CELLS Flashcards
TOPIC 2
STRUCTURE OF NUCLEUS
- Nuclear envelope: double membrane surrounding nucleus, outer membrane continuous w/RER of cell
- Nuclear pores: allow passage of larger molecules, such as mRNA, out of nucleus
- Nucleoplasm: granular, jelly-like material making up bulk of nucleus
- Chromosomes: protein-bound, linear DNA
- Nucleolus: small spherical region in nucleoplasm-Manufactures rRNA and assembles ribosomes
FUNCTION OF NUCLEUS
- Controls cell’s activities - produces mRNA and tRNA - protein synthesis-controls entry and exit of materials, and contains nuclear reactions
- Retains genetic material in form of DNA and chromosomes
- Manufactures rRNA and ribosomes
STRUCTURE OF MITOCHONDRIA
- Double membrane surrounding organelle - controls entry and exit of material
- Cristae - extensions of inner membrane, providing large surface area for attachment of enzymes and other proteins during respiration
- Matrix - makes up remainder - contains proteins, lipids, ribosomes and DNA and some respiratory enzymes
FUNCTION OF MITOCHONDRIA
responsible for ATP production
STRUCTURE OF CHLOROPLAST
- Chloroplast envelope - double plasma membrane, highly selective, surrounds organelle
- Grana - stacks of disc-shaped thylakoid membrane
- Thylakoids - contain chlorophyll used in photosynthesis, can be linked by lamellae to other grana
- Stroma - fluid-filled matrix + contains starch grains
FUNCTION OF CHLOROPLAST
Site of Photosynthesis:
Granal membranes provide large SA for photosystems, enzymes
Chloroplasts contain DNA and ribosomes - can quickly and easily manufacture some of proteins needed for photosynthesis
STRUCTURE OF ENDOPLASMIC RETICULUM
- 3D system of sheet-like membranes - continuous w/outer membrane of nuclear double membrane
- Membrane contains a network of tubules and flattened sacs called cisternae
- RER - ribosomes on outer surface of membranes
- SER - lacks ribosomes on its surface and is often more tubular in its appearance
FUNCTION OF ENDOPLASMIC RETICULUM
RER
1. Large SA for protein/glycoprotein synthesis
2. Provides a pathway for material transport throughout cell, especially for proteins
SER
1. Synthesises, stores and transports lipids and carbohydrates
STRUCTURE OF GOGLI BODY
- Compact system of flattened sacs and stacked membranes-cisternae
- Vesicles - modified proteins and lipids transported to cell membrane where they fuse with it, and then egest contents to outside
FUNCTION OF GOLGI BODY
- Form glycoproteins by adding carbs to proteins
- Produce secretory enzymes, such as those secreted by pancreas - apparatus is developed in secretory cells, especially those in small intestine
- Secrete carbs, such as cellulose for plant cell walls
- Transports, modifies and stores lipids
- Forms lysosomes
STRUCTURE OF LYSOSOMES
spherical membrane bound sacs containing lysozymes
FUNCTION OF LYSOSOMES
- Hydrolyse foreign material ingested by phagocytes
- Exocytosis of enzymes to destroy extra-cellular material
- Apoptosis - programmed cell death.
Autolysis - breaking down cells after death - Digest worn out organelles - can recycle chemicals
STRUCTURE OF RIBOSOMES
- Small cytoplasmic granules found in all cells, free-floating or associated w/RER
- 80S - found in eukaryotic cells, slightly larger
- 70S - in prokaryotic cells, slightly smaller
- 2 Subunits - large and small - contain ribosomal RNA and proteins
FUNCTIONS OF RIBOSOMES
Carry out translation stage of protein synthesis to produce polypeptides
STRUCTURE OF CELL WALL
Found in plants, algae and fungi
- Cellulose microfibrils embedded in a matrix - contribute to overall cell wall strength are considerably strong.
