Cells Flashcards
U. marinum cells ingest bacteria and digest them in the cytoplasm.
Describe the role of one named organelle in digesting these bacteria.
Lysosomes
Bind to vesicle
Release lysozymes/hydrolytic enzymes to break down bacterial cell walls
The cell-surface membrane can be seen with a transmission electron
microscope but not with an optical microscope.
Explain why.
Resolution is too low
As wavelength of light is too long
Give two structures found in all prokaryotic and eukaryotic cells
Ribosomes
Plasma membrane
DNA
Cytoplasm
Describe how a sample of chloroplasts could be isolated from a leaf.
Break open cells using a homogeniser and filter to remove large debris
Place the solution in a cold, isotonic, pH buffered solution
Place in ultracentrifuge and spin at low speed and remove nuclei
Spin at higher speed and chloroplasts should separate out
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
The nucleus contains DNA which acts as a template for mRNA which is used in translation to synthesise proteins
Ribosomes are used in translation to produce a protein
Golgi apparatus package protein with carbohydrates to allow them to be transported out of the cell
Mitochondria produce ATP for protein synthesis
Vesicles transport
A biologist separated cell components to investigate organelle activity. She
prepared a suspension of the organelles in a solution that prevented
damage to the organelles.
Describe three properties of this solution and explain how each property
prevented damage to the organelles
Cold- stops enzyme activity so they do not damage organelles
Isotonic- prevents movement of water by osmosis so organelle do not shrivel or lyse
pH buffered- so proteins in organelles are not denatured by pH changes
Contrast how an optical microscope and a transmission electron
microscope work and contrast the limitations of their use when studying
cells
TEM uses electrons and optical uses light
TEM has a greater resolution
So TEM can observe smaller organelles
TEM can only observe dead species whereas optical can view living
Optical shows colour, TEM does not
TEM requires thinner specimens
TEM requires more complex preparation
TEM uses magnets and optical uses lenses
Name two structures present in plant cells that are not present in animal cells.
Chloroplasts
Cell Wall
Permanent vacuole
Starch grain
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
(light) microscope
Place a small drop of water onto glass slide
Remove a very thin section of plant tissue and place onto slide
Stain using iodine
Place a cover slip on top using a mounted needle
Describe binary fission in bacteria
Circular DNA replicates
Plasmids replicate
Cytoplasm divides to form two new bacterium
Suggest why preventing the formation of spindle fibres stops the cell cycle
Chromosomes cannot line up on spindle
So no metaphase
Chromatids cannot separate
So no anaphase
Describe the appearance and behaviour of chromosomes during mitosis.
Prophase- chromosomes condense and become supercoiled and visible
Metaphase- chromosomes line up on the equator of the cell and spindle fibres attach to centromere
Anaphase- spindle fibres contract towards opposite poles of the cell causing the sister chromatids to separate
Telophase- Nuclear membrane reforms and chromosomes unwind
Cytokinesis- cytoplasm divides to give two identical daughter cells
Name and describe five ways substances can move across the
cell-surface membrane into a cell.
Diffusion- non-polar small molecules can diffuse passively across phospholipid bilayer
Facilitated diffusion- small ions and polar molecules move down concentration through channel or carrier proteins
Osmosis- passive movement of water down a water potential gradient
Active transport- move through carrier proteins against a concentration gradient using energy from ATP
Cotransport of two molecules using a carrier protein
The movement of Na+ out of the cell allows the absorption of glucose into
the cell lining the ileum.
Explain how.
Maintains a concentration gradient of sodium ions
Sodium ions diffuse back in by facilitated diffusion with a glucose molecule associated
Describe and explain two features you would expect to find in a cell
specialised for absorption.
Folds/microvilli to create large SA
Large number of cotransport/channel proteins to increase rate of absorption
Large number of mitochondria to release ATP by aerobic respiration
Membrane bound digestive enzymes to maintain a concentration gradient to increase rate of absorption
