Cell structure Flashcards
(121 cards)
1
Q
Animal vs plant cell size range
A
animal cells are between 0.01 mm – 0.05 mm
plant cells are between 0.01 mm – 0.10 mm
Therefore plant cells can be bigger
2
Q
What type of microscope is used in schools
A
Compound microscope
3
Q
Learn labelled diagram of microscope
A
https://www.bbc.co.uk/bitesize/guides/zpqpqhv/revision/1
4
Q
What 2 lenses are used to magnify a specimen
A
eye piece and objective lens
5
Q
How is magnification of a lens shown
A
somethingx10
6
Q
Equation for magnification of microscope working out
A
Magnification of the microscope = magnification of eyepiece × magnification of objective
So, if the magnification of an eyepiece is ×10 and the objective is ×4, the magnification of the microscope is:
magnification of eyepiece × magnification of objective
= 10 × 4
= 40
7
Q
How to calculate magnification of an image
A
magnification=size of image/real size of image
8
Q
Millimetre from a metre
A
1/1000
9
Q
Micrometre from a metre
A
1/1 million
10
Q
Nanometre from a metre
A
1/1 billion
11
Q
Learn standard form properly in relation to magnification conversions
A
https://www.bbc.co.uk/bitesize/guides/zpqpqhv/revision/2
12
Q
How to prepare cheek cells for examination
A
- put small drop of water microscope slide
- gently swab inside of cheek with clean cotton bud
- gently rub cotton bud in the drop of water
13
Q
How to prepare onion epidermal cells for examination
A
- put small drop of water microscope slide
- peel some onion skin from inside of one of bulb leaves
- use forceps to transfer skin to drop of water
14
Q
What must you ensure when transferring onion cells to microscope slide
A
Skin is flat
No air bubbles
15
Q
What do you stain onion cells on slide with
A
Iodine
16
Q
How to prepare hair or fur for examination
A
- put small drop of glycerol on slide
2. cut a small piece of hair and transfer to slide with forceps
17
Q
Why is glycerol used instead of water for fur and hair
A
Similar refractive index to hair so can see the layers in the hair with microscope
18
Q
What is name of piece of glass put over smaple before examination
A
Coverslip
19
Q
Purpose of coverslip
A
It protects the microscope and prevents the slide from drying out when it’s being examined.
20
Q
How is coverslip lowered onto specimen
A
Mounted needle
21
Q
Risks of preparing sample for microscopy
A
Care must be taken when looking down the microscope if the illumination is too bright.
Care when using microscope stains.
Care when handling coverslips, microscope slides and mounted needles.
22
Q
Why are stains used for certain samples
A
- Stains are used to add contrast.
- Certain stains are also used to stain specific cell structures or cell products.
23
Q
How to apply stains to samples
A
Put a drop of stain on the slide next to coverslip
Draw the stain under the coverslip by placing a piece of filter paper next to it
24
Q
Example of specimen where stain used
A
Fur and hair
25
Other than magnification what else is important when viewing slides
Resolution
26
What is resolution
This is the ability to see two points as two points, rather than merged into one.
Think about a digital photo. It can be enlarged, but over a certain size, you won’t be able to see any more detail. It will just become blurry.
The resolution of a light microscope is around 0.2 μm, or 200 nm. This means that it cannot distinguish two points closer than 200 nm.
27
What is difference between light and electron microscopes
Electron microscopes use a beam of electrons instead of light rays.
Much greater resolution 1nm in electron vs 200nm in light
28
Mitochondria under light microscope?
Barely visible
29
Can ribosomes be seen under light microscope?
No but can be seen under light microscope
30
Cytoplasm function
A jelly-like material that contains dissolved nutrients and salts and structures called organelles. It is where many of the chemical reactions happen.
31
Nucleus function
Contains genetic material, including DNA, which controls the cell’s activities.
