cell Structure ! Flashcards
Define magnification
The size of an image divided by the actual size of the object
Define resolution
The ability to distinguish two close points as separate
How is image produced on light microscope?
Light passes through thin specimen
Type of image produced by light microscope?
Photomicrograph, can show natural color/stains
Maximum magnification of light microscope?
X1500
Maximum resolution of light microscope?
200nm
How is image produced by TEM
Electrons pass through an extremely thin specimen
Type of image produced by TEM
Transmission electron micrograph in black-and-white false colors are often added using computer technology
Maximum useful magnification of TEM
X50,000,000
Maximum resolution of TEM
0.5 nm
How image produced by SEM
Electrons bounce off of the surface of the specimen
Which type of image produced by SEM
Scanning electron micrograph in black-and-white showing 3-D image of the surface false colors are often added using computer technology
Maximum magnification of SEM
X100,000
Maximum resolution of SEM
5 nm
Functions of cell surface membrane
- controls what enters and leaves the cell
Why are there membranes within the cell?
-so that different chemical reactions can take place without interfering with each other
Nucleus
-surrounded by a pair of membranes -> nuclear envelope
-contains chromatin, that becomes chromosomes during cell division
-chromatin is made of DNA & histones
-dark stained area called nucleolus synthesizes ribosomes
-DNA determines the sequence in which amino acids link together in the cytoplasm to form proteins
Ribosomes
-Small structures made of RNA and proteins
-found free in cytoplasm & on the surface of RER
-eukaryotic -> 80S
-prokaryotic -> 70S
RER
is an extensive network of membranes in the cytoplasm
The membranes enclose small spaces called cisternae
Proteins are made on ribosomes by linking together amino acids
If the proteins are to be processed or exported from the cell, the growing chain of amino acids move into the cisternae of the RER as they are made. They then break off to form little vesicles that travel to the Golgi apparatus
Golgi apparatus
Proteins may be modified by adding carbohydrate groups to them vesicles containing the modified proteins break away from the golgi body and are transferred to the surface membrane where they are secreted through exocytosis
SER
Involved in the synthesis of steroid hormones, and the breakdown of toxins
Mitochondria
Has an envelope
The inner membrane relative form cristae, this is where aerobic respiration takes place producing ATP
The first stage of Arabic crusta respiration called the krib cycle takes place in the matrix
The final stage of aerobic respiration oxidative Fosforo for relation takes place on the membrane of the cristae
Mitochondria contain ribosomes that are smaller than those of the cytoplasm 70 S and also a small circular molecule of DNA
Lysosomes
Small membrane bound packages of hydrolytic enzymes
Formed by breaking off from Golgi apparatus , they are used to digest bacteria or other cells taken into the cell by phagocytosis or to breakdown, unwanted or damaged organs within the cell
Centrioles, microtubules, cilia and the cytoskeleton
Centrioles are found in animal cells only
They are made of tiny structures called microtubules arranged in circular pattern. Micro tubes are made of a protein called actin.
The two centrioles lie at right angles to one another. It is from here that the microtubules are made that form spindle during cell division in animal cells.
Microtubes are also found throughout the cell, even when it is not dividing where they can help to form cytoskeleton, which keeps the cell in shape
Cilia are tiny hair like structures, composed of microtubules that project from cell surfaces. They are able to move and beat often repelling small organisms through fluids, removing substances such as mucus and larger animals.
