Chapter 4 - Cells
Vocab
Cell junction- specialized structures associated with the plasma membranes of epithelial
cells; cell adhesion and intercellular communication
Cell theory- a theory in biology that includes one or both of the statements that the cell is the
fundamental structural and functional unit of living matter and that the organism is composed
of autonomous cells with its properties being the sum of those of its cells.
Cell wall- a rigid layer of polysaccharides lying outside the plasma membrane of the cells of
plants, fungi, and bacteria. In the algae and higher plants, it consists mainly of cellulose.
Chloroplast- an organelle bound by a double membrane containing the enzymes and
pigments that perform photosynthesis; eukaryotes only
Cilia- hair-like organelle used for locomotion by many unicellular organisms and for moving
water and mucus by multicellular organisms; shorter than flagellum
Collagen- a fibrous protein found extensively in bone and connective tissue
Cytoplasm- the material or protoplasm within a living cell, excluding the nucleus.
Cytoskeleton- a microscopic network of protein filaments and tubules in the cytoplasm of
many living cells, giving them shape and coherence.
Cytosol- the aqueous component of the cytoplasm of a cell, within which various organelles
and particles are suspended.
Dynamic instability- property of actin filaments in the cytoskeleton; rapid shortening or
lengthening of individual filaments
Endomembrane system- system of intracellular membranes that exchange material with one
another; Golgi apparatus, ER, lysosomes
Endoplasmic reticulum (ER)- can be smooth or rough
Eukaryoteorganisms whose cells contain their genetic material inside a nucleus; includes all
other life besides viruses, archae, and bacteria
Extracellular matrix- a material of heterogenous composition surrounding the cells and
performing many functions including adhesion of cells
Flagella- a slender threadlike structure, especially a microscopic whiplike appendage that
enables many protozoa, bacteria, spermatozoa, etc., to swim.
Glyoxysome- organelle found in plants where stored lipids are converted to carbs
Golgi apparatus- a complex of vesicles and folded membranes within the cytoplasm of most
eukaryotic cells, involved in secretion and intracellular transport.
Intermediate filament- component of cytoskeleton whose diameters fall between those of
larger microtubules and those of smaller microfilaments
Microfilament- eukaryotic cells; fibrous structure made from actin monomers; play roles in
the cytoskeleton, cell movement, and muscle contraction
Microtubule- tubular structures in the centrioles, spindle fibers, cilia, flagella, and
cytoskeleton of eukaryotic cells; play roles in motion and maintenance of shape
Mitochondrion- an organelle found in large numbers in most cells, in which the biochemical
processes of respiration and energy production occur. It has a double membrane, the inner
layer being folded inward to form layers (cristae).
Nucleoid- region that harbors the chromosomes in a prokaryote; not bounded by a membrane
Nucleus- a dense organelle present in most eukaryotic cells, typically a single rounded
structure bounded by a double membrane, containing the genetic material.
Nucleolus- a small dense spherical structure in the nucleus of a cell during interphase.
Organelle- any of the membrane bound structures in a eukaryotic cell; nucleus, ER,
mitochondria
Peptidoglycan- cell wall material of many bacteria, consisting of a single enormous molecule
that surrounds the entire cell
Peroxisome- an organelle that houses rx in which toxic peroxides are formed and then
converted to water
Plasma membrane- a microscopic membrane of lipids and proteins that forms the external
boundary of the cytoplasm of a cell or encloses a vacuole, and that regulates the passage of
molecules in and out of the cytoplasm.
Plasmodesma/mata- cytoplasmic strand connecting 2 adjacent plant cells
Lysosome- an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes
enclosed in a membrane.
Prokaryote- unicellular organisms without a nucleus
Proteoglycan- a glycoprotein containing a protein core with attached long, linear
carbohydrate chains
Ribosome- a minute particle consisting of RNA and associated proteins, found in large
numbers in the cytoplasm of living cells. They bind messenger RNA and transfer RNA to
synthesize polypeptides and proteins.
Rough ER- a network of tubular membranes within the cytoplasm of the cell, occurring
either with a smooth surface (smooth endoplasmic reticulum) or studded with ribosomes
(rough endoplasmic reticulum) involved in the transport of materials.
Smooth ER- is an organelle found in both animal cells and plant cells. An organelle is a
subunit within a cell that has a specialized function. The main function of the smooth ER is
to make cellular products like hormones and lipids.
Surface area-to-volume ratio- important factor in setting an upper limit on the size a cell or
organism can attain
Vacuole- a space or vesicle within the cytoplasm of a cell, enclosed by a membrane and
typically containing fluid.
Vesicle- a fluid- or air-filled cavity or sac, in particular.
Questions
1. There are three parts of cell theory 1) cells are the fundamental units of life 2) All
living organisms are composed of cells and 3) all cells come from preexisting cells.
This is significant because it means that by studying cells we are studying life and
that life is continuous.
2. A cell can expand its surface area to volume ratio by flattening.
3. Smaller cells have a greater surface area to volume ratio.
4.
5. Biologists focus on the plasma membrane when studying the origin of cells because
all cells have a plasma membrane. In addition to that, the plasma membrane
separates the cell from its environment. Essentially, the plasma membrane is what
define what is part of the cells and what isn’t.
6. Eukaryotes have the evolutionary advantage of organelles with specific functions.
7. Prokaryotic cells persist because they are less specialized than eukaryotes. They can
survive in almost any kind of environment because their cells are more adaptive and
aren’t specifically suited for certain environments.
8. Having the nucleus separate from the cytoplasm is an advantage because the DNA
and chromatin is more protected in the double membrane surrounding the nucleus.
It also separates the transcription and translation of proteins.
9. Prokaryotes make endonucleases to digest foreign DNA in the cytoplasm because
they do not have organelles like lysosomes to preform this specific function. In
prokaryotes all the genetic material and everything else is floating around in the
cytoplasm. Once an invader enter through the plasma membrane they can attack
directly attack the DNA because it is not membrane bound in the nucleus.
Eukaryotes do not have this because they have membrane bound organelles and
produce lysosomes.
10. The cytoskeleton is made of a chain of intercellular proteins that give the cell its
shape, support the cell, and help with movement. There are three types of
cytoskeleton: microfilaments, intermediate filaments, and microtubules. The
cytoskeleton controls movement of the cell in its environment and controls the
movement of the cell's components.
11. Dynamic instability is the property of actin filaments in the cytoskeleton; rapid
shortening or lengthening of individual filaments. This is important because it allow
Microfilaments and microtubules to be broken down and rebuilt quickly.
12.
13.
14. The extra cellular matrix, or ECM, is a network that surrounds animal cells and it
preforms duties like adhesion of cells. It is made up of the fibrous component
protein collagen. The ECM holds the cell together in tissues, provides physical
properties, filters material moving between tissues, and orient cell movement in
development and repair.
15. Tight junction: prevents substances from moving among cells.
Desmosome: keeps cells together using protein connections and provides stability
Gap junction: (similar to plasmodesmata) channels that run between pores in the
membrane of touching cells that allow substances to pass between them.
16. Plasmodesmata are found in plant cells, and gap junctions are found in animal cells.
Plasmodesmata are channels that go through the cell wall and are primarily used for
transportation of molecules. Gap junctions, on the other hand, go through he
membrane pores, and are used for communication. Both plasmodesmata and gap
junctions allow substances to be passed to cells that are adjacent to one another.