Cell Structure Flashcards
Explain how the inner membrane of the mitochondria is adapted to its function
(3 marks)
The inner membrane is folded which increases the surface area for respiration and enzymes.
Describe the function of a chloroplast and the structural features that enable it to carry out these functions
(5 marks)
FUNCTION - chloroplasts absorb light energy for photosynthesis to produce carbohydrates and sugars.
FEATURES THAT ALLOW CHLOROPLAST TO CARRY OUT ITS FUNCTION:
- contains chlorophyll
- contains thylakoid membranes to maximised SA being exposed to light
- contains starch granules as food storage
Give 2 advantages and 2 limitations of using a TEM to investigate cell structure
(4 marks)
ADVANTAGES
- better magnification
- higher resolution as the wavelength of the electron beam is shorter
LIMITATIONS
- cells must be in a vacuum
- must be a thin specimen
- specimen may contain artefacts
- images produced are in grayscale
What is an artefacts and why should they be minimised?
(2 marks)
An artefact is a visible entity that resembles structural details of the specimen.
They should be minimised as they are a legacy of the process of preparing the specimen for viewing
Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains when using an optical microscope
(4 marks)
- add a drop of water to a glass slide
- obtain a thin section of the plant tissue and place it on the slide on the drop of water
- stain the specimen with iodine in potassium iodide
- lower a coverslip over the specimen using a mounted needle
Describe the steps required to calibrate the eyepiece graticule of an optical microscope
(4 marks)
Using a stage micrometre insert the eyepiece graticule and line up the scale of the graticule with the scale on the stage micrometre.
Count the number of subdivisions of the stage micrometre that fits into each division of the eyepiece graticule.
Multiply that number by the distance between each subdivision of the stage micrometre to give the distance between each division of the eyepiece graticule.
Describe and explain the factors that influence the duration of the cell cycle in multicellular organisms
(4 marks)
The cell type - a rapidly dividing cell vs a slow growing one
The organism - fast growing vs slow growing
The conditions - growth phase in a foetus vs an adult
Compare and contrast the process of cytokinesis in animal and plant cells
(3 marks)
SIMILARITIES
When a parent cell physically divides into 2 daughter cells it takes place directly after telophase
DIFFERENCES
- in animal cells and cleavage furrow forms and separates the daughter cell
- in plant cells a cell plate forms at the sit if the metaphase site
Compare and contrast the process of binary fission and eukaryotic cell division
(4 marks)
SIMILARITIES
- both replicate DNA
- identical daughter cells produced
DIFFERENCES (in binary fission…)
- there is no nucleus
- there are no chromosomes
- plasmids are replicated
- there are no membrane bound organelles
- there are no spindle fibres
Evaluate the claim the viruses are not living organisms
(6 marks)
CAN BE CLAIMED TO BE LIVING:
- they cause disease
- kill host cells on release
- made of biological material
- associate with larger cells
CAN BE CLAIMED TO BE NON LIVING:
- they cannot replicate on their own
- they inject their RNA into the host cell
- life processes are not all displayed
- simple structure
Explain how 3 different factors can affect the fluidity of membranes
(6 marks)
High temperatures cause molecules to vibrate more.
Higher proportion of saturated fatty acids in the phospholipid tails increases intermolecular force.
Higher cholesterol content increases fluidity.
Longer fatty acid tail length causes less fluidity
Outline the main factors the govern the rate of diffusion across a phospholipid bilayer
(4 marks)
Temperature
Steepness of concentration gradient
Surface areas
Properties of the molecules that are diffusing
Distinguish between the features of channel proteins and carrier proteins and their roles in membrane transport
(4 marks)
Channel proteins are an open pore that allow polar molecules to pass through.
Carrier proteins change shape and are required during active transport.
Carrier proteins can be active or passive and channel proteins are always passive.
Carrier proteins can transport up or down the concentration gradient and channel proteins always transport down the concentration gradient.
Describe the sequence of events that take place during phagocytosis
(3 marks)
The phagocyte engulfs the pathogen which is then contained within a phagocytic vacuole.
The phagosomes fuses with a lysosome inside the cell release lysozymes.
The lysozymes digest the pathogens and the digested parts of the pathogen are displayed on the cell surface membrane of the phagocyte
Explain the events that take place soon after antigen presentation that lead to a specific immune response
(3 marks)
T cells with complementary receptors bind to the antigens and are activated.
B cells with complementary antibodies bind to antigens and are activated.
Activated T and B cells undergo clonal selection and produce clones of themselves. This produces more T and B cells that are specific to the antigen.
