2A Flashcards
what is magnification
how much bigger a sample appears to be under the microscope than it is in real life
what is resolution
the ability to distinguish between two points on an image.
what are the advantages of an electron microscope
the resolution in x2000 more than LM microscope
it produces detailed images
SEM produces 3D image
what are the disadvantages of an electron microscope
Samples have to be placed in a vacuum
very expensive
need to be highly skilled to create samples
complex staining process
image may contain artefacts
what is the equation for magnification
magnification=size of image/size of the object
What do Transmission electron Microscope do
pass a beam of electrons through the sample.
What are the limitations of a Transmission electron microscope
Thin sections of specimen are needed for TEM as the electrons have to pass through the specimen for the image to be produced
flat 2D image
What do Scanning electron microscopes do
pass a beam of electrons over the surface, the electrons are then reflected off the surface of the specimen
what are the limitations of scanning electron microscope
The resolution is lower then that of the transmission electron microscope
what is cell fractionation
The process where cells are broken up and the different organelles they contain are separated
what is cell fractionation used for
Used to help us study cell structure and function
what is momogenisation
breaking up the cells
what is a centrifuge used for
separating the cell components
Before cell fractionation can begin what must happen
the tissue is placed in, cold, isotonic, buffer solution
why must the tissue be cold
to reduce enzyme activity, which may break down organelle
what is the role of isotonic solution
to prevent the organelle from bursting/ shrinking due to osmotic gain/ loss of water
what is the role of the solution being buffered
to maintain a constat PH
what is differential centrifugation and why does it happen in the experiment.
The size and density of any organelle is relatively constant so they all separate at a specific speed. Since the whole process involves centrifuging at different speeds it is called differential centrifugation.
In what order is the organelle separated during centrifugation
it happens in the order of most to least dense. Nuclei, chloroplast and mitochondria, lysosomes and endoplasmic reticulum, ribosomes
what is a graticule
a series of fine lines in the eyepiece of an optical device, such as a microscope, used as measuring scale. It enables scientists to estimate accurately the size of objects viewed under a microscopes.
does not change in size
what are the steps of cell centrifugation
1 chop up fresh tissue in ice cold, isotonic buffer solution.
2 Put the chopped tissue in a blender or homogeniser to break open the cells.
3 Filter the mixture to remove the debris, such as connective tissue and plant cell walls.
4 Pour the mixture into tubes and spin very quickly in a centrifuge.
5 The liquid layer on the top ( the supernatant ) is poured in to a fresh tube, leaving the pellet behind.
6 The supernatant may then be spun again at a faster rate to produce a sediment containing mitochondria and at an even higher speed for other organelle
what is the supernatant
The liquid layer on the top off the pellet, in centrifugation.
what is the cell membrane made out of
Phospholipids
How to prokaryotic cells differ from eukaryotic cells
Prokaryotic cells do not have a nucleus, whereas eukaryotic cells do. Prokaryotic cells also do not have a cell membrane
what are prokaryotic, plant and fungal cell walls made from
prokaryotic- peptidoglycan
fungal- chitin
plant- cellulose
what is a plasmid
a circular loop of DNA that contains their genetic material
what is a nucleoid
A space within a prokaryotic cell where DNA is found
what is the procedure for the calibration of a cell
1 put in the eyepiece
2 put on the stage micrometer
3 align them to calibrate
4 count divisions on the EPG = how many divisions on the micrometer
5 with the scale of the micrometer, find the length of each division on the EPG ( division on micrometer/divisions on EPG)
6 remove micrometer from stage
7 Put a cell slide on the stage
8 Measure EPG division that a cell accounts for
9 cell length = length of each division on EPG x number of EPG divisions of cell.
what is the structure and function of a nucleus for eukaryotic cells
structure: surrounded by a nuclear envelope (double membrane with pores), and it contains chromosomes (genetic material) and a dense solid structure called a nucleolus which is involved in ribosome synthesis.
Function: It contains the genetic information for the cells (including chemical reactions and cell division). It also controls when mRNA is produced, and hence controls protein production.
