A2.2 Cell structure Flashcards
(14 cards)
What is the cell theory?
- Living organisms are made up of one or more cells
- there is no smaller unit of life than cells
- Every new cell must come from a pre-existing cell
State the equations to calculate the magnifications of images and actual size of the object when a scale bar is present
- Magnification of images
measured size of image/actual size of object - measured size of image/measured size of scalebar x what the scalebar represents
Define the term resolution
smallest distance apart two objects can be for them to appear distinct
Distinguish the resolution of light + electron microscopes
- The resolution of a light microscope is appx 200nm. Resolutions of light microscopes are limited by the wavelength of visible light
- Violet light has the smallest wavelength on the visible spectrum –> 400nm (half is 200nm)
- The resolution of an electron microscope is better than 1nm
- Beams of an electron microscope have a wavelength of less than 1nm and therefore electron microscopes have a much higher resolution than light microscopes (200 times higher)
Summarise the use of freeze fracture
- Involves freezing than breaking open a biological specimen such as a cell or tissue
- Fractured sections of a cell can be viewed with an electron microscope allowing internal structures to be seen at high resolution
Summarise the use of Cryogenic electron microscopy (Cyro-EM)
- Specimens are cooled rapidly to cyrogenic temperatures, preserving their structure, before being observed by an EM
- No need for chemical fixation of sample
- Very high resolution of molecular structures (such as proteins)
Summarise fluorescent stains and immunofluorescence in light microscopy
- Fluorescent stains (or fluorophores) are attached to antibodies specific to molecules of interest
- when excited by ultraviolet light, fluorophores emit a bright light, allowing for clear visualisation
- Events occurring in living cells can be followed in real time
Outline the structures common to cells in all living organisms
DNA –> genetic material that contains the information for a cell (or organism) to develop and function
Cytoplasm –> The liquid inside of the cell. Mainly water with dissolved organic molecules and mineral ions. This is where chemical reactions occur.
Plasma membrane –> Composed of lipids. It is the perimeter of the cell and separates the inside of the cell from the outside
What is a prokaryote?
Prokaryotes are unicellular organisms. EM have revealed the structure of prokaryotes is simple with no internal compartments surrounded by membranes. Two of the three major categories of life are prokaryotes –> the bacteria and the archaeans.
Identify structures in a prokaryote cell
- 70S ribosomes
Responsible for protein synthesis - Cytoplasm
Chemical reactions happen here - Plasma membrane
Separates the inside of the cell from the outside.
Controls the entry/exit of substances - Cell wall
Protects + retains the shape of the cell - Naked DNA in a loop
Genetic material that contains the information for the organism to develop & function
Outline the function of organelles typically found in Plant cells
Nucleus
- Controls + regulates the activities of the cell.
- Contains linear chromosomes (DNA combined with histones)
Mitochondria
- Produce ATP (where most reactions of aerobic respiration occur)
Chloroplast
- Produce glucose (where photosynthesis reactions occur)
Sap Vacuole
- Storage + breakdown of materials
RER
- Synthesis of proteins (that are secreted from the cell, located in lysosomes or integrated into the plasma membrane)
Golgi apparatus
- modifies proteins arriving from RER in vesicles
Secretory vesicles
- Transport materials from inside the cell, fuse with plasma membrane and release contents outside the cell
Lysosome
- Contains hydrolytic (digestive) enzymes to break down molecules, worn out cellular components, or pathogens
SER
- Lipid synthesis (including phospholipids + steroids)
Outline the function of organelles typically found in Animal cells
What are the advantages of compartmentalisation in eukaryotic cells?
- Metabolic processes can be separated (for examples the reactions specific to aerobic respiration in mitochondria)
- hydrolytic enzymes that could damage the cell can be separated (for example in lysosomes)
- Allows for a greater surface area for processes that occur within the cell membrane –> production of ATP by chemiosmosis
Distinguish chromosomes in Prokaryotes and Eukaryotes
Prokaryote Chromosomes:
- Naked DNA
- Circular
- One chromosome
- free in the cytoplasm
Eukaryote Chromosomes
- DNA associated with histone proteins
- Linear
- At least 2 chromosomes
- Contained in the nucleus
