Chapter 3 - Cell Biology Flashcards
basic units of all living things
Cells
forms the outer boundary of the cell, through which the cell interacts with its external environment.
plasma membrane or cell
membrane
usually located centrally; it directs cell activities
nucleus
where most cell activities take place, located
between the plasma membrane and the nucleus
cytoplasm
specialized structures that perform specific
functions
organelles
Functions of cell (4)
- Cell metabolism and energy use
- Synthesis of molecules
- Communication
- Reproduction and inheritance
outer boundary of the cell; controls
the entry and exit of substances
Plasma Membrane
the control center of the cell; DNA within the
nucleus regulates protein (e.g., enzyme) synthesis and therefore the chemical reactions of the cell
Nucleus
Serves as site of protein synthesis
Ribosome
Synthesizes proteins and transports them to Golgi apparatus
Rough endoplasmic reticulum
Manufactures lipids and carbohydrates; detoxifies harmful chemicals; stores calcium
Smooth endoplasmic reticulum
Modifies, packages, and distributes proteins and lipids for secretion or internal use
Golgi apparatus
Contains digestive enzymes
Lysosome
Serves as one site of lipid and amino acid degradation; breaks down hydrogen peroxide
Peroxisome
Break down proteins in the cytoplasm
Proteasomes
Are major sites of ATP synthesis when oxygen is available
Mitochondria
Serve as centers for microtubule formation; determine cell polarity during cell division; form the basal bodies of cilia and flagella
Centrioles
Move materials over the surface of cells
Cilia
propels spermatozoa
Flagellum
Increase surface area of the plasma membrane for absorption and secretion; modified to form sensory receptors
Microvilli
Two major types of microscopes
light microscopes and electron microscopes
allow us to visualize the general features of cells, such as the nucleus. But the magnification of light microscopes is
limited, so not all cell structures can be thoroughly investigated
Light microscopes
can reveal features of the cell surface and the surfaces of internal structures
electron microscopes
In order to study the fine structures of cells, researchers use
electron microscopes
can reveal features of the cell surface and the surfaces of internal structures.
scanning electron microscope (SEM)
allows us to see “through” parts of the cell and thus to discover detailed aspects of cell
structure.
transmission electron microscope (TEM)
boundary separating the intracellular substances, those inside the cell, from extracellular substances, those outside
the cell.
plasma membrane
An electrical charge difference across the plasma membrane
membrane potential
result of the cell’s regulation
of ion movement into and out of the cell
membrane potential
The plasma membrane consists primarily of
lipids and proteins, with a very small amount of carbohydrates.
The carbohydrates combine with lipids to
form
glycolipids
with proteins to form
glycoproteins
collection of glycolipids,
glycoproteins, and carbohydrates on the outer surface of the plasma membrane
glycocalyx
The predominant lipids of the plasma membrane
phospholipids
cholesterol
double layer of phospholipid molecules
lipid bilayer
Phospholipids have a
polar (charged; hydrophilic) head and a nonpolar (uncharged; hydrophobic) tail
penetrate deeply into the lipid bilayer, in many cases extending from one surface to the other
Integral membrane proteins
are attached to either the inner or the outer surfaces of the lipid bilayer.
. Peripheral membrane proteins
cell surface molecules that allow cells to
identify other cells or other molecules.
Marker molecules (mostly glycoproteins - proteins with attached carbohydrates, or glycolipids - lipids with attached carbohydrates)
integral proteins that allow cells to attach
to other cells or to extracellular molecules
Attachment proteins
proteins that attach cells to other cells
Cadherins
proteins that attach cells to extracellular molecules
integrins
integral proteins that allow ions or molecules to move from one side of the plasma membrane to the other.
Transport Proteins
each transport protein binds to and transports only a certain type of molecule or ion
Specificity
result of molecules with similar shape binding to the transport protein
Competition
the rate of movement of molecules across the membrane is limited by the number of available transport proteins
Saturation
three major classes of transport proteins
channel proteins
carrier proteins
ATP-powered pumps
or nongated ion channels, are
always open and are responsible for the plasma membrane’s permeability to ions when the plasma membrane is at rest.
