The cell Flashcards
1
Q
How do you see specimens in a light microscope?
A
In a light microscope (LM), visible
light is passed through the specimen and then through
glass lenses. The lenses refract (bend) the light in such a way
that the image of the specimen is magnified as it is projected
into the eye or into a camera
2
Q
What is magnification?
A
Magnification is the ratio of
an object’s image size to its real size.
3
Q
What is resolution?
A
Resolution is a measure of the clarity
of the image; it is the minimum distance two points can be
separated and still be distinguished as separate points.
4
Q
What is contrast?
A
The third
parameter, contrast, is the difference in brightness between
the light and dark areas of an image.
5
Q
What are organelles?
A
organelles, the membrane-enclosed structures within eukaryotic
cells.
6
Q
What does the electron microscope do?
A
electron microscope (EM) focuses a beam of electrons
through the specimen or onto its surface
7
Q
What does the scanning electron microscope do?
A
The scanning electron microscope (SEM) is especially
useful for detailed study of the topography of a specimen. The electron beam scans the surface of the sample,
usually coated with a thin film of gold. The beam excites electrons on the surface, and these secondary electrons are
detected by a device that translates the pattern of electrons into
an electronic signal sent to a video screen. The result is an image
of the specimen’s surface that appears three-dimensional.
8
Q
What does the transmission electron microscope do?
A
The transmission electron microscope (TEM) is used
to study the internal structure of cells (see Figure 6.3). The
TEM aims an electron beam through a very thin section of the
specimen, much as a light microscope aims light through a
sample on a slide. For the TEM, the specimen has been stained
with atoms of heavy metals, which attach to certain cellular
structures, thus enhancing the electron density of some parts
of the cell more than others. The electrons passing through
the specimen are scattered more in the denser regions, so fewer
are transmitted. The image displays the pattern of transmitted
electrons.
9
Q
What do SEMs and TEMs use as lenses?
A
Instead of using glass lenses, both the SEM and TEM
use electromagnets as lenses to bend the paths of the electrons,
ultimately focusing the image onto a monitor for viewing.
10
Q
What is cryo-electron microscopy (cryo-EM)?
A
A recently developed new type of TEM called cryo-electron
microscopy (cryo-EM) (see Figure 6.3) allows specimens to be
preserved at extremely low temperatures. This avoids the use
of preservatives, allowing visualization of structures in their
cellular environment. This method is increasingly used to
complement X-ray crystallography in revealing protein complexes
and subcellular structures like ribosomes
11
Q
What is cytology?
A
the
study of cell structure.
12
Q
What is cell fractionation?
A
which takes cells apart and separates major organelles and other subcellular structures
from one another.
13
Q
What does the centrifuge do?
A
which spins test tubes holding
mixtures of disrupted cells at a series of increasing speeds,
a process called differential centrifugation.
14
Q
What do speeds correlate with the cells during differential centrifugation?
A
At each speed, the
resulting force causes a subset of the cell components to
settle to the bottom of the tube, forming a pellet. At lower
speeds, the pellet consists of larger components, and higher
speeds result in a pellet with smaller components.
15
Q
What are cells?
A
Cells—the basic structural and functional units of every
organism
16
Q
What are the 2 types of cells?
A
prokaryotic and eukaryotic.
17
Q
What do most cells have between the groups?
A
They are all bounded by a
selective barrier, called the plasma membrane (or the cell membrane).
Inside all cells is a semifluid, jellylike substance called
cytosol, in which subcellular components are suspended. All
cells contain chromosomes, which carry genes in the form of
DNA. And all cells have ribosomes, tiny complexes that make
proteins according to instructions from the genes.
18
Q
Where is DNA located in eukaryotic cells?
A
In a eukaryotic cell,
most of the DNA is in an organelle called the nucleus, which
is bounded by a double membrane
19
Q
Where is DNA located in prokaryotic cells?
A
In a
prokaryotic cell, the DNA is concentrated in a region that
is not membrane-enclosed, called the nucleoid
20
Q
What does eukrayotic and prokaryotic mean?
A
Eukaryotic means “true nucleus” (from the Greek eu, true,
and karyon, kernel, referring to the nucleus), and prokaryotic
means “before nucleus” (from the Greek pro, before), reflecting
the earlier evolution of prokaryotic cells.
21
Q
What is cytoplasm?
A
The interior of either type of cell is called the cytoplasm;
in eukaryotic cells, this term refers only to the region between
the nucleus and the plasma membrane.
22
Q
What are mycoplasmas?
A
the
smallest cells known are bacteria called mycoplasmas, which
have diameters between 0.1 and 1.0 μm.
23
Q
What is the plasma membrane?
A
the plasma membrane functions as a selective
barrier that allows passage of enough oxygen, nutrients, and
wastes to service the entire cell
24
Q
Do larger organisms have larger cells than smaller organisms?
A
Larger organisms do not generally have larger cells than
smaller organisms—they simply have more cells
25
What is the flagellum (in animal cells) (diagram)
motility
structure present in
some animal cells,
composed of a cluster of
microtubules within an
extension of the plasma
membrane
26
What is the centrosome? (diagram)
region
where the cell’s
microtubules are
initiated; contains a
pair of centrioles
27
What is the cytoskeleton? (diagram)
reinforces cell’s shape;
functions in cell movement;
components are made of
protein. Includes: Microfilaments
Intermediate
filaments
Microtubules
28
What is microvilli? (diagram)
membrane
projections that
increase the cell’s
surface area
29
What is peroxisome? (diagram)
organelle with
various specialized metabolic
functions; produces hydrogen
peroxide as a by-product and
then converts it to water
30
What is the mitochondrion? (diagram)
organelle where
cellular respiration occurs and
most ATP is generated
31
What is a lysosome? (diagram)
digestive
organelle where
macromolecules are
hydrolyzed
32
What is the golgi apparatus? (diagram)
organelle active
in synthesis, modification, sorting,
and secretion of cell products
33
What are ribosomes? (diagram)
(small brown
dots): complexes that
make proteins; free in
cytosol or bound to
rough ER or nuclear
envelope
34
What is the plasma membrane again? (diagram)
membrane
enclosing the cell
35
What are the three parts of a nucleus? (diagram)
Nuclear envelope, nucleolus, chromatin
36
What is a nuclear envelope (diagram)
double
membrane enclosing the
nucleus; perforated by
pores; continuous with ER
37
What is the nucleolus? (diagram)
nonmembranous
structure involved in production
of ribosomes; a nucleus has
one or more nucleoli
38
What is chromatin? (diagram)
material consisting
of DNA and proteins; visible in
a dividing cell as individual
condensed chromosomes
39
What is endoplasmic reticulum (diagram)
material consisting
of DNA and proteins; visible in
a dividing cell as individual
condensed chromosomes
40
What are the 2 types of ER (diagram)
Rough ER Smooth ER
41
What is the cell wall? (diagram)
outer layer that maintains
cell’s shape and protects cell from
mechanical damage; made of cellulose,
other polysaccharides, and protein
42
What is plasmodesmata? (diagram)
cytoplasmic
channels through cell walls
that connect the cytoplasms
of adjacent cells
43
What is a chloroplast? (diagram)
photosynthetic
organelle; converts energy of
sunlight to chemical energy
stored in sugar molecules
44
What does the nuclear envelope do?
The nuclear envelope encloses
the nucleus (Figure 6.9), separating its contents
from the cytoplasm.
45
Where are genes located in eukaryotic cells?
The nucleus contains most of the genes in the
eukaryotic cell. (Some genes are located in
mitochondria and chloroplasts.)
46
What does the nuclear envelope contain (specify a description on pores)?
The nuclear envelope is a double membrane.
The two membranes, each a lipid
bilayer with associated proteins, are separated
by a space of 20–40 nm. The envelope is perforated
by pore structures that are about 100 nm in diameter. At
the lip of each pore, the inner and outer membranes of
the nuclear envelope are continuous.
47
What is the nuclear lamina?
the nuclear side of the
envelope is lined by the nuclear lamina, a netlike array
of protein filaments (in animal cells, called intermediate filaments)
that maintains the shape of the nucleus by mechanically
supporting the nuclear envelope.
48
What is the nuclear matrix and what does the lamina do together?
There is also much
evidence for a nuclear matrix, a framework of protein fibers
extending throughout the nuclear interior. The nuclear
lamina and matrix may help organize the genetic material
so it functions efficiently.
49
What are chromosomes?
structures that carry the genetic
information.
50
What are small basic proteins?
histones
51
What is chromatin?
The complex of DNA
and proteins making up chromosomes is called chromatin.
52
How many chromosomes does a typical human have (including gametes)?
For example, a typical
human cell has 46 chromosomes in its nucleus; the exceptions
are human sex cells (eggs and sperm), which have only
23 chromosomes.
53
What is a nucleolus?
A prominent structure within the nondividing nucleus is
the nucleolus (plural, nucleoli), which appears through the
electron microscope as a mass of densely stained granules
and fibers adjoining part of the chromatin.
54
What happens in a nucleolus, how are ribosomes formed?
Also in the nucleolus,
proteins imported from the cytoplasm
are assembled with rRNA into large and
small subunits of ribosomes. These subunits
then exit the nucleus through the
nuclear pores to the cytoplasm, where a
large and a small subunit can assemble
into a ribosome.
55
How is the mRNA formed and what does it do for the body?
the nucleus directs
protein synthesis by synthesizing messenger RNA (mRNA)
that carries information from the DNA. The mRNA is then
transported to the cytoplasm via nuclear pores. Once an
mRNA molecule reaches the cytoplasm, ribosomes translate
the mRNA’s genetic message into the primary structure of a
specific polypeptide.
56
What are ribosomes?
Ribosomes, which are complexes made of ribosomal RNAs
and proteins, are the cellular components that carry out
protein synthesis (they are also not considered as organelles)
57
Where do ribosomes make their proteins?
