Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

B > membrane structure, function and transport > Flashcards

membrane structure, function and transport Flashcards

1
Q

what is the simplest collection of matter that can be considered a living entity

A

a cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how does a light microscope work

A

visible light is passed through the specimen and then through the glass lenses. the lenses refract the light so that the image is projected into the eye or into the camera

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the 3 important parameters in microscopy

A

resolution
magnification
contrast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is magnification

A

the ratio of an objects image size to its real size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is resolution

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

the light microscope cannot resolve detail finer than …….……. micrometres regardless of the magnification

A

0.2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is contrast

A

the difference in brightness between the light and dark areas of an image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how can contrast be enhanced

A

we can stain certain components of the specimen to make them stand out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how does the electron microscope work

A

it focusses a beam of electrons through the specimen or onto its surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

…….………. is inversely related to the wavelength of light (or electrons) a microscope uses for imaging

A

resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

electron beams have much longer/shorter wavelengths than visible light

A

shorter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the highest resolution an electron microscope can achieve

A

2 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is a scanning electron microscope used for

A

useful for detailed study of topography of a specimen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how does a scanning electron microscope SEM work

A

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 a 3D image of the specimen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how does a transmission electron microscope TEM work

A

it aims a beam of electrons through a very thin section of the specimen
the specimen has been stained with atoms of heavy metals which attach to certain cellular structures, enhancing the electron density of some parts of the cell compared to others
the electrons passing through the specimen are scattered more in the denser areas, so fewer are transmitted
the image displays a pattern of transmitted electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is a transmission electron microscope used for

A

it is used to study the internal structure of cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what kind of lenses do SEM and TEM use and why

A

they use electromagnets as lenses to bend the paths of the electrons ultimately focusing the image onto a monitor for viewing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is a disadvantage of the electron microscope

A

methods used to prepare the specimen kills the cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

specimen preparation for any kind of microscopy can introduce artefacts. what are these

A

structural features seen in micrographs that do not exist in the living cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

microscopes are the most important tools for which field of study

A

cytology - the study of cell structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is biochemistry

A

the study of the chemical processes (metabolism) of cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is cell fractionation

A

a technique used to study the structure and function of cells
it takes apart and separated major organelles and other subcellular structures from one another
the piece of equipment used is called a centrifuge
at lower speeds the pellet consists of larger components
at higher speeds the pellet consists of smaller components

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the difference between stains used for light and electron microscopy

A

light microscopy stains are coloured molecules that bind to cell components, affecting the light passing through
stains for electron microscopy involve heavy metals that affect the beams of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

eukaryotic cells have internal ………… that compartmentalize their functions

A

membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what are the 2 distinct types of cells

A

prokaryotes and eukaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

organisms of the domains bacteria and archaea consist of what type of cells

A

prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

protists, fungi, animals and plants all consist of what type of cells

A

eukaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

all cells are bonded by what kind of membrane

A

plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

inside all cells is a semifluid, jelly like substance called what

A

the cytosol - where glycolysis happens - where cellular components are suspended

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

TRUE/FALSE all cells contain chromosomes

A

TRUE - they carry genes in the form of DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

TRUE/FALSE all cells contain ribosomes

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what are the major differences between eukaryotes and prokaryotes

A

location of DNA - in E most of the DNA is found in the nucleus which is bounded by a double membrane. in P DNA is concentrated in a region that is not membrane enclosed, called the nucleoid
almost all prokaryotes lack the organelles with specialised structure and function that eukaryotes have

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

the interior of both eukaryotic and prokaryotic cells is called what

A

the cytoplasm

in eukaryotes this is the region between the nucleus and the plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

instead of membranes some prokaryotes have internal regions surrounded by what within which specific reactions take place

A

proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

eukaryotic cells are generally much larger/smaller than prokaryotes

A

larger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is the typical diameter of bacteria cells

A

1-5 micrometres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what is the typical diameter of eukaryotic cells

A

10-100 micrometres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

as a cell increases its size its surface area grows proportionally less/more compared to its volume

A

less

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

a smaller/larger object has greater surface area to volume ratio

A

smaller object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

many cells have long thin projections called microvilli why are these useful

A

they increase surface area without an appreciable increase in volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what are the advantages of having organelles

A

they provide microenvironments that support specific metabolic functions
they allow reactions that are not compatible to occur simultaneously within the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

why do plasma membranes and organelle membranes participate directly in the cell’ metabolism

A

because they have many enzymes built into the membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what is the basic fabric of most membranes

A

the phospholipid bilayer with proteins embedded in it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

what part of a eukaryotic cell contains most of the genes

A

the nucleus - some genes are located in the mitochondria and chloroplasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what is the pore complex of the nuclear membrane

A

the nuclear envelope is perforated by pore structures - the pore complex is an intricate protein structure that lines each pore
it plays an important role in the cell by regulating the entry and exit of proteins, RNAs, large complexes and macromolecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

apart from at the pores, the nuclear side of the envelope is lined by what

A

the nuclear lamina - a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

how is DNA organised in the nucleus

A

into units called chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

the complex of DNA and proteins making up the chromosomes is called what

A

the chromatin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

what is the prominent structure in the non dividing nucleus

A

nucleolus

  • where rRNA is synthesised from instructions in the DNA
  • proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes. these subunits then exit the nucleus through the pores in to the cytoplasm where a ribosome can be assembled
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

the nucleus directs protein synthesis by synthesising what according to instructions provided by DNA

A

mRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

how is mRNA transported to the cytoplasm from the nucleus

A

via the nuclear pores

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

what are ribosomes made of

A

rRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

why are ribosomes not considered as organelles

A

because they are not membrane bounded

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what are the 2 cytoplasmic locales where ribosomes build proteins

A

free ribosomes are suspended in the cytosol

bound ribosomes are attached to the outside of the ER or nuclear envelope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

TRUE/FALSE bound and free ribosomes are structurally identical

A

TRUE - ribosomes can play either role at different times

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

most proteins made on free ribosomes function where

A

the cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

bound proteins generally make proteins that function where

A

they are inserted into membranes for packaging within certain organelles or for export from the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

what does the endomembrane system include

A

it includes the ER, nuclear envelope, Golgi apparatus, lysosomes, various kinds of vesicles and vacuoles and the plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

what tasks does the endomembrane system carry out

A

synthesis of proteins
transport of proteins into membranes and organelles or out of the cell
metabolism and movement of lipids
detoxification of poisons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

the membranes of the endomembrane system are related either through direct physical continuity or by the transfer of membrane segments as tiny vesicles. What are vesicles

A

sacs made from membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

are the membranes of the endomembrane system identical

A

no - moreover, the thickness, composition and types of reaction of a membrane are not fixed and may be modified several times

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

what is the ER made of

A

a network of membranous tubules and sacs called cisternae
the ER membrane separates the ER lumen or cisternal space from the cytosol
the space between the 2 membranes of the nuclear envelope is continuous with the lumen of the ER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what are the 2 distinct regions of the ER

A

smooth ER

rough ER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

what does the surface of smooth ER lack

A

ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

ribosomes are studded on the outer surface of which type of ER

A

rough

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

…….……….. are attached to the cytoplasmic side of the nuclear envelopes outer membrane, which is continuous with the ER

A

ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

what are the functions of the smooth ER

A 
contribute in:
synthesis of lipids
metabolism of carbohydrates
detoxification of drugs and poisons 
storage of calcium ions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

detoxification of drugs by the ER usually involves adding which functional group

A

hydroxyl groups - this makes them more soluble in water and easier to flush out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

what are the functions of the rough ER

A

proteins enter the ER from bound ribosomes and form glycoproteins by attaching carbohydrates. the ER keeps these proteins separate from the proteins in the cytosol produced by free ER. the secretory proteins depart form the ER in vesicles from a region called the transitional ER
rough ER is a membrane factory for the cell - it grows by adding membrane proteins and phospholipids into its own membrane. as polypeptides destined to be membrane proteins grow from the ribosomes they are inserted into the ER membrane
phospholipid synthesis - ER membrane enzymes synthesis phospholipids from precursors in the cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

most secretory proteins are what type of protein

A

glycoproteins - proteins with carbohydrates covalently bonded to them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

what are vesicles in transit from one part of the cell to another called

A

transport vesicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

after leaving the ER where do many of the transport vesicles travel

A

to the Golgi apparatus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

what happens to products of the ER in the Golgi apparatus

A

they are modified and stored and sent to other locations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

what are the flat membranous sacs called that make up the Golgi apparatus

A

cisternae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

the membrane of each cisterna in the Golgi apparatus separates tits internal space form what

