Biology > Cell structure > Flashcards

Cell structure Flashcards

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1
Q

How big are animal and plant cells?

A

-animals = 0.01 mm-0.05mm
-plants = 0.01 mm-0.10mm

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2
Q

Why do we need microscopes to see small things?

A

-naked eye can only see objects as small as 0.05mm
>microscope is required to see cells in detail

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3
Q

The type of microscope used in a school lab is a…

A

…compound microscope.

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4
Q

What are the two lenses that magnify the specimen on a microscope?

A

-eyepiece
-objective lens

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5
Q

What is the eyepiece on a microscope?

A

-lens at the top of microscope which magnifies the image produced by the objective lens

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6
Q

What is the objective lens on a microscope?

A

-lens closest to the specimen that produces a greatly magnified image of it

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7
Q

Equation for the total magnification of the microscope

A

magnification of eyepiece × magnification of objective

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8
Q

If the magnification of an eyepiece is ×10 and the objective is ×40, what is the magnification of the microscope

A

x400

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9
Q

How do you calculate the magnification of an image?

A

magnification = size of image/ real size of object
MAKE SURE UNITS ARE THE SAME

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10
Q

How big is a micrometre compared to a metre?

A

10-6 m

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11
Q

How big is a nanometre compared to a metre?

A

10-9m

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12
Q

In a book, a micrograph of the cell measured 100 mm.
The real size of the cell shown is 0.05 mm
What is the magnification?

A

100/0.05 =200mm

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13
Q

Onion epidermal tissue:
How do you prepare a biological sample for examination?

A

-wear eye protection

-put a small drop of water on the microscope slide

-peel some onion skin from inside one of the leaves in an onion bulb using tweezers

-use forceps to transfer to drop of water
> make sure that it is flat, so no air bubbles

-stain cells with iodine + place iodine on top

-stick a coverslip on top

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14
Q

Why do we stain cells with iodine when looking at them under a microscope?

A

-it binds to starch in plant cells
-stains the originally colourless cellular structures, making them easier to see

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15
Q

What are the risks when doing the onion epidermal tissue experiment with a light microscope?

A

-care must be taken when looking down the microscope if the illumination is bright

-care when using microscope stains

-care when handling coverslips, microscope slides and mounted needles

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16
Q

Method of using a light microscope to examine cells

A

-place slide on the stage and observe using the lowest power objective lens

-focus in on the image and increase the magnification until you can clearly observe the cell’s structure

-make a drawing of what you see, label structures > ensure you record magnification used

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17
Q

What is a low power diagram used for?

A

-as a plan to show the arrangement of any distinct regions of the tissue, for example the tissues in a plant root
-to show the outline of individual cells that make up the tissue, if the tissue is uniform

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17
Q

What is a high power diagram?

A

-a detailed image of a part of the slide, usually to show a single cell

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18
Q

Throughout the development of light microscopes, what has increased?

A

-the magnification

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19
Q

What organelles does an animal cell have?

A

-cytoplasm
-nucleus
-cell membrane
-mitochondria
-ribosomes

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20
Q

What is the function of the cytoplasm?

A

-site of cellular reactions e.g. first stage of respiration
-transport medium

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21
Q

What is the nucleus?

A

-contains genetic material, including DNA, which controls the cell’s activities

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22
Q

What is the cell membrane?

A

-partly permeable structure that controls the movement of substances in and out the cell

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23
Q

What are the mitochondria?

A

-organelles containing enzymes for respiration
>most energy is released here by aerobic respiration