and other polysaccharides - Middle lamella - marks the boundary between adjacent cell walls and cements adjacent cells together
FUNCTION OF CELL WALL
- Cellulose to provide mechanical strength to prevent cell wall bursting under pressure created by osmotic entry of water
- To provide mechanical strength to cell as a whole
- Allows water to pass along it - contributes to the movement of water through the plant
STRUCTURE OF VACUOLES
- Fluid-filled sac bounded by a single membrane
- Single membrane around it called tonoplast
- Solution of mineral salts, sugars, amino acids, wastes and sometimes pigments
FUNCTION OF VACUOLES
- Support herbaceous plants and herbaceous parts of woody plants by making cells turgid
- The sugars and amino acids can act as temporary food source
- Pigments - may attract pollinating insects due to colour
OUTLINE THE ROLE OF ORGANELLES IN PRODUCTION, TRANSPORT + PROTEINS FROM EUKARYOTIC CELLS (4)
DNA in the nucleus
ribosomes produces proteins
mitochondria produce ATP
Golgi body package
vesicles fuse with cell membrane
RER transport
ALL FEATURES PROKARYOTES HAVE
70s ribosome
murine cell wall
no membrane bound organelles-no nucleus
SOME FEATURES PROKARYOTES HAVE
capsid
flagella
EUKARYOTES VS PROKARYOTES
DNA enclosed in nucleus VS DNA floating free in cytoplasm
DNA is long + linear VS DNA is circular
contains histones VS contains no histones
has membrane organelles VS has no membrane organelles
cell wall is cellulose + chitin VS cell walls contain murien
ribosomes 80s VS ribosomes 70s
no slime capsule VS sometimes have slime capsule
VIRUSES
Viruses are acellular as they have no cell surface membrane, are not made of cells, have no organelles, cannot respire and no metabolic reactions
Viruses are extremely small and cannot be seen w/light microscope-enter living cells and multiply w/assistance of the host cells, causing diseases
FEATURES ALL VIRUSES HAVE
genetic material-codes for viral proteins
capsid-protects genetic material
attachment proteins-complementary to + bind to receptors on its specific host cell
ATTACHMENT PROTEINS
specific for each virus-so different viruses will attach to different receptors that are complementary to their attachment proteins-viruses are specific and can only infect one type of cell e.g. HIV viruses only infect T helper cells + replicate inside them
MAGNIFICATION EQUATION
M= I/A
MAGNIFICATION
how much bigger image is compared to real structure
RESOLUTION
ability to see two points as two points, rather than merged into one
LIGHT MICROSCOPE
.Use lenses to focus a beam of light through specimen
.Lower resolution than electron microscopes
.Can view live specimens
.Simple staining and slide preparation
.Can see colours
ELECTRON MICROSCOPES: TEM + SEM
.Use electromagnets to focus beam of electrons through or onto specimen
.Denser parts absorb more electrons and appear darker
.Higher resolution than light, due to smaller wavelength of electrons
.Specimen must be placed in a vacuum and so must be dead
.Longer preparation time, w/more complex staining procedure, which can produce artefacts
TEM
.Can see internal structure of organelles
.Specimen must be extremely thin
.Image is only in 2D
.Black and white image only
.highest magnification and resolution
SEM
.Resolution not as high as TEM
.3D image produced of the surface
.Black & white only
USING A LIGHT MICROSCOPE
1.add drop of water
2.add a single layer of cells
3.add a drop of stain to cells
4. add a cover slip and push down gently
CELL FRACTIONATION
cell homogenisation to break open cell
filter to remove large debris
use isotonic to prevent organelles from bursting
cold reduce enzyme activity
buffered prevent enzyme denaturing
centrifuge to sperate nuclei
respin at supernatant to different speeds in pallet
HOMOGLOUS CHROMOSOMES
pairs of chromosomes that are same size w/same genes-One chromosome is inherited from each biological parent
G1 INTERPHASE
involving growth of cell and replication of its DNA
G1 IN CANCER
chemotherapy prevent synthesis of enzymes needed for DNA replication-If these aren’t produced cell is unable to enter synthesis phase disrupting cell cycle and forcing cell to kill itself
S PHASE INTERPHASE
cells DNA is replicated
S PHASE IN CANCER
radiation and some drugs damage DNA several points in cycle-DNA is checked for damage- if severe is detected cell would kill itself – preventing further tumour growth Some drugs can stop DNA unwinding prior to replication
G2 INTERPHASE
synthesises proteins needed for cell division
MITOSIS
1.Prophase-condense/become visible from chromatin
chromosomes appear as chromatids joined at centromere
