What is the definition of a eukaryote?
Any organism consisting of one+ cells that contain DNA in a membrane-bound nucleus. They have large numbers of membrane-bound organisms meaning that there is lots of compartmentalisation.
What is the nucleus?
Houses almost all of the cell’s genetic material.
Chromatin?
DNA and histone proteins to form DNA histone complexes. (seen as darkened patches on a light microscope.
What is the nucleolus?
Produces ribosomal RNA that is used to produce ribosomes which more out of the nucleus to latch onto the outside of the rough endoplasmic reticulum where proteins are produced.
What is the nuclear envelope?
A dense spherical structure that surrounds the nucleolus.
A structure that is made of two membranes (inner+outer) with fluid separating them,
The nuclear envelope is marked with nuclear pores which allow for exchange of relatively large molecules.
What is the plasma membrane?
The membrane surrounding the cell. (Cell membrane)
What does the plasma membrane do?
- Controls what enters and leaves the cells.
- Has glycolipids and glycoproteins that act as antigens for cell signalling.
What is compartmentalisation?
Membranes form compartments that keeps the contents of the cells / organelles inside. Only in eukaryotic cells.
What is a phospholipid bilayer?
Made of two layers of molecules called phospholipids.
The hydrophilic heads form the outside of the membrane and hydrophobic tails form the inside of the membrane, away from extracellular fluid and fluid in the cell cytoplasm. Acts as a barrier to water soluble molecules.
The plasma membrane is a phospholipid bilayer.
What are the two parts/sections of a phospholipid?
Head and tail.
What do you know about the head of the phospholipid?
It is polar.
It is a phosphate group (containing a phosphorous atom bonded to four oxygen atoms).
Phosphorous is less electronegative than oxygen so oxygen gets a partially negative charge because the electrons are more strongly attracted to the oxygen nucleus meanwhile the phosphorous atom has a partially positive charge.
The inner and outer surfaces of a cell membrane are hydrophilic (attracted to water).
What does polarity mean and what does it cause?
Polarity refers to the distribution of charge but causes something to be hydrophilic.
What do you know about the tail of a phospholipid?
Non-polar. Hydrophobic (repels water.)
What is a transmission electron microscope?
What are the pros and cons?
TEMS use electromagnets to transmit a beam of electrons through a specimen; denser parts of the specimen absorb more electrons, meaning that the denser parts appear darker.
Produce high resolution images and show structures within the cell. Resolution: 0.5 nm.
Can only be used on non-living specimens as it must be done in a vacuum.
Magnification: X 1 500 000
Black and white image.
How do scanning electron microscopes work?
What are the pros and cons?
SEMS pass a beam of electrons across the surface of the specimen and then detect the rate at which electrons bounce back. Reflected electrons are used to synthesise an image.
Produces images with a resolution of 5nm. High but less than TEM.
3D image but you can only view the surface of the sample.
Only works in a vacuum so cannot view living samples.
Magnification: X1 500 000
Black and white image.
What is the mitochondria?
-Energy generating organelle.
-Site of ATP production in the final stage of cellular respiration.
-Made of two membranes. Inner layer folds inwards to form cristae that project inwards into a liquid called the matrix. This membrane is coated in enzymes that catalyse the reactions of respiration to produce ATP. Cristae maximise surface area and therefore increases efficiency of ATP synthesis so if there are more cristae, there is more ATP synthesised.
-Mitochondria also controls apoptosis.
What is the rough ER?
-Series of flattened sacs called cisternae.
-Studded with ribosomes.
-Folds the polypeptide chain into its tertiary structure.
-Transport proteins that were made on the attached ribosomes by forming transport vesicles to transfer the proteins to the golgi apparatus to be modified and packaged.
-Some proteins are scattered by the cell whilst others are placed on the surface of the cell on the plasma membrane.
What are lysosomes? What is their function?
STRUCTURE:
Spherical sacs that are surrounded by a single membrane. They are specialised vesicles that contain hydrolytic enzymes (Proteases, nucleases and lipases) that break down the waste material in the cell.
FUNCTIONS:
1. Break down damaged cells/ remains.
2. Destruction of pathogens.
3. Autolysis (part of apoptosis).
4. Allows the cell to efficiently recycle waste.
5. INTRACELLULAR DIGESTION.
What are centrioles?
Self-replicating organelles made up of a bundle of microtubules that help organise cell division in animal cells. They are not always needed. Made of two microtubules that are at right angles to eachother.
What are cilia/ undulipodia important for?
Cilia are used to move fluid or materials past an immobile cell as well as moving cells.
What is a golgi apparatus?
-Stack of membrane-bound flattened sacs.
-Membrane is similar to plasma membrane (two membranes)
-Membrane surrounds an area of fluid where the complex molecules are stored and modified.
-Receives proteins from the rough ER then modifies (may add sugar) and packages in a vesicle which may take the protein to the surface of the cell to be secreted.
-Synthesises lysosomes.
What are ribosomes?
-Tiny organelles which are either in cytoplasm or bound to the rough ER.
-Consists of 2 sub-units.
Smooth ER?
-Make lipids that the cell needs.
-Same structures as rough ER without ribosomes.
What is the cell wall?
Made up of bundles of cellulose fibres.
Macrofibril structure of beta-glucose microfibrils which are long chains of beta-glucose monomers that are joined together by glycosidic bonds and hydrogen bonds between the adjacent strands of beta-glucose. High tensile strength to withstand turgor pressure.