Ribosomes build proteins in two cytoplasmic regions:
At any given time, free ribosomes are suspended in the cytosol,
while bound ribosomes are attached to the outside of the
endoplasmic reticulum or nuclear envelope
58
What does the endomembrane system include?
endomembrane system,
which includes the nuclear envelope, the endoplasmic reticulum,
the Golgi apparatus, lysosomes, various kinds of vesicles
and vacuoles, and the plasma membrane.
59
What does the endomembrane system do?
This system carries
out a variety of tasks in the cell, including synthesis of proteins,
transport of proteins into membranes and organelles
or out of the cell, metabolism and movement of lipids, and
detoxification of poisons.
60
How are the membranes related to eachother in the endomembrane system?
The membranes of this system are
related either through direct physical continuity or by the
transfer of membrane segments as tiny vesicles (sacs made
of membrane).
61
What is the endoplasmic reticulum?
The endoplasmic reticulum (ER) is such an extensive
network of membranes that it accounts for more than half
the total membrane in many eukaryotic cells.
62
What does endoplasmic and reticulum mean?
The word
endoplasmic means “within the cytoplasm,” and reticulum is
Latin for “little net.”)
63
What is in the endoplasmic reticulum of cells?
The ER consists of a network of membranous
tubules and sacs called cisternae
64
What is the ER membrane and ER lumen, what do they do?
The ER membrane separates
the internal compartment of the ER, called the ER lumen
(cavity) or cisternal space, from the cytosol.
65
What are enzymes in the smooth ER helpful for (fatty acid wise)
Enzymes of the smooth ER are important in the synthesis
of lipids, including oils, steroids, and new membrane phospholipids.
66
What are enzymes,es in the smooth ER helpful for (poison-wise)
Other enzymes of the smooth ER help detoxify drugs
and poisons, especially in liver cells. Detoxification usually
involves adding hydroxyl groups to drug molecules, making
them more water-soluble and easier to flush from the
body.
67
What does calcium ions stored in smooth ER do in muscle and regular cells?
The smooth ER also stores calcium ions. In muscle cells, for
example, the smooth ER membrane pumps calcium ions from
the cytosol into the ER lumen. When a muscle cell is stimulated
by a nerve impulse, calcium ions rush back across the
ER membrane into the cytosol and trigger contraction of the
muscle cell. In other cell types, release of calcium ions from
the smooth ER triggers different responses, such as secretion
of vesicles carrying newly synthesized proteins.
68
How do primary proteins become secondary through ER?
As a polypeptide chain
grows from a bound ribosome, the chain is threaded into
the ER lumen through a pore formed by a protein complex
in the ER membrane. The new polypeptide folds into its
functional shape as it enters the ER lumen.
69
What are glycoproteins?
Most secretory
proteins are glycoproteins, proteins with carbohydrates
covalently bonded to them.
70
How are carbohydrates attached to proteins?
The carbohydrates are attached
to the proteins in the ER lumen by enzymes built into the
ER membrane.
71
What are transport vesicles?
Vesicles in transit from one part of the cell
to another are called transport vesicles
72
What can we think the golgi apparatus as?
We can think of the Golgi as a warehouse
for receiving, sorting, shipping, and even some manufacturing.
73
What is cisternae
flattened
membranous sacs—cisternae
74
What are the sides of the golgi apparatus called?
The two sides
of a Golgi stack are referred to as the cis face and the trans face;
these act, respectively, as the receiving and shipping departments
of the Golgi apparatus.
75
What does cis mean?
The term cis means “on the same
side,” and the cis face is usually located near the ER.
76
How do transport vesicles deposit their materials?
Transport
vesicles move material from the ER to the Golgi apparatus. A
vesicle that buds from the ER can add its membrane and the
contents of its lumen to the cis face by fusing with a Golgi
membrane on that side.
77
What does the trans face of the golgi do?
The trans face (“on the opposite side”)
gives rise to vesicles that pinch off and travel to other sites.
78
What does the golgi apparatus do to materials when they enter from the endoplasmic reticulum?
Products of the endoplasmic reticulum are usually modified
during their transit from the cis region to the trans region
of the Golgi apparatus. For example, glycoproteins formed
in the ER have their carbohydrates modified, first in the ER
itself, and then as they pass through the Golgi.
79
Does the golgi apparatus secrete macromolecules, give an example
the Golgi apparatus also
manufactures some macromolecules. Many polysaccharides
secreted by cells are Golgi products.
80
What is a lysosome?
A lysosome is a membranous sac of hydrolytic enzymes that
many eukaryotic cells use to digest (hydrolyze) macromolecules.
81
Where are hydrolytic enzymes formed?
Hydrolytic enzymes and lysosomal membrane are made
by rough ER and then transferred to the Golgi apparatus for
further processing.
82
What is phagocytosis?
Amoebas and many other unicellular protists
eat by engulfing smaller organisms or food particles,
a process called phagocytosis
83
What is autophagy?
Lysosomes also use their hydrolytic enzymes to recycle the
cell’s own organic material, a process called autophagy. During
autophagy, a damaged organelle or small amount of cytosol
becomes surrounded by a double membrane (of unknown
origin), and a lysosome fuses with the outer membrane of this
vesicle
84
What are vacuoles?
