2.1.1 Cell Structure Flashcards
What is magnification?
How many times larger an image is than the actual object itself.
What is resolution?
The degree to which it is possible to distinguish between two objects that are very close together. (The higher the resolution, the greater detail you can see.)
What is the equation for total magnification?
Eyepiece lens magnification X Objective lens magnification
What processes are required to prepare a slide?
Staining and/or sectioning.
What is staining?
Coloured dyes bind to chemicals on or in the specimen so they are visible.
How do you increase contrast during staining?
Use multiple dyes called differential staining to increase contrast.
What is sectioning?
Embedding specimens in wax which can then be sliced very thinly without distorting the structure.
What type of tissue is sectioning used on and why?
What is the radiation used for electron and light microscopes?
E= Electrons
L= Light
How do electron and light microscopes focus?
E= Magnets
L= Lenses
What is the magnification of light and electron microscopes?
E= X 2,000,000
L= X 2000
What is the resolving power of electron and light microscopes?
E= 0.2nm
L= 200nm
What type of microscope requires the sample to be in a vacuum?
Electron microscope (therefore matter must be dead).
How do transmission electron microscopes work?
What type of image is created by a TEM microscope?
A 2D, black and white image.
How do scanning electron microscopes work?
Electrons don’t pass through but cause secondary electrons to bounce off the specimens surface and reflect onto a screen.
What type of image is created by a SEM?
A 3D, black and white image.
What is a confocal microscope?
A microscope that uses lasers to scan and assemble an image.
What are the pros of a confocal microscope?
- The specimen doesn’t have to be cut so it can be used to look at whole objects.
- Cheap and easy to use.
What is an eyepiece graticule?
Similar to a ruler but is variable as magnification changes.
Nucleus is surrounded by a double membrane (nuclear envelope) which has pores.
Nucleolus contains RNA.
Contains chromatin which is DNA wound around histone proteins.
What is the function of the nucleus?
Nuclear envelope separates stuff in nucleus from rest of cell.
Pores: so ribosomes can leave.
Nucleolus makes ribosomes.
Contains chromosomes.
What is the structure of the rough endoplasmic reticulum?
System of membranes with fluid filled cavities (cisternae) that continue from the nuclear envelope.
Coated in ribosomes.
What is function of the rough endoplasmic reticulum?
Intracellular transport system as the cisternae form channels.
Large surface area for ribosomes. Proteins then go through to the cisternae.
What is the structure of the smooth endoplasmic reticulum?
System of membranes with cisternae.
No ribosomes.
What is the function of the smooth endoplasmic reticulum?
Contains enzymes that catalyse reactions (For lipid metabolism. E.g. synthesis of cholesterol, lipids/phospholipids, steroid hormones.)
Involved in absorption, synthesis and transport of lipids (from gut).
What is the structure of the golgi apparatus?
A stack of membrane bound flattened stacks.
Secretory vesicles bring materials to and from the golgi apparatus.
What is the function of the golgi apparatus?
Proteins are modified (E.g. By:
- adding sugar molecules- glycoproteins
- adding lipid molecules- lipoprotiens
- being folded into a 3D shape)
Proteins are packaged into vesicles and then stored in the cell or moved to cell surface membrane.
What is the structure of the mitochondria?
Spherical, rod-shaped or branched.
2-5 micrometers long.
2 membranes with fluid filled space between.
Inner membrane = highly folded.
Inner part is a fluid filled matrix.
What is the function of the mitochondria?
Site of adenosine triphosphate production during aerobic respiration.
Self-replicating
Abundant in cells where much metabolic activity occurs.
What is the structure of chloroplasts?
Large organells 4-10 micrometers long.
Plants and some protists have them.
Double membrane.
Inner membrane is continuous stacks of flattened membrane sacs (thylakoids) containing chlorophyll. Each stack is called a granum. The whole matrix is called the stroma.
Contain loops of DNA and starch grains.
What is the function of chloroplasts?
Site of photosynthesis.
1st stage: Light being trapped occurs in the grana. Water is split to supply hydrogen ions.
