cells 3.2 Flashcards
aqa biology as level
what organelles are present in a eukaryotic cell?
- cell surface membrane
- nucleus
- mitochondria
- chloroplast (plant only)
- Golgi apparatus and vesicles
- lysosomes
- ribosomes
- RER and SER
- cell wall
- vacuole (plant only)
what is the structure of the nucleus?
- nuclear envelope
- nuclear pores
- nucleoplasm
- chromosomes
- nucleolus (site of RNA production)
what is the function of the nucleus?
it contains the genetic code of each cell and site of DNA replication and transcription (mRNA)
what is the difference between RER and SER?
both are folded cisternae with RER having ribosomes on its surface
what is the function of the RER?
protein synthesis
what is the function of the SER?
synthesis and storage of lipids and carbohydrates
what is the structure of the Golgi apparatus?
folded membranes forming cisternae from which vesicles pinch off from
what is the function of the Golgi apparatus?
- adds carbohydrates to proteins to form glycoproteins
- produce secretory enzymes
- secrete carbohydrates
- transport modify and store lipids
- form lysosomes
- labels molecules for destination
- finished products transported to surface in Golgi vesicles fusing with membrane
what is the function of lysosomes?
bag of digestive enzymes that
- hydrolyse phagocytes
- break down dead cells fully
- release enzymes to outside of cell to destroy material (exocytosis)
- digest worn out organelles
what is the structure of mitochondria?
double membrane inner membrane called cristae filled with matrix and loops of mitochondrial DNA
what is the function of mitochondria?
it is the site of aerobic respiration and ATP production and contains DNA needed to code for enzymes in respiration
what is the structure of ribosomes?
small and made up of two parts a protein and a rRNA
80s - larger ribosome found in eukaryotic
70s - smaller ribosomes in prokaryotic mitochondria and chloroplast
what is the function of ribosomes?
protein synthesis
what is the structure of vacuole?
cell sap filled sac surrounded by single membrane called tonoplast
what is the function of the vacuole?
its turgid so provides support for the cell and is a temporary store for sugar and amino acids provides pigment for petals
what is the structure of chloroplast?
surrounded by a double membrane contains thylakoids (has chlorophyll/pigment inside it) and stroma
what is the function of chloroplast?
site of photosynthesis
what is the cell wall made of in plants and animals?
plants - cellulose
animals - chitin
what is the function of the cell wall?
provide structural strength for cell
what is the function of the phospholipid bilayer?
controls exit and entrance of molecules
what are the differences between prokaryotes and eukaryotes?
- prokaryotes are smaller
- have no membrane bound organelles
- 70s ribosomes
- no nucleus
- cell wall made of murein
what are other structural features of prokaryotes?
plasma and flagella and capsule around cell
what is the specialisation order?
specialised cells form tissues
tissues form organs
organs form organ systems
what are viruses?
viruses are acellular and non living
what is the structure of a virus?
attachement proteins, lipid envelope, genetic material and capsid
where do viruses replicate?
inside the cells so difficult to destroy
what are the types of microscopes?
optical transmission electron and scanning electron
what is the definition of magnification?
how many times larger the image is compared to the actual size
what is the definition of resolution?
the minimum distance between two objects to be seen as separate
what are the pros and cons of optical microscope?
pros
- coloured image
- easier preparation
- can view living samples
- thicker samples
cons
- poor resolution as light has longer wavelength
- lower magnification
- can’t see organelles
what are the pros and cons of electron microscope?
pros
- high resolution as electrons have shorter wavelength
- high magnification
- can see organelles
cons
- long preparation
- black and white images
- non living samples
- thinner samples (TEM)
what is the difference between TEM and SEM?
TEM shows the organelle structure of sample whereas SEM shows the 3D structure of sample
what is the magnification formula?
image size = actual size x magnification
how do you calibrate the eyepiece graticule?
- Calculate the distance of each stage micrometer division.
- Line up the micrometer with your eyepiece reticle scale bar.
- Count divisions and calculate size for that magnification.
- Increase magnification and repeat calculations for each click stop.
- Create a sizing chart to keep at your workstation.
what is the process of cell fractionation?
homogenisation then ultracentrifugation
why are cells homogenised?
cells are broken apart to release the organelles and separate them in a solution
where are cells prepared?
in an ice cold isotonic and buffered solution
why is the solution ice cold?
to reduce enzyme activity
why is the solution isotonic?
must be same water potential to prevent osmotic gain or less of water
why is the solution buffered?
to prevent enzymes denaturing
describe ultracentrifugation?
the homogenate is spun at low speeds and the heaviest organelle forms a pellet at the bottom of test tube. the supernatant is spun at increasingly higher speeds until desired organelles separates
what is the order of the organelles mass?
nucleus chloroplasts mitochondria lysosomes ER ribosomes
what is the cell cycle?
interphase (G1, S, G2)
-G1- growth
-S - DNA synthesis
-G2 - growth and preparation of mitosis
M - mitosis
cytokinesis
what happens in interphase?
organelles double cell grows and DNA replicates
what are the stages of mitosis?
prophase metaphase anaphase telophase
what are mitosis features?
one nuclear division
genetically identical
diploid cells
for growth and repair
what happens in prophase?
- chromosomes condense and become visible
- centrioles separate and move to opposite sides of cells
what happens in metaphase?
- chromosomes line up along equator of cell
- spindle fibres attach to centromeres and chromatids
what happens in anaphase?
- spindle fibres retract and cause the centromere divides into two and sister chromatids taken to opposite sides of cell
- requires ATP
what happens in telophase?
- chromosomes become longer and thinner again
- spindle fibre disintegrate and nucleus starts to reform
- cytoplasm splits to create genetically identical cells (cytokinesis)
what is the mitotic index formula?
(total number of cells in mitosis/ total number of cells) x 100
what is binary fission in prokaryotic cell?
- circular DNA and plasmids replicates
- division of cytoplasm to produce two daughter cell (each with a single copy of circular DNA and variable number of plasmids)
why don’t viruses divide via cell division?
Being non-living, viruses do not undergo cell division. Following injection of their nucleic acid, the infected host cell replicates the virus particles
what is meant by the fluid mosaic model?
the phospholipid membrane is fluid due to the movement of phospholipids and mosaic due to the proteins embedded between them
what is the purpose of cholesterol in the phospholipid bilayer?
it restricts the movement of other molecules making membrane less fluid at high temperatures preventing water leaking out
what is the difference between integral and peripheral proteins?
integral - span through one side to other side
peripheral - doesnt extend across membrane
what is the purpose of peripheral proteins?
- provides mechanical support
- attach to proteins or lipids to form glycoproteins and glycolipids
- used in cell recognition as receptors
what is the purpose of integral proteins?
are proteins carriers and channel proteins involved in transport of molecules across the membrane
what is the difference between protein carriers and channel proteins?
channel proteins are water filled tubes that allow water soluble ions to diffuse whereas carrier proteins will bind with larger molecules like glucose and change shape to transport them to other side
what molecules can pass through partially permeable membrane?
only lipid soluble and small molecules not water soluble or large molecules
what is simple diffusion?
passive movement of molecules from a higher concentration to a lower concentration
what is facilitated diffusion?
passive movement of molecules from a higher concentration to a lower concentration via carrier proteins and channel proteins
what is osmosis?
passive movement of water from an area of higher water potential to an area of lower water potential
what are the types of osmosis in cells?
isotonic - same water potential
hypotonic - solution has higher water potential than cell
hypertonic - cell has higher water potential than solution
what is active transport?
movement of molecules against concentration gradient using ATP and a carrier protein
what happens in active transport?
- molecule binds to complementary receptor on carrier protein
- ATP binds to carrier protein from inside of cell and is hydrolysed into ADP and Pi
- causes the carrier protein to change shape and release molecule to other side
- phosphate ion released and protein goes back to original shape
what happens in co transport of amino acids and glucose in the ileum?
- sodium ions are actively transported out of epithelial cell into blood
- sodium ions then diffuse from lumen down the concentration gradient into epithelial cell
- at the same time glucose or amino acid attach to co transport protein which transports sodium are transported against their concentration gradient
- glucose then diffuses into blood from epithelial cell via facilitated diffusion
how can transport be increased across membrane?
larger surface area or more carrier/channel proteins
how does the body identify between cells?
each cell has a specific protein molecule on its surface to identify it that is unique because of their tertiary structure
what is an antigen?
antigens generate an immune response by lymphocyte cells when detected and re usually proteins on surface of cells
what is antigen variability?
pathogen DNA can mutate frequently which could potentially change shape of antigen any previous immunity is so long effective as memory cells have memory of old antigen shape
what is a phagocyte?
a phagocyte is a macrophage that carries out phagocytosis found in blood and tissue
is phagocytosis specific or non specific response?
non specific
how is phagocytosis performed?
- any pathogen or abnormal cell attracts the phagocyte causing it to move towards it
- receptors on surface of phagocyte bind to antigen of pathogen/abnormal cell
- the phagocyte engulfs the pathogen forming phagosome
- lysosome within phagocyte fuses with phagosome
- lysozyme enzyme released into phagosome hydrolysing pathogen and destroying it
what are lymphocytes?
t lymphocytes and b lymphocytes are type of white blood cells which provide specific immunity response
where are lymphocytes made?
bone marrow
what is an antigen presenting cell?
any cell that presents non self antigens on their surface
what happens in cell mediated response?
