1
Q
What is magnification?
A
How many times bigger the image of the object is bigger than the actual size
2
Q
What is resolution?
A
The minimum distance two objects can be apart in order for them to be seen as separate items
3
Q
What units are cells and cell organelles usually measured in?
A
μm (micrometres)
4
Q
What are the conversions from micrometres to millimetres?
A
1mm = 1000μm
Multiply the millimetres by 1000 to get to micrometres
5
Q
What is the formula for total magnification?
A
Eyepiece lens magnification x optical lens magnification
6
Q
What is the equation used to find magnification?
A
Magnification = image size/actual size
7
Q
What is the equation used to find actual size?
A
Actual size = image size/magnification
8
Q
What is the equation for actual size using a scale bar?
A
Actual size = (image length/scale bar length) x scale bar value
9
Q
What is the equation for magnification using a scale bar?
A
Scale bar length x 1000
10
Q
What is cell fractionation?
A
The process where cells are broken up and the different organelles they contain are separated
11
Q
What does cell fractionation and ultracentrifugation allow us to do?
A
Study the structure and function of organelles
12
Q
What conditions does the solution need to be before adding the tissue for cell fractionation?
A
- Cold
- Isotonic
- Buffered
13
Q
Why does the solution need to be cold when putting in the tissue for cell fractionation?
A
To reduce enzyme activity that may break down the organelles
14
Q
Why does the solution need to be isotonic when putting in the tissue for cell fractionation?
A
To prevent organelles bursting or shrinking as a result of osmotic gain or loss of water
15
Q
Why does the solution need to be buffered when putting in the tissue for cell fractionation?
A
So that the pH doesn’t fluctuate which could alter the structure of the organelles or the function of the enzymes
16
Q
What is the process of cell fractionation? (4)
A
- The cells are homogenised (broken up) by either a pestle and mortar, a blender or a homogeniser
- The fluid mixture left is called the homogenate
- The homogenate is suspended in a buffer solution
- The homogenate is filtered to remove bits of cells that have not been broken up fully
17
Q
What is used in cell fractionation to break up the cells?
A
A homogeniser (blender)
18
Q
What is the fluid called after homigenisation has happened?
A
Homogenate
19
Q
What happens after homogenisation?
A
The homogenate is filtered to remove any complete cells and large pieces of debris
20
Q
What is ultracentrifugation?
A
Process of which the fragments of filtered homogenate is separated in a centrifuge
21
Q
What is the process of ultracentrifugation for animal cells?
A
- The filtered homogenate is placed in the centrifuge and spun at a low speed
- This forces the heaviest organelles to the bottom of the tube, forming a ‘pellet’
- The supernatant is moved to another tube and span again at a faster speed
- The next heaviest organelles are forced to the bottom.
- This is repeated until the desired organelle is separated
22
Q
What are the requirements that a specimen has to be to see it in a light microscope?
A
- Must be cut thinly
- A stain may have to be used
23
Q
Why do light microscopes have poor resolution?
A
The relatively long wavelength of light
24
Q
What are pros and cons of a light microscope?
A
PROs
- Cheaper than an electron microscope
- Can see in colour
- Specimens can be living or dead
CONs
- Wavelength of light limits the resolution
- Magnification is not as good as in an electron microscope
25
What are the two types of microscope?
- Light microscope
- Electron microscope
26
What are 2 advantages of the electron microscope over the light microscope?
- The electron beam has a very short wavelength therefore it has a high resolving power
- As electrons are negatively charged the beam can be focused using electromagnets
27
What is the resolving power of a modern electron microscope?
0.1nm apart, 2000 times better than a light microscope
28
What are the two types of electron microscope?
- Transmission (TEM)
- Scanning (SEM)
29
How does a TEM work? (3)
- An electron gun produces a beam of electrons focused by a condenser electromagnet.
- The beam passes through a thin specimen, with parts absorbing electrons (appearing dark) and others allowing electrons to pass through (appearing bright).
- The image produced on a screen can be photographed to create a photomicrograph.
30
Why cant a TEM always achieve a 0.1nm resolving power?
- The preparation of the specimen is difficult so can limit the the resolution
- A higher energy electron beam is required and this may destroy the specimen
31
What are the limitations of the TEM? (4)
- Specimen must be dead as the system has to be in a vacuum
- A complex staining method is required and image isn't in colour
- Specimen must be extremely thin
- Artifacts may appear
32
What is a limitation of the TEM but not an SEM?
The specimen for an SEM doesn't have to be thin as no electrons penetrate the specimen in an SEM
33
How does an SEM work?
The SEM directs a beam of electrons onto the specimen's surface from above, scanning it in a regular pattern. The scattering of electrons, which varies with the specimen's contours, helps build a 3D image with the aid of a computer.
34
What is the resolving power of an SEM?
About 20nm
35
What do you use to measure the size of an object under a microscope?
An eyepiece graticule
36
How do you calibrate an eyepiece graticule?
- Use a stage micrometer
- Line up the start of the stage micrometer scale with the eyepiece graticule scale
- Compare how many units of one compares to the other
- As each unit on the micrometer scale = 10μm, you divide that by how many graticule units it corresponds to
37
What makes up the nucleus? (5)
- Nuclear envelope
- Nuclear pores
- Nucleoplasm
- Chromosomes
- Nucleolus
38
What is the nuclear envelope?
What does it do?
A double membrane that surrounds the nucleus. Its outer membrane is continuous with the ER of the cell and often has ribosomes on its surface
It controls the entry and exit of materials in and out of the nucleus and contains the reactions taking place within it
39
What are nuclear pores?
What do they do?
How many are usually in each nucleus?
How big are they in diameter?
Specialised channels in the nuclear envelope that regulate the transport of molecules between the cytoplasm and nucleus
3000 in each nucleus
40-100 nm
40
What is the nucleoplasm?
Granular, jelly-like material that makes up the bulk of the nucleus
41
What do chromosomes consist of?
Protein-bound, linear DNA
42
What is the nucleolus?
What does it do?
Small spherical region within the nucleoplasm
Manufactures ribosomal RNA and assembles the ribosomes
43
What are the functions of the nucleus? (3)
- Act as the control centre of the cell through the production of mRNA and tRNA and hence protein synthesis
- Retain the genetic material of the cell in the form of DNA and chromosomes
- Manufacture ribosomal RNA and ribosomes
44
What makes up a mitochondria? (3)
- Double membrane
- Cristae
- Matrix
45
What does the double membrane do in a mitochondria?
Controls entry and exit of material
46
What are cristae?
What do they do?
Extensions of the inner membrane
Provide a large surface area for the attachment of enzymes and other proteins involved in respiration
47
What is the matrix?
What does it do?
Makes up the remainder of the mitochondria
Contains proteins, lipids, ribosomes and DNA that allows the mitochondria to control the production of some of their own proteins
48
What happens in mitochondria?
What do they produce?
Stages of aerobic respiration:
- Krebs cycle
- Oxidative phosphorylation pathway
Produce ATP from glucose
49
What makes up a chloroplast? (5)
- Chloroplast envelope
- Grana
- Thylakoids
- Chlorophyll
- Stroma
50
What is the chloroplast envelope?
What does it do?
Double plasma membrane that surrounds the organelle.
Allows materials to enter and leave the cell
51
What are grana?
What are thylakoids?
What is chlorophyll?
Stacks of up to 100 disc-like structures called **thylakoids**.
Within the thylakoids are photosynthetic pigment called **chlorophyll**
52
What is the stroma?
Fluid-filled matrix where the second stage of photosynthesis takes place. Within the stroma are a number of other structures e.g. starch grains
53
How are chloroplasts adapted to their function of harvesting sunlight and carrying out photosynthesis in the following ways? (3)
- Granal membranes offer a broad, organised surface where chlorophyll, electron carriers, and key enzymes can attach, allowing the first stage of photosynthesis to happen efficiently
- The fluid of the stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis
- Chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis
54
What is the endoplasmic reticulum?
What are the 2 types?
Elaborate, three-dimensional system of sheet-like membranes, spreading through the cytoplasm of the cells
It is continuous with the outer nuclear membrane. The membranes enclose a network of tubules and flattened sacs called cisternae
- Rough Endoplasmic Reticulum
- Smooth Endoplasmic Reticulum
55
What is the difference between the smooth and rough endoplasmic reticulum?
RER has ribosomes present on the outer surfaces of the membranes, whereas the SER lacks ribosomes on its surface and is often more tubular in appearance
56
What are the functions of the rough endoplasmic reticulum? (2)
- Provide a large surface area for the synthesis of proteins and glycoproteins
- Provide a pathway for the transport of materials, especially proteins, throughout the cell
57
What are the functions of the smooth endoplasmic reticulum? (2)
- Synthesise, store and transport lipids
- Synthesise, store and transport carbohydrates
58
What is the structure of the Golgi apparatus?
