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OCR AS-level Biology > 2.1.1 cell structure > Flashcards

2.1.1 cell structure Flashcards

1
Q

units of measurement:

how to convert units

A

cm to mm = X10

mm to µm (micrometer) = X100

µm to Nm (nano meter) = x1000

Nm to µm = ÷ 1000

µm to mm = ÷ 100

mm to cm = ÷ 10

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2
Q

outline how a student could prepare a temporary mount of tissue for a light microscope

A
  1. obtain thin section of tissue

2 place plant tissue in a drop of water

3 stain tissue on a slide to make structures visible

4 add coverslip using mounted needle at 45* to avoid trapping air bubbles

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3
Q

describe how light microscopes work

A
  1. lenses focus rays of light and magnify the view of a thin slice of specimen
  2. different structures absorb different amounts of wavelengths of light
  3. reflected light is transmitted to the observer via the objective lens and eyepiece
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4
Q

Describe how a transmission electron microscope works

A
  1. pass a high energy beam of electrons through a thin slice of specimen
  2. More dense structures appear darker since they absorb more electrons
  3. Focus image onto fluorescent screen or photographic plate using magnetic lenses
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5
Q

Describe how a scanning electron microscope works

A
  1. Focus a beam of electrons onto a specimens surface using electromagnetic lenses
  2. Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
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6
Q

Describe how a laser scanning confocal microscope works

A
  1. Focus a laser beam onto a small area on a sample surface using objective lenses
  2. fluorophores in the sample emit photons
  3. photomultiplier tube amplifies the signal onto a detector, an image is produced pixel by pixel in the correct order
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7
Q

State the equation to calculate the magnification

A

magnification = image size ÷ actual size

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8
Q

Define magnification

A

How many times larger the microscope can make the image appear

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9
Q

Define resolution

A

The ability to distinguish between two objects that are close together

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10
Q

Explain why staining may be used to prepare a specimen for use in a light microscope

A

Staining provides a contrast, make organelles visible, and enables you to observe different types of cells

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11
Q

State the magnification and resolution of a light microscope

A

magnification = 200x

resolution = 200 nm

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12
Q

State the magnification and resolution of a TEM

A

magnification = 500,000 x

resolution = 0.5nm

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13
Q

State the magnification and resolution of a SEM

A

magnification = 500,000

resolution = 3-10nm

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14
Q

Explain how to use an eyepiece graticule and stage micrometer to measure the size of a structure

A
  1. Place micrometre on stage to calibrate eyepiece graticule
  2. lineup scales on graticule and micro meter. Count how many graticule divisions are in 100µm on the micrometer
  3. length of one eyepiece division = 100 µm ÷ number of divisions
  4. Use calibrated values to calculate actual length of structures
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15
Q

Describe the structure of the nucleus

A

it is surrounded by nuclear envelope, a semipermeable double membrane

nuclear pores allows substances to enter and exit

Dense nucleolus made of RNA and proteins assembles ribosomes

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16
Q

describe the function of the nucleus

A

The nucleus contains DNA coiled around chromatin into chromosomes

It controls cellular processes: gene expression determine specialisation and it is the site of mRNA transcription, mitosis, semiconservative replication

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17
Q

describe the structure and function of the endoplasmic reticulum

A

inside the membrane is cisternae, a network of tubules and flattened sacs extends from cell membrane and connect to nuclear envelope

RER: many ribosome attached for protein synthesis and transport

SER: synthesis of cholesterol, steroid hormones and the breakdown of toxins. lipid synthesis. They store and transport, lipids and carbohydrates

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18
Q

describe the structure and function of the golgi apparatus

A

planar stack of membrane bound, flattened sacs, cis face aligns with rER. molecules are processed in cisternae and vesicles bud off trans face via exocytosis

they modify and package proteins for export and synthesise glycoproteins

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19
Q

Describe the structure and function of ribosomes

A

they are formed of protein and rRNA

they have large subunit which joins amino acids and small subunit with mRNA binding site

they can be free in the cytoplasm or attached to the RER, and also found in mitochondria and chloroplasts.

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20
Q

Describe the relationship between the organelles involved in the production and secretion of proteins

A

The ribosomes that synthesise proteins are attached to the rER. The Golgi apparatus, which modifies proteins for secretion, aligns with the rER

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21
Q

Describe the structure of a mitochondria

A

they are surrounded by a double membrane.

The folded inner membrane forms cristae: Site of electron transport chain.

Fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids and proteins

The outer membrane is smooth

It is the site of aerobic stages of respiration

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22
Q

Describe the structure of a chloroplast

A

vesicular plastered with double membrane.

thylakoids: flattened discs stack to form grana which Contains photosystems with chlorophyll

intergranal lamellae: Tubes attach thylakoids in adjacent grana

stroma: fluid filled matrix.

This is where photosynthesis occurs

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23
Q

State the function of mitochondria and chloroplasts

A

Mitochondria: site of aerobic respiration to produce ATP

Chloroplasts: site of photosynthesis to convert solar energy to chemical energy

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24
Q

Describe the structure and function of a lysosome

A

they contain digestive enzymes and they are vesicles which contain hydrolytic enzymes and are formed from golgi

physics and maths tutor: Sac surrounded by single membrane. embedded H+ pump maintains acidic conditions. contains digestive hydrolase enzymes. Glycoprotein coat protect cell interior. digests contents of phagosome, exocytosis of digestive enzymes

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25
describe the structure Of the cell wall
Made of Cellulose, very strong, difficult to digest and has gaps in so small molecules and ions can pass through
26
Describe the structure of a nuclear envelope
they have a double membrane, the outer membrane links with ER, nuclear pores are large enough to let ribosomes through, mRNA out and enzymes in
27
Describe the structure and function of a plant cell wall
it is made of Celulose microfibrils for mechanical support Plasmodesmata form part of apoplast pathway to allow molecules to pass between cells Middle lamella separates adjacent cell walls
28
What are bacterial and fungal cell walls made of
bacteria : peptidoglycan (murein) fungi: chitin
29
Describe the structure and function of centrioles
Spherical group of nine microtubules arranged in triples, located in centrosomes, migrate to opposite poles of cell during prophase and spindle fibres form between them them
30
Describe the structure and function of the cell surface plasma membrane
fluid Mosaic phospholipid bilayer with extrinsic and intrinsic proteins embedded Function: it isolates cytoplasm from extracellular environment, is selectively permeable to regulate transport substances and is involved in cell signalling/cell recognition
31
Explain the role of cholesterol, glycoproteins and glycolipids in the cell surface membrane
Cholesteryl: steroid molecule connect phospholipids and reduces fluidity. Glycoproteins: cell signalling, cell recognition and binding cells together. Glycolipids: cell signalling and cell recognition
32
describe protein Synthesis and secretion
nucleus contains genes for protein on DNA, mRNA makes a template of the gene and leaves the nucleus through a nuclear pore. mRNA travels to the ribosomes on the RER and a protein is made. Versicle forms and carries the protein to the cis face of the Golgi apparatus The vessicle fuses with the golgi apparatus and the protein moves to the trans-face and during this time it is processed and packaged Vessicle buds off the golgi and moves towards the cell surface membrane The vessicle fuses with the cell surface membrane and secrete the protein by exocytosis
33
What is the cytoskeleton
A network of fibres. Important for shape and stability of the cell and holds organelles in place. Controls movement of organelles and cell movement has three components: microfilaments, microtubules, and intermediate fibres
34
What are microfilaments
globular protein ACTIN form contractile fibres It controls cell movement and contraction during cytokinesis
35
What are microtubules
globular protein TUBLIN Forms scaffold like structure, it determines shape of cell and acts as cell tracks for organelle movement. They are found in spindle fibres
36
What are intermediate fibres
Gives mechanical stability to cell
37
Define a eukaryotic cell
A cell with a nucleus
38
Describe a prokaryotic cell
a cell without a nucleus
39
Describe eukaryotes
They are larger, more complex, contain a nucleus, contain organelles, can be single celled and multicellular and contains chromosomes
40
Describe prokaryotes
they are the oldest cell type, small and simple, lack a nucleus, lack organelles, single celled, reproduce asexually, have DNA free in the cytoplasm
41
What organelles does a bacteria cell have
ribosomes pili (help environment move - waft), plasmids, DNA (long loop of chromosomes), plasma membrane, cell wall, capsule (jelly like, source of protection, nutrition), cytoplasm and flagellum
42
What do prokaryotes and eukaryotes both have
DNA, ribosomes, cytoplasm And plasma membrane
43
Describe the structure and function of flagella