Vacuoles are large vesicles derived from the endoplasmic
reticulum and Golgi apparatus.
85
What are contractile vacuoles?
Many unicellular
protists living in fresh water have contractile vacuoles that
pump excess water out of the cell, thereby maintaining a suitable
concentration of ions and molecules inside the cell
86
What are food vacuoles?
Food vacuoles are membrane-bound sacs found in certain cells, primarily in unicellular organisms like amoebas. They serve as the cell's intracellular "stomach," responsible for digesting food particles.
87
How is a large central vacuole formed?
Mature plant cells generally contain a large central
vacuole, which develops by the coalescence
of smaller vacuoles.
88
What is the solution inside the central vacuole?
The solution inside the central vacuole,
called cell sap, is the plant cell’s main repository of inorganic
ions, including potassium and chloride.
89
What are the organelles in eukaryotic cells that convert energy to forms that cells can use for work?
In eukaryotic cells, mitochondria and
chloroplasts are the organelles that convert energy to forms
that cells can use for work.
90
What are mitochondria (mention singular form)
Mitochondria (singular,
mitochondrion) are the sites of cellular respiration, the metabolic
process that uses oxygen to drive the generation of
ATP by extracting energy from sugars, fats, and other fuels.
91
What are chloroplasts? and how do they use energy to support their cell?
Chloroplasts, found in plants and algae, are the sites of
photosynthesis. This process in chloroplasts converts solar
energy to chemical energy by absorbing sunlight and using
it to drive the synthesis of organic compounds such as sugars
from carbon dioxide and water.
92
What is the peroxisome
an oxidative organelle.
93
How much mitochondria is present in cells?
Some
cells have a single large mitochondrion, but more often a
cell has hundreds or even thousands of mitochondria, number correlates with the cell’s level of metabolic activity.
94
Describe the membranes of mitochondria
Each of the two membranes enclosing the mitochondrion
is a phospholipid bilayer with a unique collection of
embedded proteins. The outer membrane is smooth, but
the inner membrane is convoluted, with infoldings called
cristae
95
What is the intermembrane space of mitochondrions?
The inner membrane divides the
mitochondrion into two internal compartments. The first
is the intermembrane space, the narrow region between the
inner and outer membranes.
96
What is the mitochondrial matrix?
The second compartment, the
mitochondrial matrix, is enclosed by the inner membrane.
The matrix contains many different enzymes as well
as the mitochondrial DNA and ribosomes.
97
How is the content of a chloroplast divided?
The contents of a chloroplast are partitioned from the
cytosol by an envelope consisting of two membranes separated
by a very narrow intermembrane space.
98
What are thylakoids?
Inside the
chloroplast is another membranous system in the form of
flattened, interconnected sacs called thylakoids.
99
What is a granum?
In some
regions, thylakoids are stacked like poker chips; each stack is
called a granum
100
What is the stroma?
The fluid outside the thylakoids
is the stroma, which contains the chloroplast DNA
and ribosomes as well as many enzymes.
101
What is a peroxisome?
The peroxisome is a specialized metabolic compartment
bounded by a single membrane (Figure 6.19). Peroxisomes
contain enzymes that remove hydrogen atoms from various
substrates and transfer them to oxygen (O2), producing
hydrogen peroxide (H2O2) as a by-product (from which
the organelle derives its name).
102
How are peroxisomes used for cellular respiration?
Some peroxisomes use oxygen to break
fatty acids down into smaller molecules that are transported
to mitochondria and used as fuel for cellular respiration.
103
How are peroxisomes helpful for detoxification?
Peroxisomes in the liver detoxify alcohol and other harmful
compounds by transferring hydrogen from the poisonous
compounds to oxygen.
104
What are glyoxysomes and where are they found?
Specialized peroxisomes called glyoxysomes are found
in the fat-storing tissues of plant seeds. These organelles
contain enzymes that initiate the conversion of fatty acids
to sugar
105
What is the cytoskeleton?
cytoskeleton, a network of fibers
extending throughout the cytoplasm
106
Main function for the cytoskeleton?
The most obvious function of the cytoskeleton is to give
mechanical support to the cell and maintain its shape.
107
What is cell motility?
The term cell motility includes both changes in cell location and movements of cell parts.
108
What does cell motility need for it to occur?
Cell motility generally
requires interaction of the cytoskeleton with motor proteins.
109
What are the three fibers that make up the cytoskeleton?
Microtubules are the thickest of
the three types; microfilaments (also called actin filaments) are
the thinnest; and intermediate filaments are fibers with diameters
in a middle range
110
What are microtubles?
microtubules, hollow rods
constructed from globular proteins called tubulins.
111
What is a tubulin protein and a dimer?
Each
tubulin protein is a dimer, a molecule made up of two components.
112
What is a tubulin dimer?
tubulin dimer consists of two slightly different
polypeptides, α-tubulin and β-tubulin.
113
Do microtubules guide vesicles? From where?
microtubules
guide vesicles from the ER to the Golgi apparatus and
from the Golgi to the plasma membrane.
