B1.1- cell structures Flashcards
Disadvantages of an EM as opposed to an LM?
Complex to set up sample Expensive to buy and operate Large and difficult to move Specimens are dead
What is aim?
Actual magnification= image size/magnification
Advantages of a LM as opposed to an EM?
Cheap to buy and operate Portable and lightweight Simple to prepare a sample Specimens can be living or dead
What are pili?
Pili are tiny hairlike structures that allows the cell to attach to structures and it also allows it to transfer genetic material between bacteria via conjugation
What sub cellular structures do both prokaryotes and eukaryotes have?
Cell wall, cell membrane and cytoplasm
What extra sub cellular structures do eukaryotes have?
Vacuole,mitochondria,nucleus and chloroplasts
What are bacteria?
Bacteria are the smallest organisms that can carry out the seven life processes MRS GREN movement respiration sensitivity growth reproduction excretion and nutrition
What are some examples of eukaryotes?
Any animals or plants
What is a cytoplasm?
A jellylike substance. The chemical reactions that keep the cell alive happen there
What are the common stains?
Methylene blue- this makes it easier to see the nucleus of an animal cell Iodine solution- this makes it easier to see plant nuclei Crystal violet- this stains bacterial cell walls
Disadvantages of an LM as opposed to an EM?
Resolution is only 0.2 micrometres Natural colour is seen
What are some examples of prokaryotes?
E. coli Streptococcus
Advantages of an EM as opposed to an LM?
Higher resolution of 0.1 Nanometres Black and white images are produced so false colour can be added
What is a flagella?
A flagella is a tail like structure that allows the cell to move through liquids
What is a plasmid?
A plasmid is a circular piece of DNA that is used to store extra genes. These genes are not needed for a bacteria’s day to day survival but are used in times of stress. (Antibiotics are found there)
Why stain cells?
many cells are colourless so scientists often stain them to make them easier to see. Some stains cell the whole cell and some only stain certain sub cellular structures
What does a nucleus do?
A nucleus controls the activities of the cell. The nucleus also contains genetic material arranged in chromosomes.This determines the cells function and appearance and also contains instructions to make new cells or organisms
What is the resolution of a microscope?
A resolution is defined as the smallest distance between two points that can be seen as separate entities
What is a light microscope?
A light microscope passes light through an object placed on the slide on the stage, then through two glass lenses an objective lens and an eyepiece lens
What is the formula for total magnification?
Total magnification=eyepiece lens magnification*objective lens magnification
What is genetic material?
Genetic material floats around in the cytoplasm. There is a long strand called the bacterial chromosome
What is an SEM microscope?
A scanning electron microscope produce a three dimensional image of a surface. They send a bean of electrons across the surface of a sample. The reflected electrons are collected to produce an image
What are electron microscopes?
Electron microscopes use electrons instead of light to produce an image. They were developed in the 1930’s to allow scientists to see in greater detail. The greater resolution is achieved by high energy electrons as the light source
What is a vacuole?
A vacuole is a watery cell sap that keeps the cell rigid and upright
What is a TEM microscope?
Transmission electron microscopes produce the most magnified images. They work in a similar way to a light microscope, electrons are passed through a thin slice of the sample the beam is focused to produce an image
What is a chloroplast?
These contain green chlorophyll. Chlorophyll transfers energy from the sun to the plant as light which are used in photosynthesis. These are only in the green parts of the plant
What is a cell wall?
This surrounds the cell and is made of a tough fibre called cellulose (peptidoglycan in bacteria)
What is a slime capsule?
A slime capsule is the layer outside the cell wall. It protects the bacteria from drying out and from poisonous substances. It also allows the bacteria to stick to smooth surfaces
What are the main differences between prokaryotic and eukaryotic cells?
Eukaryotic cells have the genetic material in a nucleus Prokaryotic cells do not have mitochondria Eukaryotes are unicellular and prokaryotes and unicellular Eukaryotes are 10-100 micrometres whereas prokaryotes are 1-10
What is a mitochondrion?
A mitochondrion is where respiration takes place. Enzymes react oxygen and glucose to make energy to transfer to the organism
What is a cell membrane?
A cell membrane is a selective barrier which controls which substances pass in and out of the cell. The cell membrane contains receptor cells
What extra sub cellular structures do prokaryotes have?
Genetic material, pili, slime capsule, plasmids and flagella
