Cells Flashcards
Structure and function of nucleus
- double membrane nuclear envelope
- small holes called nuclear pores for material like ribosomes to get out
- granular jelly like material called nucleoplasm
small sphere inside called nucleolus where rRNA is produced and makes ribosomes
Function - site of dna relocation and transcription, contains genetic code for each cell
structure and function of endoplasmic reticulum
Structure:
RER and SER have both folded membrane called cristae
RER associated w ribosomes
Function:
RER : protein synthesis
SER : synthesis and store lipids and carbohydrates
structure and function of golgi apparatus
Structure
- folded membranes
- secretary vesicles transport substances out of cell
- microvilli increase surface area for absorption
function - modify, package and transport substances
- form lysosomes
- add carbohydrates to proteins to form glycoproteins
structure and function of lysosomes
structure
- bags of digestive enzymes, can contain 50 different enzymes
function
- hydrolyse phagocytic cells
- digest worn out organelles for reuse of materials
- exocytosis: release enzymes to outside of cell to destroy material
structure and function of mitochondria
structure - double membrane - inner membrane called cristae - fluid centre called matrix - loop of mitochondria dna function - site of aerobic respiration - site of ATP production - DNA to code for enzymes needed in respiration
structure and function of ribosomes
structure
- small, made up of two subunits of protein and rRNA
- 80s in eukaryotic
- 70s in prokaryotic, mitochondria and chloroplasts
function
- site of protein synthesis
structure and function of vacuole
structure
- filled with fluid surrounded by single membrane called tonoplast
function
- makes cells turgid for support
- temporarily stores sugars and amino acids
structure and function of chloroplasts
- double membrane
- stacks of folded membranes called thylakoids
- fluid filled storms contains enzymes for photosynthesis
function - site of photosynthesis
structure and function of cell wall
structure :
plants - made of microfibrils and cellulose polymer
fungi - made of chitin, a nitrogen containing polysaccharide
function
- provides structural strength and rigidity to the cell
- prevents cell bursting or shrinking
structure and function of plasma membrane
structure
phospholipid bilayer - molecules embed within and attached in the outside
function
controls entrance and exit of molecules
compare prokaryotic and eukaryotic cells
prokaryotic smaller prokaryotic no membrane bound organelles prokaryotic 70s eukaryotic 80s prokaryotic no nucleus prokaryotic meurin cell wall eukaryotic no vacuole eukaryotic may contain plasmids capsule flagella
what are viruses
Acellular and non living, they relocate inside of cells making it difficult to destroy them without harming the host cell
what are the types of microscopes
optical (light) , transmission electron, scanning electron
what is magnification?
how many times larger an image is compared to the object
what is resolution
the ability to distinguish between two separate objects
compare optical microscope with electron microscopes
optical use beam of light where electron uses beam of electrons to make image
electrons use electromagnets to condense beam
optical have a longer wavelength so poor resolution
electron have shorter wavelength so higher resolution
optical colour electron bw
optical can view living samples
electron samples must be in a vacuum thus dead
compare SEM and TEM
SEM electrons bounce off surface of specimen where TEM electrons pass through specimen SEM 3D TEM 2D Both use magnets not lenses both produces electromicrograph both produce BW image
how to calculate magnification
image size/ actual size
process of cell fractionation and ultracentrifugation
- cells homogenised in a pestle and mortar.
ice cold to limit enzyme activity
buffeted to prevent enzymes denaturing
isotonic to maintain same water potential in and out of cell to prevent shrivelling or burst - filter to remove complete cells or large debris, leaving suspension or cells
- homogenate put in test tubes in centrifuge and spun at low speed. most dense organelles will collect at the bottom of tube forming a pellet. liquid is called supernatant
spin at a faster speed for longer and keep repeating until all is left is ice cold solution
order : nuclei, chloroplast, mitochondria, lysosomes, ER, ribosomes
why don’t viruses undergo cell division
non livint
what happens during interphase
chromosomes extended and not visible, cell bust making proteins. chromosomes replicate and nucleolus is visible
what happens during prophase
chromosomes condense, nucleolus disappears and spindle apparatus made of spindle fibres form
what happens during metaphase
nuclear membrane breaks down, chromosomes align at the equator of the cell. each chromosome is attached to spindle fibres by centromeres
what happens during anaphase
centromeres divide and spindle fibres pull individual chromatids taking the chromosome apart
what happens during telophase
chromosomes reach respective polar ends and become longer and thinner. spindle fibres disintegrate and nucleolus forms
what happens during cytokinesis
single eukaryotic cell divide into two diploid daughter cells which are identical to parent cell
how to calculate mitotic index
(number of cells in mitosis/ total number of cells) *100
what is a protoroncogene
genre that produce proteins that stimulate cell division and ihibit cell death.