2.Metaphase-chromosomes line up at equator
chromosomes attached by spindle fibres by centromere
3.Anaphase-centromere splits
chromatids are pulled to opposite poles
4.Telophase-chromosomes uncoil
CYTOKINESIS
cytoplasm divides separating into 2 daughter cells
RP2-MITOIC INDEX + PLANT ROOT TIPS
.Cut last 5mm from tip as this is where the cells dividing by mitosis occur
.Soften plant tissue with acid so that it will squash
.Add drop of toluidine blue stain to see chromosomes
.Squash so layer of cells is only 1 cell layer thick so light can pass through and can see individual cells and nuclei
.Count large numbers of cells/fields of view to ensure a representative sample-Do repeats to ensure figures are correct
.mitotic index=cells in mitosis/total no. of cell in field view
BINARY FISSION
DNA replication
plasmids replicate
cytoplasm divides + 2 daughter cells cells produced
VIRAL REPLICATION
1.attachment proteins attach to host cell receptors
2.viral nucleic acid enters cell
3.RNA converts to DNA using reverse transcriptase
4.DNA inserted to nucleus
5. DNA transcribed to mRNA
6.mRNA translated to viral proteins
HYDROPHILIC PHOSPHOLIPID HEAD
attracted to water and so phospholipids arrange themselves in bilayer w/ hydrophilic heads facing aqueous extracellular fluid + aqueous cytoplasm
HYDROPHOBIC PHOSPHOLIPID TAIL
repelled by water and so turn in forming hydrophobic interior
PHOSPHOLIPID BILAYER-FLUID MOSAIC MEMBRANE
Forms a barrier to certain molecules
Gives membrane fluidity
Hydrophobic fatty acid tails face each other
Hydrophilic phosphate heads face outwards towards water
Allows passage of non-polar substances
EXTRISIC PROTEIN-FLUID MOSAIC MEMBRANE
surface or only in half membrane-May have charged hydrophilic areas which attract to hydrophilic heads, and uncharged hydrophobic areas which associate w/ hydrophobic tails-proteins act as enzymes-Some act as receptors for hormones
CARRIER PROTIEN-FLUID MOSAIC MEMBRANE
Large molecules attach to carrier proteins-change shape and molecule is released onto opposite side of membrane-When used in facilitated diffusion-carrying molecules down concentration gradient ATP NOT required
CHANNEL PROTEIN-ON MEMBRANE-FLUID MOSAIC MEMBRANE
.Pores lined w/polar groups to make them hydrophilic so that water soluble charged ions can pass through
.Each channel protein is specific to one type of ion
.Can open and close
.Protein changes shape
MEANING BEHIND FLUID MOSAIC MEMBRANE
Fluid because individual phospholipid molecules can move relative to one another -gives membrane flexible structure that is constantly changing shape
Mosaic- protein components that are embedded in phospholipid bilayer vary in shape, size and pattern, like stones in mosaic
FUNCTION OF CELL MEMBRANE FLUID MOSAIC
.phospholipid bilayer forms protective barrier for cell-allows different environments to be maintained on either side of cell
.bilayer also prevents water soluble – meaning it is selectively permeable
.Other molecules such as water soluble must use channel protein or carrier protein by facilitated diffusion/active transport
.Fluidity of bilayer allows it to form vesicles, fuse w/other membranes
.Surface proteins-glycolipids/glycoproteins are important for cell-to-cell recognition, can act as antigens or receptors + help maintain stability for membrane
Cholesterol restricts lateral movement of molecules in the membrane and is important for stability and regulates fluidity
RP3-DILUTIONS OF SOLUTE + CALIBRATION CURVE
high salt concentrations solution has lower water potential than potato cytoplasm so water moves out of cytoplasm by osmosis, and so cells decrease in mass- lower salt concentrations, there is gain in mass of potato tissue as water moves down water potential gradient by osmosis to potato cells Plot your results and draw graph to find concentration of salt solution that is isotonic w/potato cells- use conversion table to find water potential of this concentration of salt solution
RP4-PERMEABILITY OF CELL SURFACE MEMBRANE
.Increase cholesterol – decrease fluidity
.Increase saturated– decrease fluidity
.Increase temperature – increase fluidity
.Increase in concentration of ethanol – dissolves phospholipids so increases permeability
EFFECT OF TEMPERATURE ON MOVEMENT OF PIGMENT OUT OF BEETROOT CELL
.little increase at first: Membrane proteins are stable at low temperatures
.Rapid rise from 50oC: Cell membrane has been damaged at high temperatures w/ proteins denaturing-phospholipid bilayer is damaged and fluidity is increased, so membrane is now permeable and pigment leaks out
.little further increase from 60oC: Most pigment has already leaked out
