Unit 2.1- Cell structure Flashcards
Nucleus definition:
- Surrounded by a double membrane
- Contains genetic material that controls what the cell does.
What does the cytoplasm do?
Contains enzymes that speed up biochemical reactions
What does the cell membrane do?
Holds the cell together and controls what goes in and out.
Mitochondrion definition:
- Spherical, rod shaped or branched
- Surrounded by 2 membranes
- Where glucose and oxygen are used to produce energy.
What does the cell wall do?
It is rigid and made of cellulose to give the cell support.
What does the vacuole do?
Contains cell sap, a weak solution of sugar and salts.
What do chloroplasts do?
Contain chlorophyll for photosynthesis. They are found in the green parts of plants e.g. stems and leaves.
What is the benefit of electron microscopes over light microscopes?
They have a greater magnification, (up to 1,500,00 times), so can see greater detail.
What is the image recorded by an electron microscope called?
An electron micrograph.
What is DNA needed for?
Making proteins.
What happens to chromosomes during cell division?
The chromosome carrying the long DNA molecule coils up, becoming shorter and thicker and visible under a light microscope.
What type of membrane is there around a nucleus?
A double membrane.
What are organisms made up of cells containing a nucleus called?
Eukaryotic.
What types of organisms have cells that are eukaryotic?
All plants and animals.
What are organisms without a membrane around their DNA called?
Prokaryotic.
What is an example of a prokaryotic organism?
Bacteria.
What type of microscope can mitochondria be seen with?
A light microscope. They are about the size of bacteria.
What type of microscope is needed to see the detail in a mitochondria?
An electron microscope.
What type of membrane does a mitochondria have?
A smooth outer membrane and a folded inner membrane.
Where does aerobic respiration happen?
Inside the mitochondria.
What is the job of the mitochondria?
To capture the energy in glucose into a form that the cell can use. The energy ends up in molecules of ATP.
What does ATP stand for?
Adenosine triphosphate.
What is ATP used in the cell for?
- Muscle contraction
- Active transport
- Building large molecules from small ones
- Many other processes
What does the cell wall consist of?
Mainly cellulose molecules, laid side by side to form microfibrils.
Magnification definition:
How much bigger an image appears compared to the original object. Microscopes have a linear magnification.
Resolution definition:
The ability of an optical instrument to see or produce an image that shows fine detail clearly.
How to optical (light) microscopes work?
By focusing visible light, using lenses.
How much can optical microscopes magnify an image?
1500 to 2000 times. Enables us to see some of the larger structures in cells.
What are the benefits of optical microscopes?
- Cheap
- Easy to use
- Transportable
- Can examine whole, living organisms.
What are the disadvantages of using optical microscopes?
- The resolution is limited.
- Objects that are closer together than 200 nm appear as one object because visible light is used which has a wavelength of 400-700nm.
- Ribosomes are too small to be studied.
What is the laser scanning microscope also known as?
Confocal microscope.
How does a laser scanning microscope work?
A laser is used to transmit the image pixel by pixel onto a screen. They have depth selectivity and can focus on structures at different depths within a specimen e.g. whole living specimens and cell walls.
What are the benefits of laser scanning microscopes?
- The image is high resolution.
- High contrast
What are laser scanning microscopes being used for?
- Detecting fungal filaments in corneas early on.
- They are used for research purposes.
How do electron microscopes work?
High speed electrons with a wave length of 0.04nm are used to create an image. An electron is fired from a cathode and magnets are used to project the image onto a screen or photographic plate.
What is the wavelength of an electron used in an electron microscope?
0.04nm, (125,000 times smaller than light), this means that it can create a high resolution image.
What are the advantages of using an electron microscope?
- High resolution
- High magnification
How do transmission electron microscopes work?
The sample has to be dehydrated and stained. The electron goes through the sample which contains a stained metal salt solution. Some electrons pass through to create an image on a screen or a photographic plate.
What type of image does a transmission electron microscope produce?
2D balck and white image with a magnification of up to 2,000,000 times.
How does a scanning electron microscope work?