what can be said about oncogenes
hey can’t be controlled by suppressors and thus keep stimulating cell division resulting in a tumour
describe the process of binary fission
- circular dna of bacterium is replicated
- undergoes cytokinesis, cytoplasm divided forming two new cells that are genetically identical
- each daughter cell contains single copy of circular dna
describe the fluid mosaic model
mixture and movement of proteins, glycoproteins and cholesterol arranged within a phospholipid bilayer consisting of hydrophilic heads and hydrophobic tails. can be described as a partially permeable membrane as only lipid soluble substances and very small molecules can pass through.
what are channel proteins
hydrophilic pores that allow select ions such as Ca, K that travel in water into and out of cell
what are carrier proteins
proteins that allow substances to pass through via facilitated diffusion. they act as carriers for active transport and as receptor sites for hormones
what is diffusion
net movement of particles from an area of high to low concentration due to the random movement of particles. passive process meaning atp is not required (no energy needed) molecules must be lipid soluble and small to diffuse across membranes
what is facilitated diffusion
movement of particles from area of high to low concentration using a channel or carrier protein.
- channel proteins form tubes filled with water allowing water soluble ions to pass though
- carrier proteins bind with a molecule such as glucose causing a change in the shape of the protein, enabling the molecule to be released to the other side of the membrane
what is osmosis
movement of water from areas of high to low WP across a partially permeable membrane
what is water potential
pressure created by molecules measured in kPa
what is meant by isotonic
WP is the same in solution and cell within solution
what is meant by hypotonic
WP of solution is more positive that that it the cell. more water moving in by osmosis, risking cell bursting
what is meant by hypertonic
WP it if solution is more negative than that of cell. more water moving out by osmosis causing cell to shrivel
what is active transport
movement of substances from low to high concentration using metabolic energy and a carrier protein
describe process of cotransport
- sodium ions leave epithelial cell and enter blood via active transport using carrier protein
- sodium concentration in cell is lower in the lumen
- sodium ions enter by facilitated diffusion
- glucose absorbed with sodium ions against concentration gradient
what is a lymphocyte
cells that identify the presence of pathogens and potentially harmful foreign substances in the body and destroy it neutralise them to prevent harm
how can lymphocytes identify and remove foreign substances
they can distinguish between pathogens and self cells due to the molecules on its surface, usually proteins as their tertiary structure enable lots of unique identifiable shapes to be made
what can lymphocytes identify
pathogens eg bacteria
cells from other organisms or same species
abnormal body cells eg cancer cells
toxins eg cholera
what are antigens
molecules that generate an immune response by lymphocyte cells when detente’s in the body. usually found on surface of crlls
what adaptations do cells have for rapid transport
increased SA
increased number of protein channels and carrier molecules in membranes
what is meant by antigen variability
mutations of pathogens occurring in a gene that codes for the antigen will cause the shape of the antigen to change. this means previous immunity is no longer effective as memory cells will only have information of the old antigen shape
describe process of phagocytosis
- phagocyte recognises antigens on pathogen
- phagocyte engulfs pathogen
- pathogen contained in the vacuole or vesicle in cytoplasm of her he phagocyte
- lysosome fuses with phagocytic vacuole and release hydrolytic enzymes to break down pathogen
- phagocyte presents pathogens antigens on its surface to activate other immune system cells
what are antigen presenting cells
infected body cells that present viral antigens on their surface
describe the cell mediated response
- complimentary tH lymphocytes bond to foreign antigen on antigen presenting cell
- cytokines released which stimulate:
a. clonal expansion of complementary t cells which become memory cells or trigger humoral response.
