Biology > Cell Structure 2.1 > Flashcards

Cell Structure 2.1 Flashcards

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1
Q

What is the function of the nucleus?

A

-Contains genetic information
-Provides the instructions for protein synthesis

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2
Q

What is the structure of the nucleus?

A
  • nuclear envelope( double membrane with pores that allow entry and exit of substances e.g exit of MRNA)
    -nucleolus (has no membrane) where ribosomes are made
    -contains the genetic material chromatin
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3
Q

What is the function of the rough endoplasmic reticulum?

A

-transports assembled proteins through cisternae into vesicles to be transported into the Golgi apparatus

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4
Q

What is the structure of the rough endoplasmic reticulum?

A

-System of membranes, containing cisternae that are continuous with the nuclear membrane
-Provides a large surface area for ribosomes
-The RER is coated with ribosomes

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5
Q

What is the function of the smooth endoplasmic reticulum?

A

-Involved in lipid metabolism:
.Synthesises cholesterol
.Synthesises lipids and phospholipids needed by cell
.Synthesises steroid hormones .e.g. sex hormones

-Involved with absorption, synthesis and transport of lipids (from the gut)

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6
Q

What is the structure of the smooth endoplasmic reticulum?

A

-System of membranes ,containing cisternae that are continuous with the nuclear membrane
-No ribosomes on surface(unlike RER)
-Contains enzymes that catalyse reactions involved with lipid metabolism

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7
Q

What is the function of the Golgi apparatus ?

A

-Proteins are modified .e.g. by adding sugar molecules to make glycoproteins, being folded into their 3D shape
-Packages proteins into vesicles either for exocytosis or to be stored in cell

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8
Q

What is the structure of the Golgi apparatus?

A
  • Consists of stacks of membrane-bound flattened sacs
  • Secretory vesicles bring materials to and from the Golgi apparatus
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9
Q

What is the function of ribosomes?

A

PROTEIN SYNTHESIS

-ribosomes bound to exterior of RER mainly for synthesising proteins to be exported out of cell
-ribosomes free in the cytoplasm are primarily sight of assembly of proteins to be used inside of cell

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10
Q

What is the structure of ribosomes?

A

-Small spherical organelles (around 20nm in diameter )
-made of ribosomal RNA
-Made in nucleolus as two separate subunits, which pass through nuclear envelope into cytoplasm and then combine
-Some ribosomes are free in cytoplasm and some attach to RER

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11
Q

What is the function of mitochondria?

A

AEROBIC RESPIRATION

  • site of ATP ( energy currency) production during aerobic respiration
    -self replicating more can be made if the cells energy needs to increase
    -abundant in cells where much metabolic activity takes place .e.g. in liver cells and muscle cells
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12
Q

What is the structure of Mitochondria?

A

-May be spherical rod shaped or branched
-2-5micrometers long
- double membrane
- inner membrane highly folded ( folds called cristae)
-fluid filled matrix
- has DNA

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13
Q

What is the function of lysosomes?

A

BREAKS DOWN WORN OUT ORGANELLES

-keeps powerful hydrolytic enzymes separate from rest of cell
-engulfs old cell organelles and foreign matter ,digest them and return digested components to cell for reuse

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14
Q

What is the function of chloroplasts ?

A

-site of photosynthesis

1.light dependent stage (in grana)
2.light independent stage (in stroma)

Abundant in leaf cells, particularly the palisade mesophyll layer

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15
Q

What is the structure of chloroplasts?

A

-large organelles 4-10micrometers long
-double membrane
-inner membrane -stacks of thylakoids (which contains chlorophyll)
-each stack is called a granum (plural grana)
-fluid filled matrix called stroma
-contains loops of DNA and starch grains

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16
Q

What is the function of the cell plasma membrane?

A

-controls entrance and exit of molecules
-barrier
-selectively permeable
- phospholipid bilayer

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17
Q

What is the structure of the cell plasma membrane?

A

-2 layers of phospholipids
-contains proteins (cell signalling)
-contains cholesterol

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18
Q

What is the function of centrioles?

A

-makes spindle fibres (made out of tubulin) before a cell divides
-involved in the formation of cilia and undulipodium

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19
Q

What is the structure of centrioles?

A
  • consist of 2 bundles of microtubules at right angles to each other
    -microtubules are made of tubulin protein subunits and are arranged to form a cylinder
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20
Q

What is the function of a cell wall?

A

-not in animal cells , is strong and can prevent plant cells from bursting
-fully permeable
-provides strength and support
-maintain the cells shape

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21
Q

What is the structure of the cell wall?

A
  • made of cellulose fibres(in plants)
  • made of chitin in fungi
    -can include plasomdesmata(gaps in cell wall for exchange between cells)
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22
Q

What is the function of flagella?

A

. Flagella help the cell move. Flagella also have microtubules inside of it like cilia, which contract to help the flagella move. This type of movement propels the cell and allow it to be mobile

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23
Q

What is the function of cilia?

