Cell Structure and biological membranes Flashcards
(106 cards)
1
Q
What are membrane bound organelles
A
Organelles have membranes around the outside
2
Q
Describe the structure of the nucleus
A
Surrounded by a double membrane called a nuclear envelope
Nucleolus containing RNA
3
Q
Describe the function of the nucleus
A
Is the control centre of the cell.
Stores the organism genotype
Transmits genetic information
Provides the instructions for protein synthesis
4
Q
Describe the rough endoplasmic reticulum structure
A
This is a System of membrane containing fluid filled cavities that are continuous with the nuclear membrane. It’s coated with ribosomes
5
Q
Rough endoplasmic reticulum function
A
Intracellular transport system
Provides large surface area for ribosomes which assemble amino acids into proteins which are transported to the Golgi apparatus for modification
6
Q
Describe the smooth endoplasmic reticulum structure
A
System of membranes containing fluid filled cavities , continuous with the nuclear membrane
No ribosomes on its surface
7
Q
Describe smooth endoplasmic reticulum function
A
Contains enzymes that catalysed reactions involved with lipid metabolism
8
Q
Describe the Golgi apparatus structure
A
Consists of a stack of membranes bound flattened sacs . Secretory vesicles being materials to and from the Golgi apparatus
9
Q
Golgi apparatus function
A
Proteins are modified. The proteins are packaged into vesicles that are pinched off and then stored in the cell or moved to the plasma Membrane, to be incorporated or exported
10
Q
Describe the mitochondria structure
A
These may be spherical , rod shaped or branched . Surrounded by two membranes with a fluid space in between them . The inner part of a mitochondria is a fluid filled matrix
11
Q
Describe the function of the mitochondria
A
Site of ATP production during aerobic respiration. They are self replicating . They’re abundant in cells where much metabolic activities take place .
12
Q
Describe the chloroplasts structure
A
Large organelles found only in plant cells . They’re surrounded by a double membrane or envelope
They contain loops of DNA and starch grains
13
Q
Describe chloroplasts function
A
Site of photosynthesis
14
Q
Describe the vacuole structure
A
Surrounded by a membrane called the tonoplast and contains fluid
15
Q
Describe the vacuole function
A
Filled with water and solute and maintains cell stability - turgid
Helps support
16
Q
Describe lysosomes structure
A
Small bags formed from the Golgi apparatus . Each is surrounded by a single membrane
They contain digestive enzymes
17
Q
Describe lysosomes function
A
They can engulf old cell organelles and foreign matters and digest them
18
Q
Describe the cilia and undulipodia structures
A
Surrounded by the cell surface membrane . Each contains micro tubes. They are formed from the centrioles
19
Q
Describe cilia and undulipodia function
A
Acts as an antenna. It contains receptors and allows the cell to detect signals about its immediate environment
20
Q
Describe ribosomes structure
A
Small spherical organelles made of ribosomal RNA made on the nucleus. As two separate subunits which pass through the nuclear envelope into the cell cytoplasm and then combine
21
Q
Describe ribosomes function
A
Bound to the exterior of RER mainly for synthesising proteins that will be exporters outside the cell
22
Q
Describe the centrioles structure
A
Consists of two bundles of micro tubes at right angles to each other . The micro tubes are made from tubulin proteins subunits and are arranged to form a cylinder
23
Q
Describe the centrioles function
A
Are involved in the formation of cilia and undulipodia
24
Q
Describe the cytoskeleton structure
A
A network of protein structures with in the cytoplasm and consists of a rod like microfilaments made of subunits of the protein acetic . They are enzymes and have a site to allow ATP
25
Describe the cytoskeleton function
The protein microfilaments give support and mechanical strengths , keeps the cell shape stable and allows cell movements
26
Describe cellulose structure
Made from bundles of cellulose fibres
27
Describe cellulose function
Strong and can Prevent plant cells from bursting when turgid . Provides strength and support
Maintains the cell shape
28
Describe making and secreting proteins
mRNA copy of the instructions for protein is made in the nucleus
mRNA leaves the nucleus through a nuclear pore
mRNA attaches to a ribosomes on the RER . Ribosomes read the instruction to assemble the protein
Protein molecules are pinched off in a vesicles and travels towards the Golgi apparatus
Vesicles fuse the the Golgi apparatus
Golgi apparatus processes and packages protein molecules ready to release
Packaged proteins molecules are pinched off in vesicles from the Golgi apparatus and move toward the plasma membrane
Vesicles fuse with the plasma membrane
Plasma membrane opens to releases proteins molecules outside - exocytosis
29
Proteins can be modified by
Adding sugar molecules to make glycoproteins
Adding lipids molecules to make lipoproteins
Being folded into their 3D shape
30
What are motor proteins
Carry things along
Drag organelles from one part of the cell to another
31
Describe micro filaments
Gives support and strength
Allows cell to move
32
Describe intermediate filaments
Anchor the nucleus
33
Describe micro tubules
Provides shape and support helps substances move through the cytoplasm
34
Cilia are ? And can be found in large numbers
Eg ?
