3. Cell structure Flashcards
What is the definition of magnification?
by how much an image is enlarged under a microscope
what is magnification controlled by?
power of the lense
what is the definition of resolution?
the minimum distance between two objects at which the microscope can distinguish them as separate entities.
what is the resolution controlled by?
the wavelength of the illumination used
what equation can you use to calculate image size?
actual size x magnification
what is the matrix?
the fluid within the mitochondria.
where is the nuclear envelope located?
membrane enclosing the nucleus.
what is the basic role of the nuclear envelope?
protein-lined pores allow material to move in and out of the nucleus.
what is chromatin?
DNA plus associated proteins
what is the nucleolous?
A condensed region where ribosomes are formed.
what is the basic role of the peroxisome?
metabolizes waste.
What does the cell wall do?
helps maintain cell shape.
what is the central vacuole filled with?
cell sap
what function does the central vacuole perform?
maintains pressure against the cell wall.
holds materials and waste.
what are chloroplasts the site of?
photosynthesis
what is stored in the plastid?
pigments
what is contained in the endoplasmic reticulum?
Rough and smooth ER
what is the rough ER?
found within the endoplasmic reticulum, associated with ribosomes.
what is the basic role of the rough ER?
makes secretary and membrane proteins
what is the basic role of the smooth ER?
makes cellular products like hormones and lipids
what function do the lysosomes perform?
digests food and waste materials
what does the golgi apparatus do?
modifies proteins
what function do the mitochondria perform?
production of energy
what do the plasmodesmata do?
channels allow two plant cells to connect.
what can be found within the cytoskeleton?
microtubules
centrosome
intermediate filaments
microfilaments
what function do microtubules have?
they form the mitotic spindle and maintain the cell shape
what is the centrosome?
microtubule-organizing centre
what are the intermediate filaments?
fibrous proteins that hold organelles in place
what are microfilaments?
fibrous proteins that form the cellular cortex.
What is a tissue?
Many cells of the same type grouped together in a structural unit.
What is a organ?
many types of tissue which together form a function
what is an organ system?
many organs working together to perform a specific function
define a specialised cell?
a cell that has differentiated to form a specific function.
what do specialised cells differ in?
function
shape
organelles
What main features would you expect to find in a cell that produces lots of ATP?
lots of mitochondria
What main features would you expect to find in a cell that exchanges substances with their environment?
large golgi apparatus and a high functioning cell membrane
What main features would you expect to find in a cell that secretes many enzymes?
ribosomes
what is a cell?
one singular component of an organism.
what can we use to measure the size of objects under a microscope?
An eyepiece graticule
how do you calibrate an eyepiece graticule?
we use a microscope slide called a stage micrometer
How do you calculate the scale for different objective lenses?
divide the differences in magnification
what is the typical scale of an eyepiece graticule?
10mm long and is divided into 100 sub-sections.
What is cell fractionation and centrifugation?
The process used to separate cellular components while preserving individual functions of each component.
What effect does solution being cold have during cell fractionation and centrifugation?
This slows enzyme reactions
what effect does the solution being isotonic have during cell fractionation and centrifugation?
stops osmosis, so organelles dont burst
what effect does the solution being buffered have during cell fractionation and centrifugation?
stops PH changes
How do we break open the cells during cell fractionation and centrifugation?
grind the tissue in a blender
Why do we filter the cells after blending during the process of cell fractionation and centrifugation?
it removes insoluble tissue
After filtering what do we call the filtrate? - cell fractionation and centrifugation
a cell-free extract
what is the cell-free extract capable of? -cell fractionation and centrifugation
carrying out most of the normal and basic reactions
What happens when we centrifuge filtrate at a low speed during cell fractionation and centrifugation?
this pellets nuclei which can then be resuspended.
What happens when we centrifuge the supernatant at medium speed - 10000 x g for 30 min during cell fractionation and centrifugation?
pellets mitochondria and chloroplasts.
which can then be resuspended
What happens when we centrifuge the supernatant at high speed - 100000 x g for 1 hr during cell fractionation and centrifugation?
pellets the ER, golgi and other membrane fragments
which can then be resuspended
What happens when we centrifuge the supernatant at very high speed - 300000 x g for 3hr during cell fractionation and centrifugation?
pellets ribosomes.
which can then be resuspended
Explain the process of cell fractionation and centrifugation?
cells are broken up and ordered by size ready for study of the organelles.
What does cell fractionation and centrifugation do?
takes cells apart and separates the major organelles and other subcellular structures from one another
What is stage one of cell fractionation and centrifugation?
cells placed in a cold, buffered, isotonic solution
What happens during stage 2 of cell fractionation and centrifugation?
cells are blended
What happens during stage 3 of cell fractionation and centrifugation?
filter to produce filtrate
What happens during stage 4 of cell fractionation and centrifugation?
centrifuge filtrate
What is left after the supernatant has been through the entire process of ‘cell fractionation and centrifugation’?
organelle-free cytoplasm.
what are bacterial and yeast cells an example of?
prokaryotic cells
List some of the main features of prokaryotic cells.
singular celled organism
dna is not in a nucleus but in a plasmid
smaller than eukaryotic cells
lack a membrane bound nucleus or any other membrane bound cells
what is the cell wall made of in prokaryotic cells?
muerin
explain the function of the nucleoid in prokaryotic cells?
where the dna is housed
lacks the membrane that is found around the nucleus of eukaryotic cells.
may also contain rna, proteins, and enzymes that can be used for cellular processes
explain the function of pili in prokaryotic cells?
found on the outside of cell
attach a bacterial cell to specific surfaces or to other cells, can also aid in attachment between bacterial cells
explain the function of the mesosome in prokaryotic cells?
infoldings in the plasma membrane, these are rich in enzymes that help perform functions like cellular respiration, DNA replication, secretion of glycocalyx and cell division.
increases the surface area of the cell membrane
what happens to the nucleus during mitosis
the nucleus divided into 2
what happens to the nucleus during meiosis
the nucleus divides into 4
what is cytokenesis
the division of the cytoplasm
at what stage of the cell cycle is a large majority of the cells time spent, and doing what?
interphase, ‘resting phase’
no division takes place as the DNA replicates
How do tumours form?
there are checkpoints between each stage of the cell cycle, these are regulated by control genes
Mutated control genes can cause cells to divide uncontrollably
List and describe the types of tumour.
Benign: slow growing, do not spread to other parts of the body, not classed as cancer.
Malignant: fast growing, often spread, classed as cancer
How can almost half of all cancers be prevented?
change in lifestyle
List what treatments can be used in the treatment of cancerous tumours.
surgery
radiotherapy
chemotherapy
How is surgery used to treat cancer?
removal of tumour
how is radiotherapy used to treat cancer?
radiation damages the DNA of cells in the tumour.
how is chemotherapy used to treat cancer?
- blocking enzymes involved in DNA synthesis
- preventing DNA unwinding
- inhibiting synthesis of new nucleotides
- preventing development of the spindle
List some examples of chemotherapy that can be used in the treatment of cancer?
Adriamycin and Cytoxan inhibit DNA helicase, so stops DNA replication
Methotrexate inhibits nucleotide synthesis, so stops DNA replication
Taxol and Vincristine inhibit the formation of the mitosis spindle, so stop mitosis.
why do cells perform mitosis?
growth of tissues
replacement of lost cells
repair of damaged tissue
asexual reproduction
what type of cells division do eukaryotic cells perform?
mitosis, production of identical body cells
when given a diagram of a chromosome what 2 parts may you be asked to label and roughly where would they be?
chromatids, two sticks either side of a central circle
centromere, central circle joining both chromatids together
what is the chromosome made of?
chromatin
what is a chromatid?
the two identical arms of an x-shaped chromosome
what is a centromere?
point at which chromatids are joined
what is a chromosome, in simple terms?
compact x or I shaped form of chromatin formed during cell division
what are the 6 stages of mitosis?
interphase prophase metaphase anaphase telophase cytokenesis
what happens during interphase?
the cell grows and the dna replicates itself
the chromosomes are not visible
not strictly part of mitosis
what happens during prophase?
chromosomes condense and become visible
centrioles move to opposite ends/poles of the cell
spindle apparatus forms from spindle fibres at the centriole
what happens during metaphase?
the nuclear envelope breaks down completely
chromosomes align along the equator/centre of the cell pulled by spindle aparatus
what happens during anaphase?
centromeres split, allowing chromatids to separate.
chromatids move towards poles, pulled by spindle fibres
what happens during telophase?
spindle fibres disperse
nuclear envelopes reform
chromosomes decondense
what happens during cytokenesis?
a ring of protein filaments form around the equator of the cell and then the cells splits into two.
calculation for mitotic index?
number of cells in mitosis / total number of cells.
multiplied by 100
