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Flashcards in Cells Deck (41):

Equation for magnification



Light microscope

+easy to use
+portable and cheap
+use visible
+can use live specimens
+colour images
-max magnification
-focused using glass lenses
-max resolution=200nm


Staining techniques

•Eosin - cytoplasm pink
•Feulgens stain - stains DNA red/purple
•methylene blue - stains nuclei blue



+Electron beam has short wave length so high resolving power
+High magnification
-not portable
-very expensive
-organisms have to be dead, due to a vacuum
-Black and white, 2D images
-often contain artefacts from tissue preparation



+specimens don't need to be very thin; elections don't penetrate the tissue
+a computer is used to build a 3D image of the specimen
+low resolving power than TEM's but higher than light microscopes


Cell Fractionation

-Tissue is placed in a cold, buffered solution
-cells are broken up by homogenisation (blended) and then filtered to remove any complete cells and large debris
-ultracentrifugation-the homogenate is spun at high speed to create centrifugal force which allow the separation of the cell organelles sue to them being different weights


The cold buffered solution

•cold - to reduce lysozyme

•same water potential as tissue - to prevent the organelles from shrinking/bursting

•buffered - maintain pH so the structure of organelles do not change


Eukaryotic cell

Any cell the contains a clearly defined nucleus



•nuclear envelope - double membrane that surrounds the nucleus; constructs and he exit and entry of materials in and out of the nucleus and contains reactions taking place within it
•nuclear pores - allow the passage of large molecules, such as mRNA, out of the nucleus
•nucleoplasm - a granola, jelly-like material that makes up the bulk of the nucleus
•nucleolus - a small spherical region within the nucleoplasm - manufactures rRNA and assembles ribosomes
•chromosomes - consists of protein-bound linear DNA


Nucleus function

Manufacture rRNA and ribosomes, retain genetic material of cell in th form of DNA and chromosomes, and control the cell through production of mRNA, tRNA and protein synthesis



•double membrane - controls entry and exit of material - the inner is folded to form cristae
•cristae - provide a large surface area for the attachment of enzymes and proteins involved in respiration
•matrix - contains proteins, lipids, ribosomes and DNA that allows it to control its own production or proteins. Many enzymes involved in respiration are found here


Mitochondria function

The sites of the aerobic stages of respiration so are responsible for the production of ATP. The number and size of mitochondria and cristae are higher in cells which need more energy



•envelope - double plasma membrane which is highly selective
•Grana - stacks of disc structures called thylakoids - within these are chlorophyll. This is where light absorption takes place
•stroma - fluid filled matrix where the second stage of PHS takes place. It also contain starch grains


Chloroplasts function

Granal membranes provide a large SA for the attachment of chlorophyll (electrons carriers and enzymes that carry out the first stage of PHS). The fluid of the stroma possess all enzymes needed for second stage of PHS. They also contain both DNA and ribosomes so they can easily make their own proteins needed for PHS.


Rough endoplasmic reticulum

had ribosomes present on outer surfaces of membrane


REM function

-Provide large SA for the synthesis of proteins and glycoproteins
-provide pathway for the transport of material especially proteins, throughout the cell


Smooth endoplasmic reticulum

Lack ribosomes on its surface and is more tubular


SEM function

Synthesise, store and transport lipids and carbohydrates


Golgi apparatus

•Stack of membrane that make flattened sacs (cisternae) with small rounded hollow structures called vesicles.
•Proteins and lipids produced in the ER are passed through this in a strict sequence; the Golgi modifies these proteins often adding non-protein (CHO's) components to them.
•also "labels" them to be accurately stored and sent to correct locations.
• once they are sorted they are transported in Golgi vesicles which are regularly pinched off from the cisternae. These vesicles move to and fuse with the cell membrane, releasing the contents to the outside of the cell


Golgi apparatus function

-*transport, modify and store lipids
-add CHO's to proteins to form glycoproteins
-produce secretory enzymes such as those secreted by the pancreas
-secretes carbohydrates such as those used in making cell walls in plants
-forms lysosomes



•abundant in secretory cells
•are formed when the vesicles produced by the Golgi contain enzymes such as proteases and lipases. They also contain lysozymes
•they isolate these enzymes before releasing them either outside the cell or into a phagocytic vesicle wishing the cell


Lysosome function

-Completely break down cells after they have died
-digest worn out organelles so it can be recycled
-release enzymes to the outside of the cell in order to destroy material around the cell
- hydrolyse material ingested by phagocytic cells, such as white blood cells and bacteria



•small cytoplasmic granules
•Have 2 sub-units. 1 large, 1 small each containing rRNA and protein.
•they can account for up to 25% of the dry mass of the cell
•80s are found in eukaryotic cells
•70s are found in prokaryotic cells, mitochondria and chloroplasts (indirect evidence for evolution) and are slightly smaller


Rising function

Sites of protein synthesis (makes proteins)


Cell wall

•consist of a No. of polysaccharides, such as cellulose
•there is a thin layer (middle lamella) which marks the boundary between adjacent call walls and cement cell walls together.


Cell wall function

-Provide mechanical strength in order to prevent the cell bursting under the pressure of osmosis
-give mechanical to the plant as a whole
-allows water to pass along it and so contributes to transpiration



•fluid-filled sacs bounded by a single membrane (tonoplast) containing a solution of mineral salts, sugars, amino acids, wastes and sometimes pigments


Vacuole function

-Support herbaceous plants/herbaceous parts of woody plants making the cells turgid
- the sugars and amino acids may act as temporary food stores
-the pigments (anthocyanins) may colour petals to attract pollinating insects


Prokaryotic cells

A uni-cellular organism that lacks membrane bound organelles



•possesses the genes that may aid the survival of bacteria in adverse conditions e.g produce enzymes that's break down antibiotics


Circular DNA

Possesses the genetic info for the replication of bacterial


Cell-surface membrane

Acts as a differentially permeable layer, which controls entry and exit of chemicals



•Mucilaginous slime around the cell wall
•Protect bacterium from other cells and helps groups of cells to stick together for further protection


Cell wall

•Physical barrier that excludes certain substances and protect against mechanical damage and osmotic lysis
•made up of murein - a polymer or polysaccharides and peptides


Other structures in bacteria

•cytoplasm - contains 70s ribosomes that synthesise proteins
•flagellum - used for locomotion


Properties of bacteria

-versatile, adaptable and very successful. They are only about é - 10um in size
-stores food resources as glycogen granules and oil droplets



Acellular, non-living particles - smaller than bacteria (20-300nm)


A Virus' features

•contain nucleus acid such as DNA or RNA as genetic material but can only multiply inside living host cells.
•the nucleus acid is enclosed by a protein coat called a capsid


HIV features

•HIV is a retro virus; uses reverse transcriptase to make DNA out of the RNA genetic material, which will go further to incorporate it into the host cell genome
•further surrounded by a lipid envelope, or if this is not present, attachment proteins which are essential to allow the virus to identify and attach to a host cell


Prokaryotic summary

-not true nucleus
-DNA is not associated with protein
-come DNA may be in circular strands called plasmids
-no membrane bound organelles
-no chloroplasts, only chlorophyll associates with the cell surface membrane of some bacteria
-70s ribosomes
-cell wall made up of murein (peptidoglycon)
-may have an outer mucilaginous layer called a capsule



-distinct nucleus, with a nuclear envelope
-DNA is associated with proteins
-there are no plasmids and DNA is linear
-membrane bound organelles are present
-chloroplast present (in plants and algae)
-80s ribosomes
-where present, cell wall is made mostly of cellulose
-no capsule