3.2.1 - CELL STRUCTURE + MICROSCOPY Flashcards
explain why it is not possible to determine the identity of structure X using an optical microscope (2)
- the resolution is too low
- because the wavelength of light is too long
U. marinum cells ingest bacteria and digest them in the cytoplasm.
describe the role of one named organelle in digesting these bacteria (3)
- lysosomes
- fuse with the phagosome (vesicle)
- releases lysozymes (hydrolytic enzymes)
describe how a sample of chloroplasts could be isolated from leaves (4)
- homogenise (break open the cells) and then filter to remove insoluble tissue and debris
- in cold, isotonic, buffered solution
- centrifuge to remove nuclei
- centrifuge at a higher speed, chloroplasts will then pellet
suggest why a nucleus is not visible in the above image (1)
any one:
- only a section of the cell, nucleus may be in another part of the cell
- nucleus is not stained
give two structures found in all prokaryotic and eukaryotic cells (2)
any two:
- cell membrane
- ribosomes
- cytoplasm
- DNA
give one feature of the chloroplast that allows protein to be synthesised inside the chloroplast.
describe one difference between this feature in the chloroplast and similar features in the rest of the cell (2)
answer 1:
1. DNA
2. it is not associated with histones but nuclear DNA is/it is circular but nuclear DNA is linear/it is shorter than nuclear DNA
answer 2:
1. ribosomes
2. are smaller than ribosomes in the chloroplast - 70S ribosomes in chloroplast, 80S chloroplasts in cytoplasm
scientists have found that the rate of plasmid replication is faster in cells growing in a culture with a high concentration of amino acids than in a culture with a lower concentration of amino acids.
suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration (2)
answer 1:
1. amino acids are used in protein synthesis
2. so more enzymes (DNA polymerase) for DNA (plasmid) replication
answer 2:
1. amino acids are used in respiration
2. so more ATP for DNA (plasmid) replication
eukaryotic cells produce and release proteins.
outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.
do not include details of transcription and translation in your answer. (4)
- DNA in the nucleus is the code for protein
- ribosomes produce protein
- mitochondria produce ATP for protein synthesis
- Golgi body package and modify/carbohydrate added (glycoprotein produced) by Golgi
- vesicles transport
- vesicles fuse with cell surface membrane
give one advantage of viewing a biological specimen using a transmission electron microscope compared to a scanning electron microscope (1)
- higher resolution
OR
- view internal structures
name an organelle found both in a chloroplast and a prokaryotic cell (1)
70S ribosome
a biologist separated cell components to investigate organelle activity. she prepared a suspension of the organelles in a solution. this solution prevented damage to the organelles.
describe three properties of this solution and explain how each property prevented damage to the organelles (3)
- cold to reduce enzyme activity
- buffered to prevent denaturing of enzymes
- isotonic to prevent organelles bursting
contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells (6)
- TEM uses electrons and optical uses light
- TEM allows greater resolution
- so with TEM smaller organelles (ribosomes) can be observed
- TEM can only view dead specimens, optical can view live specimen
- TEM does not show colour, optical can
- TEM requires thinner specimens
- TEM requires a more complex preparation
- TEM focuses using magnets and optical uses glass lenses
name two structures present in plant cells but not in animal cells (2)
any two:
- chloroplasts
- cell wall
- cell vacuole
- starch grains
the cell-surface membrane can be seen with a TEM but not an optical microscope. explain why (1)
- electron microscope has higher resolution than optical
no organelles are visible in the cytoplasm of a red blood cell. suggest why (1)
- the cytoplasm is filled with haemoglobin
before the cell was examined using the electron microscope, it was stained. this stain caused parts of the structure of the cell-surface membrane to appear as two dark lines.
suggest an explanation for the appearance of the cell-surface membrane as two dark lines (3)
- membrane has phospholipid bilayer
- stain binds to the phosphate/glycerol (phosphate head)
- on the inside and outside of the membrane
name two structures in a eukaryotic cell that cannot be identified using an optical microscope (1)
any two:
- mitochondria
- ribosome
- endoplasmic reticulum
- lysosome
- cell-surface membrane
describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical microscope (4)
- add drop of water to the glass slide
- obtain a thin section of the plant tissue and place it on the slide
- add potassium iodide
- lower cover slip using mounted needle
scientists measured cell damage by measuring the activity of lysosomes. give one function of lysosomes (1)
break down cells/toxins
H. pylori cells produce an enzyme that neutralises acid. suggest one advantage to the H. pylori of producing this enzyme (2)
- to stop them being killed
- by stomach acid
cells that secrete enzymes contain a lot of rough endoplasmic reticulum and a large Golgi apparatus.
describe how the RER is involved in the production of enzymes (2)
- RER (has) contains ribosomes
- ribosomes make proteins
- enzyme is a protein
describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells (5)
any five from:
- cell homogenisation to break open cells
- filter to remove large debris and insoluble tissue
- use isotonic solution to prevent damage to organelles
- use cold solution to prevent enzyme activity
- use buffer solution to prevent enzyme denaturing
- centrifuge at lower speed to separate
- re-spin at higher speed to get mitochondria to pellet to the bottom
describe the principles and the limitations of using a TEM to investigate cell structure (5)
principles:
1. electrons pass through thin specimen
2. denser parts absorb more electrons
3. so denser parts appear darker
4. electrons have a short wavelength so they give a high resolution
limitations:
1. cannot look at living material
2. specimen must be very thing
3. there may be artefacts present
4. there is a long, complex staining process (preparation time)
5. the image produced is in 2D not 3D
a student cut thin sections of tissue to view with an optical microscope. explain why it was important that the sections were thin. (2)
- to allow more light to through
- so that a few layers of cells can be viewed
give the function of a mitochondrion (1)
site of aerobic respiration
name two structures found in all bacteria that are not found in plant cells (2)
- murein/peptidoglycan/glycoprotein cell wall
- 70S ribosomes
- circular DNA
name two features of HIV particles that are not found in bacteria (2)
do not include attachment protein in your answer
- capsid
- RNA genome
- reverse transcriptase
- envelope
how is Golgi apparatus involved in absorption of lipids (3)
- modifies/processes triglycerides
- combined triglycerides with proteins
- forms vesicles
human breast milk is produced and secreted by gland cells. these gland cells have adaptations that include many mitochondria and many Golgi vesicles. the milk contains a high concentration of protein.
explain the role of these cell adaptations in the production and secretion of breast milk (2)
- mitochondria release energy for protein synthesis
- Golgi vesicles transport protein to cell membrane, out of the cell
describe the structure and function of the nucleus (4)
structure:
1. nuclear envelope and pores
2. chromosomes
3. nucleolus
function:
1. stores genetic information
2. DNA replication occurs
3. transcription occurs
4. production of ribosomes/rRNA
give one advantage of viewing a biological specimen using a TEM compared with using a SEM (1)
- higher resolution
- view internal structures
kidney cells produce a glycoprotein called EPO
identify two organelles in kidney cells that enable the production of EPO (1)
- ribosomes
- Golgi apparatus
outline the similarities in, and the differences between, the structures of chloroplasts and mitochondria (4)
similarities:
1. double membrane
2. both contain circular DNA
3. both contain ribosomes
differences:
1. thylakoids/grana vs cristae
2. stroma vs matrix
3. pigment vs no pigment
4. starch grains vs no starch grains
give the three structural features found in all virus particles and describe the function of one of these features (2)
- genetic material, capsid, and attachment protein
- genetic material codes for viral protein OR capsid protected geneticist material OR attachment proteins binds to recipe items on cell
explain why viruses are described as acellular and non-living (2)
- acellular - no cell-surface membrane OR not made of cells
- non-living - have no metabolism/metabolic reactions OR cannot replicate independently
describe two functions of the Golgi apparatus in a eukaryotic cell (2)
- modify/package/transport proteins OR make/transport glycoproteins
- modify/package/transport lipids OR make/transport glycolipids
- forms/releases vesicles/lysosomes
name the main polymer that forms the following cell walls (1)
- plant cell wall
- fungal cell wall
- plant = cellulose
- fungal = chitin