32
Cell membrane
Its structure is permeable to some substances but not to others. It therefore controls the movement of substances in and out of the cell
33
Mitochondria function
Organelles that contain the enzymes for respiration, and where most energy is released in respiration
34
Ribosomes function
Tiny structures where protein synthesis occurs
35
Chloroplast function
Organelles that contains the green pigment, chlorophyll, which absorbs light energy for photosynthesis. Contains the enzymes needed for photosynthesis.
36
Cell wall function
Made from cellulose fibres and strengthens the cell and supports the plant.
37
Vacuole function
Filled with cell sap to help keep the cell turgid
38
Are there vacuoles in animal cells
Animal cells may also have vacuoles, but these are small and temporary. In animals, they are commonly used to store or transport substances.
39
What is used to measure cell size
Eyepiece graticule
40
Measuring cell size of microscope see bitesize
https://www.bbc.co.uk/bitesize/guides/zpqpqhv/revision/9
41
Look at orders of magnitude
https://www.bbc.co.uk/bitesize/guides/zpqpqhv/revision/10
42
Differences in size of eukaryotes and prokaryotes
Eukaryotes
Most are 5 μm – 100 μm
Prokaryotes
Most are 0.2 μm – 2.0 μm
43
Difference of outer laters eukaroytes and prokaryotes
Eukaryotes
Cell membrane - surrounded by cell wall in plants and fungi
Prokaryotes
Cell membrane - surrounded by cell wall
44
Difference of cell contents eukaroytes and prokaryotes
Eukaryotes
Cytoplasm, cell organelles include mitochondria, chloroplasts in plants and ribosomes
Prokaryotes
Cytoplasm, ribosomes, no mitochondria or chloroplasts
45
Difference in genetic material eukaryotes and prokaryotes
Eukaryote
DNA in a nucleus - plasmids are found in a few simple eukaryotic organisms
Prokaryote
DNA is a single molecule, found free in the cytoplasm - additional DNA is found on one or more rings called plasmids
46
Types of cell division eukaryotes and prokaryotes
Eukaryotes
Mitosis
Prokaryotes
Binary fission
47
Sperm cell structure adapted to function
The head of the sperm contains the genetic material for fertilisation. The acrosome in the head contains enzymes so that the sperm can penetrate an egg. The middle piece is packed with mitochondria to release energy needed to swim and fertilise the egg. The tail enables the sperm to swim.
48
Nerve cell structure adapted to function
| + learn specific labels online
The nerve cell is extended, so that nerves can run to and from different parts of the body to the central nervous system. The cell has extensions and branches, so that it can communicate with other nerve cells, muscles and glands. The nerve cell is covered with a fatty sheath, which insulates the nerve cell and speeds up the nerve impulse.
49
Muscle structure adapted to function
Muscle cells contain filaments of protein that slide over each other to cause muscle contraction. The arrangement of these filaments causes the banded appearance of heart muscle and skeletal muscle. They contain many well-developed mitochondria to provide the energy for muscle contraction. In skeletal muscle, the cells merge so that the muscle fibres contract in unison.
50
Root hair cell adapted to structure
The root hair cell has a large surface area to provide contact with soil water. It has thin walls so as not to restrict the movement of water
51
Xylem hair cell adapted to structure
There are no top and bottom walls between xylem vessels, so there is a continuous column of water running through them. Their walls become thickened and woody. They therefore support the plant.
52
Phloem cell structure adapted to function
Dissolved sugars and amino acids can be transported both up and down the stem. Companion cells, adjacent to the sieve tubes provide energy required to transport substances in the phloem.
53
What is a gene
section of a chromosome that contains the code for the production of a particular protein
54
How many chromosomes are there in a body cell
46- 23 pairs
55
Male vs female sex chromosomes
XY male
| XX female
56
When do cells divide
- an organism grows
| - an organism becomes damaged and needs to produce new cells
57
What are stem cells
are cells that have not undergone differentiation. A cell which has not yet become specialised is called undifferentiated.
58
What is embryo
An embryo develops from a fertilised egg. .
59
What cells make up embryo at in early development
stem cells
60
What could be done with cells removed from embryo
they will differentiate into any cell type.
