Cell Structure Flashcards
What is exocytosis ?
Transport of material out of cell by vesicles
Define mesosomes
Structures within bacterial cells that are an inward extension of the cell membrane
What is endocytosis?
Transporting material into cell by engulfing it with its membrane
What is a microscope that uses pairs of convex lenses called?
A compound microscope
What is the resolution and magnification of a light microscope?
0.2 um
X1500
What is the eye piece also know as?
Ocular Lens
How do you calculate total magnification?
Mag of eyepiece X mag of objective lens
What is magnification?
How many times bigger the image is than real life
What is resolution?
The ability to distinguish between two adjacent points as separate structures
What is the equation for magnification ?
Drawn size / actual size
What is the limit of resolution?
The smallest distance between 2 distinct points. (After this point increasing mag doesn’t reveal more detail)
Why do electron microscopes have a higher resolution?
Shorter wavelength compared to light
How does an electron microscope work?
An electron beam gets focused by electromagnets onto specimen. Denser regions absorb electrons and appear lighter
What is the resolution and magnification of a TEM?
Mag = X500,000
Res= 0.1 nm
What does the condenser magnet do in a TEM?
Focus electron beam onto specimen
How must the specimen be prepared before using a TEM ?
Must be very thin, preserved in heavy metals and dead
Why must the specimen be dead for a TEM?
Uses vacuum
Why might the 0.1 non resolution be met for a TEM?
Lower energy beam used to not damage structure of specimen
Difficulties preparing specimen
What are the limitations of TEM?
Time consuming Complex process (training needed) Specimen must be dead No color 2D image Artefacts
What does TEM and SEM stand for?
Transition and scanning electron microscope
What are the two types of electron microscope?
TEM and SEM
How is a TEM different to a SEM?
TEM= electron beam goes through specimen
SEM= electrons pass along surface and are reflected back.
What are the advantages of using a SEM compared to a TEM?
3D looking image produced
Preparation is less complex
Specimen can be thick
What are the disadvantages of using a SEM over a TEM?
Lower resolution (20nm VS 0.1nm )
What are the main advantages and disadvantages of using a SEM over a light microscope?
Ad = higher resolution
Dis = specimen must be dead
Place in order of increasing resolution
TEM
light microscope
SEM
Light
SEM
TEM
When using a SEM what do the dark and light areas indicate?
Dark = depressions
Light = extensions
What is the difference between an eyepiece and scale graticule ?
Eyepiece graticule has no fixed scale and so must be calibrated
Scale graticule has a fixed length and acts as a ruler
When must a eyepiece graticule be calibrated?
For every new magnification
For every new microscope (will differ due to lenses)
What are the rules for drawing from microscope observation?
Clear and unbroken lines Large and clear No shading Correct proportion Pencil only
What is cell fractionation?
The process of separating cell components
Why might cell fractionation be used?
To determine the function of an organelle
To obtain a pure sample of an organelle
What must the solution used in cell fractionation be?
+why
Cold= prevent gutter enzyme activity that might digest organelles
Isotonic (sane water potential)= prevent osmotic lysis
Buffered = prevent PH change so proteins don’t denature
What are the two main steps in cell fractionation?
Homogenisation (releasing organelles from cells)
Ultracentrifugation = separating organelles
What occurs during homogenisation?
Tissue is broken into cells, cells broken into organelles by homogeniser.
Homogenate is filtered to form filtrate
What is a homogenate?
A solution of organelles produced after a homogeniser breaks down a tissue
Why is the homogenate filtered?
To remove debris (unbroken tissue)
Why occurs during ultracentrifugation?
The filtrate I’d spin in a centrifuge at high speeds
Creates a centrifugal force that drives the largest organelle to form pellets at the bottom of the test tube.
What is a centrifugal force?
An increase in gravitational field
What is the supernatant?
The liquid fraction after cebtrifugation
Order these by increasing size.
Nuclei Mitochondrion Chloroplast Ribosomes Lysosome
Nuclei Chloroplast Mitochondrion Lysosomes Ribosomes
What does ultrastructure mean?
The adapted internal structure of a cell
Define eukaryotic cell
A cell with a nucleus and membrane bound organelles
What is the function of the nucleus ?