2nd stage: H reduced CO2 to make carbs (occurs in the stroma)
What is the structure of a vacuole?
Surrounded by a membrane: tonoplast- contains fluid.
What is the function of a vacuole?
Plant cells.
Filled with water, solutes and maintains cell stability as when full it pushes against wall.
Supports plant.
What is the structure of lysosomes?
Small bags containing enzymes formed in the golgi apparatus.
Abundant in phagocytes so they can engulf pathogens.
What is the function of lysosomes?
Keep the enzymes separate from the rest of cell.
Engulf old cell organelles and digest them.
What is the structure of cilia and undulipodia?
Protrusions from the cell and are surrounded by cell surface membrane.
Contains microtubules.
Formed by centrioles.
What is the function of cilia and undulipodia?
Move mucus.
Acts as antenna on cells- signals and contains receptors.
What is the structure of ribosomes?
Small, spherical organelles, 20 micrometers in diameter.
Made of ribosomal RNA.
Made in nucleus (as 2 units) pass through the nuclear envelope then combine.
Some in cytoplasm and others in RER.
What is the function of ribosomes?
On RER used for synthesising proteins.
Free in cytoplasm used as site of assembly of proteins to be used in the cell.
What is the structure of centrioles?
Made of microtubules.
9 triplets of microtubules make hollow bundles.
Eukaryotic cells (Not flowering plants or fungi)
Found in pairs.
What is the function of centrioles?
Before cell divides, the spindles, made of threads of tubulin forms from the centrioles.
Chromosomes attach to middle of spindle and motor proteins walk along them.
What is the structure of a cell wall?
Made of cellulose.
Freely permeable, but rigid.
What is the function of a cell wall?
Strong and prevents cells from bursting when turgid.
Also help maintain cell shape.
Permeable and allow solutions to go through.
What is the function of the cytoskeleton?
Cellular movement (cilia and flagella)
Form tracks inside cells for organelles to move along.
Strength and support- ‘scaffolding’ to keep cell shape and strengthen.
What are microtubules?
Small, tubular structures in the cytoplasm.
Diameter of around 25nm.
Composed of globular proteins.
Arranged in spirals.
Centrioles, cilia and flagella are made of them.
What are microfilaments?
Small, rodlike structure present in numbers in the cytoplasm of many eukaryotes.
Diameter of 5-8nm.
Can assemble and disassemble to help cells change shape.
Made of protein which allows them to move.
What is structure of flagella?
Made of microtubules.
9 pairs of microtubules surrounding 2 central ones.
Found on the surface of cells (Pro and Eukaryotes)
Singular (one)
What is the function of flagella?
Enable cell motility.
Some detect chemical changes in an environment.
What is the structure of cilia?
Made of microtubules.
Ring of 9 pairs of microtubules around 2 central microtubules.
Stationary cilia are found on the surface of cells (E.g. ciliated epithelial cells)
What is the function of cilia?
Mobile cilia beat rhythmically to make a current which makes things move.
What is the size of prokaryotes and eukaryotes?
P= 0.1-10um
E= 10-100um
Where is genetic material found in prokaryotes and eukaryotes?
P= Nucleoid and plasmids
E= Linear chromosomes in the nucleus.
Do prokaryotes and eukaryotes have organelles?
P= No
E= Many
What is the size of ribosomes in prokaryotes and eukaryotes?
P= Smaller (70s)
E= Larger (80s)
Where does respiration take place in prokaryotes and eukaryotes?
P= Mesosomes
E= Mitochondria
What are flagella like in prokaryotes and eukaryotes?
P= Simple, no microtubules.
E= Complex, microtubules.
Where does photosynthesis take place in prokaryotes and eukaryotes?
P= Unstacked membranes
E= Chloroplasts (plant cells only)
What are examples of prokaryotes and eukaryotes?
P= Bacteria
E= Plant, animal and fungi.
What is endosymbiont theory?
Mitochondria and chloroplasts were once prokaryotic cells that were engulfed but not digested. This began a symbiotic relationship where they both provided each other something.
