Topic 2 - Cells Flashcards
What is the function of a nucleus?
Contains all of the genetic material in the cell
What is the nucleus crucial for?
Protein synthesis
What does the nucleolus do?
Manufactures ribosomal RNA and ensembles the ribosomes
What do the nuclear pores do?
Allow large molecules in & out of the nucleus e.g messenger RNA
What is the nuclear envelope?
A double membrane which surrounds the nucleus
Its outer membrane is continuous with the endoplasmic reticulum of the cell and often has ribosomes on its surface
Contains the reactions taking place within it
What is nucleoplasm?
Granular, jelly-like material that makes up the bulk of the nucleus
What does mitochondria do?
The site of aerobic respiration.
Responsible for the production of the energy-carrier molecule, ATP, from respiratory substrates such as glucose. – because of this, the number and size of the mitochondria, and the number of their cristae, are high in cells that have a high level of metabolic activity, and therefore require lots of ATP.
What does the Cristae (in mitochondria) do?
Provide a large surface area for the attachment of enzymes and other proteins involved in respiration
(extensions of the inner membrane)
What does the matrix (in mitochondria) do?
It contains proteins, lipids, ribosomes and DNA that allows the mitochondria to control the production of some of their own proteins. Many enzymes involved in respiration are found in the matrix.
What does the rough endoplasmic reticulum (RER) do?
Synthesises and transports proteins, has ribosomes
What does the smooth endoplasmic reticulum (SER) do?
Synthesises, stores and transports lipids and carbohydrates, no ribosomes
What does the golgi apparatus do?
It is the sorting office & it is constantly moving and changing – directs molecules to where they are needed in the cell
What are lysosomes?
A membrane-bound organelle that releases hydrolytic enzymes
When are lysosomes formed?
When the vesicles produced by the golgi apparatus contain enzymes such as proteases and lipases
What are ribosomes?
Site of in protein synthesis
80s Ribosomes
Found in eukaryotic cells, around 25nm in diameter
70s Ribosomes
Found in prokaryotic cells, mitochondria and chloroplasts, is slightly smaller than 80s ribosomes
What are Eukaryotic cells?
Cells with a membrane-bound nucleus
What are prokaryotic cells?
Cells without a membrane-bound nucleus
When are centriples needed?
when the cell divides
What is the function of of Cytoskeleton?
Holds the cell organelles in specific positions
How do you distinguish between chloroplasts and mitochondria on a diagram?
Chloroplasts are bigger than mitochondria
What is the function of chloroplasts?
Absorb sunlight for photosynthesis
What is the chloroplast envelope?
A double plasma membrane that surrounds the organelle. Highly selective in what it allows to enter and leave the chloroplast.
What is the grana in a chloroplast?
Stacks of up to 100 disc-like structures called thylakoids. These create a large surface area to absorb light. Thylakoids contain chlorophyll. The thylakoids in the grana is where the first stage of photosynthesis (light absorption) takes place.
What is the stroma in a chloroplast?
A fluid-filled cavity where the light independent stage of photosynthesis takes place.
Cell walls : Plants
Made from cellulose middle lamellae - a thin boundary between cell walls (cement).
Cell walls : Fungi
Made from chitin
Cell walls : Algae
Made from cellulose or glycoproteins or a mixture of both
Cell vacuole (in Plants)
A fluid-filled sac bounded by a single membrane called the tonoplast
What does a cell vacuole contain?
A solution of mineral salts, sugars, amino acids, wastes and sometimes pigments such as anythocyanins
What form is the genetic material in a bacterial cell?
A circular strand of DNA
What are the separate smaller circular pieces of DNA in a bacteria cell?
Plasmids
What are plasmids extensively used for?
Vectors (carriers of genetic information) in genetic engineering
Bacteria : Cell wall
A physical barrier that excludes certain substances and protects against mechanical damage and osmotic lysis
Bacteria : Capsule
Protects bacterium from other cells and helps groups of bacteria to stick together for further protection
Bacteria : Cell-surface membrane
Acts as a differentially permeable layer, which controls the entry and exit of chemicals
Bacteria : Circular DNA
Possesses the genetic information for the replication of bacterial cells
Bacteria : Plasmid
Possesses genes that may aid the survival of bacteria in adverse conditions, e.g. produces enzymes that break down antibiotics
(PROKARYOTIC CELLS CAN HAVE ONE OR MORE PLASMIDS)
Bacteria : Flagella
Used for locomotion (only certain species)
(PROKARYOTIC CELLS CAN HAVE ONE OR MORE FLAGELLA’S)
True or False : Prokaryotic cells are much SMALLER than Eukaryotic cells
TRUE
Prokaryotic cells are much different form Eukaryotic cells in having :
- Cytoplasm that lacks membrane-bound organelles
- Smaller ribosomes (70s)
- No nucleus : instead they have a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins
- A cell wall that contains murein, a glycoprotein.
What are viruses?
Acellular and non-living
Are viruses smaller that bacteria?
Yes
What do viruses contain?
They contain nucleic acids such as DNA or RNA as a genetic material.
What is nucleic acid enclosed within?
A protein coat called Capsid
How do viruses multiply?
Inside living host cells
What do lipid envelopes (if not present, Capsid) have?
Attachment proteins which are essential to allow the virus to identify and attach to a host cell
What are microscopes?
Instruments that produce a magnified image of an object
What is the magnification of an object?
How many times bigger the image is when compared to the object
How do you work out the magnification?
Size of image / Actual size
How do you covert mm to um?
Times mm by 1000
How do you convert um to nm?
Times um by 1000
What is the resolution?
The minimum distance apart that two objects can be in order for them to appear as separate items
What does the resolving power depend on?
The wavelength or form of radiation used
What is the resolution of light (optical) microscopes?
0.2um
What does greater resolution mean?
Greater clarity (clearer & more precise)
Advantages of Light (optical) microscopes :
- Easy to use
- Portable
- Cheaper
- Can use live specimens
- Images are in colour
Disadvantages of Light (optical) microscopes :
- Low magnification
- Low resolution
What is CELL FRACTIONATION?
The process where cells are broken up an the different organelles they contain are separated out
What are the 3 things you have to do to make sure organelles are healthy before separation?
Make sure the tissue is placed in an ice cold, buffered solution of the same water potential as the tissue.
Why does the tissue have to be ice cold?
To reduce enzyme activity that might break down the organelles
Why does the tissue have to be in a buffered solution?
pH does not fluctuate - this could lead to the acids & alkalis damaging the organelles. This could be by damaging the structure or affect the functioning of enzymes