A

the cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

what are the 2 sides of a Golgi stack referred to as

A

the cis and trans faces which act as the receiving and shipping departments respectively

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

how does a transport vesicle that has bud from the ER add its lumen contents to the Golgi apparatus

A

it fuses with the Golgi membrane on the cis side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

how do vesicles leave the Golgi apparatus to go to other locations

A

they leave via the trans side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

give some examples of the tweeking that the Golgi apparatus does to products of the ER

A

remove and substitute sugar monomers

alter membrane phospholipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

many polysaccharides secreted by cells are products of what cell structure

A

the Golgi apparatus

81
Q

how does the Golgi stack label its products and target them for various parts of the cell

A

by adding identification tags such as phosphate groups

82
Q

how do vesicles know where to take Golgi apparatus products

A

they may have external molecules on their membranes that recognise parts of particular organelles

83
Q

in what environment to lysosomal enzymes work best

A

acidic environment

84
Q

what can happen if a large number of lysosomes leak in a cell

A

the cell becomes digested due to the acidity

85
Q

what structure makes hydrolytic enzymes and lysosomal membrane

A

the rough ER and are then modified in the GA

86
Q

how are is the lysosomal membrane not damaged by the acidic conditions of the lysosome

A

the shapes of the proteins protect vulnerable bonds from enzymatic attack

87
Q

what are the 3 steps in lysosome phagocytosis

A
  1. lysosome contains active hydrolytic enzymes
  2. lysosome fuses with food vacuole
  3. hydrolytic enzymes digest food particles
88
Q

what are the 3 steps in lysosome autophagy

A
  1. lysosome fuses with vesicle containing damaged organelles
  2. hydrolytic enzymes digest organelle components
  3. the resulting small organic compounds are released into the cytosol for reuse
89
Q

what are vacuoles

A

large vesicles derived from the ER and Golgi apparatus

90
Q

what is the result of the vacuole membrane being selective in solute transport

A

the solution inside the vacuole varies from the cytosol

91
Q

by what process are food vacuoles formed

A

phagocytosis

92
Q

what do contractile vacuoles do

A

pump excess water out of the cell of fresh water eukaryotes

93
Q

how can vacuoles help protect plants

A

they can store poisonous substances to protect them from animals

94
Q

what is the solution inside the vacuole called

A

the cell sap

95
Q

describe in 6 steps the flow through the endomembrane system

A
  1. the nuclear envelope is connected to the rough ER which is also continuous with the smooth ER
  2. membranes and proteins produced by the ER move via transport vesicles to the Golgi
  3. the Golgi pinches off transport vesicles and other vesicles that give rise to lysosomes, other types of specialised vesicles and vacuoles
  4. the lysosome is available for fusion with another vesicle for digestion
  5. a transport vesicle carries proteins to the plasma membrane for secretion
  6. the plasma membrane expands by fusion of the vesicle and proteins are secreted from the cell
96
Q

what does the endosymbiont theory state

A
  1. an ancestor of eukaryotic cells engulfed an oxygen using nonphotosynthetic cell
  2. the engulfed cell became and endosymbiont (a cell living in another)
  3. this developed into a eukaryotic cell with a mitochondrion
  4. one of these cells took up a photosynthetic prokaryote becoming the ancestor of eukaryotic cells that contained chloroplasts
97
Q

what evidence supports the endosymbiont theory

A

mitochondria and chloroplasts have double membranes
chloroplasts have an internal system of membranous sacs
like prokaryotes, mitochondria and chloroplast contain ribosomes and circular DNA
mitochondria and chloroplasts are autonomous (independent) - they grow and reproduce independently