61
Can you find stem cells in adult
```
Yes in limited areas such as
brain
eyes
blood
heart
liver
bone marrow
skin
muscle
```
62
Where does cell division in plants occur
meristem
63
Where are most meristems
close to the tip of the shoot, and the tip of the root.
64
What is special about cells at meristems
Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant- unspecialised and undifferentiated pretty much like stem cells
65
What happens to plant cells as they become older
As the cells become older, further away from the tip, they become differentiated – they enlarge and develop vacuoles.
66
Function of circulatory system
Transport substances, defend the body, regulate temperature
67
Function of excretory system
Remove waste products and unwanted substances, regulate the water content of the body
68
Function of muscular system
Bring about movement
69
Function of nervous system
Respond to internal and external stimuli and conditions, carry messages for the body work as a coordinated whole
70
Function of respiratory system
Deliver oxygen for respiration and remove waste
71
Function of reproductive system
Bring about fertilisation to produce new offspring
72
Function of skeletal system
To bring about movement, support and protect internal structures, produce blood cells, store and release calcium
73
Cell types of leaf
Palisade mesophyll
Spongy mesophyll
Guard cells
74
Cell types of phloem
Sieve tubes
| Companion cells
75
Function of palisade mesophyll
carry out photosynthesis
76
Function of spongy mesophyll
Allow gases to circulate for the exchange of gases between the leaf and the environment, carry out some photosynthesis
77
Function of guard cells
Open and close to control the exchange of gases – carbon dioxide, water vapour and oxygen
78
Function of sieve tubes
Transport products of photosynthesis, including sugars and amino acids, from the leaf to where they are needed
79
Function of companion cells
Provide the energy required for transporting substances in sieve tubes
80
Function of xylem vessels
Transport water and dissolved minerals from the roots, up the plant
81
Function of meristems
Produce new cells as they divide
82
How are cells from meristems useful
Cells from meristems can be cloned. Meristematic cells are removed from a plant and grown in tissue culture.
83
How are cells grown in tissue culture
The cells are grown in a culture medium that contains agar – to provide support and water for the growing cells – along with nutrients and plant hormones to stimulate growth and cell division.
84
How are
Clones will be genetically identical to the original plant providing the meristem cells. This is useful to provide crop plants for large-scale cultivation that have desirable characteristics such as disease resistance.
Producing new plants by cloning is quicker than allowing plants to reproduce and collecting and sowing seeds. It’s therefore an effective way of producing new individuals from rare and endangered plants, helping to preserve the species.
85
Uses of human stem cells
Transplanted into patients to help treat disease and their conditions or replace destroyed cells
86
Examples of uses of stem cells
- in type 1 diabetes
- in cases of multiple sclerosis, which can lead to paralysis
- in cases of spinal cord or brain injury, that have led to paralysis
87
What stem cells can be used for humans
embryonic stem cells
| adult stem cells
88
Differences between embryonic and adult stem cells
Embryonic cells can differentiate into a wider range of cells.
Adult stem cells have much narrower options to differentiate into- for example bone marrow cells can only differentiate into blood cells
89
Problems of embryonic stem cells
Difficult to obtain
| Ethical issues
90
When are bone marrow transplants useful
in cases of blood cell cancer such as leukaemia and lymphoma
| when blood cells have been destroyed by cancer treatment
91
How does therapeutic cloning work
The technique involves the transfer of the nucleus from a cell of the patient, to an egg cell whose nucleus has been removed.
92
Clinical issues of stem cells
There is no guarantee how successful these therapies will be, for example the use of stem cells in replacing nerve cells lost in Parkinson’s disease patients.
The current difficulty in finding suitable stem cell donors.
The difficulty in obtaining and storing a patient’s embryonic stem cells. These would have to be collected before birth - some clinics offer to store blood from the umbilical cord when a person is born.
Mutations have been observed in stem cells cultured for a number of generations, and some mutated stem cells have been observed to behave like cancer cells.