- after destroying pathogen pathgocyte presents its antigens on its surface (APC)
- helper T cells have receptors which can attach to antigen on APC
- once attached this activates helper T cells to divide by mitosis to replicate and make lots of clones
- cloned T cells either become
. some remain as helper T cells and activate b lymphocytes
. some stimulate macrophages to perform phagocytosis
. some become memory cells for that antigen
. some become cytotoxic T cells (killer T cells)
what do cytotoxic T cells do?
killer T cells destroy abnormal or infected cells by releasing a protein called perforin which embeds into cell surface membrane forming a pore so substances can enter and leave cell
how are B cells activated?
- antigens collide with complementary antibody on B cell surface and the B cell takes in the antigen and presents its on its surface
- when B cells collide with helper T cells it activates the B cell to go through clonal expansion and differentiation
- B cell under goes mitosis to make a large number of cells these differentiate into plasma cells or memory B cells
- plasma cells make antibodies
- memory B cells divide quickly into plasma cells when reinfected with same pathogen to make large number of antibodies
how does memory B cells follow active immunity?
memory B cells live for decades in bodies and divide by mitosis rapidly to form plasma cells which form large amounts of antibodies destroying pathogen before symptoms occur
what is primary and secondary response?
primary response - first encounter to pathogen so slow immunity response
secondary response - pathogen encountered again but quick immediate response due to presence of memory B cells and plasma cells
what is the antibody structure?
heavy chain light chain and variable region and antigen binding site
4 polypeptide chain structure
what is agglutination?
antibodies are flexible and bind to multiple antigens to clump them together so it is easier for phagocytes to locate pathogens for phagocytosis
what is passive immunity?
antibodies are introduced to body but the pathogen doesnt enter body so no plasma or memory cells produced so no long term immunity
what is active immunity?
immunity created by own immune system due to exposure of pathogen or antigen
what are the types of active immunity?
natural active immunity and artificial active immunity
what happens in natural immunity?
following an infection and the creation of bodies own antibodies and memory cells
what happens in artificial immunity?
following the introduction of a weakened version of a pathogen or antigen via a vaccine
what happens in vaccines?
- small amounts of weakened pathogen introduced to body
- exposure to antigen activates B cell to go through clonal expansion and differentiation (clonal selection)
- B cells undergo mitosis to make large number of cells which differentiate into plasma or memory B cells
- plasma cells make antibodies
- memory B cells can divide rapidly into plasma cells when reinfected with same pathogen to make large number of antibodies rapidly
what is herd immunity?
if enough of the population are vaccinated the pathogen can’t spread easily amongst people providing protection for those who are not vaccinated/ vulnerable
what is HIV structure?
core - genetic material (RNA) and the enzyme reverse transcriptase which are needed for viral repliaction
capsid - outer protein coating
envelope - extra outer layer made out of membrane taken from the hosts cell membrane
protein attachment - on exterior of envelope to enable the virus to attach to the hosts helper T cell
how is HIV replicated in helper T cells?
- HIV is transported around in the blood until it attaches to a CD4 protein on a helper T cell
- the HIV protein capsule then fuses with the helper T cell membrane enabling the RNA and enzymes of HIV to enter
- reverse transcriptase enzyme copies the viral RNA into a DNA copy and moves to the helper T cell nucleus
- here mRNA is transcribed and the helper T cell starts to create viral proteins to make new viral particles
what is AIDs?
AIDs is when the replicating viruses in the helper T cells interfere with their normal functioning of the immune system as helper T cells destroyed by virus so host is unable to produce adequate immune response leaving person vulnerable to cancer etc
what is a monoclonal antibody?
a monoclonal antibody is a single type of antibody that can be isolated and cloned
what are antibodies?
are antibodies are proteins which have binding sites complementary in shape to antigens
what is monoclonal antibodies used?
medical treatment medical diagnosis and pregnancy test
how is ELISA testing carried out?
- add the test sample from a patient to the base of the beaker
- wash to remove any unbound test sample
- add an antibody complementary in shape to the antigen you are testing the presence of in the test sample
- wash to remove any unbound antibodies
- add a second antibody that is complementary in shape to first antibody and binds to the first. the second antibody has an enzyme attached to it, rinse any unbound antibodies out
- the substrate for the enzyme which is colourless is added this, substrate produces coloured products in the presence of the enzyme
- the presence of the colour indicates the presence of antigen in the test sample and the intensity of the colour indicates the quantity presents
what are ethical issues linked to monoclonal antibodies?
animal testing and harm (antibodies made with mice)