98
Q

describe the structure of the 2 membranes of the mitochondrion

A

both membranes are made from phospholipids
the outer membrane is smooth
the inner membrane is convoluted with infoldings called cristae

99
Q

what is the intermembrane space of the mitochondrion

A

the area between the 2 membranes

100
Q

what is the mitochondrial matrix

A

the area enclosed by the inner membrane which contains many enzymes, mitochondrial DNA and ribosomes

101
Q

what gives the inner mitochondrial membrane a large surface area

A

the cristae

102
Q

what is the green pigment that chloroplasts contain called

A

chlorophyll

103
Q

what is the membranous system inside the chloroplast called and what is it made of

A

thylakoids - flattened interconnected sacs
they contain stacks called grana
the fluid outside the thylakoid is called the stroma which contains DNA, ribosomes and enzymes

104
Q

what are the 3 membrane compartments of the chloroplast

A

intermembrane space (between the membranes)
the stroma
the thylakoids

105
Q

what is a plastid

A

found in cells of photosynthetic eukaryotes - closely related to chloroplasts

106
Q

what is a peroxisome

A

an organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen, producing then degrading hydrogen peroxide to water

107
Q

what do glyoxysomes do

A

they contain an enzyme that converts plant fatty acids to sugars which seedlings use as a source of energy and carbon until they can photosynthesise

108
Q

what are the functions of the cytoskeleton

A
  1. give mechanical support to the cell and maintain its shape (important because animal cells lack walls)
  2. provides anchorage for many organelles and cytosolic enzymes
  3. it contributes to cell motility
109
Q

what to things need to interact for cell motility

A

the cytoskeleton and motor proteins

110
Q

describe microtubules

A
  • they are the thickest fibre of the cytoskeleton
  • they are hollow tubes composed of globular tubulin dimers (2 subunits) made of beta and alpha tubulin
    main functions
  • maintenance of cell shape
  • cell motility (cilia and flagella)
  • chromosome movement in cell division
  • organelle movements
111
Q

describe intermediate filaments

A
  • fibrous proteins e.g. keratin coiled into cables
  • intermediate thickness
    main functions
  • maintenance of cell shape
  • anchorage of nucleus and other organelles
  • formation of nuclear lamina
112
Q

describe microfilaments

A
  • two intertwined strands of actin
  • thinnest
    main functions
  • maintenance of cell shape
  • changes in cell shape
  • muscle contraction
  • cytoplasmic streaming in plant cells
  • cell motility (amoeboid movement)
  • division of animal cells
113
Q

how do microtubules change length

A

they can grow by adding tubulin dimers

they can disassemble by removing dimers that can then be used in microtubules elsewhere

114
Q

what is the plus end of a microtubule

A

the end that can assemble and disassemble the quickest

115
Q

give some examples of how microtubules are involved in cellular activities

A
  • they serve as tracks along which organelles with motor proteins can move
  • microtubules guide vesicles from the ER to the Golgi and then to the plasma membrane
  • microtubules are involved in separation of chromosomes during cell division
116
Q

what is a centrosome

A

a region that is often located near the nucleus from which microtubules grow out of - these microtubules function as compression-resisting girders of the cytoskeleton

117
Q

what is a centriole

A

they are found in pairs within the centrosome each centriole is composed of 9 sets of triplet microtubules arranged in a ring

118
Q

what are cilia and flagella

A
  • microtubule containing extensions that project form the cells
  • cilia and flagella often act as locomotor appendages
  • there are often many cilia per cell but only one or two flagella per cell. A cell cannot have cilia and flagella
  • flagella and cilia differ in their beating patterns
119
Q

describe the motion of flagella

A

a flagellum moves in an undulating motion
flagella bending involves dynein proteins, bound on each microtubule doublet
dynein has two projections that move using energy from ATP hydrolysis
One projection remains attached to the microtubule whilst the other detaches and binds further along
this causes an bend
this repeated motion creates wave like movement