The electrons don’t go through the sample but cause lots of secondary electrons to bounce off the specimen’s surface and create an image on the screen. The sample has to be in a vacuum and covered with a metal film.
What type of image does a scanning electron microscope create?
A 3D image between 15 and 200,000 times magnification. It creates a black and white image but artificial colour can be added on a computer.
What are the negatives of both types of electron microscope?
- Very expensive
- Large
- Need a great deal of skill and training to use.
What is an eyepiece graticule?
A measuring device placed in the eyepiece of a microscope and acts as a ruler when you view an object under a microscope.
What is a stage graticule?
Small scale measuring device placed on a microscope and used to calibrate the value of eyepiece divisions at different magnifications.
Eukaryotes definition:
Organisms that have cell organelles which are bound with a membrane.
Prokaryotes definition:
Organisms that have cell organelles which are not bound with a membrane.
Pinyocytitic vesicle definition:
Forms a bubble of extended cell membrane to to surround the targeted liquid and fuse inwards.
Cytosol definition:
The fluid in which the other organelles are in.
Smooth endoplasmic reticulum definition:
System of membranes containing fluid filled cavities (cisternae) that are continuous with the nuclear membrane.
Nucleolus definition:
- Does not have a membrane around it.
- Where ribosomes and RNA are made.
Golgi body/ apparatus definition:
- A stack of membrane bound flattened sacks.
- Secretary vesicles bring materials to and from the golgi.
- Proteins are modified and then packaged into vesicles.
Plasma membrane definition:
- Membrane that separates the interior of the cell from the outside environment.
- It is composed of a phospholipid bilayer with embedded proteins.
- It’s permeable and regulates the movement of substances in and out of the cell.
Lysosome definition:
Small bags formed from the golgi body. They engulf old cell organelles and foreign matter.
Nuclear membrane definition:
- Separates the nucleus from the rest of the cell.
- There are pores in it for mRNA to pass through.
Rough endoplasmic reticulum definition:
System of membranes containing fluid filled cavities (cisternae) that are continuous with the nuclear membrane. It is coated with ribosomes.
Centriole definition:
Two bundles of microtubles at right angles to each other.
Ribosomes definition:
- Small spherical organelles made of ribosomal mRNA. –Made in the nucleus.
- Some remain free in the cytoplasm and some attach the the endoplasmic reticulum.
What features do both eukaryotic and prokaryotic cells have?
- Plasma membrane
- Cytoplasm
- Ribosomes for assembling amino acids into proteins
- DNA and mRNA
What features do eukaryotic cells have but not prokaryotic cells?
- Larger than prokaryotic cells
- Better developed cytoskeleton with centriols
- Nucleus
- Membrane bound organelles
- Cell wall made of cellulose
- Larger ribosomes
- DNA is in the nucleus.
What features do prokaryotic cells have but not eukaryotic cells?
- Smaller than eukaryotic
- Less well developed cytoskeleton and has no centrioles
- No nucleus
- No membrane bound organelles
- Cell wall is made of peptidoglycon
- Smaller ribosomes
- Naked DNA
What extra features do some prokaryotic cells have?
- Protective waxy capsule surrounding their cell wall
- Small loops of DNA called plasmids as well as the main, large loop of DNA
- Flagella- long whip like projections that allow them to move
- Pili- smaller hair-like projections that enable the bacteria to adhere to the host cells or to each other and allow the passage of the plasmid DNA from one cell to another.
What structures make up the cytoskeleton?
- Actin filaments
- Microtubles
What are actin filaments?
- Move against each other
- Cause the movement seen in white blood cells
- Move some organelles around within cells
What are microtubles?
- Cylinders
- About 25nm in diameter
- Made from Tubulin
- May be used to move microorganisms through a liquid or waft a liquid past a cell
- Microtuble motors (proteins) present on microtubles use ATP to move cell contents along the fibres
What is the role of the cytoskeleton?
- Provides mechanical strength for cell
- Aids active transport within cells (movement of chromosomes during cell division, movement of vesicles from ER to Golgi)
- Enable cell movement