Store genetic information
Produce ribosomal RNA and ribosomes
Control mRNA and tRNA production
Control cell activities
What are the main components that make up the nucleus?
Nuclear envelope
Nuclear pores
Nucleolus
Nuclearplasm
Chromosomes
Describe the nuclear envelope and its function
Double envelope, outer is continuos with the RER
Contains nuclear pores
Controls entry and exit of materials
Reactions occur within
Describe nuclear pores and its function
Pores roughly 40-100 nm in diameter
Allow diffusion of large molecules in and out of nucleus
Describe the nucleoplasm and its function
Granular and jelly like
Makes bulk of nucleus
Describe the nucleolus and its function
Small spherical
Makes ribosomal RNA
Assembles ribosomes
Describe the chromosomes found in the nucleus
Protein bound linear DNA
diffuse form so not visible
What is the function of mitochondria?
Produce ATP during aerobic respiration for energy release needed for metabolic reactions
What are mitochondria made of ?
Double membrane
Cristae
Matrix
What is cristae and it’s functions?
Extensions of the inner membrane from mitochondrion
Provide large SA for attachment of enzymes and proteins invoked in aerobic respiration
Describe the matrix of mitochondrion and its function
Semi-rigid material
Contains proteins lipids DNA and ribosomes for synthesis of own proteins (for respiration)
How can you tell a cell has a high metabolic rate from its mitochondria?
Lots of large mitochondria with extensive cristae
What is the function of chloroplast?
Absorb light and carry out photosynthesis
What are the components of chloroplast?
Chloroplast envelope
Grana
Thylakoids
Integranal lamella
Stroma
Describe the chloroplast envelope and its function
Double membrane
Highly selective entrance and exit of molecules
Describe stroma and its function
Fluid filled matrix
Contains starch, DNA and ribosomes (synthesis of proteins for photosynthesis)
Synthesis of sugars
Describe grana and its function
Make of stack of thylakoids with intergranal lamella
Chlorophyll within thylakoids absorb light
Large SA for attachment of chlorophyll, enzymes and electron carriers (light absorption)
Describe endoplasmic reticulum and its function
Network of tubules and flattened sacs continuous with outer nuclear membrane.
Spaces within cisternae for transportation of materials
Lamella = double membrane
What is the difference between SER and RER?
Rough = ribosomes
Smooth= more tubular appearance
What is the function of RER ?
Protein and glycoproteins synthesis (large SA)
transportation of materials (specifically proteins.
Process polypeptides synthesised by ribosomes
What is the function of SER?
Synthesis, storage and transport of lipids and carbohydrates
What are the functions of the Golgi apparatus?
Synthesis glycoproteins
Produce secretory enzymes (vesicles and lysosomes)
Secrete carbs
Transport, modify and store lipids
(Label using non-protein components)
What analogy can be used for the Golgi apparatus?
A post office
Sorting , labelling and delivering materials
What is the structure of the Golgi apparatus?
A stack of flattened sacks called cisternae
More compact than SER
cisternae are membrane bound
Vesicles pinches off from ends
Describe lysosomes
Vesicles from Golgi apparatus containing digestive enzymes (protease, lipase and lysozymes)
Separates potentially dangerous enzymes from rest of cell via membrane
Describe lysosome function
Hydrolysed (digest and recycle) old organelles, cell when dead and pathogens engulfed by phagocytic cells.
What does exocytosis mean?
The transport of materials to outer cell environment.
Describe the stages in the digestion of a bacterium engulfed by a phagocyte
1) lysosome pinches off end of Golgi apparatus (contains protease, lipase and lysozymes)
2) phagocytic cell that has engulfed pathogen fuses with lysosome
3) enzymes hydrolyse pathogenic material
4) soluble product diffuse into cytoplasm
5) insoluble products are egested when membrane of lysosome fuses with membrane of cell
Describe ribosomes and their function
A large and small subunit made of ribosomal DNA and protein
Polypeptide synthesis from mRNA and amino acids
Do ribosomes have a membrane?
No, found in prokaryotes
What type of ribosomes are there ?
80S
70S
Describe the cell wall and its function (eukaryotes)
Made of cellulose and glycoproteins (plants) or chitin, glycan and glycoproteins (fungi)
Mechanical strength, prevent osmotic lysis
What is chitin?