What is the structure and function of the different types of endoplasmic reticulum in a eukaryotic cell
structure: surrounds the nucleus, rough ER has ribosomes, smooth ER doesn’t
function of rough ER: site of protein synthesis
function of smooth ER: site of lipid and carbohydrate metabolism including hormone synthesis.
what is the structure and function of the Golgi apparatus in a eukaryotic cell
structure: flattened disc shaped sacs that are stacked on top of each other.
function: processed; carbohydrate may be added to proteins
Packaged: protein wrapped in a membrane vesicle
transported: vesicles move elsewhere in the cell
modified.
what is the structure and function of the plasma membrane in a eukaryotic cell
structure- a bilayer that is made of phospholipids
function- controls the movement of substances in and out the cell
what is the structure and function of mitochondria in a eukaryotic cell
structure-inner membrane is folded into eristae- where ATP is generated in the cell by aerobic respiration
the fluid inside is called the matrix- and contains energy for respiration
the no. of mitochondria depends upon the cells metabolic activity (sperm cells need more to move)
function- bounded by a double membrane, responsible for producing ATP (free energy) in respiration.
what is the structure and function of lysosomes in a eukaryotic cell
structure- small sphere of liquid surrounded by a membrane
pinched off areas of the Golgi apparatus
function- contain enzymes that break down and hydrolyse food and foreign matter in cells.
They digest the cell after it dies and hydrolyse pathogens.
What is the structure and function of ribosomes in a eukaryotic cell
structure- small structures that can be associated with ER or free within the cells cytoplasm
function- involved in protein synthesis, they assemble amino acids in the right order to produce new proteins.
what are the two types of ribosomes and where are they found, and why are they different sizes
80s ribosomes- eukaryotes
70s ribosomes- prokaryotes
they are different sizes because prokaryotic cells are smaller, therefore needing smaller ribosomes
what is the structure and function of chloroplasts
structure- disc shaped structure with a double membrane.
function- to carry out photosynthesis produce energy through photosynthesis and oxygen-release processes, which sustain plant growth and crop yield.
what is the structure and function of a cell wall in a eukaryotic cell
structure- consists of cellulose membrane embedded in a matrix
middle lamella is the junction between one cell and the next which sticks the cells together
function- gives the cell strength. Prevents the cell bursting under osmotic pressure.
what is the structure and function of a vacuole in a eukaryotic cell
structure- large permanent vacuole surrounded by a membrane called the lonoplat- contains sugars, salts, wastes and pigments
function- supports the cell by making cells turgid, acts as temporary food storage
provides colour
what do single celled organisms have
Larger surface area to volume ratio
all cells are exposed to the environment
Effective exchange surface for gases, nutrients and waste, by simple diffusion
what do all cells perform
Movement
respiration
sensitivity
control
growth
reproduction
excretion
nutrition
what are the traits of multi cellular organisms
smaller surface area to volume ratio
not all cells in contact with external environment, therefore specialised cells have to perform different functions
what is differentitation
when a cell becomes specialised to carry out a particular function.
what are the categories of differentiation
1) change number of particular organelles- muscle cells have more mitochondria.
2) change shape of the cell( root hair cell- more surface area)
3)change co tents of the cell(e.g red blood cell xnucleus)
what is the role of xylem+phloem and how is it adapted for this role.
dead cells, phocilitating water
transports minerals and sugars up and down the plant.
what are the different levels of organisation and there definitions
tissue: groups of the same type of cells that perform the same function( muscle tissue in animals)
organ: groups of different tissues that perform a common function( stomach consists of mucus membrane tissue)
organ system:groups of different organs that perform a common function- respiratory system- muscle diaphram
how are the cells on a a Erythrocyte specialised(red blood cell)
biconcave shape: increases surface area over which oxygen can be absorbed
cytoplasm-high amounts of permanent haemoglobin which binds with oxygen
no nucleus present- more space inside cell for haemoglobin molecules
how are the cells on a Neutrophil specialised( white blood cell)
very flexible shape, allows them to squeeze through cell junctions in the capillary wall and engulf microorganisms
more lysosomes- help to digest and destroy invading cells
flexible nuclear membrane- further helps the cell to penetrate cell junctions
how is a sperm cell specialised
head contains a nucleus, which contains half the normal number of chromosomes
acrosome(head)- contains digestive enzymes that can bread down the egg cell wall.