Leak ion channels
one or more integral membrane proteins
arranged so that they form a tiny channel through the plasma
membrane (
channel proteins
open and close depending on certain conditions of the cell.
Gated ion channels
a generic term for any chemical signal molecule used by cells to communicate with each other
Ligand
ion channels that respond to
these signals
ligand-gated ion channels
open or close when there is a change in the membrane potential.
voltage-gated ion channels
a genetic disorder
that affects chloride ion channels
Cystic fibrosis
or transporters, are integral membrane proteins
that move ions or molecules from one side of the plasma membrane to the other. S
Carrier Proteins
movement of one specific ion or
molecule across the membrane.
Uniport
movement of two different ions or molecules in the same direction across
the plasma membrane,
Symport
movement of two different ions or molecules in opposite directions
across the plasma membrane
antiport
transport proteins that require cellular
energy to move specific ions or molecules from one side of the plasma membrane to the other.
ATP-powered pumps
membrane proteins or glycoproteins that
have an exposed receptor site on the outer cell surface.
Receptor Proteins
catalyze chemical reactions on either the inner or the outer surface of the
plasma membrane.
enzymes
he plasma membrane separates extracellular material from intracellular material and is __
selectively permeable (allows
only certain substances to pass through it.)
Transport mechanisms (3)
Passive Transport Mechanisms
Active Transport Mechanisms
Vesicular Transport
the cell does not expend metabolic energy.
passive membrane
transport
does require the cell to expend metabolic energy
Active membrane transport
Passive membrane transport (3)
diffusion
osmosis
facilitated diffusion
Random movement of molecules results in
net movement from areas of higher
to lower concentration
Diffusion
Water diffuses across a selectively
permeable membrane.
Osmosis
Water diffuses through the lipid
bilayer.
osmosis
Substances too large to pass
through channels and too polar to
dissolve in the lipid bilayer are transported; substances that are accumulated in concentrations higher on
one side of the membrane than on
the other are transported.
Active transport
TP-powered pumps combine with substances and move them across the plasma
membrane: ATP is used; substances can be
moved from areas of lower to higher concentration
Active transport
Ions are moved across the plasma membrane by active transport, which establishes
an ion concentration gradient; ATP is
required; ions then move back down their
concentration gradient by facilitated diffusion, and another ion or molecule moves
with the diffusion ion (symport) or in the
opposite direction (antiport).
Secondary
active transpor
Ions are moved across the plasma membrane by active transport, which establishes
an ion concentration gradient; ATP is
required; ions then move back down their
concentration gradient by facilitated diffusion, and another ion or molecule moves
with the diffusion ion (symport) or in the
opposite direction (antiport).
Secondary
active transport
movement of
solutes from an area of higher solute concentration to an area of
lower solute concentration
Diffusion
The concentration difference between
two points, divided by the distance between the two points, is called
concentration gradient
measure of a
fluid’s resistance to flow
Viscosity
diffusion of water (solvent) across a
selectively permeable membrane, such as a plasma membrane
osmosis
water channel proteins, that open and close to
adjust membrane permeability to water.
aquaporins
force required to prevent water from
moving by osmosis across a selectively permeable membrane.
Osmotic pressure
three osmotic pressures
isosmotic
hyperosmotic
hyposmotic
Solutions with the same concentration of solute particles have the same osmotic pressure
isosmotic
If one solution has a greater concentration of solute particles, and
therefore, a greater osmotic pressure than another solution
hyperosmotic
The more dilute solution, with the
lower osmotic pressure
hyposmotic
a cell placed
into a solution neither shrinks nor swells, the solution is said to be
isotonic
the shape of the cell
remains constant maintaining its internal tension or tone, a condition called tonicity
isotonic
If a cell is placed into a solution and
water moves out of the cell by osmosis, causing the cell to shrink,
the solution
hypertonic
If a cell is placed
into a solution and water moves into the cell by osmosis, causing the
cell to swell
hypotonic
refer to the concentration of the solutions
-osmotic terms
refer to the tendency of cells to swell or shrink
-tonic terms
membrane transport proteins mediate, or assist, the movement of large, water-soluble
molecules or electrically charged molecules or ions across the plasma membrane
mediated transport
mediated transport process that moves
substances into or out of cells from a higher to a lower concentration
Facilitated diffusion
proteins that carry out facilitated diffusion
Carrier proteins and channel proteins
does not require metabolic
energy to transport substances across the plasma membrane.