EFFECT OF ETHANOL CONCENTRATION ON CELL MEMBRANE
.Increase in movement w/increasing ethanol concentration
.Ethanol dissolves phospholipids, so creates gaps in cell membrane structure
.Graph would level off when most pigment has leaked out
DIFFUSION
movement of molecules or ions from region of higher concentration to one of lower concentration down gradient
Passive process, no ATP energy
DIFFUSION ACROSS PHOSPHOLIPID MEMBRANE
.gaps between phospholipid are small, and the centre of bilayer is hydrophobic
.simple diffusion to occur across phospholipid bilayer of membrane, particles must be small and lipid soluble
.Larger molecules and charged particles cannot move by diffusion
RATE OF DIFFUSION DEPENDS ON
.Concentration gradient- rate is proportional to concentration gradient
.Distance of travel -shorter distance faster rate
.Temperature -increase in temperature increases molecular kinetic energy, so increases rate
.Size of molecule -Smaller molecules diffuse more quickly as can pass between phospholipids easier and more kinetic energy-If molecule is too big it cannot cross through
.Membrane surface area -More surface area faster rate
.Lipid solubility -Lipid soluble molecules diffuse across plasma membranes- are soluble in phospholipid bilayer
FALLICITATED DIFFUSION
diffusion of particles across membrane using protein carriers or channels without needing any ATP energy – passive process
ACTIVE TRANSPORT
movement of molecules or ions AGAINST concentration gradient using ATP and PROTEIN CARRIERS-its active process
CO-TRANSPORT
coupled movement of substances across cell membrane via carrier protein
CO-TRANSPORT OF AMINO ACID + GLUCOSE
co-transport, glucose are drawn into cells along w/sodium ions, down sodium ion concentration that has been set up by active transport of sodium ions out of cells by potassium pumps
OSMOSIS
solution of higher water potential to solution of lower water potential across partially permeable membrane
WATER POTENTIAL
tendency of water to leave or enter system or cell-greater number of free water molecules greater water potential
ISOTONIC
solution of equal water potential
HYOPERTONIC
very concentrated solution w/lower or more negative water potential
HYPOTONIC
dilute solution w/higher or less negative water potential
NAME + DESCRIBE 5 WAYS SUBSTANCES CAN MOVE ACROSS CELL MEMBRANE TO CELL
1.diffusion of small molecules down concentration gradient
2.Facilitated diffusion down concentration gradient via protein carrier/channel;
3.Osmosis of water down water potential gradient
4.Active transport against concentration gradient via protein carrier using ATP
5.Co-transport of 2 different substances using carrier protein
ENDOCYTOSIS
cell membrane invaginate and pinches off to form vesicle-phagocytosis when phagocyte takes in pathogen in this way
EXOCYTOSIS
vesicle carrying material fuses w/cell surface membrane to release material
MOLECULES IMMUNE SYSTEM IDENFIFY
.Pathogens
.Cell from other organisms
.Abnormal body cells eg cancer cells
.Toxins
ANTIGEN
recognised as foreign protein + production of antibodies
ANTIBODY
protein specific to antigen
produce B cells
ANTIBODY-CONSTANT REGION
same sequence of amino acids
ANTIBODY-VARIABLE REGION
specific tertiary structure which is complimentary to one antigen so is ‘antigen binding site’
ANTIBODY-HINGE
antibody can bind more easily w/up to 2 antigens forming an antibody-antigen complex
ANTIGENIC VARIBILITY
pathogens can change their surface antigens as their DNA mutates which changes tertiary structure of surface proteins-could affect the ability of immune system to recognise and destroy them
PHAGOCTOSIS
1.Phagocytes recognise antigens on pathogens as foreign and engulfs it into vesicle called phagosome
2.lysosome fuses w/phagosome and releases lysozyme into it
3.Lysozymes hydrolyse pathogen and harmless products of digestion are absorbed by phagocyte or released by exocytosis
4.Antigens from pathogen are displayed on phagocytes cell membrane, turning to antigen presenting cell
ANTIGEN-PRESENTING CELL
Any cell that presents a non-self antigen on their surface
.Infected body cells will present the viral antigens on their surface
.phagocyte which has engulfed and destroyed pathogen will present antigens on their surface
.Cells of transplanted organ will have different shaped antigens on their surface compared to your self-cell antigens
.Cancer cells will have abnormal shaped self-cell antigens
T CELLS
cell mediated response include T Helper cells Killer T cells and T memory cells
CYTOXIC T CELLS
kill abnormal cells and cells that are infected by pathogens by producing protein called perforin
CELL MEDIATED RESPONSE
