Lesson II: The Cell and its Functions Flashcards
is separated from the cytoplasm
by a nuclear membrane
nucleus
is separated from the surrounding fluids by a cell membrane, also
called the PLASMA MEMBRANE
cytoplasm
The different substances that make up the cell are
collectively called
protoplasm
Protoplasm is composed mainly of five basic substances:
✓ water
✓ electrolytes
✓ proteins
✓ lipids
✓ carbohydrates
The principal fluid medium of the cell, which is present in most cells, except for fat cells, in a concentration of 70 to 85 percent.
water
Important ions in the cell include
✓ potassium
✓ magnesium
✓ phosphate
✓ sulfate
✓ bicarbonate
✓ and smaller quantities of sodium, chloride and calcium
provide inorganic chemicals for cellular reactions
ions
they are necessary for operation of some of
the cellular control mechanisms.
ions
acting at the cell membrane are required for transmission of
electrochemical impulses in nerve and muscle fibers.
ions
the most abundant substances
in most cells
proteins
proteins, which normally constitute ___ to ___ percent of the cell mass.
10-20 percent
proteins can be divided into two
types:
structural and functional proteins
present in the cell mainly in the
form of long filaments that are polymers of many individual protein molecules.
structural proteins
a prominent use of such intracellular filaments is to form _________ that provide the __________ of such cellular organelles as ______, _________, the
________, and a tangled mass of thin
__________ that hold the parts of the cytoplasm and
nucleoplasm together in their respective compartments
microtubules
cytoskeleton
cilia, nerve axons, mitotic of mitosing cells, filamentous tubules
are found especially in the
collagen and elastin fibers of connective tissue and in blood
vessel walls, tendons, ligaments, and so forth
fibrillar proteins
are an entirely different type
of protein, usually composed of combinations of a few
molecules in tubular-globular form.
functional proteins
are several types of substances that are grouped together because of their common property of
being soluble in fat solvents.
lipids
important lipids
are ____________ and ___________ which together constitute only about 2 percent of the total cell mass
phospholipids and cholesterol
some cells
contain large quantities of triglycerides, also called
neutral fat
triglycerides often account for as much
as how many percent of the cell mass.
95%
have little structural
function in the cell except as parts of glycoprotein molecules, but they play a major role in nutrition of the cell.
carbohydrates
small amount
of carbohydrate is stored in the cells in the form of
glycogen
which is an insoluble polymer of glucose that can
be depolymerized and used rapidly to supply the cells’
energy needs.
glycogen
The cell is not merely a bag of fluid, enzymes, and chemicals; it also contains highly organized physical structures,
called
intracellular organelles
more than 95 percent of the cell’s energy release from nutrients would cease immediately.
mitochondria
membranes include;
✓ cell membrane
✓ nuclear membrane,
✓membrane of the endoplasmic reticulum
✓ membranes of the mitochondria,
✓ lysosomes
✓ Golgi apparatus
for passage of specific substances through
the membrane
actual pores
(also called the plasma membrane),
which envelops the cell, is a thin, pliable, elastic structure
only 7.5 to 10 nanometers thick. It is composed almost
entirely of proteins and lipids.
cell membrane
The approximate composition is;
proteins, 55 percent
phospholipids, 25 percent
cholesterol, 13 percent
other lipids, 4 percent
carbohydrates, 3 percent.
is composed of phospholipid
molecules.
basic lipid bilayer
One end of each phospholipid molecule is soluble in water; that is, it is
hydrophilic
The other end is
soluble only in fats; that is, it is
hydrophobic
The phosphate end of the phospholipid
hydrophilic
the fatty
acid portion
hydrophobic
The lipid layer in the middle of the membrane is
impermeable to the usual water-soluble substances, such
as;
ions, glucose, urea
fat-soluble substances such as; can
penetrate this portion of the membrane with ease.
oxygen, carbon dioxide and alcohol
are attached to the protein
molecules on the out side of the membrane and to additional
protein molecules on the inside.
carbohydrate moieties
controls much of the fluidity of the membrane as well
cholesterol
These are membrane proteins, most of which
are
glycoproteins
There are two types of cell membrane
proteins:
integral proteins and peripheral proteins
that protrude all the way
through the membrane
Integral proteins
that are
attached only to one surface of the membrane and do not
penetrate all the way through.
peripheral proteins
through which water molecules and water-soluble substances, especially ions, can diffuse between
the extracellular and intracellular fluids.
structural channels or pores
Other integral proteins act as ________for transporting substances that otherwise could not penetrate the
lipid bilayer
carrier proteins
Sometimes these even transport substances
in the direction opposite to their electrochemical gradients for diffusion, which is called?
active transport
can also serve as receptors for water-soluble chemicals, such as peptide hormones,that do not easily penetrate the cell membrane.
integral membrane proteins
Interaction
of cell membrane receptors with specific _________ that bind
to the receptor causes conformational changes in the
receptor protein
ligands
enzymatically activates the
intracellular part of the protein or induces interactions
between the receptor and proteins in the cytoplasm that act as
second messenger
thereby relaying the signal from
the extracellular part of the receptor to the interior of the
cell.
second messengers
spanning the cell membrane provide a means of conveying information about
the environment to the cell interior.