A
  • epithelial cells lining your airways each have many hundred of cilia that beat and move the band of mucus
    -nearly all cell types in your body have one cilium that’s act as an antenna (that contain receptors that allow cell to detect signals about its immediate environment)
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24
Q

What is the structure of cilia?

A

-protrusions from the cell surrounded by the cell surface membrane
- each contain microtubules
-they are formed from centrioles

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25
What is the function of a vacuole?
-only in plant cells -filled with water and solutes and maintains cell stability because when full it pushes against cell wall making it turgid -if all plant cells are turgid it helps support plant especially in non-woody plants
26
What is the structure of a vacuole?
-surrounded by a membrane called tonoplast and contains fluid
27
What is the magnification formula?
I=AM
28
List 4 ways that prokaryotic cells are similar to eukaryotic cells
Prokaryotic cells (e.g. bacteria ) are similar to eukaryotic cells in that they have : .a plasma membrane .cytoplasm .ribosomes for assembling amino acids into proteins .DNA and RNA
29
How are prokaryotic cells different from eukaryotic cells?
.they are much smaller .have a less well developed cytoskeleton with no centrioles .do not have a nucleus .do not have membrane bound organelles e.g. mitochondria, endoplasmic reticulum,Golgi apparatus .have a cell wall that is made of petidoglycan not cellulose .have smaller ribosomes .have naked DNA that is not wound around histone proteins but floats free in cytoplasm as a loop(not linear chromosomes)
30
List some other features of prokaryotic cells
.they have a protective waxy (slime) capsule surrounding their cell wall .some have small loops of DNA called plasmids(contain essential genes) as well as the main large loop of DNA .they have pili-small hair like projections that enable bacteria to adhere to host cells or each other and allow the passage of plasmid DNA from one cell to another .flagella-the structure of these flagella differ from that of the eukaryotic undulipodia
31
Describe the endosymbiont theory and the evidence behind it
A theory as to how eukaryotic cells arose from prokaryotic cells.As from fossil evidence, both chloroplasts and mitochondria share characteristics with prokaryotic cells. They: .have small ribosomes .have loops of DNA .also contain RNA .can divide by binary fission
32
What are the 4 main functions of the cytoskeleton
1.provides mechanical strength to cells 2.aids transport within cells 3.enables cell movement 4.keeps the cell’s shape stable
33
What is the cytoskeleton?
A network of protein structures within the cytoplasm.
34
How does the cytoskeleton provide mechanical strength to cells?
The protein microfilaments within the cytoplasm give support and mechanical strength, they keep the cell’s shape stable and allow cell movement . Microtubules also provide shape and support to cells
35
How does the cytoskeleton aid transport within cells?
Microtubules help substances and organelles to move through the cytoplasm within a cell. .They form the track along which motor proteins (dynein, kinesin and myosin)walk and drag organelles from one part of the cell to another .During mitosis chromosomes are moved along the microtubules of a spindle .Microtubules also make up the cilia,undulipodia and centrioles
36
What do intermediate filaments in the cytoskeleton do?
Intermediate filaments are made of a variety of proteins. They : .anchor the nucleus within the cytoplasm .extend between cells in some tissues,between special junctions,enable cell to cell signalling and allowing cells to adhere (stick to ) a basement membrane(cytoskeleton under cell membrane )therefore stabilising tissues
37
Why is staining used?
-coloured stains bind to chemicals on or in the specimen which allows the specimen to become visible e.g.to see certain (named e.g nucleus) organelles -improves contrast
38
What is differential staining?
a technique which involves many chemical stains being used to stain different parts of a cell in different colours.
39
Light (optical) microscopes
-use light to form an image -poor resolution due to lights long wavelength -can be used to observe eukaryotic cells, their nuclei and possibly mitochondria and chloroplasts -cannot be used to observe smaller organelles .e.g. ribosomes ,ER or lysosomes
40
Transmission electron microscope (TEM)
-use electromagnets to focus a beam of electrons. Beams of electrons transmitted through specimen -denser parts absorb more electrons makes denser parts appear darker -produces 2D black and white detailed image (electron micrograph )
41
Advantages of transmission electron microscope (TEM)
-high resolution images ,high magnification -internal structures within cells and even organelles can be seen (since high resolution)
42
Describe what happens during protein synthesis
TRANSCRIPTION 1.in the nucleus a copy of a section of DNA is made which is called mRNA. 2.mRNA leaves nucleus through nuclear pore TRANSLATION 3.mRNA attaches to a ribosome the instructions for the protein is translated and protein molecules are assembled 4.protein is transported through the cisternae of the RER 5.vesicles with protein inside are pinched off from RER and pass via microtubules and motor proteins, to the Golgi apparatus 6.vesicles fuse with Golgi apparatus where the protein molecules may be modified for release 7.the proteins are released through exocytosis
43
What does the cytoskeleton consist of?
It consists of: .rod-like microfilaments made up of subunits of the protein actin, they are polymers of actin and each microfilament is about 7nm in diameter .intermediate filaments about 10nm in diameter .straight ,cylindrical microtubules made of protein subunits called Tubulidentata about 18-30nm in diameter