Smaller
Ciliates epithelial cells eg airways
35
Undulipodia are ? And occur as ? Structures
Eg ?
Longer
Single
Sperm
36
In prokaryotic cells we call the protrusions ?
Flagella
37
Describe prokaryotic cells
No nucleus
DNA circular
Smaller
Less developed cytoskeleton
No centrioles
Flagella
DNA is naked
Mesosome
38
Describe eukaryotic cells
Nucleus
DNA linear
Larger
Well developed cytoskeleton
Centrioles
Membrane bound organelles
Cellulose
Cilia , undulipodia
39
What is resolution
Is the ability To distinguishes between 2 points
Enables you to see things Jan greater detail
40
What is magnification
The number of times larger an object is compared with the original
41
What's the magnification equation
Size of image / actual size
42
What is the magnification triangle
Image on top
Magnification and actual size at the bottom
43
What are stains and why do we stain things
Stains are coloured chemicals that bind to molecules in or on the specimen
Make it easier to see
44
An example of a stain
Iodine in potassium iodine solutions stains the cellulose in plants cell walls yellow and starch granules blue / black
45
How do you observe prepared specimens
Dehydrate the specimen
Embedding them in wax to prevent distortion during slicing
Using special instruments to make very thing slices called sections
They are stained and mounted in a special chemical to preserve them
46
Optical (light ) microscopes
How it works and examples of what you see
Uses visible light ( focused beam ) to magnify objects
Large structures inside the cell
Eg cell wall
Mitochondria
47
What's the magnification and resolution of optical microscopes
M- x1500- x2000
R- 200nm
48
Optical microscopes
Ads and disads
Ads
- relatively cheap
- easily to use
- portable to use in lab and field study
Disads
- cannot see small organelles
- limited resolutions
- low magnification
49
Laser scanning microscopes
How it works and examples of what you can see
Use laser light to scan an object point by point and assemble by compute the image displayed
-structures in depth eg cells in the retina
50
Laser scanning microscopes
Magnification and resolution
M- x2009
R-633nm , high
51
Laser scanning microscopes ads and disads
Ads
- build up clean three dimensional images
- high resolutions
- assist diagnosis for eye problems
Disads
- expensive
- not portable
52
Transmissions electron microscopes
Magnification and resolution
M- x2000000
R- 0.2nm
53
Transmission electron microscopes
How it works , what can they see
Beam of electrons pass through the specimen which is stained with metal salts . Some electrons pass through and are focused on the screen . The electrons form a black and white image
Smaller structures e.g. Ribosomes
54
Transmission electron microscopes
Ads and disads
Ads
- most powerful magnification
- wide range of applications
- images are high quality and detailed
- easy to operate with special training
Disads
- large and expensive
- laborious sample preparation
- images are black and white
55
Scanning electron microscopes
How it works and examples of what you see
Electrons do not pass through the specimen, which is whole but causes secondary electrons to bounce off the surface and focused onto a screen , this gives 3D image , has to be placed in a vacuum
Smaller structures e.g. Red blood cells
56
Scanning electron microscopes
Magnification and resolution
M- x15 to x 200000
R- o.2nm
57
Scanning electron microscopes
Ads / disads
Ads
Easy to operate with training
Software user friendly
Works fast
Samples require minimum preparation
Disads
Expressive
Large
Training required
Small risk of radiation poising
58
What is an eyepiece graticule
A measuring device . It is placed in the eyepiece of a microscope and acts as a ruler when you view on object under the microscopes
59
What is a stage graticule
A precise measuring device . It is a small scale that is placed on a microscope stage and used to calibrate the values of eyepiece divisions at different magnification
60
The head and the tail of the phospholipid , when there's a big group in a line what is it called
Phospholipids bilayer
61
The head is
Hydrophilic
62
The tail is
Hydrophobic
63
Why is the plasma membrane describe as being partially permeable
Cells form a barrier and separates the cell contents from the cell exterior environment , or separate organelles from cytoplasm , they need to allow some molecules through in or out of the cell - determines which molecule it allows through
