Describe the structure of centrioles
Consists of 2 bundles of microtubules at right angles to each other
Microtubules are made of tubulin protein subunits, arranged to form cylinder
Prokaryotic cells contain membrane bound organelles
Eukaryotic cells contain membrane bound organelles
What’s the function of the centrioles?
Spindles of tubulin from from centrioles before cell divides - chromosomes attach to middle of spindle and motor proteins walk along tubulin threads pulling chromosomes either ends of cell
Centrioles involved formation cilia and undulipodia
Describe the structure of the smooth endoplasmic reticulum
System of membranes containing cisternae that are continuous with the nuclear membrane
No ribosomes on surface
Describe the structure of the golgi apparatus
Membrane bound flattened sacs
Made from cisternae
What do secretory vessels do?
Bring materials to and from golgi apparatus
What’s the function of lysosomes?
Contains hydrolytic enzymes
Engulfs and digests old organelles nad debris then returns to be reused
What do lysosomes contain?
Hydrolytic enzymes
What’s the function of the Golgi apparatus?
Proteins and lipids modified e.g adding sugar molecules to make glycolipids/proteins or folded into 3D shape
Packaged into vesicles then:
Stored in cell
Moved to plasma membrane
What’s the function of the smooth endoplasmic reticulum?
Contains enzymes that catalyse reactions involved with lipid metabolism:
Synthesis of cholesterol
Synthesis of lipids/phospholipids
Synthesis of steroid hormones
Involved with absorption, synthesis and transport of lipids
What don’t plant cells contain that animal cells do?
Lysosomes and centrioles
What’s the cellulose cell wall made from?
Bundles cellulose fibres
Describe the structure of the cytoskeleton
Network protein structures within cytoplasm
Consists of:
Microfilaments - polymers of actin, 7nm diameter
Intermediate filaments - 10nm diameter
Microtubules - made tubulin, straight and cylindrical
Cytoskeletal motor proteins, myosins, kinesins, dyneins
Enzymes - site to allow binding of ATP for hydrolysis as energy source
Function of cytoskeleton microfilaments within cytoplasm
Give support and mechanical strength
Keep cell shape stable and allows cell movement
Function of cytoskeleton microtubules
Provide shape and support to cells and help substances and organelles move through cytoplasm:
Form track which motor proteins walk and drag organelles along
Form spindle before cell divides
Make up cilia, undulipodia and centrioles
Function of cytoskeleton intermediate filaments
Anchor nucleus within cytoplasm
Stabalise tissues extending between cells
Describe the structure of cell wall
Made of bundles of cellulose fibres
Outside of cell membrane
What are fungi cell walls made of?
Chitin
Describe the function of cellulose cell wall
String and can prevent plant cells from bursting when turgid
Provides strength and support
Maintains cell shape
Contributes to shape and strength of whole plant
Permeable to allow solutions to pass through
Describe the first 4 steps of protein synthesis
The gene …
mRNA …
mRNA attaches …
Molecules are …
Has coded instructions for a protein housed of chromatin. Gene is transcribed into length of mRNA in nucleus
Leaves nucleus through nuclear pore
To a ribosome on RER. mRNA is translated
Packaged into vesicles and move travel towards golgi body via microtubules and motor proteins
Describe the steps of protein secretion 5+
Vesicles …
Golgi body …
Vesicles move…
Vesicles fuse …
Plasma membrane…
Fuse with golgi body
Modifies and processes proteins and repackages molecules into vesicles
From golgi body towards plasma membrane
With plasma membrane
Opens to release molecules outside of cell
What type of bulk transport is protein secretion?
Exocytosis
What type of process is protein secretion and what does this mean?
Active process to energy is needed
Where is cytoplasm found?
Within the membrane
What does the cytoplasm contain?
Organelles
What’s the function of the cytoplasm?
Where cellular functions and chemical reactions take place
What’s the undulipodia called in prokaryotic cells?
Flagella
Describe the structure of cilia and undulipodia
Made of tubulin
Protrusions from cell, surrounded by cell surface membrane
Contain microtubules
Formed from centrioles
What’s the function of cilia?
Airway - push away mucus
1 Cilium - contains receptors and allows cells to detect signals about immediate environment
Describe the structure of lysosomes
Small bags, formed from Golgi body
Each surrounded by single membrane
Contain hydrolytic enzymes
What are lysosomes formed from?
Golgi body
Describe the structure of the rough endoplasmic reticulum
System of membranes, containing fluid filled cavities (cisternae) that are continuous with nuclear membrane
Coated with ribosomes
What’s the function of the rough endoplasmic reticulum?
Intracellular transport system: transport substances around cell
Provides large S.A fro ribosomes which assemble AAs into proteins - proteins actively pass through membrane into cisternae and transported to golgi body
What’s the function of mitochondria?
