Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

a level biology > Cell Structure > Flashcards

Cell Structure Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards
1
Q

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

A
  1. Obtain thin section of tissue e.g. using ultra tome or by maceration
  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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
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 and wavelengths of light
  3. Reflected light is transmitted to the observer via the objective lens and eyepiece
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe how a TEM 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe how a SEM 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe how a laser scanning confocal microscope works

A
  1. Focus a laser beam onto a small area on a samples surface
  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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How should the field of view in microscopy be recorded

A

Draw a diagram with a sharp pencil. Do not use sketchy lines or shading
Include a scale bar
Annotate visible structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

State an equation to calculate the actual size of a structure from microscopy

A

Actual size = Image size / magnification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define magnification and resolution

A

Magnification: Factor by which the image is larger than the actual specimen
Resolution: Smallest separation distance at which two separate structures can be distinguished from one another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why do samples need to be stained for light microscopes

A

Coloured dye binds to the structures
Facilitates absorption of wavelengths of light to produce image. Differential staining : contrast between heavily and lightly stained areas distinguishes structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

State the magnification and resolution of a compound light microscope

A

Magnification - x2000
Resolution - 200 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

State the magnification and resolution of a TEM

A

Magnification - x500000
Resolution - 0.5nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

State the magnification and resolution of a SEM

A

Magnification - x500,000
Resolution - 3-10nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

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

A
  1. Place micrometer on stage to calibrate eyepiece graticule
  2. Line up scales on graticules and micrometer. Count how many graticule divisions are in 100um on the micrometer
  3. Length of 1 eyepiece division = 100um / number of divisions
  4. Use calibrated values to calculate actual length of structures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the structure of the nucleus

A
  • Surrounded by a nuclear envelope, a semipermeable double membrane
  • Nuclear pores allow substances to enter / exit
  • Dense nucleolus made of RNA and proteins assemble ribosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the function of the nucleus

A
  • Contains DNA coiled around chromatin into chromosomes
  • Controls cellular processes: gene expression determines specialisation & site of mRNA transcription, mitosis, semi conservative
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the structure and function of the ER

A

Cisternae: network of tubules and flattened sacs extends from cell membranes and connects to nuclear envelope:
- Rough ER: many ribosomes attached for protein synthesis & transport
- Smooth ER: Lipid synthesis

17
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. Vesicles bud off trans face via exocytosis
- Modifies & packages proteins for export
- Synthesises glycoproteins

18
Q

Describe the structure and function of ribosomes

A

Formed of protein and rRNA
Have large subunit which joins amino acids and small subunit with mRNA binding site

19
Q

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

A

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

20
Q

Describe the structure of a mitochondrion

A

Surrounded by double membrane
Folded inner membrane forms cristae: site of electron transport chain
Fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids, proteins

21
Q

Describe the structure of a chloroplast

A
  • Vesicular plastid with double membrane
  • Thylakoids : flattened discs stacks to form grana which contain photosystems with chlorophyll
    Intergranal lamallae: tubes attach thylakoids in adjacent grana
    Stroma: Fluid-filled matrix
22
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

23
Q

Describe the structure and function of a lysosome

A

Sac surrounded by single membrane embedded H+ pump maintains acidic conditions contains digestive hydrolase enzymes
Glycoprotein coat protects cell interior:
Digests contents of phagsome
Exocytosis of digestive enzymes

24
Q

Describe the structure and function of a plant cell wall

A
  • Made of cellulose microfibrils for mechanical support
  • Plasmodesmata from part of apoplast pathway to allow molecules to pass between cells
  • Middle lamella separates adjacent cell wells
25
Q

What are bacterial and fungal walls made of?

A

Bacteria : peptidoglycan
Fungi : Chitin

26
Q

Describe the structure and function of the centrioles

A

-Spherical group of 9 microtubules arranged in triples
- Located in centrosomes
- Migrate to opposite poles of cell during prophase & spindle fibres from between them

27
Q

Describe the structure and function of the cell-surface plasma membrane

A

‘Fluid mosaic’ phospholipid bilayer with extrinsic and intrinsic proteins embedded
- Isolates cytoplasm from extracellular environment
- Selectively permeable to regulate transport of substances
- Involved in cell signalling / cell recognition

28
Q

Explain the role of cholestrol, glycoproteins and glycolipids in the cell surface membrane

A

Cholesterol: Steroid molecule connects phospholipids & reduces fluidity
Glycoproteins: Cell signalling, cell recognition (antigens) & binding cells together
Glycolipids : Cell signalling and cell recognition

29
Q

Describe the structure and function of the flagella

A

Hollow helical tube made of the protein flagellin
Rotates to propel (usually unicellular) organism

30
Q

Describe the structure and function of cilia

A

Hairlike protrusions on eukaryotic cells
Move back and forth rhythmically to sweep foreign substances e.g. dust or pathogens away / to enable the to move

31
Q

Why is the cytoskeleton important

A

Provides mechanical strength
Aids transport within cells
Enables cell movement

32
Q

Compare Eukaryotic and prokaryotic cells

A

Both have:
Cell membrane
Cytoplasm
Ribosomes

33
Q

Contrast eukaryotic and prokaryotic cells

A

Prokaryotic :
Small cells and always unicellular
No membrane bound organelles and no nucleus
Circular DNA not associated with proteins
Small ribosomes (70S)
Binary Fission - always asexual reproduction
Made of murein (also known as peptidoglycan
Capsule, sometimes plasmids 7 cytoskeleton

Eukaryotic :
Larger cells and often multicellular
Always have organelles and nucleus
Linear chromosomes associated with histones
Larger ribosomes (80S)
Mitosis and meiosis - sexual and/or asexual
Absent in animal cells, cellulose cell wall (plants) / chitin (Fungus)
No capsule, No plasmids, always cytoskeleton

34
Q
A

a level biology (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions