All of studying cells Flashcards
Structure and function of the Nucleus
Nuclear envelope/double membrane and pores
Chromosomes/chromatin
Nucleolus
Stores genetic information for polypeptide production
site of DNA replication
site of production of mRNA and tRNA
Site of production for rRNA
Structure and function of mitochondria
Double membrane
inner membrane highly folded to form cristae
matrix containing mitochondrial DNA, ribosomes, proteins and lipids
Site of ATP production for aerobic respiration
cells that need a lot of ATP have lots of mitochondria such as muscle cells
Structure and function of RER
Highly folded membrane with 80s ribosomes embedded
membrane folded into flattened sacs called cisternae
joined to nucleus
synthesis and transport of proteins throughout the cell
Structure and function SER
Highly folded membranes flattened into sacks called cisternae
recombines glycerol and fatty acids to make triglycerides
packages triglycerides into vesicles and transports to Golgi body
Structure and function of cytoplasmic ribosome
made up of 2 subunits made of long strands of rRNA and ribosomal proteins
eukaryotic cells contain 80s ribosomes
site of protein synthesis for amino acids
Structure and function of Golgi body
Flattened sacs of membrane filled with fluid
golgi vesicles pinch off the main membrane
sorts, modifies and packages proteins and triglycerides into vesicles, can be used to form lysosomes
Structure and function of lysosome
membrane bound organelles that store and release many hydrolytic enzymes
contain hydrolytic enzymes that hydrolyse invading bacteria and pathogens
Structure and function of CSM
made up of phospholipids, specific transport proteins and carbohydrates arranged in fluid mosaic model
controls the passage of molecules into and out of the cell
Structure and function of centrioles
microtubules
form a network of spindle fibers onto which chromosomes attach, pull chromosomes apart during mitosis
not found in plant cells
Structure of the chloroplast and definitions
Granum- stack of thylakoid membrane
Thylakoid membrane- contains chlorophyll for photosynthesis and ATP synthase enzyme to produce ATP
Stroma- fluid filled part, some photosynthetic reactions occur here
starch grains- the energy storage molecule of a plants
DNA and ribosomes- contain their own DNA and 70s ribosomes for synthesis of enzymes needed for photosynthesis
plasmodium- connects cells
Plasmodesmata- gaps in cell walls that connect cell cytoplasm’s together to allow easy movement of water soluble molecules
What is the name of the cell wall found in Fungi
Chitin, not cellulose
Prokaryotic cells
No nucleus or membrane bound organelles
DNA free in cytoplasm- 70s ribosomes, flagellum, mesosome( highly folded section of inner membrane), plasmid, cell wall(Made from murein or peptido glycan- a blend of polypeptides and polysaccharides), cell membrane, capsule(slime layer)
Prokaryotic cell vs eukaryotic
DNA is circular and not associated with histones: DNA is linear and associated with histones
Contains no membrane bound organelles: Contains membrane bound organelles
DNA is free in cytoplasm: Has a nucleus, DNA contained within nuclear membrane
Contains 70s ribosomes: Contains 80s
Some have a capsule, one or more flagella, one or more plasmids: Do not have capsule
Have mesosomes for ATP synthesis: Foes not have mesosomes
Cell wall made of murein or peptidoglycan: Plants have a cell wall made of cellulose
Light microscope
Magnification is limited, low resolution- limited by the wavelength oflight
the shorter the wavelength of light, the better the resolution
electron microscopes
Both types use a beam of electrons, rather than light. Electrons behave like waves and focus using electromagnetics, detected using a phosphorous screen or photographic film. Electrons so have small wave length so higher resolution
TEM
Electrons pass through allowing to view internal structures
more dense areas absorb more electrons so appear darker
SEM
No sliced but electrons bounce off the surface. produces a 3D image.
