A LEVEL BIOLOGY 2 > Module 2.1.1 - Cell Structure > Flashcards

Module 2.1.1 - Cell Structure Flashcards

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1
Q

State the difference between prokaryotic and eukaryotic organisms (2)

A
  • Prokaryotic organisms are made up of single prokaryotic cells
  • Eukaryotic organisms are made up of eukaryotic cells
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2
Q

Describe the features common to both prokaryotic and eukaryotic cells (2)

A
  • Both types of cells contain organelles
  • Which are specialised structures with specific functions
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3
Q

Explain the main structural difference between prokaryotic and eukaryotic cells (2)

A
  • Eukaryotic cells are complex and include all animal and plant cells
  • Prokaryotic cells are smaller and structurally simpler, such as bacteria.
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4
Q

learn a labelled diagram of structure of a plant cell (6)

A
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5
Q

learn a labelled diagram of a structure of a animal cell (6)

A
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6
Q

Describe differences between plant and animal cell (3)

A
  • Plant cells contain all the organelles found in animal cells but also have a cell wall with plasmodesmata for substance exchange with neighbouring cells
  • Plant cells also contain a vacuole, which stores cell sap
  • Plant cells also have chloroplasts for photosynthesis
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7
Q

learn labelled diagram of the structure of a nucleus (6)

A

nucleolus
chromatin
nuclear envelope
nucleoplasm
ribosome
endoplasmic reticulum
nuclear pore

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8
Q

Describe the structure and function of the nucleus (3)

A
  • Contains DNA that controls cell activities by providing the base sequences (instructions) for protein synthesis
  • DNA is associated with histone proteins , forming chromatin , which coils into chromosomes
  • surrounded by the nuclear envelope and contains the nucleolus
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9
Q

function of the nucleolus (1)

A

the central region within the nucleus where ribosomes are produced

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10
Q

Describe the structure and function of the nuclear envelope (2)

A
  • A double membrane surrounding the nucleus that contains pores
  • Pores allow small molecules, such as RNA, to pass into the cytoplasm while keeping chromosomes safely inside
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11
Q

Describe structure and function of the RER (2)

A
  • An extension of the nuclear envelope with ribosomes on its surface , providing a large area for protein synthesis
  • Transports newly made proteins to the Golgi apparatus for modification.
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12
Q

Function of the SER (1)

A

Synthesises lipids , including cholesterol, and steroid hormones such as oestrogen

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13
Q
A
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14
Q

Learn a labelled diagram of the structure of the Golgi apparatus (4)

A
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15
Q

Describe the structure and function of the Golgi apparatus (3)

A
  • A stack of flattened membrane-bound sacs surrounded by vesicles
  • Receives proteins from the RER and lipids from the SER, modifies them, and repackages them into vesicles
  • it also produces lysosomes
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16
Q

State the function of ribosomes (2)

A
  • Carries out protein synthesis by translating RNA into proteins
  • Either free in the cytoplasm or attached to the RER
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17
Q

Learn labelled diagram of the structure of mitochondria (6)

A
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18
Q

Describe the structure and function of mitochondria (3)

A
  • Site of ATP production during aerobic respiration
  • Surrounded by a double membrane with inner folds called cristae, providing a large surface area for respiration
  • Self-replicating and found in large numbers in cells with high energy demands
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19
Q

Structure and function of lysosomes (2)

A
  • membrane-bound sacs containing digestive enzymes
  • Break down old organelles or foreign material by engulfing and digesting them
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20
Q

Learn labelled diagram of structure of chloroplasts (6)

A
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21
Q

Describe the structure and function of chloroplasts (3)

A
  • site of photosynthesis , found in only plants and certain photosynthetic bacteria and protists
  • Surrounded by a double membrane, with internal thylakoid membrane arranged into stacks called grana, linked by lamellae
  • Contains chlorophyll which are photosynthetic pigments for capturing light energy
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22
Q

Describe the structure and function of the plasma membrane (2)

A
  • composed of a phospholipid bilayer with embedded proteins and cholesterol for fluidity regulation
  • encloses cell contents, maintains cell shape , and controls the movement of substances in and out of cell
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23
Q