114
Where do microtubules grow out from?
In animal cells, microtubules
grow out from a centrosome
115
What is a centrosome?
a region that is often
located near the nucleus.
116
What consists in a centrosome and what are centrioles?
Within the
centrosome is a pair of centrioles, each composed of nine
sets of triplet microtubules arranged in a ring
117
What are microfilaments and actin?
Microfilaments are thin solid rods. They are also called
actin filaments because they are built from molecules of
actin, a globular protein.
118
What are cortical microfilaments?
Cortical microfilaments, primarily composed of actin, are essential components of the cell cytoskeleton. They provide structural support, enabling cells to maintain their shape and withstand mechanical stress.
119
What is cytoplasmic streaming?
cytoplasmic streaming, a circular
flow of cytoplasm within cells
120
What are intermediate filaments?
Intermediate filaments are named for their diameter,
which is larger than the diameter of microfilaments but
smaller than that of microtubules
121
Are intermediate filaments found in all organisms?
intermediate filaments are only found in the
cells of some animals, including vertebrates.
122
What is the cell wall?
The cell wall is an extracellular structure of plant cells
(Figure 6.27). The wall protects the plant
cell, maintains its shape, and prevents excessive uptake of
water.
123
What is the primary cell wall?
A young plant cell first secretes a relatively thin and
flexible wall called the primary cell wall
124
Where is the middle lamena and what is it? What are pectins?
Between primary walls of
adjacent cells is the middle lamella, a thin layer rich in
sticky polysaccharides called pectins.
125
What is the secondary wall?
The secondary wall, often deposited in several laminated
layers, has a strong and durable matrix that affords
the cell protection and support.
126
What do animals have to replace cell walls?
Although animal cells lack walls akin to those of plant
cells, they do have an elaborate extracellular matrix
(ECM).
127
What are the main ingredients for extracellular matrix?
The main ingredients of the ECM are glycoproteins
and other carbohydrate-containing molecules secreted
by the cells.
128
What is the most abundant glycoprotein in the extracellular matrix?
The most abundant
glycoprotein in the ECM of most animal cells is collagen,
which forms strong fibers outside the cells
129
What does a proteoglycan molecule consist of?
A proteoglycan molecule consists of a
small core protein with many carbohydrate chains covalently
attached, so that it may be up to 95% carbohydrate.
130
What is fibronectin?
Fibronectin is one
ECM protein that
attaches the ECM
to integrins
embedded in
the plasma
membrane. It helps to connect cells together
131
What is fibronectin?
Fibronectin is one
ECM protein that
attaches the ECM
to integrins
embedded in
the plasma
membrane. It helps to connect cells together
132
What is plasmodesmata, where are they found?
many plant cell walls are perforated with
plasmodesmata channels that connect cells.
133
How do macromolecules from neighboring cells be transported between each other?
The macromolecules transported to neighboring
cells appear to reach the plasmodesmata by moving
along fibers of the cytoskeleton.
134
What are the 3 main types of cell junctions?
In animals, there are three main types of cell junctions: tight
junctions, desmosomes, and gap junctions.
135
What are tight junctions?
At tight junctions, the plasma
membranes of neighboring cells are
very tightly pressed against each
other, bound together by specific
proteins.
136
What are desmosomes?
Desmosomes are specialized cell structures that function like rivets, holding cells together in tissues that experience significant mechanical stress. They form strong connections between cells, anchoring them together and providing structural support.
137
What are gap junctions?
Gap junctions provide
cytoplasmic channels from one
cell to an adjacent cell.
138
What is cellular order?
Cellular functions arise from cellular order: The cell is a
living unit greater than the sum of its parts.
139
Exocytosis?
Exocytosis: Large molecules
are secreted when
a vesicle fuses
with the plasma
membrane.
140
Endocytosis
Endocytosis: Large
molecules are
taken in when
the plasma
membrane pinches
inward, forming a vesicle.
141
What are the three main ingredients for membranes?
Lipids and proteins are the staple ingredients of membranes,
although carbohydrates are also important.
142
What is an amphipathic molecule? Are phospholipids one?
A phospholipid is an amphipathic molecule, meaning
it has both a hydrophilic (“water-loving”) region and a hydrophobic
(“water-fearing”)
143
Are proteins randomly distributed in cell membranes?
Groups of proteins are often associated in
long-lasting, specialized patches, where they carry out common
functions.
144
How are membranes held together?
Groups of proteins are often associated in
long-lasting, specialized patches, where they carry out common
functions.
145
Where is cholesterol in cell membranes?
The steroid cholesterol, which is wedged between phospholipid
molecules in the plasma membranes of animal
cells
146
What does cholesterol do in cell membranes if there are high body temperatures?
At relatively high temperatures—
at 37°C, the body temperature of humans, for example—
cholesterol makes the membrane less fluid by restraining
phospholipid movement.
147
What do phospholipids and proteins do for the cell membrane?
Phospholipids
form the main fabric of the
membrane, but proteins determine
most of the membrane’s functions.
148
What are the main 2 types of proteins found in cell membranes?