Facilitated diffusion
mediated transport process that requires
energy provided by ATP
Active transport
moves Na+ out of cells and K+ into cells
sodium-potassium (Na+–K+) pump
The result is a higher concentration of Na+ outside the cell and a higher concentration of K+inside the cell.
sodium-potassium (Na+–K+) pump
Because ATP is broken down
during the transport of Na+ and K+, the pump is
also called
sodium-potassium ATP-ase
involves the active
transport of an ion, such as sodium, out of a cell, establishing a concentration gradient, with a higher concentration of the ions outside the cell.
Secondary active transport
movement of larger volumes of substances across the plasma membrane through the formation or release of vesicles, membrane-bound sacs, in the cytoplasm.
Vesicular Transpor
Secondary Active Transport: occurs when material moves through the plasma membrane and into the cytoplasm by the formation of a vesicle.
Endocytosis
two types of endocytosis:
phagocytosis and pinocytosis
cell-eating
phagocytosis
cell-drinking
Pinocytosis
often forms vesicles near the tips
of deep invaginations of the plasma membrane.
Pinocytosis
important in eliminating harmful substances from the body
phagocytosis
The plasma membrane may contain specific receptor molecules that recognize certain substances and allow them to be transported into the cell by phagocytosis or pinocytosis. This
is called
receptor-mediated endocytosis,
Common genetic disorder characterized by the reduction in or absence of low-density lipoprotein (LDL) receptors on cell surfaces, which interferes with the receptor-mediated endocytosis of LDL cholesterol.
Hypercholesterolemia
cells release material through a vesicular transport mechanism called
exocytosis (secretions accumulate within vesicles)
the cellular material outside the nucleus but inside the plasma membrane
Cytoplasm
half cytosol and half organelles
Cytoplasm
fluid portion of the cytoplasm
cytosol
a colloid, a viscous solution containing dissolved ions and molecules as well as suspended molecules, especially
proteins.
cytosol
supports the cell and holds the nucleus and other organelles in place.
cytoskeleton
The cytoskeleton consists of three groups of
proteins:
microtubules
actin filaments
intermediate filaments
hollow tubes composed primarily of protein
units called tubulin
microtubules
provide support and structure
to the cytoplasm of the cell
microtubules
also called microfilaments
actin filaments
involved in cell division and in the transport of intracellular materials, form essential components such as centrioles, spindle fibers, cilia, and flagella.
microtubules
provide structure to the cytoplasm and
mechanical support for microvilli.
actin filaments
protein fibers that provide mechanical strength to cell
Intermediate filaments
aggregates of chemicals either produced or taken in by the cell.
cytoplasmic inclusions
pigments that increase in amount with age.
lipochromes
lose their nuclei as they develop
red blood cells,
contain more than one nucleus
skeletal muscle cells and osteoclasts
surrounded by a
nuclear envelope
nucleoplasm
composed of two membranes separated by a space.
nuclear envelope
inner and outer membranes
fuse to form pore like structures called
nuclear pores
organized into discrete structures called
chromosomes
DNA and associated proteins
important for the structural
organization of DNA
histones
During most of the cell’s life cycle, the chromosomes are dispersed throughout the nucleus as delicate filaments collectively referred to as
chromatin
can leave the nucleus through
nuclear pores.
ribonucleic acid (RNA)
a region of a
DNA molecule that specifies an RNA molecule
gene
a dense region within the
nucleus
nucleolus
ribosomal subunits consist of
ribosomal RNA (rRNA) (produced
in the nucleolus of the nucleus and proteins produced in the cytoplasm)
primarily synthesize proteins used inside the cell
Free ribosomes
produce integral membrane proteins
and proteins that are secreted from the cell.