Hollow helical tube made of the protein flagellin, rotate to propel usually unicellular organism
44
Describe the structure and function of cilia
hairlike protrusions on eukaryotic cells they move back and forth rhythmically to sweep foreign substances like dust or pathogens away and to enable the cell to move
45
ppq:Which of the following, a - b , is a feature of both light microscopy And confocal microscopy A: can be used to observe ribosomes B: can be used with live tissues C: obtains images using Laser light D: requires a great deal of training to use
B
46
ppq: What can you see with light microscopes, transmission electron microscope’s, scanning electron microscope and laser scanning confocal microscope
light microscope: whole cells and tissues transmission electron microscope: organelles Laser scanning confocal microscope: an object at a certain depth within a cell scanning electron microscope: Cell surfaces
47
ppq: which of the options, a to D, occurs in the nucleus of a cell A: synthesis of enzymes B: synthesis of RNA C: modification of polypeptides D: synthesis of carbohydrates
B
48
ppq: Which organelle, A-D, is not involved in the production and secretion of enzymes in eukaryotes A:Golgi apparatus B: Ribosomes C: Smooth endoplasmic reticulum D: Vesicle
C
49
ppq: Which of the following best describes a microscope with high resolution A: The microscope can distinguish structures that are very close together B: The microscope can view structures that are very small C:The microscope is capable of high magnification D: The microscope has an inbuilt eyepiece graticule
A
50
ppq: Chloroplasts and bacteria are: A: similar in size B: at different ends of the size range C: exactly the same D: none of these
A similar in size
51
ppq: Which of these materials is not a major component of the plasma membrane A: Phospholipids B: Glycoproteins C: Proteins D: DNA
D dna
52
ppq: Which polysaccharide is a major component of plant cell walls A: chitin B: peptidoglycan C: cellulose D: cholesterol
C cellulose
53
ppq: where are Ribosomes constructed in A: Endoplasmic reticulum B: Nucleoid C: Nucleolus D: Nuclear pore
C nuclelous
54
ppq: rough endoplasmic reticulum is the area in a cell where what are synthesised A: Polysaccharides B: Proteins C: Lipids D: DNA
B, proteins
55
ppq: The smooth endoplasmic reticulum is the area in a cell where what are synthesised A: Polysaccharides B: Proteins C: Lipids D: DNA
C lipids
56
ppq: The thin extensions of the inner mitochondrial membrane are known as what A: Cristae B: Matrix C: thylakoids D:stroma
A cristae
57
ppq: Which of these cellular organelles have their own DNA A: Chloroplast B: Nucleus C: Mitochondria D: All of the above
D All of the above
58
ppq: Which of the following statements describes an organelle which is not membrane-bound A: Contains Cristae B: Modifies and packages proteins C: Contains digestive enzymes D: is made of rRNA and proteins
D
59
ppq: List three organelles found in both animal and plant cells
ribosomes, mitochondria, cytoplasm
60
ppq: Suggest why organelles are normally surrounded by membranes
It keeps each organelle separate from the rest of the cell so that it is a discrete compartment
61
ppq: Name and describe the function of an animal cell organelle which is absent from plant cells
Centrioles make spindle fibres and are only found in animal cells as it helps with cell division
62
ppq: Name two functions the lysosomes carry out
Lysosomes keep the powerful hydrolytic enzymes separate from the rest of the cell, lysosomes can engulf old organelles And foreign matter, digests them and returns the digested components to the cell for re use Removes waste from the cell and apoctosis
63
ppq: Function of the Golgi apparatus
Process and package proteins into vesicles
64
ppq: What would the vesicles that bud off the RER contain
Proteins
65
ppq: Name one structure present in animal cells that is not present in plant cells
Centrioles
66
ppq: Name two features of plant cells that are not features of animal cells
Permanent vacuole and cell wall
67
ppq: State two features of a eukaryotic cell that would not be visible using medium power of a light microscope
Ribosomes and mitochondria
68
ppq: which of the following do plant cells have, animal cells have, and bacterial cells have ``` Mitochondria Chloroplasts Cellulose cell wall Centrioles Ribosomes ```
Plant cells have mitochondria, chloroplasts, cellulose cell wall, and ribosomes. They do not have centrioles animal cells have mitochondria, centrioles and ribosomes. They do not have chloroplasts or cellulose cell walls Bacterial cells only have ribosomes. They do not have mitochondria, chloroplasts, cell walls, centrioles
69
ppq: which of the organelles listed is smallest in size A: Nuclei B: Ribosomes C: Mitochondria D: Lysosomes
b Ribosomes
70
ppq: Suggest one stage during the secretion of a protein that requires energy
Exocytosis (fusing vessicle to membrane)
71
ppq: name one feature that Would be present in the cytoplasm of a prokaryotic cell that is not found in a eukaryotic cell