Describe the structure and function of centrioles (2)

A
  • Bundles of microtubules involved in forming spindle fibres during mitosis to separate sister chromatids
  • Also important for forming cilia and flagella which is absent in plant and bacterial cells
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24
Q

Describe the structure and function of cell wall (2)

A
  • a rigid outer layer made of cellulose in plants , chitin in fungi, and murein in prokaryotes
  • which provides structural support to the cell
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25
Describe the structure and function of flagella (2)
- Tall whip-like structures made from bundles of microtubules that contract to move the cell - Present in cells such as sperm, which use flagella to swim towards the egg cell
26
Describe the structure and function of cilia (2)
- Har-like projections containing bundles of microtubules that contract to create movement - Found on epithelial cells in the trachea , where they sweep mucus up the windpipe
27
Describe the structure and function of the vacuole (2)
- A membrane-bound compartment containing cell sap, and sometimes nutrients and proteins - Helps maintain turgidity in plant cells; some vacuoles can digest large molecules like lysosomes
28
Explain the stages in the synthesis and transport of proteins (4)
1. mRNA is translated into a polypeptide chain at ribosomes , either free in the cytoplasm or attached to the rough ER 2. At the RER, the polypeptide chain is folded and transported in vesicles to the Golgi apparatus 3. Proteins are modified and processed in the Golgi, for example by adding carbohydrate, sulfate, or phosphate groups 4. Packaged into vesicles, which transport them to their destination in the cell or to the plasma membrane for secretion
29
Describe the structure and function of the cytoskeleton (3)
- A network of protein threads running through the cytoplasm in eukaryotic cells - includes microfilaments and microtubules, which support organelles and keep them in position - Maintains cell shape , strengthens the cell, and is involved in the movement of cilia and flagella
30
State the main structural differences between prokaryotic and eukaryotic cells (6)
- Prokaryotic cells lack membrane-bound organelles such as mitochondria, Golgi, and nucleus - Prokaryotic DNA is a single circular chromosome, whereas eukaryotic DNA is linear and wrapped around proteins to form chromosomes - Prokaryotes may have small circular DNA molecules called plasmids - Prokaryotic ribosomes are smaller (70S) than eukaryotic (80S) - Cells walls in plants and fungi (eukaryotes) are made of cellulose or chitin, while bacterial cell walls are made of murein. - Prokaryotic cells are smaller than eukaryotic cells
31
Explain how flagella differ between prokaryotes and eukaryotes (2)
- Both cell types can have flagella - In prokaryotes, flagella are made from the protein flagellin, whereas in eukaryotes, when present, they are made from microtubules
32
Learn a labelled diagram of the structure of a typical prokaryotic cells
lack of membrane-bound organelles , have smaller ribosomes (70S) than eukaroytic cells, cell wall is made of peptidoglycn
33
Describe the structure and function of pili in prokaryotic cells (2)
- Hair-like structures that extend from the plasma membrane - Used for communication between cells, including transferring plasmids between bacteria
34
Describe the structure and possible function of mesosomes (3)
- folded regions of inner membrane - some scientists believe they may have a role in respiration or other chemical reactions - But others suggest they may be artefacts from sample preparation for microscopy.
35
Describe the structure and function of plasmids in prokaryotic cells (2)
- Small, circular DNA molecules separate from the main chromosome - Contain genes not essential for survival but potentially beneficial, such as antibiotic resistance; can replicate independently of chromosomal DNA
36
Describe the structure and function of the slime capsule in prokaryotic cells (2)
- An outer layer made of slime found in some bacteria , in addition to the cell wall - Protects the bacterium from attacks by the immune system
37
Describe the uses of microscopy (2)
- Microscopes are used to observe and study cell structure in detail - Different types of microscopes, such as light and electron microscopes, can study cells at different levels of magnification and resolution
38
Describe the structure and use of a light microscope (3)
- Uses light to form an image - Has a maximum resolution of about 0.2 nanometres and maximum useful magnification of around x1500 - Used to observe larger structures such as whole cells,nuclei, mitochondria, and chloroplasts
39
Advantages of light microscopes (3)
- Small, relatively inexpensive and straightforward to prepare specimens for - can produce colour images - allow viewing of living specimens
40
Describe the structure and use of an electron microscope (3)