64
Role of membranes at the surface is cell/ plans membranes
- separates the cell components from its external environment
May be the site of chemical reactions
Regulates transport of materials into and out of the cell
May realise chemicals that signals other cells
Has antigens
65
Roles of membranes with thin the cell
The membrane around many organelles present in eukaryotic cells separate the organelles contents from the cell cytoplasm so that each organelle is a discrete entity and able to perform its function
66
The fluid mosaic model contains
```
Phospholipids
Glycoprotein
Glycolipids
Extrinsic proteins
Integral proteins
Cholesterol
Channel proteins
Carrier proteins
```
67
What is diffusion
The movement of water from a high concentration to a low concentration
Down the concentration gradient
68
What molecules can diffuse through the membrane and why
Small molecules - e.g. Oxygen because they're small enough to pass through the membrane by simple diffusion
Lipid molecules - because they dissolve in the hydrophobic fatty tails
Non charged particles - because they don't dissolve in water
69
What is facilitated diffusion
Movement of molecules from an area of high concentration to low concentration across a partially permeable membrane via a protein channel or carrier molecules
70
Factors that affect the rate of diffusion
```
Temperature
Diffusion distance
Surface area
Size of diffusing distance
Concentration gradient
```
71
How does temperature affect rate of diffusion
As temp increase the molecules have more kinetic energy do their rate is diffusion will increase
Conversely as they lose heat their rate is diffusion will slow down
72
How does distance affect diffusion rate
The thicker the membrane across which molecules have to diffuse the slower the rate of diffusion
73
Describe how surface area affects the rate of diffusion
More diffusion can take place across a large surface area. Cells specialised for absorption have extensions to their cell surface membranes , increasing surface area
74
Describe how the size of diffusing molecule affects surface area
Smaller ions or molecules diffuse more rapidly than larger molecules
75
Describe how the concentration gradient affects the rate of diffusion
The steeper the gradient the more molecules there are on the other side of the membrane compared with the other side . The faster diffusion to the other side where there are fewer molecules down the gradient
76
How does a temperature increase affect membrane structures and permeability
The phospholipids acquire more KE and move around more in a random way , this increases membrane fluidity
Increases permeability
An increase in membrane fluidity may effect the unfolding of plasma membrane during phagocytosis
77
How does temperature and proteins affect membrane structure
High temperatures cause the atoms within their large molecules to vibrate and this breaks the hydrogen bonds and ionic bonds that hold their structure together, unfold and denature
Their tertiary structure changes and cannot change back
78
When temperature drops , how does it affect membrane structure and permeability
Membranes have less permeable , however there are many unsaturated fatty acids making up the cell membrane phospholipid bilayer and as they become compressed the kinks in the tails push adjacent phospholipids molecules away . This maintains membrane fluidity
79
The proportions of unsaturated and saturated fatty acids within a cell membrane determines the
Membrane fluidity at cold temperatures
80
Effects of solvents on phospholipid
Organic solvents such as acetone and ethonal will damage cell membranes as they di
81
Describe Cholestrol
Provides stability in the membrane and helps fluidity, when temperatures drop buffer effects and helps maintain the fluidity
82
Describe channel proteins
Span the whole phospholipids bilayer - there integral proteins . Molecules containing charged ions are allowed to pass through facilitated diffusion allowed of polar molecules
83
Describe Cartier proteins
Span the whole phospholipids bilayer . Carries larger molecules through the membrane
Eg glucose via facilitated diffusion
84
Describe glycolipids
Lipids attached with carbs
85
Describe glycoproteins
Proteins with carbs attached to them
86
Describe what glycoproteins and glycolipids do
Both involved in cell signalling to allow recognition by the immune system
87
Diffusion and facilitated diffusion are ? And require no ?