Principles and limitations of TEM
Electrons pass through, denser parts absorb more electrons, denser parts appear darker, electrons have a short wavelength so give high resolution
cannot look at living material
must be thinly sliced
artefacts present
long preparation time
describe how you would make a temporary mount
add a drop of water to the microscope slide
get a thin section of plant tissue and float on the drop of water
stain with KI
lower the cover slip using a mounted needle to avoid air bubbles
describe how a student would use an eyepiece graticule
measure each sample using an eye piece graticule
calibrate the eyepiece graticule against a stage micrometer
take at least 5 measurements and calculate mean
scale factor measurements
1m= 1000mm
1mm=1000um
1um= 1000nm
Cell fractionation and differential centrifugation
Homogenise by placing sample in a blender
Place in an
Ice cold: to reduce the action of enzymes that would digest organelles
Isotonic- prevents osmosis of water in or out of organelles, prevent cell lysis
Buffered: stop ph changes that could cause enzyme to denature
solution
filter to remove debris
centrifuge at high speed. densest organelles settle at bottom in a pellet. supernatant removed and spun again at a higher speed
Phopsholipids
Form micelles when submerged in water. hydrophobic fatty acid tails point inwards towards the middle, hydrophilic heads point outwards towards the extracellular fluid. Forms the basis of a cell membrane- selectively permeable
Allow lipid soluble non polar molecules to pass through by simple diffusion and prevents the passage of small polar lipid isnoluble molecules
The fluid-mosaic model
Forms a phospholipid bilayer which is constantly moving around, giving a fluid structure. the selective permeability is related to distribution of specific proteins- mosaic
Role of cholesterol
Decreases permeability and increases stability of membrane
more cholesterol= less fluidity of membrane
Chanel proteins
pores within the membrane that allow only specific molecules to move across by FD. Intrinsic
Proteins have specific tertiary structure so are specific and can only transport molecules that are complementary to shape of channel proteins
carrier proteins
aid transport of polar ions by FD and AT. Allow diffusion of larger molecules- attaches to binding site and changes shape, releasing the molecule through to the other side of the membrane
Glycoproteins
Composed of carbohydrates and proteins, important in cell recognition as act as antigens. Immune cells detect the specific shapes of glycoproteins to help identify self and non self cells
Diffusion
Passive process- does not require ATP, will stop when there are equal numbers of that specific molecule on each side- when they have reached equilibrium. Involves small non-polar lipid soluble molecules
Definition: Net movement of molecules from an area of higher concentration to a lower concentration across a partially permeable membrane
factors affecting diffusion
temperature- increase in kinetic energy- faster rate of diffusion
Surface area- the larger the surface area the more space for molecules to pass through
Concentration gradient- as concentration difference increases, rate of diffusion increases
diffusion distance- the shorter the diffusion distance, the faster molecules will travel from one area to the next. Phospholipid bilayer are all the same thickness
Facilitated diffusion
specific proteins help specific molecules to pass through the phospholipid bilayer. All have binding sites not active sites
FD levels off when all the carrier proteins are saturated- number of carrier proteins will become a limiting factor
Osmosis
The net movement of water from higher water potential to lower water potential through a partially permeable membrane down a water potential gradient
WP- water molecules and their ability to collide with a membrane
The affects of osmosis- higher, lower WP and isotonic
high- causes swelling and cell lysis- causes increase in mass
low- results in shriveling of the cell- plant cell membrane pulls away from the cell wall
isotonic-no net movement of water into and out of the cells
AT
Movement of substances from low to high concentration moving against their concentration gradient. Requires carrier proteins. requires ATP- the hydrolysis of ATP allows protein to change shape and transport the molecule across the membrane
Other forms of Active transport
Bulk transport by exocytosis- uses golgi body to move large quantities of molecules
Co-transport
- Na+ (sodium ions) are actively transported out of epithelial cell into the blood (by sodium potassium pump)
- This creates a concentration gradient of Na+ (between lumen of the ilium and the epithelial cell) (Cotransporter proteins have 2 binding sites complementary to Na+ and glucose. Only when both molecules bind will the molecules be moved across the membrane)
- Na+ and glucose enter by facilitated diffusion using (complementary) cotransporter proteins.
- Na+ diffuse into the cell down its concentration gradient
- Glucose moves into the cell against its concentration gradient / down an electrochemical gradient
- Glucose moves into the blood by facilitated diffusion
2 ways in which pathogens cause disease
Release toxins which can directly damage tissue
Burst cells, replicating inside and take over by destroying host cells
Antigen definition and what will happen if not recognized as self
A molecule, a protein, that stimulates an immune response that results in the production of a specific antibody
If antigen not recognized the body will treat it as non-self and initiate an immune response leading to the destruction of the cell
process of phagocytosis
Pathogen is engulfed by the phagocyte
engulfed pathogen enters the cytoplasm of the phagocyte in a vesicle and forms a phagosome
Lysosome fuses with phagosome releasing hydrolytic digestive enzymes
lysosome enzymes hydrolyze the pathogen
waste materials are released from the cell by exocytosis and antigens presented on the cell surface membrane and the phagocyte become an antigen presenting cell
process is non-specific
Specific cellular response definition
a specific response to a specific antigen on the surface of a cell or pathogen that has been identified as non-self
T Helper cell response
what are they: These cells respond directly to a specific pathogen or its antigens or they respond to antigen presenting cells that present specifically complementary antigen to their receptors
How they respond: Phagocyte engulfed and hydrolyses the pathogen and presents the antigen on the cell surface membrane
TH cell with specific receptor molecule binds to presented antigen
Once TH cell binds to the presented antigen it is activated, it then rapidly clones by mitosis
.