120
Q

describe the motion of cilia

A

cilia have motor proteins that travel along the microtubules and create a bend.
a power stroke occurs resulting in the cilia moving back by 90° so they are perpendicular to the original position.
During a recovery stroke the cilia bend and slowly return to the original position.
This repeated motion of the cilia moving back and forth drives cell movement

121
Q

describe the structure that cilia and flagella share

A

9 doublets of microtubules are arranged in a ring with 2 single microtubules in its centre (the 9+2 arrangement)
the microtubule assembly is anchored in the cell by a basal body (similar to a centriole) with a 9+0 arrangement

122
Q

how do dyneins work

A

dyneins are attached along each outer microtubule doublet
dynein has 2 projections that walk along the microtubule of the adjacent doublet using ATP to power this
One projection remains attached to the microtubule whilst the other detaches and binds further along
this causes an bend
doublets and the central microtubules are held together by proteins so that when the dynein travels along the microtubule, the unit is held together and bends as a whole

123
Q

TRUE/FALSE microtubules and microfilaments are present in all eukaryotic cells

A

TRUE

124
Q

what is the main role of microfilaments in the cytoskeleton

A

to bear tension

muscle contraction

125
Q

the 3D network formed just inside the plasma membrane is formed by what kind of microfilaments what is its function

A

cortical microfilaments

helps support the cell’s shape and gives the cortex the semisolid consistency of a gel

126
Q

what is the cortex

A

the outer cytoplasmic layer of the cell

127
Q

describe amoeboid movement

A

amoeba form temporary cytoplasmic extensions called pseudopodia
results from changes in structure of actin filaments (microfilaments) in the cytoskeleton.
The actin filaments interact with myosin, causing cell contraction that results in the cell being pulled forward.
The cytoplasm consists of fluid plasmasol surrounded by plasmagel. The pseudopodia are formed when the plasmagel is converted to plasmasol and travels to the front of the cell
This movement launches the cell forward

128
Q

what is cytoplasmic streaming

A

a circular flow of cytoplasm within cells - speeds up distribution of materials
it occurs due to actin protein interactions

129
Q

TRUE/FALSE intermediate filaments are found in all eukaryotic cells

A

FALSE they are only found in some animal cells

130
Q

which two components of the cytoskeleton specialise in bearing tension

A

intermediate filament and microfilament

131
Q

which of the components of the cytoskeleton differ in diameter and composition

A

intermediate filaments - they are not always the same whereas microtubules and microfilaments are always the same composition

132
Q

which of the components of the cytoskeleton is the most permanent

A

intermediate filaments - they are still there after the cell dies e.g. the skin contains lots of keratin filaments

133
Q

which of the components of the cytoskeleton forms a cage around the nucleus to fix it in position

A

intermediate filaments

134
Q

which of the components of the cytoskeleton makes up the nuclear lamina (this lines the interior of the nuclear envelope)

A

intermediate filaments

135
Q

which of the components of the cytoskeleton can function on its own in its various forms to provide the entire framework of the cell

A

intermediate filaments

136
Q

what is one of the main features that distinguishes plant cells from animal cells

A

animal cells don’t have a cells wall

137
Q

what is thicker the plasma membrane or the plant cell wall

A

the cell wall

138
Q

what is the primary cell wall

A

the cell wall of a young plant that is relatively thin and flexible

139
Q

between the primary cells walls of adjacent cells lies the …………

A

middle lamella

140
Q

what is the middle lamella

A

a thin sticky layer containing pectins (polysaccharides) that glues the cells together

141
Q

describe the secondary cell wall

A

the cell wall of a mature plant between the plasma membrane and the primary cell wall
it is a strong durable matrix that protects and supports the cell

142
Q

what is the extracellular matrix

A

made of glycoproteins (e.g. collagen) and carbohydrates

it helps coordinate the behaviour of all the cells of that tissue

143
Q

in the EMC where are collagen fibres found

A

embedded in web of proteoglycan complexes

144
Q

in the ECM what does fibronectin do

A

attaches the ECM to integrins embedded in the plasma membrane

145
Q

what are integrins

A

membrane proteins that bind to the ECM on the outside and to associated proteins on microfilaments on the inside
the linkage allows signals to be transmitted
they are transmembrane proteins