A polysaccharide that contains nitrogen
Describe the vacuole
Fluid filled sac Single membrane (tonoplast)
Fluid contains amino acids, mineral salts, sugars waste and pigments
Describe the function of the vacuole
Make cell turgid to support herbacious parts of plant
Sugars and amino acids act a food store
Pigments attract pollinators
How does specialisation make an organism more efficient?
Cells evolve to perform particular function
Perform function effectively as have adapted
Organism works more efficiently because one cell can’t carry out all functions at optimal levels
(However, become dependent as they lose ability to carry out other functions)
How do cells become specialised?
All cells have same genes
Genes are turned on or off (expresses or not)
Determines proteins produced and so function
Define a cell
A membrane bound structure that contains biomolecules
Define a tissue
A group of similar specialised cells that work together to perform a specific function
Why are cells aggregated?
For optimal efficiency
Cells can transfer molecules easily
Give examples of a tissue
Xylem
Phloem
Capillaries
Epithelial tissue
Define organ
A combination of different tissues working together to perform a specific function
Give an example of an organ
Stomach (epithelial, muscle , connective)
Leaf (epidermis ,phloem , xylem, palisade, mesophyll)
Why are capillaries not classed as an organ when arteries and veins are?
Capillaries are only made of epithelial cells so are a tissue
Arteries and veins are made of various different tissues (muscle, elastic fibre , epithelial)
Are arteries and veins a tissue or organ?
Why?
Organs
Arteries and veins are made of various different tissues (muscle, elastic fibre , epithelial)
Define organ system
Multiple organs working together as a single unit to perform a specific function
Give an example of an organ system and its function
Digestive system (digest and process food)
Respitory (breathing and Gad exchange )
Nervous (communication)
Define a prokaryotic cell
Small, simple
No nucleus or membrane bound organelles
What does unicellular mean ?
Only one cell
What are the main components found in a prokaryotic cell?
Pilli Flagellum Plasmids Ribosomes Cell membrane Cell wall Slime capsule Circular DNA (nucleoid) Cytoplasm
What do prokaryotic cells use to transfer genetic info to other prokaryotic cells?
Pilli
Define the flagellum of prokaryotic cells and its function
Tail like protrusion
Allows for directed movement (locomotion)
Define the slime of prokaryotic cells and its function
Mucilaginous slime outer layer
May contain waste and toxins
Allows for cells to stick together
Escape phagocytosis
Prevents drying out
Define the cell wall of prokaryotic cells and its function
Strengthened by murein (glycoprotein)
Prevents cell bursting
Gives mechanical strength
Define plasmids and their function
Circular ring of DNA
contains additional genes such as antibiotic resistance
Can be passed into other cells (vectors)
Can reproduce themselves
What is the anther name for circular DNA in prokaryotes?
Nucleoid
Define the nucleoid of prokaryotic cells and its function
Circular DNA of a prokaryotic cells
Non-linear, not associated with proteins or introns
Carries genes for replication of cell and protein synthesis
Where might you find bacteria chlorophyll?
Cell membrane
What we the food reserve granules in prokaryotic cells?
Granules of glycogen or lipid droplets
What does acelluar mean?
No cells
What are the basic components of a virus ?
Capsid
RNA /DNA
enzymes
Define the attachment proteins of viruses and its function
Proteins found on the outer most surface of viruses (lipid envelope or capsid)
Allow virus to identify host cells
Define the lipid envelope of viruses and its function
Not always present
Helps avoid immune system
Define the matrix of viruses and its function
Layer of proteins immediately under lipid envelope
Structural role
Define the capsid of viruses and its function
Protein capsule
Made of capsomeres
Encloses genetic info and enzymes
What is the genetic info in viruses stored as?
RNA or DNA
Not both
What is the name of the enzyme found in viruses’ capsid and what does it do?
Reverse transcriptase
Catalyse DNA syntheses from RNA
What cell structure is found in both mitochondria and prokaryotes?
70s ribosomes
How do you find the mean diameter of stomata using a optical. Microscope?
Calibrate eyepiece graticle
Measure diameter of multiple stomata
Calculate mean