ribosomes attached
to the endoplasmic reticulum
consists of broad,
flattened, interconnecting sacs and tubules
endoplasmic
reticulum
interior spaces of those sacs and tubules which are isolated from the rest of the cytoplasm
cisternae
called “rough” because
ribosomes are attached to it
rough endoplasmic reticulum
sites where proteins are produced and modified
for use as integral membrane proteins and for secretion into the extracellular space.
ribosomes of the rough endoplasmic reticulum
endoplasmic reticulum without attached ribosomes, that manufactures lipids, such
as phospholipids, cholesterol, and steroid hormones, as well as carbohydrates.
Smooth endoplasmic reticulum
also participates in detoxification
Smooth endoplasmic reticulum
processes by which enzymes act on chemicals and drugs to change their structure and reduce their toxicity.
detoxification
composed of flattened, membranous sacs, containing cisternae, stacked on each other like
dinner plates
Golgi Apparatus
Proteins produced at the ribosomes attached to the rough endoplasmic reticulum move into the endoplasmic reticulum that are later packed into __ that then move to the Golgi apparatus.
transport vesicles
most highly developed in cells that
secrete large amounts of protein or glycoproteins, such as cells in
the salivary glands and the pancreas.
Golgi apparatus
membrane-bound vesicles that form
at the Golgi apparatus
Lysosomes
contain a variety of
hydrolytic enzymes that function as intracellular digestive systems.
Lysosomes
Lysosomes also digest the organelles of the cell that are no longer functional, a process called
autophagy
membrane-bound vesicles that
are smaller than lysosomes.
Peroxisomes
contain the enzyme catalase, which breaks down hydrogen peroxide to water and oxygen thereby eliminating the
toxic substance.
Peroxisomes
large protein complexes containing enzymes that break down and recycle other proteins within the
cell.
Proteasomes
pinch off from the Golgi apparatus move to the surface of the cell, their membranes fuse with the plasma membrane, and the contents of the
vesicles are released to the exterior by exocytosis.
secretory vesicles
organelles that provide
the majority of the energy for the cell.
Mitochondria
The outer membrane has a smooth contour, but the inner membrane has numerous infoldings called
cristae
The material located inside the inner membrane is called the
matrix
also contain DNA and ribosomes.
Mitochondria
specialized zone of cytoplasm
close to the nucleus, is the center of microtubule formation in the
cell.
centrosome
structures that project from the surface of cells
and are capable of movement.
Cilia
proteins connecting adjacent pairs of microtubules
Dynein arms
(a modified centriole) is located in
the cytoplasm at the base of the cilium
basal body
are the only human cells that
possess flagella, and usually only one flagellum exists per cell.
Sperm cells
similar to that of cilia, but
they are longer
flagella
move small particles across the cell
surface
cilia
move the entire cell
flagella
cylindrically shaped
extensions of the plasma membrane
Microvilli
are found on the cells of the
intestine, kidney, and other areas where absorption is an important
function.
Microvilli
functional units of heredity
gene
the transmission of genetic traits from parent to offspring.
heredity
The production of RNA and/or proteins from the information stored in DNA
gene expression
Gene expression
that produces proteins involves two steps:
transcription and translation
cell makes a copy of the gene necessary to make a particular protein
transcription
The copy, which is called mRNA,
travels from the nucleus to ribosomes (the kitchen) in the cytoplasm, where the information in the copy is used to construct a protein
translation
Specialized transport molecules that carry the amino acids to the ribosomes
transfer RNA (tRNA)
synthesis of mRNA, tRNA, and rRNA molecules based on the nucleotide sequence in DNA
transcription
occurs when a section of a DNA molecule unwinds and its complementary strands separate.
transcription
an enzyme that synthesizes the complementary RNA molecule from DNA
RNA polymerase
signals the beginning of the
gene and is the site for initial RNA polymerase binding
promoter
Regions of the mRNA that do code for proteins a
exons
regions that do not code for a
protein
introns
mRNA that contains introns
pre-mRNA
various combinations
of exons are incorporated into mRNA.
alternative splicing
information contained in mRNA and it
relates the nucleotide sequence of mRNA to the amino acid sequence
of a protein.