146
Q

what is a proteoglycan complex

A

consists of hundred of proteoglycan molecules attached noncovalently to a single polysaccharide molecule

147
Q

what is meant by the selective permeability of the plasma membrane

A

it allows some substances to cross it more easily than others

148
Q

what is the fluid mosaic model

A

a mosaic of protein molecules in a fluid bilayer of phospholipids

149
Q

by what interactions are membranes held together

A

hydrophobic interactions (weaker than covalent bonds)

150
Q

can adjacent phospholipids in the bilayer switch positions

A

yes and they can do so very rapidly

151
Q

how do proteins in the membrane of a cell move

A

in a highly directed manner, driven along cytoskeletal fibres in the cell by motor proteins connected to the membrane proteins’ cytoplasmic regions
some proteins are immobile, often due to being attached to the ECM or the cytoskeleton

152
Q

with decreasing temperature a membrane remains fluid for longer if its structure is what

A

rich in phospholipids with unsaturated hydrocarbon tails (cannot pack together as closely not as many interactions to overcome, lower mp)

153
Q

what is the effect of cholesterol on membranes

A

it hinders the close packing so the membrane remains fluid for longer with decreasing temperature

154
Q

how can fluidity affect membranes

A

too fluid - can’t support protein function

too solid - renders some proteins inactive because they can’t move

155
Q

what part of the membrane most influences its function

A

the membrane proteins

156
Q

what are integral proteins

A

proteins that penetrate the phospholipid bilayer
transmembrane proteins span the entire bilayer whereas other integral proteins extend only partially into the hydrophobic interior

157
Q

what is usually the secondary structure of the hydrophobic parts of an integral protein

A

alpha helix

158
Q

what are peripheral proteins

A

proteins that are not embedded in the membrane but are instead loosely bound to the surface and often exposed to parts of integral proteins or the ECM

159
Q

can proteins be found on the cytoplasmic side of the membrane

A

yes they can be held in place by attachment to the cytoskeleton

160
Q

what are the 6 main functions of membrane proteins

A 
transport 
enzyme activity 
signal transduction
cell-cell recognition 
intercellular joining 
attachment to the cytoskeleton and ECM
161
Q

discuss HIV in terms of membrane proteins

A

CD4 protein attached to the membrane helps HIV infect cells leading to AIDS
Some people don’t develop AIDS
they don’t produce CCR5
if HIV doesn’t bind to both CD4 and CCR5 then AIDS won’t occur

162
Q

how do cells recognise each other

A

by binding to molecules often containing carbohydrates on the extracellular surface of the plasma membrane

163
Q

what are the 4 steps in making a membrane

A
  1. lipids and proteins synthesised in association with the ER. in the ER carbohydrates are added to the transmembrane proteins, making glycoproteins
  2. in Golgi the glycoproteins undergo further carbohydrate modification and the lipids become glycolipids
  3. glycoproteins, glycolipids and secretory proteins are transported in vesicles to the plasma membrane
  4. vesicles fuse with the plasma membrane and secretory proteins are released from the cell by exocytosis and glycoproteins and glycolipids are positioned on the membrane
164
Q

what are channel proteins

A

transmembrane transport proteins that have a hydrophilic channel that certain molecules or ions can pass through

165
Q

what are carrier proteins

A

transport proteins that that bind to their substance and change shape to facilitate passage

166
Q

what is the diffusion of a substance over a biological membrane called

A

passive transport

167
Q

a solution with a higher/lower solute concentration has a lower free water concentration

A

higher

168
Q

what is the diffusion of water across a membrane called

A

osmosis

169
Q

what is tonicity

A

the ability of a surrounding solution to cause a cell to gain or lose water

170
Q

what is an isotonic solution

A

the solution is the same concentration as the inside of the cell

171
Q

what is a hypertonic solution

A

greater concentration than the inside of the cell

172
Q

hypotonic solution

A

lower concentration than the inside of the cell

173
Q

what happens to the flow of water in isotonic, hypertonic and hypotonic solutions