Cultured stem cells could be contaminated with viruses which would be transferred to a patient.
93
Ethical issues of stem cells
A source of embryonic stem cells is unused embryos produced by in vitro fertilisation (IVF)
For therapeutic cloning is it right to create embryos for therapy, and destroy them in the process?
Embryos could come to be viewed as a commodity, and not as an embryo that could develop into a person.
At what stage of its development should an embryo be regarded as, and treated as a person?
94
Social issues of stem cells
Educating the public about what stem cells can, and can't do, is important.
Whether the benefits of stem cell use outweigh the objections.
Much of the research is being carried out by commercial clinics, so reported successes are not subject to peer review. Patients could be exploited by paying for expensive treatments and being given false hope of a cure as stem cell therapies are only in their developmental stages.
95
Important distinction with diffusion
Individual particles will move in both directions not all in direction of high to low concentration. It is a NET movement in high to low
96
3 factors affecting rate of diffusion
How great the concentration gradient is
Temperature
Surface area
97
What happens to surface area to volume ratio as size of organism increases
Increases- as animals increase in size their surface area doesnt increase at same rate as that of volume. Eg ratio much larger in puppies compared to dogs
98
Implications of greater surface area to volume ratio
A puppy will lose heat much faster than that of a dog
99
BBC bitesize page very good for maths explanation of surface area to volume ratio
https://www.bbc.co.uk/bitesize/guides/zs63tv4/revision/3
100
What gives cells their concentration
Dissolved ions, sugars and amino acids
101
What allows transfer of solutes between cell and surroundings
Cell membrane is partially permeable
102
What happens when equal concentrations either side of permeable membrane
Movement between both sides but NO NET movement
103
Where do plants take up water
Root hair cells if soil is wet and moist
104
Where do plants lose water
Leaves but only if is dry and not humid
105
What is different about plant cells structurally to animals when comes to water mocement
Plant cells have a strong cellulose cell wall outside the cell membrane. The cell wall is fully permeable to all molecules and supports the cell and stops it bursting when it gains water by osmosis.
106
What happens when plant cell placed in pure water
In pure water, the cell contents (the cytoplasm and vacuole) push against the cell wall and the cell becomes turgid.
107
What is use of fully turgid cells
Fully turgid cells support the stems of non-woody plants
108
What ahppens when plant cell is placed in a concentrated solution
In a more concentrated solution, the cell contents lose water by osmosis. They shrink and pull away from the cell wall. The cell becomes flaccid. It is becoming plasmolysed
109
What happens when plant cell placed in highly concentrated solutions
In a very concentrated solution, the cell undergoes full plasmolysis as the cells lose more water.
110
What scenario could result in a loss of water from a plant
Plants would be exposed to higher concentrations of solutes if there was less water in the soil - for instance, if plants were not watered, or plants in drought conditions. Plant cells would then lose water by osmosis.
111
What happens when animal cell placed in hypertonic solution
lose water and shrink
112
what is hypertonic
highly concentrated solution
113
what happens when animal cell placed in hypotonic solution
gain water, swell then burst as NO CELL WALL
114
Maths on measures of rates relating to increase in mass after osmosis
https://www.bbc.co.uk/bitesize/guides/zs63tv4/revision/6
115
How do plants take up minerals
In soil there is a low nitrate concentration whereas in root hair a high concentration so active transport is used to uptake ions it needs from soil
116
When is active transport used in animals
When absorbing glucose or any other nutrient in the gut. A lot of time glucose concentration in the gut lumen (tube hole) may be higher than that of blood so can diffuse however if the concentration in lumen drops below that of blood active transport is needed to uptake glucose to blood
117
What produces energy for active transport
respiration
118
Out of diffusion, osmosis and active transoport which process requires energy
active transport
119
What substances are moved by diffusion
Carbon dioxide, oxygen, water, food substances, wastes, eg urea
120
What substances are moved by active transport
Water
121
What substances are moved by osmosis
Mineral ions into plant roots, glucose from the gut into intestinal cells, from where it moves into the blood