Site of ATP production during aerobic respiration
Mitochondria are …
Self-replicating
What cells are mitochondria abundant in?
Cells where much metabolic activity takes place
How long are mitochondria?
2-5 micrometers
Describe the structure of mitochondria
Spherical, rod-shaped or branched
Surrounded by 2 membranes with fluid-filled space between them. Inner membran’s folded into cisternae
Inner part of mitochondria is fluid filled matrix
How long are chloroplasts?
4-10 micrometers
What’s the function of chloroplasts?
Site of photosynthesis - light energy trapped inside chlorophyll and used to make ATP
Describe the structure of chloroplasts
Surrounded by double membrane - inner is continuous with stacks of membrane sacs (thylakoid) containing chlorophyll
Contains loops of DNA and starch grains
Describe the structure of the vacuole
Surrounded by membrane called tonoplast
Contains cell sap/fluid
What’s the function of the vacuole?
Maintains cell stability - when full, pushes on cell wall making it turgid. If all plant cells turgid, supports whole plant
What’s the vacuole filled with?
Water and solutes
What cells contain a large permanent vacuole?
Plant cells
What type of cells contain chloroplasts?
Plant and some protocists
What organelles don’t plant cells contain but animal cells do?
Plant cell ultrastructure
Plasma membrane
Nucleus
Nucleolus
Nuclear envelope
SER
RER
Ribosomes
Mitochondria
Cytoskeleton
Vacuole
Cellulose cell wall
Animal cell ultrastructure
Cytoplasm
Mitichondria
Cilia
Centrioles
Lysosomes
Peroxisomes
Eukaryotic cell ultrastructure
Chloroplasts
Cell wall
Why are some organelles membrane-bound?
Seperate them from rest of cell
What type of cells contain membrane-bound organelles?
Eukaryotic (prokaryotic don’t)
Why does each organelle have a specific function?
Provides division of labour meaning every cell can carry out its functions efficiently
What’s the function of the nuclear envelope?
Seperates contents of nucleus from rest of cell
What’s the function of the nucleolus?
Where ribsomes are made
What do nuclear pores do?
Enable larger substances to leave or enter nucleus
What do chromsomes contain?
Organisms genes
What’s the function of the nucleus?
Control centre of cell
Stores organisms genome
Transmits genetic material
Provides instructions for proteinsynthesis
Describe the structure of the nucleus
Surrounded by double membrane - nuclear envelope with contains pores
Describe the structure of the nucleolus
Found inside nucleus
Doesn’t have a membrane
Contains RNA
What is chromatin?
The genetic material consisting of DNA wound around histone proteins
Describe the structure of chromatin
Spread out and extended when not dividing
Condenses and coils tightly into chromsomes when about to divide
Definition of electron micrograph
Photograph of an image seen using an electron microscope
Definition of magnification
The number of times larger an image appears comapred with the size of the image
Definition of organelles
Small sturctures within cells, each of which has a specific function
Definition of photomicrograph
Photograph of an image seen using an optical microscope
Definition of resolution
Measure of the microscopes ability to distinguish between two points which are close together. The clarity of the image
The higher the resolution…
The clearer the image
Definition of eyepiece graticule
Measuring device placed in eyepiece of microscope and acts as ruler when viewing objects under microscope
Definition of stage graticule
Measuring device placed on stage of microscope to calibrate value of eyepiece divisions at different magnifications
Bacteria are…
Microorganisms
What are the similarities between eukaryotic and prokaryotic cells?
DNA and RNA
What are the structural differences between eukaryotic and prokaryotic cells?
Eukaryotic - nucleus within membrane, nucleolus present, linear DNA, membrane-bound organelles, larger ribosomes, when present has cellulose cell wall, flagella have 9+2 microtubule arrangement
Prokaryotic - no nucleus, no nucleolus, circulaar DNA, no membrane bound organelles, smaller ribosomes, when present has peptidoglycan cell wall, simple flagella
What’s a nucleoid?
Area within cytoplasm where DNA is positioned
How do prokaryotic cells divide?
Binary fission
How do eukaryotic cells divide?
Mitosis
Why do prokaryotic cells divide by binary fission instead of mitosis?
Hvae circular DNA rather than linear chromosomes so can’t carry out mitosis
What happens before prokaryotic cells divide?
DNA copied so each new cell recieves large loop of DNA and smaller plasmids
What’s the endosymbiant theory?
Theory as how eukaryotic cells arose from proakryotic cells
Describe the endosymbiant theory
Some prokaryotic cells with infolded membranes inavded or were engulfed by another prokaryotic but not digested. As invaded, plasma membrane folded inwards around invading cell, producing double membrane (what are now chloroplasts and mitochondria).