mid piece- packed with mitochondria to release energy for tail movement
tail- rotates propelling the sperm cell forward
how is a palisade cell specialised
large no. of chloroplasts- site of photosynthesis-maximises the absorption of light
tall+ thin shape- allows light to penetrate deeper before encountering another cell wall. ( cell walls absorb/reflect light), cells densly packed together.
how are the root hair cells specialised for their functions
elongated to increase surface area, the the uptake of water by osmosis is greater
thinner walls than other plant cells- osmosis easier
Permanent vacuole- contains sap- more concentrated than soil water maintaining water potential
how are guard cells specialised
open in the daytime- use water for photosynthesis.
inner cell walls thicker, while outer cell walls thinner - allows cells to bend when turgid
cytoplasm- high density of chloroplasts .
mitochondria- play role in opening the stomata.
how are ciliated epithelial cells specialised (throat)
cilia- hair like structures, that beat in coordinated way to shift materials along the surface of the epithelium tissue.
goblet cells(mucus secreting cells)- secrete mucus which helps to trap dust, dirt and microorganism- preventing them from entering vital organs where they might cause infection.
what is the role off plasmids in a prokaryotic cell
contain genetic material such as antibiotic resistance
what is the role of the slime capsule in a prokaryotic cell
helps to protect bacteria from attack by cells of the immune system
what is mitosis
cell division that produces genetically identical cells
what are the two types of cell division in eukaryotic cells
mitosis and meiosis
what happens in mitosis
a parent cell divides to produce two genetically identical daughter cells
why is mitosis needed
for growth of multicellular organisms, and for repairing damaged tissues
what does the cell cycle consist of, and what happens in the stages
growth phase 1- this is where the cell growths and new organelles and proteins are made
synthesis- cell replicates its DNA ready to divide for mitosis
growth phase 2- cell keeps growing and proteins needed for cell division are made
mitosis- the start and end of the cell cycle
what are the four stages of mitosis
prophase
metaphase
Anaphase
telophase
what happens in the interphase
cell prepares to divide
DNA is unravelled and replicated, to double its genetic content. Organelles are also replicated, and ATP content is increased to provide energy for mitosis to happen.
what happens in prophase
Chromosomes condense, getting shorter and fatter. Tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres called spindle fibres. Nuclear envelope breaks down and chromosomes lie free in the cytosoplasm
what happens in metaphase
the chromosomes line up along the equator of the cell and become attached to the spindle fibres by their centromere
what happens in the anaphase
The centromeres divide, separating each pair of sister chromotads. The spindles contract, pilling chromotads to opposite poles of the spindle, centromere first
what happens in the telophase
chromatids reach opposite poles of the spindle. They uncoil and become long and thin again. Nuclear envelope forms around each group of chromosomes, so there are now two nuclei. cytokinesis finishes. now two genetically identical daughter cells.
what is mitosis controlled by
genes
how does cancer form
if there is a mutation in a gene that controls cell division, the cell grows out of control. Cells keep dividing to make more and more cells, resulting in a tumour. Cancer is a tumour that invades other tissue. result of damage to the genes that control mitosis and cell division
how can some cancer treatment target cell cycle
control the rate of cell division by disrupting the cell cycle. this kills the tumour cells.
What is G1
some chemical drugs prevent the synthesis of enzymes needed for DNA replication. if these aren’t produced- cell is unable to enter the synthesis phase. disrupting the cell and forcing it to kill itself
what is S phase
Radiation and some drugs damage DN. several point in the cell cycle the cell is checked for damage. If it is detected, the cell will kill itself, preventing tumour growth.
wha are the names of the genes that control cell division
tumour suppressor genes-repress the cell cycle and promote apoptosis. less cell division.
porto-oncogenes- promote the cell cycle and stimulate cell division
both ensure cell divides at a fairly constant rate.
what are benign tumours
cells are not cancerous
tumour cell division is slower than malignant
tumours do not invade tissues to firm secondary tumours.
moist of the time harmless
sometimes cause blockages
put pressure on organs
removed by surgery
what are malignant tumours
cells are cancerous
divide by mitosis
tumour cell division is uncontrolled
cells can spread to other tissues to for secondary tumours by metastasis via blood or lymph system
requires radiotherapy or chemotherapy as well as surgery.