- uses electrons to form an image - has a maximum resolution of around 0.0002 micrometers (0.2 nm) and magnification from x1,000,000 to several million - can observe small cell structures such as membranes , ribosomes, ER , and lysosomes
41
Explain limitation of electron microscopes (3)
- Large and expensive, with complex specimen preparation - Require a vacuum, so live specimens cannot be observed - images are black and white , can be artificially coloured later
42
State two main types of electron microscopes (2)
Transmission electron microscope (TEM) Scanning electron microscopes (SEM)
43
Describe the structure and function of a TEM (3)
- uses electromagnets to direct a beam of electrons through a thin specimen - Denser areas absorb more electrons and appear darker on the image - produces high-resolution, two-dimensional images that reveal internal cell and organelle structures
44
Describe the structure and function of a SEM (3)
- Passes a beam of electrons across the surface of a specimen and detects how electrons are scattered back. - Has a lower maximum resolution than TEMs - produces 3 dimensional images showing specimen surface detail
45
Explain why microscopes are important in biology (2)
- Many cell structures are too small to be see with the naked eye, so microscopes are essential for studying them - Allow scientists to observe tissues, cells, and organelles , for example viewing chromosome movement during mitosis
46
Learn a labelled diagram of the structure of an optical (light) microscope (5)
47
Describe how an optical microscope works (3)
1. Light is passed through a thin layer of specimen on a glass slide 2. The light is focused through multiple lenses so that an image is seen through the eyepiece 3. Magnification is adjusted by rotating different objective lenses into place.
48
Describe how to prepare a microscope slide using a liquid specimen (3)
1. Add a few drops of the sample to the slide with a pipettes 2. Cover with a coverslip and press gently to remove air bubbles 3. Wear gloves to prevent contamination with foreign cells
49
Describe how to prepare a microscope slide using a solid specimen (5) marks
1. Take care with sharp tools and wear gloves to avoid contact with stains 2. Cut a small sample of tissue with scissors 3. Peel or cut a very thin layer of cells so light can pass through clearly 4. Apply a stain to make structures more visible 5. Place a coverslip on top and press gently to remove air bubbles
50
51
State why you should start with the low-power objective lens when using a optical microscope (2)
- easier to locate the area of interest in the field of view - reduces the risk of damaging the lens of coverslip if the stage is raised to high
52
Explain how to prevent dehydration of specimens on microscope slides (2)
- Thin samples can dry out quickly - adding a drop of water beneath the coverslip helps prevent cell damage from dehydration
53
State ways to improve or unclear blurry or microscopic images (3)
- Use a lower-power objective lens and coarse focus for a clearer view - Check specimen is thin enough for light to pass through clearly - Prevent contamination with foreign cells or debris
54
Describe how a graticule is used to measure cells (5)
1. A graticule is a small disc with an engraved ruler. 2. It is inserted into the eyepiece of a microscope so it can act as a ruler in the field of view. 3. As the graticule has no set units, it must be calibrated for the objective lens being used, which is done by comparing it to a scale engraved on a microscope slide called a stage micrometer. 4. By comparing the two scales, the number of micrometres that each graticule unit represents can be calculated. 5. Once calibrated, the graticule can be used like a ruler to measure cells in the field of view.
55
State three limitations of using an optical microscope to measure cell size (4)
- the size of cells of tissue structures may appear inconsistent in different specimen slides - because cell structures are 3D and tissue samples may be cut at different planes , causing inconsistencies when viewed on a 2D slide - optical microscopes have lower magnification compared to other microscopic types, so some structures cannot be seen.
56
The roles of dyes in light microscopy (2).
- dyes absorb certain wavelengths of light and reflect others, making stained structured visible - the type of dye absorbed depends on the chemical properties of the tissue
57
Three limitations of using an optical microscope to measure cell size (4)
- The size of cells or tissue structures may appear inconsistent in different specimen slides - Because cell structures are 3D and tissue samples may be cut at different planes, causing inconsistencies when viewed on a 2D slide - Optical microscopes have lower magnification compared to other microscopic types, so some structures cannot be seen - The process of preparing and treating specimens for slides may alter the structure of the cells