Similar to the SER in structure except more compact. Consists of a stack of membranes that make up flattened sacs (cisternae), with small rounded hollow structures called vesicles.
59
What is the function of the Golgi apparatus? (5)
- Add carbohydrate to proteins to form glycoproteins
- Produce secretory enzymes, such as those secreted by the pancreas
- Secrete carbohydrates, such as those used in making cell walls in plants
- Transport, modify and store lipids
- Form lysosomes
60
When are lysosomes formed?
When the vesicles produced by the Golgi apparatus contain enzymes such as proteases and lipases
61
What are the functions of lysosomes? (4)
- Hydrolyse material ingested by phagocytic cells, such as white blood cells and bacteria
- Release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell
- Digest worn out organelles so that the useful chemicals they are made of can be re-used
- Completely break down cells after they have died (autolysis)
62
What are ribosomes?
Where can they be found?
- Small cytoplasmic granules found in all cells
- They may occur in the cytoplasm or be associated with the RER
63
What are the 2 types of ribosome? Where are each found? How big are they?
- 80S - found in eukaryotic cells - around 25nm in diameter
- 70S - found in prokaryotic cells, mitochondria and chloroplasts - smaller than 80S
64
What are the features of a cell wall? (2)
- Consist of a number of polysaccharides e.g. cellulose
- There is a thin layer, called the middle lamellae, which marks the boundary between adjacent cell walls and cements adjacent cells together
65
What are the functions of the cell wall? (3)
- To provide mechanical strength in order to prevent the cell bursting under the pressure created by the osmotic entry of water
- To give mechanical strength to the plant as a whole
- To allow water to pass along it and so contribute to the movement of water through the plant
66
What is different about the cell walls of fungi?
Does not contain cellulose, but contains other polysaccharides chitin and glycan, and glycoproteins
67
What is a vacuole?
A fluid-filled sac bounded by a single membrane
68
What is in the plant vacuole fluid? (5)
Mineral salts, sugars, amino acids, wastes and sometimes pigments called anthocyanins
69
What are the functions of plant vacuoles? (3)
- Supports non woody (herbaceous) parts of plants by being turgid
- The sugars and amino acids may act as a temporary food store
- The pigments may colour petals to attract pollinating
70
What are examples of types of tissue? (2)
- Epithelial tissues
- Xylem
71
What are epithelial tissues?
Epithelial tissues in animals form sheets of cells that cover organ surfaces, providing protection or secretion. Variants include thin, flat cells for rapid diffusion (like in alveoli) and ciliated cells that move substances along passages such as the trachea.
72
What are the function of xylem tissues?
Used to transport water and mineral ions throughout the plant and also gives mechanical support
73
What is the definition of an organ?
A combination of tissues that are coordinated to perform a variety of functions, although they often have one predominant major function
74
What ribosomes do prokaryotic cells have?
70s
75
What structures are found in a prokaryotic cell that aren't in a eukaryotic cell?
- Capsule
- Circular DNA
- Plasmid
- Flagellum
76
What is the function of the capsule in a prokaryotic cell?
Protects bacterium from other cells and helps groups of bacteria to stick together for further protection
77
What is the function of circular DNA in a prokaryotic cell?
Possesses the genetic information for the replication of bacterial cells
78
What is the function of plasmids in a prokaryotic cell?
Possesses genes that may aid the survival of bacteria in adverse conditions e.g. enzymes that break down antibiotics
79
What is the function of flagellum in prokaryotic cells?
Used for locomotion
80
What are 4 differences between a prokaryotic cell and a eukaryotic cell?
- Prokaryotic cells have no true nucleus, whereas eukaryotic
cells have a distinct nucleus, with a nuclear envelope
- In prokaryotic cells, DNA is not associated with proteins, whereas in eukaryotic cells, DNA is associated with proteins called histones
- In prokaryotes, Their cell wall is made out of murein, whereas in plant cells they are mainly made out of cellulose
81
What is the structure of a virus particle?
Nucleic acids are enclosed within a capsid. Some viruses are further surrounded by a lipid envelope. On the capsid of if the virus has them, the lipid envelope, there are attachment proteins
82
How big is a virus particle?
Between 20-300 nm
83
Define mitosis:
Division of a cell that results in each of the daughter cells having an exact copy of the DNA in the parent cell
84
What is the period in the cell cycle where mitosis is not happening called?
