Cells Flashcards
Describe the role of one named organelle in digesting bacteria.
- Lysosomes fuse with vesicles release hydrolytic enzymes
Suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration.
- more amino acid for protein synthesis
- so more DNA synthesis
Describe how a sample of chloroplasts could be isolated from leaves ?
- blend and the filter to remove unbroken cells
- add to cold, same w.p, buffered solution
- centrifuge once to remove nuclei and continue to centrifuge at higher speed to remove chloroplasts
What does it mean if the band is lower down on the test tube after centrifuging?
more dense
Give on feature of chloroplasts that allows proteins to be synthesised and describe one difference between this feature and similar features in the cell
Feature: Chloroplast DNA
structural difference: shorter/not associated with histones
which is the current sequence?
a. 50nm < 0.5um < 5x10-2mm <0.5 x 10 -5,
b. 50nm < 0.5um < 0.5 x 10-5m < 5x10-2mm
b
Why must the solution be centrifuged be cold?
- reduce enzyme activity
What is algae’s cell wall made out of?
cellulose
Contrast and compare optical and TEM microscopes.
- optical uses light whereas TEM uses electrons
- optical longer wavelength of light means lower resolution and TEM high resolution
- Optical live specimen and TEM use dead
- Optical colour and TEM - black and white
- TEM - thinner
- TEM - more complex to prep
Does a virus have a cell membrane or cytoplasm?
NO
No organelles are visible in the red blood cell. Suggest why?
- cytoplasm - filled with haemoglobin
Suggest an explanation for the appearance of the cell surface membrane as two lines when stained under an electron microscope.
- phosopholipid bilayer
- stain binds to phosphate on the outside and inside
How does TEM work, and what are the necessary requirements?
- Transmission electron microscope - specimen absorbs electrons and therefore appears dark
- The specimen must be extremely thin, 2D image, complex staining process required
How does SEM work, and what are the necessary requirements?
Scanning electron microscope: directs a beam of electrons on the surface of the specimen
Build up 3D image, lower resolution than TEM.
How does centrifugation work?
Centrifugation: cold, buffered, same w.p solution,
The heaviest organelles, the nuclei, are forced to the bottom of the tube
What are the components of the nucleus and what are their roles? (4 marks)
Nuclear pores: allow substances in and out
Nucleolus: a small spherical region that contains RNA and can form ribosomes
Nuclear envelope: double membrane
Nucleoplasm: jelly-like, granular substanc
What are some characteristics of mitochondria? (2 marks)
Double membrane - inner of two folded to form cristae -> large surface area for attachment of enzymes
Matrix - enzymes for respiration found there
What are some characteristics of chloroplasts? (4 marks)
Envelope - double plasma membrane
Grana - made out of stacks of thylakoids (large surface area for attachment of chlorophyll, electron carriers)
Thylakoids contain pigments like chlorophyll
Stroma - the second stage of photosynthesis takes place (possess all the enzymes needed to make sugars)
What are the characteristics and function of the 2 types of ER?
RER: has ribosomes on the surface - provides large surface area for protein synthesis
SER: more tubular in appearance - synthesise, store and transport lipids and carbohydrates
What are the characteristics and function of the golgi apparatus?
Golgi apparatus: consists of stacks of membranes that make up cisternae and have vesicles - modifies proteins into glycoproteins, form lysosomes, transported by fusing with vesicle membrane
What are the 2 types of ribosome?
Ribosomes - RNA and Subunit - 80s found in eukaryotic (larger), 70s found in prokaryotic (smaller)
What is the function of cell wall and the type of substance that makes different cell walls in different organisms?
Cell wall - cellulose with microfibrils - providing strength. Meurin - prokaryotes, Cellulose - Eukaryotes, Chitin - fungi
What are some characteristics of the cell wall?
All possess a cell wall some have slime capsule for further protection
Cell surface membrane, 70s ribosomes
Circular strands of DNA free-floating in cytoplasm and plasmids, DNA is not associated with Histones
No membrane bound organelles
What are some characteristics of Viruses?
Contain nucleic acids (DNA or RNA)
Capsid can also be further surrounded with a lipid envelope
Attachment proteins
What is the vacuole?
fluid-filled sac bounded by a single membrane = tonoplast
What are lysosomes?
Lysosomes - produced by GA have enzymes that hydrolyse cell walls of certain bacteria