58
Explain why calibration it’s important when using a graticule (1)
Without calibration, the measurements taken will be meaningless and inaccurate
59
Describe why staining is used in light microscopy (3)
- Many tissues used in microscopy are naturally transparent, allowing both light and electrons to pass through - This transparency makes it difficult to see details in the tissue when viewed under a microscope - stains are applied to colour the tissue, making structures more visible
60
Describe the roles of dyes in light microscopy (2)
- Dyes absorb certain wavelengths of light and reflect others , making stained structures visible - the type of of dye absorbed depends on the chemical properties of the tissue
61
What is meant by differential staining (2)
- differential staining uses more than one dye at the same time - this ensures that different tissues in the specimen can be distinguished from eachother
62
State two examples of stains used in light microscopy and their effects (2)
- Toluidine blue stains cells blue - Phloroglucinol stains cells red or pink
63
Describe why most colours seen in photomicrographs are not natural (2)
- Many colours result from the dyes used in staining rather than the natural appearance of the tissues - some structures, like chloroplasts, appear in their natural colour and do not require staining,
64
Explain why staining is needed for Transmission electron microscopes (TEM) (3)
- Staining allows tissues to absorb electrons, which have no colour - This causes the tissues to appear black or in various shades of grey - Heavy metal compounds such as osmosium tetroxide are commonly used because they absorb electrons well
65
State how colours are added to electron micrographs (1)
Colours are added artificially using image-processing software
66
Describe what a biological drawing is (2)
- a labelled line diagram showing scientific features observed in a specimen under a microscope - it is used to accurately record microscopic observations
67
State the main rules for microscope drawings (5)
1. Include a title 2. Record the magnification used for the observations 3. Use a sharp HB pencil and plain white paper 4. Draw clear , single lines with no shading 5. Keep label lines straight with a ruler , not crossing each other , and connecting directly to the structures
68
Explain how microscope drawings should be presented for accuracy (3)
- the drawing should take up as much space as possible on the page - Structures should be clearly defined and draw in proper proportion - Labels should be placed to one side of the drawing and kept parallel to the page top
69
State the difference between cell drawings and plan drawings (2)
- Cell drawings are made at higher magnification to show individual cell details - Plan drawings are made a lower magnification to show the arrangement of tissues, not individual cells
70
Magnification calculation
I AM Magnification = image size / actual
71
Learn unit conversions for microscopy calculations
72
Define magnification and resolution (2)
- Magnification is the number times larger an image is compared to thr actual object - Resolution is the ability to distinguish separate points in an image as two distinct objects
73
Explain how magnification is determined in a light microscope (2)
- The magnification is calculated by multiplying the magnification of the eyepiece lens by the magnification of the objective lens - The ability to magnify depends on the type and features of the microscope
74
Explain the relationship between resolution and wavelength (3)
- in light microscopes, resolution is limited by the wavelength of visible light - As light passes close to small structures , it is diffracted, causing the waves to spread and overlap - Objects closer together than half the wavelength of light cannot be distinguished as separate points
75
Explain why electron microscopes have higher resolution than light microscopes (2)
- electrons have a much smaller wavelength than visible light - This allows objects that are closer together to be distinguished before diffraction causes the beams to overlap.
76
compare the resolution and magnification of light and electron microscopes (2)
- Electron microscopes have a much greater resolution than light microscopes - TEMs can achieve higher magnification than SEMs due to a greater resolution
77
Compare the uses of light and electron microscopes (2)
- Light microscopes can view living or dead specimens, whole cells, small organisms, and tissues - Electron microscopes can only view dead specimens but are useful for organelles, viruses, and detailed whole cell imaging
78
State two practical differences between light and electron microscopes (2)
- Light microscopes are small, portable , require no vacuum , and have simple sample preparation - Electron microscopes are large, fixed in placed, require a vacuum , and need complex sample preparation
A LEVEL BIOLOGY 2
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