Integral proteins and peripheral proteins.
149
What do integral proteins do to the phospholipid bilayer?
Integral proteins penetrate the hydrophobic interior of the
lipid bilayer.
150
What consists of the hydrophobic region of an integral protein?
The hydrophobic
regions of an integral protein consist of one or more stretches of
nonpolar amino acids.
151
Where are peripheral proteins cell membrane wise?
Peripheral proteins are not embedded in the lipid
bilayer at all; they are loosely bound to the surface of the membrane,
often to exposed parts of integral proteins
152
What are the 7 functions of proteins in the cell membrane?
Transport
Enzymatic Activity (Proteins are enzymes that take material and digest them)
Signal Transduction (Recieves a signal to carry out a function)
Cell-cell recognition (Uses glyco-proteins to recognize each other)
Intercellular Joining
Attachment to the cytoskeleton and
extracellular matrix (ECM)
153
What is cell cell recognition?
Cell-cell recognition, a cell’s ability to distinguish one type of
neighboring cell from another,
154
What are glycolipids?
Glycolipids are lipids with a carbohydrate attached by a glycosidic bond.
155
What can membrane carbohydrates function as?
The diversity of the molecules and their
location on the cell’s surface enable membrane carbohydrates
to function as markers that distinguish one cell from another.
156
What determines our blood groups?
For example, the four human blood types designated A, B, AB,
and O reflect variation in the carbohydrate part of glycoproteins
on the surface of red blood cells.
157
What is selective permeability? Does a membrane exhibit it?
A membrane exhibits selective permeability; that is,
it allows some substances to cross more easily than others.
158
How do hydrophilic substances get through the lipid bilayer of a cell membrane?
these hydrophilic
substances can avoid contact with the lipid bilayer by
passing through transport proteins that span the membrane.
159
What are aquaporins?
the passage of water molecules through the membrane
in certain cells is greatly facilitated by channel proteins
known as aquaporins
160
What does an aquaporin consist of?
Most aquaporin proteins
consist of four identical polypeptide subunits. Each polypeptide
forms a channel that water molecules pass through
161
What is diffusion?
diffusion, the movement of particles of any substance
so that they spread out into the available space.
162
What is the rule for diffusion?
rule of diffusion: In the absence of any other
forces, a substance will diffuse from where it is more concentrated to where it is less concentrated.
163
What is a concentration gradient?
concentration gradient, the region along
which the density of a chemical substance increases or decreases
164
What is osmosis?
The
diffusion of free water across a selectively permeable membrane,
whether artificial or cellular, is called osmosis.
165
What is tonicity?
tonicity, the
ability of a surrounding solution to cause a cell to gain or lose
water.
166
What determines the tonicity of a solution?
The tonicity of a solution depends in part on its concentration
of solutes that cannot cross the membrane
167
What does isotonic mean?
Having the same environment to the cell
168
What happens if a cell is in an isotonic environment?
is immersed
in an environment that is isotonic to the cell (iso means “same”),
there will be no net movement of water across the plasma membrane.
169
Hypertonic meaning?
Hypertonic means having a higher concentration of solutes (dissolved substances) compared to another solution.
170
What will happen if you put a cell in a hypertonic solution
The cell will lose water, shrivel,
and probably die as there is more freewater in the cell, causing it to diffuse outwards
171
Hypotonic meaning?
The cell will lose water, shrivel,
and probably die.
172
Lyse?
Burst
173
What will happen if you put a cell in a hypotonic solution?
water will enter the cell faster
than it leaves, and the cell will swell and lyse
(burst) like an overfilled water balloon.
174
What is osmoregulation
osmoregulation,
the control of solute concentrations and
water balance.
175
What happens when excess water enters a plant cell?
the plant cell
swells as water enters by osmosis
176
What is turgor pressure?
Turgor pressure is the force within a plant cell that pushes the plasma membrane against the cell wall.
177
Turgid meaning?
turgid
(very firm)
178
Flaccid meaning?
Limp
179
What happens if a plant cell's surrounding is isotonic?solution. If a plant’s cells and surroundings are isotonic,
there is no net tendency for water to enter and the cells
become flaccid
solution. If a plant’s cells and surroundings are isotonic,
there is no net tendency for water to enter and the cells
become flaccid
180
What is plasmolysis?
Plasmolysis is the process in which plant cells lose water when placed in a hypertonic solution
181
What is facilitated diffusion?
Facilitated diffusion is a process of passive transport that allows molecules to move across a cell membrane with the help of special proteins.
182
What are the two main types of transport proteins?
Channel and carrier proteins
183
What do channel proteins do?
Channel proteins simply
provide corridors that allow specific molecules or ions to cross
the membrane. The hydrophilic passageways provided
by these proteins can allow water molecules or small ions to
diffuse very quickly from one side of the membrane to the other.
184
What are ion channels?
Channel proteins that transport ions are called ion
channels.
185
What are gated channels, do ion channels function as them?
Many ion channels function as gated channels,
which open or close in response to a stimulus
186
What do carrier proteins do?
Carrier proteins seem to undergo a subtle change in shape
that somehow translocates the solute-binding site across the
membrane
187
What is active transport
Active transport is the energy-consuming process by which cells move molecules against their concentration gradient, using membrane proteins to maintain cellular balance and function.
188
Explain how active transport proteins use ATP to transfer ions through potassium and sodium regulation
The sodium-potassium pump is a transmembrane protein that actively transports sodium ions out of the cell and potassium ions into the cell against their concentration gradients. This process requires energy in the form of ATP. When ATP binds to the pump, it undergoes a conformational change, expelling sodium ions to the extracellular fluid. Subsequently, the pump binds to potassium ions, and upon dephosphorylation, it releases the potassium ions into the intracellular fluid, returning to its original conformation to repeat the cycle.
189
What do all cells have across their membrane (electrical wise)
All cells have voltages across their plasma membranes.
190
What is voltage?
Voltage is electrical potential energy, a
separation of opposite charges.
191
What are the charges of the cell membrane?
The cytoplasmic side of the
membrane is negative in charge relative to the extracellular
side because of an unequal distribution of anions and cations
on the two sides.
192
What is the membrane potential?
The voltage across a membrane, called a
membrane potential,
ranges from about
-50 to -200 millivolts (mV).
193
Why is passive transport of cations entering and anions exiting the cell favored amongst the cell?
Because the inside of the cell is negative compared
with the outside, the membrane potential favors the
passive transport of cations into the cell and anions out of the
cell.
194
What is the electrochemical gradient
An electrochemical gradient is a combined force created by the difference in concentration of ions (chemical gradient) and the difference in electrical charge (electrical gradient) across a membrane.
195
What is an electrogenic pump?
A transport protein that generates
voltage across a membrane is called an electrogenic pump.
196
What is the proton pump?
The main electrogenic pump of
plants, fungi, and bacteria is a proton pump, which actively
transports protons (hydrogen ions, H+) out of the cell.
197
What is cotransport
Cotransport is a type of cellular transport mechanism that involves the coupled movement of two different molecules across a cell membrane using a single transport protein.
198
How do macromolecules get transported between the cells?
they usually enter and leave the cell in bulk,
packaged in vesicles.
199
How do transport vesicles transport macromolecules outside of the cell?
A transport vesicle that has budded from the
Golgi apparatus moves along a microtubule of the cytoskeleton
to the plasma membrane. When the vesicle membrane
and plasma membrane come into contact, specific proteins
in both membranes rearrange the lipid molecules of the two
bilayers so that the two membranes fuse. The contents of
the vesicle spill out of the cell, and the vesicle membrane
becomes part of the plasma membrane.
200
What is exocytosis?
Exocytosis is a cellular process that involves the release of substances from a cell by fusing vesicles containing those substances with the plasma membrane.
201
What happens in endocytosis?
In endocytosis, the cell takes in molecules and particulate
matter by forming new vesicles from the plasma membrane.
202
What is the process of endocytosis?
First, a small area of the plasma membrane sinks inward to
form a pocket. Then, as the pocket deepens, it pinches in,
forming a vesicle containing material that had been outside
the cell.
203
What are the three types of endocytosis?
Phagocytosis, Pinocytosis, receptor-mediated endocytosis
204
What is phagocytosis?
In phagocytosis, a cell engulfs a particle
by extending pseudopodia (tentacles) around it and packaging
it within a membranous sac called a food
vacuole.
205
What is pinocytosis?
In
pinocytosis,
a cell continually “gulps”
droplets of extracellular fluid into tiny
vesicles, formed by infoldings of the plasma
membrane.
206
What is receptor-mediated endocytosis
Receptor-mediated endocytosis is a
specialized type of pinocytosis that enables
the cell to acquire bulk quantities of specific
substances, even though those substances
may not be very concentrated in the
extracellular fluid.
207
What is metabolism?
The totality of an organism’s chemical reactions is called
metabolism. Metabolism as a whole manages the material and energy resources of the cell.
208
What happens in metabolic pathways?
In a metabolic pathway, a specific
molecule is altered in a series of defined steps, resulting in a
certain product.
209
What are catabolic pathways?
Breakthrough pathways.
210
What is cellular respiration?
One major
catabolic pathway is cellular respiration, which breaks down
glucose and other organic fuels in the presence of oxygen to
carbon dioxide and water.
211
What are anabolic pathways and biosynthetic pathways?
Anabolic
pathways, in contrast, consume energy to build complicated
molecules from simpler ones; they are sometimes
called biosynthetic pathways.
212
What are bioenergetics?
bioenergetics, the study of how energy flows
through living organisms.
213
What is energy?
Energy is the capacity to cause change.
214
What is kinetic energy?
Energy can be associated with the relative motion of objects;
this energy is called kinetic energy
215
What is thermal energy?
Thermal energy is kinetic energy associated with the
random movement of atoms or molecules;
216
What is heat?
thermal energy in
transfer from one object to another is called heat.
217
What is potential energy?
potential energy; it is
energy that matter possesses because of its location or structure.
218
Chemical energy?