Interphase
85
What happens in interphase? (3)
3 stages: G1, S, and G2
G1 = growth stage: cell increases in size and synthesises mRNA and proteins for...
S = DNA replication: chromosomes are replicated
G2 = cell continues to grow, organelles are duplicated, and the cell is assessed whether it can undergo mitosis or not
86
What are the 4 stages of mitosis? (name)
- Prophase
- Metaphase
- Anaphase
- Telophase
87
What happens in the prophase stage of mitosis? (3)
- Chromosomes become visible
- Centrioles move to the poles of the cell, and spindle fibres develop from them
- Nucleolus disappears and nuclear envelope breaks down, leaving the chromosomes free in the cytoplasm
88
What happens in the metaphase stage of mitosis? (4)
- Chromosomes are seen to be made up of 2 chromatids
- Each chromatid is an identical copy of DNA from the parent cell
- The chromatids are joined by the centromere
- The chromosomes are pulled by the spindle apparatus and are aligned along the equator of the cell
89
What happens in the anaphase stage of mitosis? (3)
- Centromeres divide into two
- Spindle fibres pull the individual chromatids making up the chromosome apart
- The chromatids move rapidly to the opposite poles of the cell and are referred to as chromosomes
90
Is anaphase an active or passive process?
Active, it uses ATP produced by mitochondria
91
What happens in the telophase stage of mitosis? (2)
- The chromosomes reach their respective poles and disappear
- Spindle fibres disintegrate and the nuclear envelope and nucleolus re-form
92
What is cytokinesis and when does it happen?
When the cytoplasm divides at the end of mitosis
93
What is cell division in prokaryotic cells called?
Binary fission
94
Explain the process of binary fission: (4)
- Circular DNA molecule replicates and both copies attach to the cell membrane
- The plasmids also replicate
- The cell membrane begins to grow between the two DNA molecules and begins to pinch inward, dividing the cytoplasm in two
- A new cell wall forms between the two molecules of DNA, dividing the original cell into two identical daughter cells, each with a single copy of the circular DNA and a variable number of copies of the plasmids
95
How do viruses replicate? (3)
- Attach to host cell with the attachment proteins
- Inject nucleic acid into the host cell
- The genetic information on the nucleic acid provides the instructions for the host cell to start producing the viral components (nucleic acid, enzymes, structural proteins) which are assembled into new virus particles
96
What is cancer caused by?
A mutation to one of the two genes that regulate mitosis and the cell cycle
97
What are the two types of tumour and what is the difference between them?
Malignant - Grow rapidly and are more likely to be life-threatening
Benign - Grow slower and are less likely to be life-threatening
98
What does the treatment of cancer often involve?
Killing dividing cells by blocking a part of the cell cycle, disrupting it, so cancer growth stops
99
How do drugs used to treat cancer work?
- Preventing DNA from replicating
- Inhibiting the metaphase stage of mitosis by interfering with spindle formation
100
What is a side effect of cancer-treating drugs?
Because it halts cell division in all cells, it also affects healthy tissues. As a result, fast‑dividing cells, such as those in hair follicles, stop dividing, which can lead to hair loss.
Bio
flashcards
Decks in class (31)
# Cards
-
1. Biological Molecules64
-
2. Nucleic Acids42
-
transport across cell membranes (needs work cos yappy)(damn Right It Is Bitch)52
-
3. Cell Structure100
-
Transport Across Cell Membranes24
-
4.3. Osmosis22
-
5. Cell Recognition and the Immune System49
-
5.5 Antibodies30
-
6.1 - 6.5. Exchange50
-
6.6. Human Gas Exchange System37
-
6.9 - 6.10. Human Digestive System61
-
7.1 - 7.2. Movement of Oxygen22
-
7.3 - 7.6. Circulatory System64
-
7.7 - 7.9. Mass Transport in Plants69
-
8.1 - 8.3. DNA, Genes and Protein Synthesis23
-
8.4 - 8.5. Polypeptide synthesis20
-
9. Genetic Diversity41
-
10. Biodiversity46
-
Paper 1 EQs22
-
11. Photosynthesis33
-
12. Respiration33
-
13. Energy And Ecosystems46
-
14. Response to Stimuli84
-
15. Nervous Coordination and Muscles74
-
16. Homeostasis83
-
17. Inherited Change24
-
18. Populations and Evolution30
-
19. Populations in Ecosystems50
-
20. Gene Expression29
-
21. Recombinant DNA technology46
-
Paper 2 Exam Qs30