44
What is the magnification and resolution of a light microscope ?
Magnification = x1500 Resolution = 200nm
45
What is the magnification and resolution of a transmission electron microscope?
Magnification = x500000 Resolution = 0.2nm
46
What is the magnification and resolution of a scanning electron microscope ?
Magnification = x100000 Resolution =0.2nm
47
Define magnification
-the number of times larger an image appears compared with the size of the object
48
Define resolution
-a measure of the microscope’s ability to distinguish between two separate points
49
Name two structures present in animal cells but not plant cells
Centriole Lysosomes
50
How do you convert from centimetre (cm) to millimetre (mm) to micrometre (μm) to nanometre(nm)?
-cm x10 = mm -mm x 1000= μm -μm x 1000= nm
51
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52
A light microscope can be used to observe yeast cells. State the equipment that would be needed, in addition to a microscope, to measure the average diameter of yeast cells (2 marks)
-eyepiece graticule -STAGE micrometer
53
Scanning electron microscopes
-3D image -black and white but computer software programs can add false colour -specimen has to be placed in a vacuum and is often coated with a fine film of metal
54
What is a dry mount?
-are when thin slices or whole specimens are viewed, with just a coverslip placed on top -Dry mount - this is used for specimens such as hairs, parts of insects, pollen, parts of flowers etc. a) Slice the specimen into a thin piece so light can pass through b) Use tweezers to pick it up and put it in the middle of the slide c) Put a cover slip on top of it.
55
How to do a wet mount?
this is used for a variety of live specimens, such as aquatic animals a) Use a pipette to put a drop of water on the slide. b) Use tweezers to place the specimen in the water. c) Put the cover slip on by standing it upright on the slide, next to the water droplet, then carefully tilt it down onto the specimen. Be careful to not add bubbles - these will obstruct the view of the image d) Add a stain. Put a drop on one edge of the cover slip. Put a paper towel on the opposite edge. The paper towel will absorb the stain, drawing it under the coverslip, staining the specimen. (You want to make sure the stain used is not toxic to the live specimen).
56
What is a squash slide?
-are wet mounts which you then push down on the coverslip to squash the sample to ensure you have a thin layer to enable light tp pass through
57
What are smear slides?
-created by placing a drop of the sample at one end of the slide and using the edge of another slide (held at an angle) to smear the sample across the first slide to create a smooth, thin even coated specimen. A cover slip is placed on top after smearing
58
How do you calibrate an eyepiece graticule?
Step 1 - Line up the stage micrometer and eyepiece graticule whilst looking through the eyepiece Step 2 - Count how many divisions on the eyepiece graticule fit into one division on the micrometer scale. Step 3 - Each division on the micrometer is 10micrometers so this can be used to calculate what one division on the eyepiece graticule is at that current magnification
59
What are the steps for using a light microscope?
1-clip the prepared microscope slide onto the stage 2-select the objetive lens with the lowest power 3-use the coarse focus to bring the stage just below the objetive lens 4-look down the eyepiece and use the coarse focus to move the stage downwards until the image is roughly in focus 5-use the fine focus to make the image clearer 6-if a higher magnification is needed, swap to a moree powerful objective lense and refocus
60
What are the shoulds and should nots of biological drawings?
Biological drawings should not: Include shading or colouring Include arrow heads for labels  Involve lines overlapping each other  Biological drawings should:  Include a title State the magnification or scale Be drawn with a sharp pencil  Include smooth, continuous lines  Include labels Include accurate sizes of observable structures 
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63
What is a stain you can use when observing plant tissue?
Toluidine blue
64
A group of students wanted to observe the position of xylem vessels in the leaf stalks of celery describe a procedure they could use to do this (2 marks)
-cut a thin, transverse/ cross section -add Toluidine blue/ observe with microscope under low power
65
Describe dissection of fish gill
-cut away operculum to observe gills -carefully cut out one gill, note the gill arch and the gill filaments that make up each gill
66
When using a light microscope when do you use low power and when do you use high power?
a light microscope should be used at low power when initially locating and identifying different tissues or when needing to survey a wider area of a sample. High power should be used for detailed observation of cellular structures, such as individual cells within a tissue, once you've located them at low powe
67
What is homogenisation?
Cells are broken up using a homogeniser (blender) This breaks the plasma membrane of the cells and releases the organelles into a solution called the homogenate Carried out in a cold, isotonic, buffered solution: Cold: slows enzyme activity Isotonic: prevents osmotic damage to organelles Buffered: maintains pH to avoid protein/enzyme denaturation
68
What is a centrifuge and what does it do?
A centrifuge is a machine that separates materials by spinning Filtrate is spun in a centrifuge at increasing speeds Heaviest organelles form a pellet at the bottom The rest of the organelles stay suspended in the solution above the pellet This solution is known as the supernatant Supernatant is re-spun at higher speeds to isolate lighter organelles
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