Chemical energy is a term used by
biologists to refer to the potential energy available for release
in a chemical reaction.
219
What is thermodynamics?
The study of the energy transformations that occur in a collection
of matter is called thermodynamics.
220
What is the first law of thermodynamics?
According to the
first law of thermodynamics,
the
energy of the universe is constant: Energy can be transferred
and transformed, but it cannot be created or destroyed.
221
second law of thermodynamics?
Every energy transfer or transformation increases
the entropy (disorder) of the universe. For
example, during every energy transformation,
some energy is converted to thermal energy and
released as heat
222
What is entropy?
entropy as a measure of
molecular disorder, or randomness.
223
What is a spontaneous process?
A process that causes entropy without the need of energy
224
What does nonspontaneous mean?
A process that, on its own, leads to a decrease in entropy
is said to be nonspontaneous: It will happen only if energy is
supplied.
225
What is the system and surroundings?
Recall that the universe is really equivalent to “the system”
plus “the surroundings.”
226
What does G mean?
Gibbs
free energy of a system (without considering its surroundings),
symbolized by the letter G.
227
What is free energy
Free energy is the portion of
a system’s energy that can perform work when temperature
and pressure are uniform throughout the system, as in a living
cell.
228
How to calculate free energy?
DH symbolizes the change in the system’s
enthalpy (in biological systems, equivalent to total energy);
DS is the change in the system’s entropy; and T is the absolute
temperature in Kelvin (K) units
229
Enthalpy meaning
Total energy
230
What does free energy tell us?
Free energy tells us if a reaction is spontaneous, if it is negative then that means the reaction is spontaneous, otherwise it isn't.
231
What is G in equilibrium
For a system at equilibrium, G is at its lowest
232
What is an exergonic reaction?
An exergonic reaction proceeds
with a net release of free energy
233
What does cG tell us for exergonic reactions?
Using cG as a standard
for spontaneity, exergonic reactions are those that occur
spontaneously.
234
What are endergonic reactions?
An endergonic reaction is one that absorbs free
energy from its surroundings
235
Why do endergonic reactions absorb G?
Because their G is very low, so they need an input of energy to make the cG larger than one.
236
What are the three functions of cells?
Chemical work, the pushing of endergonic reactions
that would not occur spontaneously, such as the synthesis
of polymers from monomers (chemical work
will be discussed further here; examples are shown in
Chapters 9 and 10)
* Transport work, the pumping of substances across membranes
against the direction of spontaneous movement
(see Concept 7.4)
* Mechanical work, such as the beating of cilia (see
Concept 6.6), the contraction of muscle cells, and the
movement of chromosomes during cellular reproduction
237
What is energy coupling?
A key feature in the way cells manage their energy
resources to do this work is energy coupling, the use of an
exergonic process to drive an endergonic one.
238
What does ATP handle?
ATP is responsible
for mediating most energy coupling in cells, and in most
cases it acts as the immediate source of energy that powers
cellular work.
239
What makes ATP?
ATP (adenosine triphosphate; see Concept 4.3) contains
the sugar ribose, with the nitrogenous base adenine and a
chain of three phosphate groups (the triphosphate group)
bonded to it
240
What can ATP do in terms of nucleic acids?
In addition to its role in energy
coupling, ATP is also one of the nucleoside triphosphates
used to make RNA
241
How can the bonds of the triphosphate group in ATP be broken down?
The bonds between the phosphate groups of ATP can be
broken by hydrolysis.
242
What happens when ATP reacts with water?
243
What are phosphate bonds in ATP reffered to as?
the phosphate
bonds of ATP are sometimes referred to as high-energy
phosphate bonds
244
Are the phosphate bonds in ATP strong?
The phosphate
bonds of ATP are not unusually strong bonds, as
“high-energy” may imply; rather, the reactants (ATP and
water) themselves have high energy relative to the energy of
the products
245
What does shivering do (ATP wise)?
For instance, the process of shivering uses ATP hydrolysis
during muscle contraction to warm the body.
246
What is phosphorylation?
phosphorylation, the
transfer of a phosphate group from ATP to some other
molecule
247
What is a phosphorylated intermediate?
The recipient molecule
with the phosphate group covalently bonded to it is then
called a phosphorylated intermediate.
248
How does ATP power endergonic reactions (use glutamine example)
The conversion of glutamic acid to glutamine is an endergonic reaction, meaning it requires energy to proceed. To make this reaction happen, it is coupled with ATP hydrolysis, an exergonic process that releases energy. In the first step, ATP is hydrolyzed to ADP and inorganic phosphate, and the phosphate group is transferred to glutamic acid, forming a high-energy intermediate called glutamyl phosphate (Glu-P). This phosphorylation step increases the free energy of glutamic acid, making it less stable and more reactive. In the second step, ammonia reacts with the phosphorylated intermediate, displacing the phosphate group and forming glutamine. The energy released from ATP hydrolysis powers the phosphorylation, which lowers the activation energy for the reaction with ammonia and drives the overall process forward. The net free energy change (ΔG) for the combined reactions is negative, making the process spontaneous.
249