b. clonal expansion of cytotoxic cells which secrete enzyme preform to destroy infected cells
describe what happens in the humoral response
B cell takes in antigen by endocytosis
1. complimentary tH lymphocytes bind to foreign antigen on APC
2. cytokines released that stimulate clonal expansion of complementary B lymphocytes
3. B cells differentiate to plasma cells
4. Plasma cells secrete antibodies with a complementary variable region to antigen
B memory cells can divide into plasma cells when reinfected with the same pathogen to make large numbers of antibodies rapidly
features memory B cells
live for decades in the body where plasma cells are short lived
divide by mitosis and make plasma cells rapidly if they collide with antigens theyve previously encountered
this means large numbers of antibodies can be produced so rapidly jay the pathogen is destroyed before any symptoms can happen
what is agglutination
antibodies are flexible and bind to multiple antigens to clump them together. makes it easier for phagocytes to locate and destroy pathogens
what is passive immunity
antibodies introduced into the body but the pathogen doesn’t enter the body, meaning plasma and memory cells aren’t made. thus no long term immunity. e.g. antibodies passed from breast milk to baby
what is active immunity
immunity created by one’s own immune system following the exposure of a pathogen or its antigen
what is natural active immunity
following infection and the creation of the body’s own antibodies and memory cells
what is artificial active immunity
following the introduction of a weakened version of the pathogen or pathogens through a vaccine
state process of vaccination
- small amounts of weakened or dead pathogen or antigens introduced in mouth or via injection
- exposure to antigens activate B cell to go through clonal selection
- B cells undergo mitosis and make large number of cells that differentiate into plasma or memory B cells
- B cells make antibodies
- B memory cells divide rapidly when reinjected with same pathogen to make large numbers of antibodies rapidly
what is here immunity
if enough of the population are vaccinated the pathogen can’t spread easily amongst it. this provides protection to those who aren’t vaccinated e.g. those too ill to get a vaccine, with lowered immunity or those too young
describe structure of HIV
- RNA and enzyme reverse transcriptase needed for viral replication
- capsid outer fist
- envelope made of membrane taken from host cells
- protein attachments allowing virus to attach to hosts tH cell
describe replication of HIV in tH cells
- HIV transported in blood until it’s attached to CD4 protein in tH cells
- HIV protein capsule fuses with tH cell membrane enabling RNA and reverse transcriptase to enter
- Reverse transcriptase copies viral RNA into DNA and movies to tH nucleus. this is why it’s called a retrovirus
- mRNA transcribed and tH cells start to create viral proteins to make new viral proteins
what is aids and what does it result in the body
Aids is when replicating viruses by tH cells interfere with the functioning of the immune system
With tH being destroyed the host can’t produce an adequate immune response for other pathogens and left vulnerable to infections and cancer
what is a monoclonal antibody
a single type of antibody that can be isolated and cloned
what is an antibody
proteins are out binding sites complimentary in shape to certain antigens
what are monoclonal antibodies used for
medical treatment
medical diagnosis
pregnancy tests
what is direct monoclonal antibody therapy
monoclonal antibodies prevent cancer cells growing by preventing chemicals binding to cancer antigens which enable uncontrolled cell division. they are only designed to attach to cancer cells as it is complementary to antigens on cancer cells
what is indirect monoclonal antibody therapy
monoclonal antibodies have a drug attached to them, so when they bind to complementary antigens on cancer cells the drug is taken to the cancer cells and kills them. reduces side effects that chemotherapy and radiotherapy use
what can monoclonal antibodies he used to test for
pregnancy, influenza, hepatitis, chlamydia, prostate cancer
describe process of ELISA test
- HIV antigens are on surface of well place
- blood from test user placed on test site
- HIV antibodies attach. rinse with water to rid of any other present antibodies
- second antibody with enzyme attached. rinse to get rid of any unbound enzyme antibodies
- colourless substrate added. if positive, substrate digested with enzyme colour changes
ethical issues for monoclonal antibody production
- uses mice to create MAB and tumour cells, leads to debates whether animal use to enable better treatments and detection of disease for humans is justifiable