desctribe clonal selection of Th cells
a specific TH cell binds to presented antigen via its complementary receptor
the cell is activated and clones to produce many TH cells with complementary receptors to its antigen
Role of Th cell
Specific Th cell binds to the antigen presenting cell
release cytokines that attract phagocytes to the area of infection
release cytokines that activate cytotoxic killer T cells
activates a specifically complementary B cell
form memory Th cells
Role of Tc cells
locates and destroys infected body cells that present the correct antigen
binds to antigen presenting cells
releases perforin which creates holes in the cell membrane which destroys the antigen presenting cell
Humoral response
/
primary response
Involves the activation of B cells to produce antibodies
- specific Th cell with the correct receptor binds to presented antigen and then locates and activates specifically complementary B cells
The Th releases cytokines that signal the B cell to clone by mitosis
the B cell then differentiates into plasma cells, producing and secreting a vast quantity of antibodies and memory cells, remain in the body to release antibodies when secondary infection approaches
Antibody definition
protein made in response to a foreign antigen- has binding sites which bind specifically to an antigen. a specific antibody is produced by a specific plasma cell
What type of proteins are antibodies and describe their structure
quaternary- has a constant region and variable regions so different tertiary structure as have different primary structure. The variable region and therefore the binding site is specific for each antibody
Binds to form antigen antibody complex
Role of antibodies in destroying pathogens
Agglutination- specific antibodies bind to antigens on pathogen and clump them together
Opsonisation- marking of pathogens so phagocytes recognize and destroy the pathogen more efficiently
secondary response definition
The activation of memory cells to produce antibodies- rapid and extensive production of antibodies
Effective as most pathogens have the same antigens on their surface and so are recognized by memory cells when re-infection occurs
How may secondary response fail?
Antigenic variability- gene mutations change tertiary structure of antigens specific to B cells- no longer complementary to produce antibodies.
passive vs active immunity
P V A
No exposure to antigen: Exposure to antigen
Antibodies are given: Antibodies are produced
No memory cells are provided: Memory cells are produced
Short term: Long term
Fast acting: Takes time to develop
Vaccination
Contain antigens from dead, weakened or attenuated pathogens
pathogen is engulfed by phagocyte and displayed on an antigen presenting cell
a specific t helper cell binds to antigen and stimulated B cells through the release of cytokines.
B cells divide by mitosis to produce plasma cells and memory cells
plasma cells produce and release antibodies
memory cells recognize antigen on second infection
herd immunity
If enough individuals in the population are vaccinated (85%) then there is little chance of the disease spreading, therefore even non-vaccinated individuals will be protected
Ethical issues associated with vaccination
Development using the testing on animals
Human testing
available to everyone or only those who can afford
balancing risk of side effects with benefits
vaccination programmes compulsory?
Loss of genetic variability through eliminating and organism
Monoclonal antibody definition and its uses
Antibodies that all have the same tertiary structure
Use: research, immuno assays, diagnosis, targeting drugs, killing specific cells, isolating specific chemicals
The indirect ELISA test
Antigen-coated well, specific antibody binds to antigen, enzyme-linked antibody binds to specific antibody, substrate is added and converted by enzymes into coloured product- rate of colour formation is equal to the amount of specific antibody
wash in-between to remove excess antibody
The sandwich ELISA test
Antibody-coated well, add antigen to be measured, add enzyme conjugated secondary antibody, add substrate and measure colour
HIV structure and replication
Structure: Attachment proteins, lipid envelope, reverse transcriptase, HIV RNA, capsid
Replication: Attachment proteins on HIV binds with a protein receptor found on Th cells
Capsid fuses with cell-surface membrane and releases viral RNA and enzymes into the helper T cell
The HIV’s reverse transcriptase converts Viral RNA into cDNA using host nucleotides and cDNA converted to dsDNA by DNA polymerase
Viral cDNA moves into nucleus of T cell and is inserted into host cell genome. the person is now infected
Transcription of viral DNA into mRNA which is translated to produce HIV proteins. The infected t helper cell starts to manufacture HIV proteins
Particles break away with a section of the host cell membrane which forms the lipid envelope
Reduces the number of Th cells
AIDS
Not a pathogen- can be detected by screening for number of TH cells
Cell mediated immunity of an individual is compromised
More HIV, destruction of more TH cells, less activation of B cells, less able to destroy pathogen
What three process happen in interphase
G1 phase Cell increases in size and new biomass is made (proteins)
S phase DNA replicates by semi-conservative DNA replication
G2 phase Cell prepares for division, synthesis & stores of ATP and new organelles synthesised.