Integral proteins
moecules are often attached to
the integral proteins.
peripheral proteins
enzymes or as controllers of transport
of substances through the cell membrane “pores ”
peripheral proteins
Membrane carbohydrates occur almost invariably in
combination with proteins or lipids in the form of
glycoproteins and glycolipids
most of the integral proteins
glycoproteins
one tenth of the membrane
lipid molecules are
glycolipids
which are mainly carbohydrate substances bound
to small protein cores—are loosely attached to the outer
surface of the cell as well.
proteoglycans
loose carbohydrate coat
glycocalyx
is filled with both minute and large dispersed particles and organelles.
cytoplasm
clear fluid portion
of the cytoplasm in which the particles are dispersed
cytosol
cytosol contains mainly dissolved;
proteins,
electrolytes, and glucose.
Dispersed in the cytoplasm are
neutral fat globules,
glycogen granules, ribosomes, secretory vesicles
five
especially important organelles:
✓ Endoplasmic reticulum
✓ Golgi apparatus
✓ Mitochondria
✓ Lysosome
✓ Peroxisomes
their walls are constructed of
lipid bilayer membranes that contain large amounts of
proteins, similar to the cell membrane.
endoplasmic reticulum
a watery medium that is different from the fluid in the cytosol outside the endoplasmic reticulum
endoplasmic matrix
show that the space inside the endoplasmic reticulum is connected with the space between the two
membrane surfaces of the nuclear membrane.
electron micrographs
Attached to the outer surfaces of many parts of the endoplasmic reticulum are large numbers of minute granular
particles
ribosome
when these are present, reticulum is called the?
granular endoplasmic reticulum
are composed of a mixture of RNA and
proteins, and they function to synthesize new protein
molecules in the cel
ribosomes
Part of the endoplasmic reticulum has no attached ribosomes. This part
is called the
agranular, or smooth, endoplasmic reticulum
are similar physically to lysosomes, but they
are different in two important ways.
peroxisome
another oxidase enzyme present in large quantities in peroxisomes, to oxidize many substances that might otherwise be poisonous to the cell
catalase
small
“transport vesicles” (lalso called
endoplasmic reticulum vesicles
are vesicular organelles that form by breaking off from the Golgi apparatus and then dispersing throughout the cytoplasm
lysosomes
The
lysosomes provide an ____________ that
allows the cell to digest (1) damaged cellular structures,
(2) food particles that have been ingested by the cell,
and (3) unwanted matter such as bacteria
intracellular digestive system
is capable of splitting an organic compound into two or more parts by combining hydrogen from a water molecule with one part of the compound and combining the
hydroxyl portion of the water molecule with the other
part of the compound.
hydrolytic enzymes
protein is hydrolyzed to form
amino acids
glycogen is hydrolyzed to form
glucose
lipids are hydrolyzed to form
fatty acids and glycerol
Almost all such secretory
substances are formed by the endoplasmic reticulum Golgi apparatus system and are then released from the
Golgi apparatus into the cytoplasm in the form of stor-
age vesicles called
secretory vesicles or secretory granules
secreted later through the outer cell membrane into the
pancreatic duct and thence into the duodenum, where
they become activated and perform digestive functions
on the food in the intestinal tract.
proenzymes
called the “powerhouses” of the cell.
mitochondria
are concentrated in those portions of the cell that
are responsible for the major share of its energy metabolism.
mitochondria
composed mainly of two lipid bilayer–
protein membranes
outer and inner membrane
The liberated energy is
used to synthesize a “high-energy” substance called
adenosine triphosphate (ATP)
are self-replicative, which means that
one mitochondrion can form a second one, a third one,
and soon, whenever there is a need in the cell for increased
amounts of ATP.
mitochondria
is the basic chemical of the nucleus that
controls replication of the cell.
DNA
The precursor molecules then polymerize to form
filaments
large numbers of actin filaments
frequently occur in the outer zone of the cytoplasm,
called the
ectoplasm
A special type of stiff filament composed of polymerized tubulin molecules is used in all cells to construct strong tubular structures
microtubules
both the centrioles and the mitotic spindle of the mitosing cell are composed
stiff microtubules
primary function of microtubules is to act as a
cytoskeleton
providing rigid physical structures for certain parts of cells.
cytoskeleton
the control center of the cell
nucleus
nucleus contains large quantities of DNA
genes
determine the characteristics of the
cell’s proteins, including the structural proteins, as well
as the intracellular enzymes that control cytoplasmic and
nuclear activities.
genes
nuclear membrane, also called
nuclear envelope
The nuclear membrane is penetrated by several thousand
nuclear pores
The nuclei of most cells contain one or more highly staining structures called
nucleoli
(1) the smallest known virus, (2) a large virus, (3)
a rickettsia, (4) a bacterium, and (5) a nucleated cell,
The essential life-giving constituent of the small virus is a
nucleic acid
is composed of the same basic nucleic acid constituents
(DNA or RNA) found in mammalian cells, and it is capable
of reproducing itself under appropriate conditions
nucleic acid
Most substances pass through the cell membrane by
diffusion and active transport
involves simple movement through the membrane caused by the random motion of the molecules of the substance; substances move either through
cell membrane pores or, in the case of lipid-soluble substances, through the lipid matrix of the membrane.
diffusion
involves the actual carrying of a substance through the membrane by a physical protein.structure that penetrates all the way through the membrane.
active transport
Very large particles enter the cell by a specialized function of the cell membrane called
endocytosis
The principal forms of endocytosis are
pinocytosis and phagocytosis
means ingestion
of large particles, such as bacteria, whole cells, or portions
of degenerating tissue.
phagocytosis
means ingestion of minute particles that form
vesicles of extracellular fluid and particulate constituents
inside the cell cytoplasm
pinocytosis