1.Pathogens invade body cells or are taken up by phagocytes
2.cells become APC as they place the pathogen antigens on to their cell surface membrane
3.Receptors on specific T helper cell fit exactly onto these antigens
4.attachment activates T cell to divide rapidly by mitosis and form clone of genetically identical cells
5. they develop to memory cells that enable rapid response to future infections by same pathogen + stimulate phagocytes to engulf more pathogens + stimulate correct B cells to divide and secrete antibodies + activate cytotoxic T cells
B CELLS
humoral response- plasma cells and B memory cells
HUMORAL RESPONSE
1.Pathogen invades body
2.Antibody on surface of B-cell bind to specific antigen and forms antigen-antibody complex + activate the B-cell-clonal selection
3.activated B-cell divides by mitosis into plasma cells and memory cells
4.Plasma cells are clones of B-cell which secrete specific monoclonal antibody-Antibody transported + combines w/antigen on surface of pathogenic cells to produce antibody-antigen complex
5.Memory B-cells remain in body for many years Can reproduce rapidly to produce an instant supply of plasma cells if same pathogen invades body again
AGGULATION
clumping together – slows pathogen down to enable phagocytosis
PRIMARY IMMUNE RESPONSE
First time that an individual comes into contact w/particular antigen- Slower as there aren’t many specific B-cells to produce specific antibodies-patient will develop symptoms as pathogen increases in number and damages cells
B and T cells produce memory cells which remain in body for long time
SECONDARY IMMUNE RESPONSE
next time individual comes into contact w/ antigen-Clonal selection is much faster, more antibodies are produced in short space of time
rapid response prevents full infection so person is ‘immune’
ACTIVE IMMUNITY
.Involves memory cells
.involves antibodies by plasma cells
.long term-antibody produced in response to antigen
.can take time to develop
NATRURAL IMMUNITY
exposure to disease organism through infection w/actual disease
PASSIVE IMMUNITY
.doesn’t involve memory cells
.doesn’t involve antibodies by plasma cells
.short term-antibody is broken down
.faster acting
ARTIFICAL IMMUNITY
protection acquired by giving a person an injection or transfusion of antibodies made by someone else
VACCINATION
.Contains antigen-dead/weakened form of pathogen-stimulates production of antigen presenting cells antibodies/plasma cells/memory cells
.Specific Helper T-cells detect antigen and stimulate specific B-cells
.B-cells divide by mitosis to give plasma cells which produce antibodies and memory cells
.second dose could produce antibodies in secondary immune response in higher concentration and quickly
ETHICAL ISSUES WITH VACCINATION
.testing on animals in development and production
.Testing: Risk to people in medical trials
.Side effects – how can risk of side effects be balanced against risk of developing disease?
.Compulsory vaccination: Need herd immunity, personal beliefs?
.Expense: Vaccines are expensive so less money for other treatments
.Priorities: Who should get vaccine first in new epidemic?
MONOCLONAL ANTIBODIES
specific tertiary strcure
from single clone of plasma cells
HOW A PREGNANCY/ COVID TEST WORKS
.Antigen binds to complementary specific antibodies in result window
.Mobile antibodies also bind to antigen
.Build up of mobile antibodies, builds up blue dye and creates visible line
.Mobile antibodies bind to complementary antibodies in control window-Build up creates visible blue line
USES OF MEDICAL ANTIBODIES
.MEDICAL TREATMENT -Can target specific cells -Cancer cells have antigens called tumour markers- attach anti-cancer drugs to antibodies, so drug will only accumulate near cancer cells, reducing side effect problems and avoid damage to healthy cells
.MEDICAL DIAGNOSIS- pregnancy tests
ELISA TEST
1.antibody binds to antigen + is attached to test well
2.blood sample is added-Any complementary antibodies bind to antigen + Well is washed
3. second antibody w/enzyme attached is added-binds to the first antibody if it is present and attached to antigen + Well is washed
4. yellow substrate solution is added-If enzyme linked antibody is present, then it turns into blue product
ETHICAL ISSUES WITH MONOCLONAL ANTIBODIES
.Suffering of animals
HIV TO AIDS
.helper T-cell count drops
.Immune system deteriorates and eventually fails
.person is then more vulnerable to other infections
.Antibiotics do not work, as only kill bacteria by interfering w/their cell wall, metabolism and enzymes- Viruses do not have murein cell wall and only use human metabolism and enzymes