free dna
72
ppq: A student wanted to observe some red blood cells under the microscope. The student placed a small sample of blood onto a microscope slide and added a drop of distilled water. When viewed at higher power, the student observed that the red blood cells had burst. In a similar procedure using plant epidermis, the student observed that the plant cells did not burst. Explain these observations
The cell cytoplasm has a lower water potential than distilled water. Water moves into the cells, down the water potential gradient and water enters the cell by osmosis. The cell surface membrane is weak so bursts as it cannot withstand the pressure. But the plant cell wall is strong so does not burst and the plant cell becomes turgid which reduces water uptake
73
ppq: Suggest how the student could modify the procedure to observe red blood cells without them bursting
Use a salt or sugar solution or add a solute to water
74
ppq: Name the process in which a cell become specialised
Differentiation
75
ppq: Neutrophils are phagocytic blood cells that can engulf and digest foreign cells found in the blood. Describe how the ultrastructure of a neutrophil is specialised to enable it to perform this function
It has many lysosomes containing hydrolytic enzymes. Has a well-developed cytoskeleton including many microfilaments. It has many ribosomes and a lot of rough endoplasmic reticulum, many mitochondria, lots of golgi and many receptors on the cell surface membrane
76
ppq: What process do ribosomes Carry out
Protein synthesis
77
ppq: Suggest two processes inside cells that rely on the cytoskeleton for movement
movement inside cells of Chromosomes in cell division and RNA and protein synthesis
78
ppq: State three roles of membranes inside cells
They make compartments to separate organelles within a cell for example mitochondria. They isolate the contents of the organelle like the hydrolytic enzymes in lysosomes , provide selective permeability
79
ppq: Cells contain a large number of membrane-bound vesicles, many of these vesicles transport substances between organelles . Outline how the vessicles are moved from one organism to another
The cytoskeleton provides tracks for movement. The vesicle moves along the microfilaments and microtubules and the microtubules are broken down. this uses ATP
80
ppq: The proteins embedded in the membranes of vesicles have different functions. COPI and COPII proteins are known as “address proteins”. vesicles that transport materials from the golgi to the rer are coated in COPI proteins. vesicles that transport materials to the golgi from the RER are coated in COPII proteins suggest how these proteins ensure that a vesicle is transported to the correct target organelle
The receptor is found only on the correct target. The address protein provides a way of labelling/identifying the vesicles. The COPI has a specific shape and therefore the address proteins are complimentary to the receptor and the receptor will then fit the shape of the protein (COPI)
81
ppq: Cells in the pancreas secretes proteins such as the enzymes pancreatic amylase and protease. Describe how these extracellular enzymes are secreted from the cells
Through exocytosis. The vesicle fuses with the cell surface membrane which releases enzymes to the exterior
82
ppq: In the lungs, goblet cells secrete mucus. The mucus is then moved by Cilia. name 1 cellular structure from the list below that is associated with each of the following functions. you must select a structure once only mitochondria, ribosome, golgi vesicle, centriole, nucleus, cytoskeleton (I) release of energy (II) movement of cillia (III) secrete mucus
(I) release of energy = mitochondria (II) movement of cillia = cytoskeleton (III) secrete mucus = golgi vesicle
83
ppq: and organelle has the properties listed below: there are pairs of microtubules inside the structure, it is found on the surface of the cell, it is surrounded by a membrane which organelle, A - D , is being described A: Cell wall B: Chloroplast C: Flagellum D: Centriole
C flagellum
84
ppq: Describe the function of a cells nucleus
It controls the cells activities by controlling the transcription of DNA
85
ppq: The scientist added eosin Y, methylene blue and azure B stains to the sample. eosin Y Stains the cytoplasm of cells and orange/pink colour. Together, methylene blue and azure B stain cell nuclei a blue/purple colour. Suggest and explain why the scientist used the stains to observe white blood cells in the sample
eosin y Stained the side to present so this allowed the scientist to see the cells against the background. Methylene blue and azure B Stay in the nucleus so this allowed the scientist to differentiate between white blood cells and red blood cells as white blood cells Contain a nucleus and red blood cells do not

OCR AS-level Biology (12 decks)

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