds that the
cells can use
o two membranes – inner one is folded up
o in humans nearly all mitochondria comes from the egg cell
o has its own DNA
 Cell Membrane – controls what enters and leaves the cell, supports and
protects the cell
o all cells have a cell membrane
o double-layer called a lipid bilayer allows for flexibility
 fatty acid tails are hydrophobic – “water hating”
 opposite side is hydrophilic – “water loving”
 when mixed with water the fatty acid tails clump together on the
inside of the bilayer and the water loving heads attract to the
water
o described as a fluid mosaic model – the cell membrane has proteins
and carbohydrates embedded in it that float around among the lipids
 proteins are involved in movement of molecules across the
membrane (some have channels, others act as pumps)
 carbohydrates act as identification tags so cells recognize each
other
o semipermeable (selectively permeable): describes the cell membrane
 some substances are too large or too strongly charged to pass
through the membrane
 other substances can pass into and out of the cell
 Cell wall: supports, shapes, and protects the cells of certain organisms
o Found in most prokaryotes and all plants
o Provide the strength plants need to withstand gravity
o Porous – allows water, oxygen, carbon dioxide, and some other
materials to cross easily
o Cells with a cell wall also have a cell membrane.