Passive
Energy
88
Define active transport
The movement of substances against Their concentration gradient (lie to high) across a cell membrane using ATP and protein carriers
89
Describe carrier proteins
Site to which substances binds and also has another site for ATP this energy helps carrier protein change shape.
90
Describe bulk transport
Some cells need to transport large molecules and particles that are too large to pass through the plasma membrane . They require ATP . The energy released from hydrolysis at ATP enables the pump protein to change its shape so that three ions are now on the outside of the cell and two potassium ions are inside the cell
91
What is endocytosis
the taking in of matter by a living cell by invagination of its membrane to form a vacuole.
92
What is phagocytosis
Eating cells and refers to this type of intake of solid matter
93
What is pinocytosis
If cells ingest liquids by endocytosis
94
What is exocytosis
process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.
95
Define osmosis
Is the net movement of water molecules from a high water potential to a low water water potential through a partially permeable membrane
96
What is water potential
Measure of the tendency of molecules to diffuse from one region to another
97
What can affect the water potential of a solution and why
Solute molecules - water attaches because they're polar , therefore cannot move , reducing water potential
98
Describe cytolysis
if A lot of water molecules enter , the cell will swell and burst as the plasma membrane breaks
99
Describe turgid
The strong cellulose cell wall will prevent bursting . The cell wall swell up to a certain size . When it's contents push against the cell wall which will resist any further swelling , helps support
100
Describe crenated
Animal cells shrivel and are describe as crenated
101
Describe plasmolysed
The cytoplasm of the plant cells shrinks and the membrane pulls away from the cell wall , flaccid
102
Glycoprotein functions
Acts as antigens
Cell receptors
Cell signals
Stabilise the cell membrane
103
Factors effecting membrane structure and permeability
Temperature drops
Temperature increases
Proteins and temperature
104
How a drop in temperature affects membrane structure and permeability
Less permeable
When temperature drops
• Saturated fatty acids become compressed.
• However, there are many unsaturated fatty acids making
up the cell membrane phospholipid bilayer, and as they
become compressed the kinks in their tails push adjacent
phospholipid molecules away. This maintains the membrane
fluidity.
Therefore, the proportions of unsaturated and saturated fatty
acids within a cell membrane determine the membrane's
fluidity at cold temperatures.
Cholesterol in the membrane also buffers the effect of lowered
temperature, to prevent a reduction in the membrane's fluidity
It does this by preventing the phospholipid molecules from
packing together too closely, because cholesterol molecules are
in between groups of phospholipid molecules.
105
How a temperature increase effects membrane structure and permeability
More permeable
When temperature increases
The phospholipids acquire more kinetic energy and move
around more, in a random way. This increases the membrane's
fluidity
• Permeability increases.
• It also affects the way membrane-embedded proteins are
positioned and may function. If some of the proteins that act
as enzymes in a membrane drift sideways, this could alter the
rate of the reactions they catalyse.
• An increase in membrane fluidity may affect the infolding of
the plasma membrane during phagocytosis.
• An increase in membrane fluidity may also change the ability
of cells to signal to other cells by releasing chemicals, often by
exocytosis.
The presence of cholesterol molecules buffers, to some extent,
the effects of increasing heat as it reduces the increase in
membrane fluidity.
106
Effects of solvents on phospholipids
Organic solvents such as acetone and ethanol will damage cell membranes as the dissolve lipids