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24
What are ribosomes?
-tiny structures where protein synthesis happens
25
Organelles of a plant cell
-cytoplasm -nucleus -cell membrane -mitochondria -ribosomes -chloroplast -cell wall -permanent vacuole
26
What is chloroplast?
-organelles containing chlorophyll, which absorbs light energy for photosynthesis -contains enzymes for photosynthesis
27
What is the function of the cell wall?
-provides strength and gives a shape to the cell -prevents the cell bursting when water enters by osmosis
28
What is the function of the permanent vacuole?
-supports the cell, maintaining its turgidity
29
What is the difference in order of magnitude for a human hair and HIV? The width of a human hair is 100 μm, while the width of the HIV is 100 nm
The width of the human hair is 100 μm = 10-4 m The width of the HIV is 100 nm = 10-7 m 10-4/10-3 = 3
30
How is a sperm cell specialised to carry out its function?
-head of sperm contains haploid nucleus (containing genetic material) for fertilisation -acrosome contains enzymes so sperm can penetrate egg -midpiece packed with mitochondria to release energy by respiration needed to swim -it has a tail (flagella) and streamlined shape, enabling it to swim towards egg to fertilise it
31
How is a nerve cell specialised to carry out its function?
-long axon allows electrical impulses to be transmitted all over the body from the central nervous system -dendrites on main cell body connect to other nerve cells, muscles, glands -myelin sheath, insulates axon, speeding up nerve impulse
32
How is a muscle cell specialised to carry out its function?
-filaments of protein that slide over each other to cause muscle contraction -many well-developed mitochondria provide energy for muscle contraction -merged cells in skeletal muscle for muscle fibre contraction in unison
33
How is a root hair cell specialised to carry out its function?
-thin projection penetrates into the soil increases surface area >can come into contact with more of it and absorb more water and minerals -small root hairs increase surface area of root in contact with soil so it can absorb more water and minerals -thin cell walls to not restrict the movement of water and nutrients
34
How is a xylem cell specialised to carry out its function?
-no top and bottom walls between xylem vessels, so continuous route for water to flow -thick woody side walls strengthen structure -cells are dead as not to require feeding and waste energy
35
How is a phloem cell specialised to carry out its function?
-sieve plates let dissolved sugars/amino acids flow from one cell to the next -companion cells provide energy required for active transport substances in the phloem -form a column or tube for continuous route of transfer
36
What organelles does a prokaryotic cell have?
-cell membrane -cell wall -cytoplasm -ribosomes -plasmids
37
Cells of animals, plants and fungi are called... Cells of bacteria are called...
...eukaryotic cells. ... prokaryotic cells.
38
Why can't antibiotics be used to treat viruses and diseases?
-viruses live inside cells
39
Why do human skin cells need to divide?
-for growth/repair, to replace cells
40
What are the two types of cells?
-eukaryotic (plant and animal) -prokaryotic (bacteria)
41
What are the differences between eukaryotic and prokaryotic cells?
-prokaryotic are much smaller -eukaryotic have a nucleus
42
What is the prokaryotic cell wall made of?
-peptidoglycan
43
What are plasmids?
-small circular DNA loops found free in the cytoplasm and separate from main DNA > carries genes that provide genetic advantages
44
What is the order of magnitude?
-a power to the base 10 used to quantify and compare size
45
What is a cm?
1 x 10-2 metres
46
What is a mm?
1x10-3 metres
47
What is the difference in order of magnitude of a human hair (100 micrometres) and the HIV virus (100nm)?
1x10-4/ 1x10-7 3
48
List the components of both plant and animal cells
-nucleus -cytoplasm -mitochondria -cell membrane -ribosomes
49
List the additional cell components found in plant cells
-chloroplast -cell wall -permanent vacuole
50
Other than storing genetic information, what is the function of the nucleus?
-controls cellular activities
51
Describe the structure of the cytoplasm
-jelly-like fluid component of the cell >contains enzymes, organelles, dissolved ions + nutrients
52
What is the plant cell wall made out of?
-cellulose
53
What does the permanent vacuole contain?
- cell sap (solution of salts, sugars, organic acids)
54
What is cell differentiation?
-process by which cells become specialised/adapted for a particular function
55
Why is cell differentiation important?
-they need to undergo differentiation >to become specialised for specific purposes -carry out vital functions throughout the body
56
At what point in life do most animal cells differentiate?
-early in their life cycle
57
For how long do plant cells retain the ability to differentiate?
-throughout their entire life cycle
58
What is the purpose of cell division in mature animals?
-repair and replacement of old cells
59
What changes does a cell go through as it differentiates?
-obtaining different sub-cellular structures to enable a specific function performed by the cell
60
What is magnification?
-number of times bigger an image appears compared to its real size
61
What is resolution?
-smallest distance that can be distinguished between two objects
62
What are the advantages of light microscopes?
-inexpensive -easy to use -portable
63
What is the disadvantage of light microscopes?
-limited resolution