Genetic Code
three nucleotides
sequences
codons
How many possible codons exist?
64
acts as a start codon
AUG
act as stop
codons
UAA
UGA
UAG
synthesis of a protein at the ribosome based on the sequence of the codons of mRNA
Translation
Another part of the tRNA consists of three nucleotides and is complementary to a particular codon of mRNA.
anticodon
efficient way to produce many copies of the same protein using a single mRNA molecule
polyribosomes
proteins are longer when they are first made than in their final, functional state.
proproteins
Many proteins are enzymes, and the proproteins of those enzymes are
called
proenzymes
includes the changes a cell undergoes from the
time it is formed until it divides to produce two new cells.
cell life cycle
The life cycle of a cell has two stages:
interphase and cell division
includes mitosis, the division of the
nucleus, and cytokinesis, the division of the cytoplasm
Cell division
phase between cell divisions; nearly all of the
life cycle of a typical cell is spent in interphase.
Interphase
he cell carries out the metabolic activities necessary for life and performs its specialized functions—for example, secreting digestive
enzymes
Interphase
Interphase can be divided into three subphases:
G1
S
G2
the cell carries out routine
metabolic activities
G1
(the synthesis phase), the
DNA is replicated (new DNA is synthesized).
S phase
(the second gap phase), the cell prepares for cell division.
G2
These “resting” cells do not follow the normal pattern of the cell cycle but instead enter what is called the __ phase, in which they remain
unless stimulated to divide
G0
the process in which the two strands of a DNA
molecule each serve as the template for making complementary new strands of nucleotides.
DNA Replication
an enzyme that adds new nucleotides to the 3′ end of the growing strands.
DNA
polymerase
forms as a continuous strand
leading strand
forms in short segments
called Okazaki fragments
lagging strand
The Okazaki fragments are then spliced
by
DNA ligase
produces the new cells necessary for growth and tissue repair.
Cell Division
Cell division involves two major events:
division of the chromosomes into two new nuclei and division of the cytoplasm
to form two new cells, each of which contains one of the newly
formed nuclei.
The nuclear events are called
mitosis
the cytoplasmic division is called
cytokinesis
the division of a cell’s nucleus into two new
nuclei, each containing the same amount and type of DNA as the
original nucleus.
Mitosis
During mitosis, the chromatin becomes very
densely coiled to form compact chromosomes called
mitotic chromosomes
Each copy is called a
chromatid
The chromatids are attached at the
centromere
a protein structure that binds the centromere and provides a point of
attachment for microtubules that will separate and move the chromatids during mitosis.
kinetochore
Mitosis is divided into four phases:
prophase
metaphase
anaphase
telophase
he chromatin condenses
to form mitotic chromosomes.
prophase
Also, the centrioles in the cytoplasm divide and migrate to each pole of the cell
prophase
Microtubules called spindle fibers extend from
the centrioles to the centromeres of the chromosomes.
prophase
the chromosomes align
near the center of the cell.
metaphase
the chromatids separate. At this point, one of the two identical sets of chromosomes is moved by the spindle fibers toward the centrioles at each of the poles of the cell. At the end of anaphase, each set of chromosomes has reached an opposite pole of the
cell, and the cytoplasm begins to divide
anaphase
nuclear envelopes
form around each set of chromosomes to form two separate nuclei. The chromosomes begin to uncoil and resemble the genetic material characteristic of interphase.
telophase
the division of the cell’s cytoplasm
to produce two new cells.
Cytokinesis
The first sign of cytokinesis is the formation of a
cleavage furrow
complete when the membranes of the halves separate at the cleavage furrow to form two separate cells.
Cytokinesis
programmed cell death, is a normal
process by which cell number within various tissues is adjusted
and controlled.
Apoptosis