What characteristics do chloroplasts and mitochondria share with prokaryotic cells?
Small ribosomes
Loops of DNA
Divide by binary fission
What type of organelles don’t prokaryotes have?
Membrane bound organelles
What is pili?
Smaller hair-like projections on prokaryotic cells that allow bacteria to adhere to host cells or each other to allow passage of plasmid DNA
Mag of eyepiece = x10
Mag of objective lense = x4
Total mag =
x40
Mag of objective lense = x10
x100
Mag of objective lense = x40
x400
Mag of objective lense = x100
x1000
What does magnification describe?
How much bigger an image appears compared with the origional object
What type of magnification do microscopes produce and what does this mean?
Linear - is specimen seen at magnified x100, it appears to be 100 times wider and longer than it actually is
Differences between a light and electron microscope
Light - lower mag, lower res, living and dead, staining, uses beam of light
Electron - higher mag, higher resolution, dead only, no staining, uses beam of electrons
What’s the maximum resolution of a light microscope?
200nm
What’s the max magnification of a light microscope?
x1500
What’s the max magnification of an electron microscope?
x200,000
Why are light/optical microscopes widely used?
Cheap, easy to use, portable, study whole organisms
What’s a disadvantage of using a light/optical microscope?
Resolution limited so can’t magnify any higher whilst giving clear image
Name a structure that can’t be seen using a light/optical microscope?
Total magnification =
magnification of objective lense x magnification of eyepiece lense
How would you look at a specimen using a light/optical microscope?
Specimen on slide, placed on stage and clipped into plate
Rotate nosepiece so lowest powered objective lense over specimen
Adjust coarse adjustment knob while looking into eyepiece until image clear and in focus
Whilst viewing image, adjust iris diaphram for optimum light
Rotate nosepiece to x10 objective lense over specimen and use fine adjustment to focus
Repeat with x40 objective lense
What are laser scanning microscopes also called?
Focal microscopes
How do laser scanning microscopes produce an image?
Use laser light to scan specimen point by point and assemble on computer pixel info into one image
What type of microscopes have high resolution and high contrast?
Focal
Where are focal microscopes typically used?
Medical profession
How must specimens be prepared before being observed through a transmission electron microscope?
Chemically fixed by being dehydrated and stained
How are images produced using a transmission electron microscope?
Beams of electrons pass through specimen, stained with metal salts. Some electrons pass through and are focused on screen
What type of images do transmission electron microscopes produce?
2D black and white
What’s the optimum magnification of a transmision electron microscope?
x2,000,000
How are images produced using a scanning electron microscope?
Uses beam of electrons - electrons don’t pass through whole specimens but cause secondary electrons to bounce off specimens surface and focused onto screen
What type of images do scanning electron microscopes produce?
3D black and white
Are specimens dead or alive whilst using a transmission or scanning electron microscope and why?
Dead and viewed while in a vaccum
What type of microscope produces coloured images?
Light
Are specimens thinly or thickly sliced when being viewed under a microscope and why?
Thinly - allows more light to pass through specimen so structures can be seen in more detail
Why are specimens stained?
So can see in detail and distinguish features/organelles
When is it useful to observe unstained specimens?
Observing live specimens
Why is it not always necessary to stain specimens when being observed?
Some microscopes use light differences rather than absorption - uses dark background which the illuminated specimen shows up
What are stains?
Coloured chemicals that bind to molecules in or on specimen, making it easy to see
What does acetin orcein bind to and what colour does it go?
DNA - dark red
What stain binds to DNA?
Acetin orcein
What does eosin bind to and what colour?
Cytoplasm - pink
What stain binds to cytoplasm?
Eosin
What stain binds to lipids?
Sudan red
What does sudan red bind to and what colour?
Lipids - red
What satin does cellulose and starch bind to?
Iodine
What does iodine bind to and what colour?
Starch and cellulose - blue/black
What does nile blue stain to and what colour?
Nucleus - blue
What stain binds to the nucleus?
Nile blue
Gram staining is an example of __
Differential staining
What is gram staining?
When different stains applied to same specimen to stain different structures
What is gram staining used for?
Observing bacteria - puts into categories, gram positive or gram negative
What are the characteristics of gram positive bacteria?
Thick peptidoglycan cell walls that retain stain
What’s the microtubule arrangement for eukaryotic flagella?
9+2
What’s the function of ribosomes bound to the exterior of RER?
Protein syntheis of proteins exported out of cell
What’s the function of ribosomes free in cytoplasm?
Proteins syntheisis of proteins used inside of cell
What are ribosomes made of?
ribosomal RNA
Where and how are ribosomes made?
Nucleus as 2 seperate subunits and pass out through nuclear envelope into cytoplasm and combine
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