64
Name 2 types of electron microscopes
-transmission electron microscope -scanning electron microscope
65
What is the advantage of electron microscopes?
-greater magnification and resolution
66
Why do electron microscopes have a greater magnification and resolution?
-use a beam of electrons which has a shorter wavelength than photons of light
67
What are the disadvantages of electron microscopes?
-expensive -large, less portable -require training to use -only dead specimens can be observed
68
What is 0.005 in standard form?
5 x 10-3
69
What is 10382 in standard form?
1.0382 x10 ^4
70
How do bacteria multiply?
-binary fission (simple cell division)
71
How often do bacteria multiply?
-once every 20 minutes if enough nutrients are available and the temperature is suitable
72
What are uncontaminated cultures of microorganisms needed for?
-investigating disinfectant and antibiotic action
73
Why must Petri dishes and culture media be sterilised before use?
-to kill any microorganisms already present -to prevent other microorganisms affecting the results
74
Why must inoculating loops be sterilised by passing through a bunsen burner flame?
-to kill any bacteria present on the inoculating loop
75
Why must the petri dish be secured with adhesive tape?
-stops bacteria in the air contaminating the culture
76
Why are cultures incubated at 25 degrees in school labs?
-prevents growth of harmful pathogens
77
Key characteristics of all cells
-between 0.01-0.1mm across -made of a cell membrane that contains a cytoplasm, DNA and ribosomes
78
What animal cells don't have a nucleus?
-red blood cells
79
Why are most plant roots white?
-plant root cells don't have chloroplast that have chlorophyll, which gives plants their green pigment
80
How much bigger are eukaryotic cells compared to prokaryotic?
10x-100x larger
81
What are the 4 different bases (monomers) of DNA?
-adnene (A) -thymine (T) -cytosine (C) -guanine (G)
82
Base pairs of DNA: A matches with... G matches with...
...T ...C
83
DNA is very big, so how does it fit in your cells?
-it is very tightly coiled into chromosomes, slotted inside the nucleus
84
Why would the students repeat their mitosis experiment?
-to improve reliability
85
Why are there muscle cells in the stomach?
-to allow it to contract and expand -to churn food
86
There are areas of the agar jelly with the disinfectant where no bacteria was growing. Why?
-the bacteria was killed by the disinfectant
87
Suggest how a vaccination program against TB would stop it from growing
-it provides immunity to TB -stops it from spreading
88
Give a reason why plant cells do not burst
-cell wall prevents bursting
89
The flagellum helps the cell to move through water. Scientists that the flagellum and the light-sensitive spot work together to increase photosynthesis How might this happen?
-light-sensitive spot detects light -guides movement of flagellum towards light
90
Explain why single-celled organisms do not need complex structures for gas exchange
-cells of single celled organisms have a high sa:v -short diffusion distance, maximising rate of diffusion - diffusion via cell membrane is good enough, no need for complex structures
91
Explain why active transport is necessary in root hair cells
-there are less mineral ions in the soil than in the root hair cell -ions need to move from an area of low concentration to an area of high concentration (against the concentration gradient) > requires energy
92
All tools should be washed in disinfectant after using them on plants with viruses Why?
-in order to kill the virus and stop it from spreading when used later
93
Suggest how scientists can use a plant that has virus-resistant gene to produce many that have this
-they can use stem cells from meristems of the plant >will produce a plant with the same genetic makeup and favourable characteristic (virus-resistant)
94
How to calculate the length of time a stage lasts in a cell in minutes
(cells produced in stage/ total cells produced) x total hours taken x 60
95
Why might the number of cells level out during mitosis?
-shortage of nutrients so cells die
96
Suggest how fibres help in blood clot formation
-hold cells together
97
Explain the advantages of red blood cells passing through a capillary one at a time
-slows down flow -more surface area of the blood cell will be exposed >increases rate of diffusion
98
The movement of chloride ions causes water to pass out of the cells into the mucus. Explain why
-this is by osmosis -the mucus is more concentrated -so the water in the chloride ions moves from a more dilute to concentrated solution
99
Explain how oxygen passes from the blood to the mitochondria
-diffusion -it moves from a high concentration in the blood -to a low concentration in the mitochondria -through the cell membrane
100
Why is it better to use stem cells from the patient themselves?
-will most likely not be attacked by their immune system
101
How is a red blood cell adapted to absorb more oxygen?
-biconcave shape to allow oxygen to be absorbed more quickly -no nucleus so it has more area to absorb oxygen
102
Why is an embryonic stem cell better than an adult stem cell?
-totipotent and so can develop into many more cell types -can be used to treat more conditions
103
Why might a cell not be visible when viewed under a microscope?
-objective lens not clicked into place -no cells in the field of view
104
Why do adults still have adult stem cells?
-still need new cells -to heal from injuries or to replace cells when they wear out
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