A

isotonic - no change
hypertonic - water leaves cell the cell shrivels
hypotonic - water enters cell the cell lyses
this is why we need osmoregulation

174
Q

what structure of plants, prokaryotes and fungi can help maintain the cell’s water balance

A

the cell wall - it expands only so much before it exerts pressure back on the cell

175
Q

when a cell wall exerts pressure on a cell once it has expanded what is this pressure called

A

turgor pressure - it opposes further water uptake

176
Q

what is a cell like if it is turgid (healthy state)

A

very firm - when in hypotonic solution

177
Q

what is a cell like if it is flaccid (wilted)

A

limp - when in isotonic solution

178
Q

what is plasmolysis

A

it happens when a cell shrivels and its plasma membrane pulls away from the cell wall - happens when the plant cell (fungi and bacteria too) is in a hypertonic condition - the plant wilts and dies

179
Q

what is facilitated diffusion

A

when substance pass through the membrane with help form transporter proteins (channel and carrier proteins)

180
Q

what are ion channels

A

channel proteins that transport ions

181
Q

what ae gated channels

A

channel proteins that open and close in response to stimuli (voltage or ligand gated)

182
Q

why is facilitated diffusion considered a passive movement

A

because the solute is moving down its concentration gradient - a process that requires no energy

183
Q

what is active transport

A

pumping of a solute against its concentration gradient across the membrane - this requires energy

184
Q

what type of transport proteins carry out active transport

A

carrier proteins - pumps

185
Q

what is voltage

A

electrical potential energy

186
Q

which side of the membrane is most negative

A

the cytoplasmic side

187
Q

what is the voltage across a membrane referred to as

A

the membrane potential

188
Q

what are the steps in the sodium potassium pump

A
  1. 3 Na bind to pump from cytoplasm
  2. pump phosphorylated by ATP
  3. conformational change releases Na to the extracellular environment
  4. high affinity for K so 2 bind which triggers release of phosphate
  5. conformational change releases K into the cytoplasm
189
Q

what is the electrochemical gradient

A

the net force when considering the chemical gradient and the electrical gradient

190
Q

what is a transport pump that generates voltage across a membrane called

A

an electrogenic pump

191
Q

give an example of an electrogenic pump

A 
sodium potassium pump (main one in animal cells)
proton pumps (main one in plants, fungi and bacteria)
192
Q

what does the proton pump to

A

actively transports hydrogen ions out of the cell - usually using ATP hydrolysis a an energy source

193
Q

what is cotransport

A

when the downhill movement of a substance is coupled to the uphill movement of another substance
e.g. the diffusion of H down its electrochemical gradient into the cell to drive the uptake of sucrose. a H pump maintains the concentration gradient of hydrogen so it continues to move into thee cell

194
Q

bulk transport across the membrane occurs by which processes

A

endocytosis and exocytosis

195
Q

what is exocytosis

A

when the cell secretes certain molecules by fusing with the plasma membrane

  • a transport vesicle from the Golgi moves along microtubules of the cytoskeleton to the plasma membrane
  • specific proteins rearrange the lipid molecules of the 2 bilayers so that the 2 membranes fuse
  • the contents of the vesicle spill out the cell ad the vesicle membrane becomes part of the plasma membrane
196
Q

what is endocytosis

A

reverse exocytosis
the cell takes in molecules and matter by forming new vesicles from the plasma membrane
- the plasma membrane sinks inwards to form a pocket
- the pocket then pinches in forming a vesicle containing material from the outside of the cell

197
Q

what are the 3 different types of endocytosis

A

phagocytosis - eating
pinocytosis - drinking
receptor mediated endocytosis

198
Q

what causes familial hypercholesterolemia

A

cholesterol travels in the blood as LDLs
LDLs bind to receptors on plasma membranes and then enter the cells by endocytosis
- in the disease LDLs cannot enter the cell because their receptors are missing or defective
- the disease is characterized by very high levels of cholesterol in the blood contributing to atherosclerosis (the build up of lipids in the walls of blood cells impeding blood flow)

B (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions