Chapter 3 - Cell Structure Flashcards
what is an object
the material placed under the microscope
what is an image
the appearance of the material viewed under the microscope
why is the resolution of an electron microscope greater than that of an optical microscope
electrons have a very small wavelength compared to light
equation for magnification
magnification = size of image/size of real object
what is magnification
how much bigger the image is than the specimen you’re looking at
what is resolution
how well a microscope can distinguish between two points that are close together
what do optical microscopes use to form an image
light
what do electron microscopes use to form an image
electrons
maximum resolution of a light microscope
0.2 micrometres
maximum resolution of light microscopes
1500 x
maximum resolution of electron microscopes
0.0002 micrometres
maximum magnification of electron microscopes
1,500,000 x
what are the two types of electron microscopes
transmission electron microscopes TEM
scanning electron microscopes SEM
hoe do transmission electron microscopes work
a beam of electrons is focussed onto a specimen using electromagnets
the electrons are transmitted through the specimen
denser parts of the specimen absorb more electrons so they appear darker
what are the main limitations of TEM 3
they can only be used on thin specimens
the whole system must be observed in vacuum- living specimens can’t be viewed
a complex preparation process mans artefacts are common
what are artefacts
things that you can see on the microscope but aren’t part of your specimen
how many micrometers are in a millimetre
1000
how many nanometers in a micrometre
1000
how do scanning electron microscopes work
a beam of electrons is scanned onto the surface of a specimen
this knocks electrons off of the specimen which are gathered in a cathode ray tube to form an image
advantages of TEM
high resolution images mean you can see internal structures like chloroplasts
advantages of SEM
they can be used on thick and living specimens
disadvantages of SEM
the resolution is lower than TEM
what is an eyepiece graticule
a transparent rule with number but no units
how to calibrate a microscope
1) divide total length of stage micrometer by how many intervals to find one micrometer unit
2) find a point where the two lines are equal
3) work out how many micrometers units equal how many eyepiece units
4) convert the stage micrometre units to micrometers
5) divide stage units by eyepiece units to find the value of one eyepiece unit
6) this can be used in calculations
what is cell fractionation
the process where cells are broken up and different organelles they contain are separated out
during homogenisation why is the solution
a) cold
b) same water potential as the tissue
c) buffered
a) to reduce enzyme activity that could break down organelles
b) to prevent organelles bursting or shrivelling due to osmosis
c) any change in pH could affect the organelles or enzymes
what happens during homogenisation
cells are broken up in a blender to release organelles
what happens during filtration
the homogenate is filtered to remove any large sections of cell and debris
what happens during ultracentrifugation
the filtrate is poured into a test tube place in the centrifuge and spun slowly
the heaviest organelles sink to the bottom forming the pellet whilst the rest of the organelles stay suspended in a fluid called the supernatant
the supernatant is drained off, poured into another test tube and spun at an even higher speed
the next heaviest organelles form the pellet and are remove
description of the nucleus
nuclear envelope surrounding chromatin and nucleoplatism
function of the nucleus
stores genetic info DNA
decription of mitochondria
double membrane. inner highly folded-cristae
function of mitochondria
makes energy ATP rich molecules during aerobic respiration
description of cell surface membrane
free in cytoplasm attached to RER smaller in prokaryotic cells
function of cell surface membrane
makes proteins
rough size of mitochondria
between 2 and 10 um
what is the chloroplast envelope
a double membrane surrounding the organelle
what are grana
stacks of thylakoid membranes inside chloroplasts
what is stroma
a matrix where the sugar are synthesised during photosynthesis
function of chloroplasts
site of photosynthesis
how are chloroplasts adapted for photosynthesis
the grana provide a large surface area for the first stage of photosynthesis
chloroplasts contain ribosomes and DNA so they can quickly make proteins required for photosynthesis
what are the two types of endoplasmic reticulum
smooth endoplasmic reticulum SER
rough endoplasmic reticulum RER
what is the RER
a system of membranes covered in ribosomes
network of interlined sheets with ribosomes
functions of RER
ribosomes make protein and channel transport these proteins
what are cistern
a stack of membranes that make flattened sacks
functions of Golgi apparatus
processes and packages new lipids and proteins
description of Golgi apparatus
contains vesicles for export
what are Golgi vesicles
fluid filled sacks produced by the Golgi apparatus
function of Golgi vesicles
stores lipids and proteins made by the Golgi apparatus and transports them out of the cell
when are lysosomes formed
when vesicles contain enzymes like lipase and proteases
description of lysosomes
vesicles contain hydralytic enzymes
functions of lysosomes
modify proteins or lipids. package them is vesicles for export
description of ribosomes
free in cytoplasm
attached to RER
smaller in prokaryotic cells
function of ribosomes
makes proteins
protein synthesis
function of microvilli
increase surface area for absorption and diffusion
what is a cell wall
a rigid structure surrounding cells in plants algae and fungi
it consists of cellulose embedded in a matrix
functions of the cell wall
to prevent the cell bursting form the movement of water
gives mechanical support to the cell
what are cell walls made from in fungi
chitin
what is tonoplast
the membrane surrounding the vacuole
what is a vacuole
a fluid filled sack surrounded by the tonoplast
function of a vacuole
stores water to keep the cell rigid and the plant turgid
helps to isolate unwanted chemicals
why do cells become specialised
to carry out specific functions
how do cells become specialised
certain genes can be turned on and off
what is a tissue
a group of cells working together to perform a specific function
function of the epithelial tissue
covers the inside and outside of organs
function of xylem
transports water and mineral ions throughout the cell and also gives mechanical support
what is an organ
a variety of tissues coordinated to perform a variety of functions
what do muscular tissues do in the stomach
churns content
what does epithelial tissues do in the stomach
protects stomach lining
which of the blood vessels are organs and which are tissues
organs arteries and veins
tissue capillaries
function of phloem
moves food away from the leaves in a plant
function of the epidermis in a plant
to protect the leaf
function of the spongy mesophyll in a plant
gaseous diffusion
function of the palisade mesophyll in a plant
photosynthesis
what does the digestive system do
digests and processes food
what does the respiratory system do
breathing and gas exchange
what does the circulatory system do
pumps and circulates blood
what are cell walls made from in bacteria
the glycoprotein murine
function of slime capsule
protects bacterium from other cells and helps them group together
function of circular DNA
contains informations needed for bacteria cells to replicate
function of plasmid
contains genes that may help the bacteria survive in adverse conditions
is the DNA of bacteria cells associated with proteins
no
why are viruses described as acellular
they are nucleic acids surrounded by a protein called the cashed they aren’t alive
what is the function of attachment proteins an where are they found
they are found sticking out from around the cased and help virus cling to a host cell
how do viruses replicate
they use proteins to attach to host cells
they inject their DNA into the host cell
why can viruses only infect one type of cell
their attachment proteins are complementary to just one receptor cell
process of binary fission
the DNA and plasmids in the cell replicate
the cell gets bigger and the DNA moves to the opposite end of the cell where it attaches to the membrane
the cytoplasm begins to divide and new cell walls begin to form
a new cell wall forms between the the two molecules of DNA creating two identical daughter cells
what is mitosis
a parent cell divides to produce two genetically identical daughter cells
3 uses of mitosis
growth repair and reproduction
what are the three stages in the cell cycle
interphase
nuclear division
cytokinesis
which stage isn’t part of mitosis
interphase
what happens during interphase 2
the cells DNA unravels and replicates
the organelles and ATP are replicated
what happens during prophase 3
the chromosomes condense and become visible
centrioles move to opposite ends of the cell forming the spindle apparatus
the nuclear envelope breaks down
what happens in metaphase 2
the chromosomes line up along the cells equate
the spindle fibres attach to the centimetre
what happens in anaphase 2
the centromeres divide separating the chromatids
the spindles contract and pull chromatids to the cells pores
what happens during telophase 2
the chromosomes reach the poles and unravel
the cytoplasm divides and two nuclear envelopes form leaving two identical daughter cells
what is cytokinesis
the process by which the cytoplasm divides
what is cancer
a group od diseases characterised by a growing disorder of cells
characteristics of benign tumours
grow slowly are more compact and less life threatening
characteristics of malignant tumours
grow quickly less compact and are more life threatening
how do cancer drugs work
they disrupt the cell cycle to stop the tumour diving and growing
how does chemotherapy work
chemicals prevent the synthesis of enzymes needed for DNA replication
how does radiotherapy work
radiation damages DNA so the cell kills itself
formula for mitotic index
number of cells with visible chromosomes / total number of cells observed
why are hair cells often affected by the cancer drugs
the drugs target cells that divide rapidly such as hair cells
why do specimens have to be kept in a vacuum before using an electron microscope
the air would otherwise absorb the elctorns and prevent them from reaching the specimen
what chromosomes do women have
XX
what chromosomes do men have
XY