Gene definition and base sequence
A gene is a section of DNA that codes for one specific polypeptide (protein). The base sequence of DNA on the DNA codes for the sequence of amino acids in a protein.
What is a chromosome
A chromosome is an independent DNA molecule which has been supercoiled into a condensed form
Homologous chromosomes definition
Homologus chromosomes –have the same genes in the same gene loci (positions) but may have different alleles (versions) of the genes. (one chromosome is Maternal and the other is Paternal)
How are diploid chromosomes represented in the form of N
2N
Uses of mitosis- The 2 daughter cells are genetically identical
Increasing cell numbers and growth of an organism
· Repair of damaged tissues (not cells)
· Replacement of worn out/ dead cells
It is also used by some organisms for asexual reproduction. All the offspring will be identical. This tends to occur in favourable, stable environments (where there is no environmental change).
prophase
1) The nuclear membrane starts to break down.
2) The centrioles start to move to the poles of the cell and make spindle fibres
3) The chromosomes supercoil and condense / shorten / thicken and become visible.
4) Each chromosome appear as 2 identical sister chromatids joined at the centromere
metaphase
The centrioles complete the production of spindle fibres (contractile protein fibres)
2)The chromosomes are attached to the spindle fibres by their centromere
3) the chromosomes align down the equator of the cell.
anaphase
The spindle fibres contract/shorten.
2)The centromere splits 3)The identical sister chromatids are pulled to opposite poles 4) making a “V” shape
telophase
A nuclear membrane starts to reform around each set of chromosomes
2)The chromatids / chromosomes unwind / uncoil / become longer / thinner and become invisible
cytokinesis.
the cell surface membrane pinches together, the cytoplasm divides forming two daughter cells.
Describe the appearance and behavior of chromosomes during mitosis:
During prophase, chromosomes supercoil and condense to become visible;
2. Chromosomes appear as 2 identical sister chromatids joined by a centromere;
3. During metaphase chromosomes line up on the equator of the cell; 4. Chromosomes attach to the spindle fibres;
5. By their centromeres;
6. During anaphase, the centromere splits;
7. Sister chromatids are pulled to opposite poles of the cell making a V shape;
8. During telophase, chromatids uncoil and become thinner;
allele definition
gene definition
chromosome definition
sister chromatid definition
haploid definition
diploid definition
somatic cell definition
Control genes
Tumour suppressor genes code for proteins that slow down the cell cycle.
· Proto-onco genes code for proteins that speed up the cell cycle.
tumor definition
cells that undergo uncontrolled mitosis
What do tumor suppressor drugs do
DNA replication, spindle formation, Cytokinesis or other processes linked to mitosis.
binary fission
- replication of the circular DNA (not associated with histones) and of plasmids
- division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids.
mitotic index formula
Mitotic index = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑒𝑙𝑙𝑠 𝑖𝑛 𝑃𝑀𝐴𝑇/𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑣𝑖𝑠𝑖𝑏𝑙𝑒 𝑐𝑒𝑙𝑙𝑠
Serial dilution
M1 X V1 = M2 X V2
M1 = Desired diluted concentration (mol dm-3)
V1 = Desired Volume (cm3)
M2 = Original concentration (mol dm-3)
V2 = Unknown Volume of stock solution (cm3)
Meiosis
In a meiotic division, the DNA is replicated in S phase (interphase) of the cell cycle. The chromosomes then go through two nuclear divisions. Each division has a prophase, metaphase, anaphase and telophase.
In the first meiotic division, the homologous chromosomes pair up and are separated
(INDEPENDENT SEGREGATION 2n to n).
In the second division, the chromatids are separated.
What causes variation in meisois
Random fertilizations of haploid gametes produced by meiosis
crossing over
independent segregation
Crossing over
- The homologous chromosomes associate (Bivalent is formed).
- Chiasmata form (Chromosomes entangle / twist).
- Equal lengths of (non-sister) chromatids / alleles are exchanged.
- Producing new combinations of alleles.
Describe and explain the processes that occur during meiosis that increase genetic variation
Homologous chromosomes pair up/ bivalents form; 2. Independent segregation occurs; 3. Maternal and paternal chromosomes are reshuffled in any combination; 4. Crossing over leads to exchange of parts of (non-sister) chromatids/alleles between homologous chromosomes; 5. (both) create new combinations of alleles.
