What is the structure and function of the nucleus
Structure
Nuclear Envelope- double membrane
Nuclear pores
Nucleoplasm- granular jelly like material
Chromosomes- protein bound, linear DNA
Nucleolus- smaller sphere inside which is the site of rRNA production and makes ribosomes
Function
Site of DNA replication and transcription (making mRNA)
Contains the genetic code for each cell
What is the structure and function of the plasma membrane
Structure
Found in all cells
Phospholipid bilayer - molecules embedded within and attached on the outside (proteins, carbohydrates, cholesterol
Function
Controls entry and exit of molecules
What is the structure and function of the mitochondria
Structure
Double membrane
Inner membrane called the cristae
Fluid centre called the mitochondrial matrix
Loop of mitochondrial DNA
70S ribosomes
Function
Site of aerobic respiration
Site of ATP production
DNA to code for enzymes needed in respiration
What is the structure and function of the chloroplasts
Structure
Surrounded by a double membrane
Contains thylakoids (folded membranes embedded with pigment)
Fluid filled stroma contains enzymes for photosynthesis
Found in plants
Function
Site of photosynthesis
What is the structure and function of the Golgi apparatus and Golgi vesicles
Structure
Folded membranes making cisternae
Secretary vesicles pinch off from the cisternae
Function
Add carbohydrates to proteins to form glycoproteins
The Golgi apparatus modifies proteins (such as enzymes) and packages them into vesicles for transport to the cell surface for secretion.
Secrete carbohydrates
Transport, modify and store lipids
Form lysosomes
Molecules are ‘labelled’ with their destination
Finished products are transported to cell surface in golgi vesicles where they fuse with the membrane and the contents are released
What is the structure and function of lysosomes
Structure
Bags of digestive enzymes - can contain 50 different enzymes
Function
Hydrolyse pathogens in phagosomes
Completely break down dead cells (autolysis)
Exocytosis release enzymes to outside of cell to destroy material
Digest worn out organelles for reuse of materials
What is the structure and function of the ribosomes
Structure
Small, made up of two sub-units of protein and rRNA
80s- large ribosome found in eukaryotic cells
70S- smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts
Function
The site of protein synthesis
What is the structure and function of the rough and smooth endoplasmic reticulum
Structure
Rough and Smooth ER both have folded membranes called cisternae
Rough have ribosomes on the cisternae
Function
RER- protein synthesis
SER- synthesis and store lipids and carbohydrates
What is the structure and function of the cell wall
Structure
In plant and fungi cells
Plants- made of microfibrils of the cellulose polymer
Fungi- made of chitin, a nitrogen-containing polysaccharide
Function
Provide structural strength to the cell
What is the structure and function of the vacuole (in plants)
Structure
Filled with fluid surrounded by a single membrane called a tonoplast
Function
Make cells turgid and therefore provide support
Temporary store of sugars and amino acids
The pigments may colour petals to attract pollinators
What are specialized cells organized into
Specialised cells are organised into tissues, tissues into organs and organs into systems.
Differences between prokaryotes and eukaryotes
Prokaryotes are much smaller
cytoplasm that lacks membrane-bound organelles
smaller ribosomes
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.
In addition, many prokaryotic cells have:
one or more plasmids
a capsule surrounding the cell
one or more flagella.
What are viruses? Describe structure.
Are non living and acellular
Non living: no metabolic reactions, cannot move, respire, replicate and no nutrition (no FREG: feed, respire, excrete and grow no MRS GREN))
Acellular: not made of cells, no cell membranes
Viruses are smaller than bacteria and only contain three structures
Describe the differences between optical microscopes and electron microscopes (scanning and transmission)
Optical (light microscope)
a beam of light is condensed to create the image
poorer resolution due to light having a longer wavelength
lower magnification
colour images
can view living samples
Electron microscope (scanning/transmission)
a beam of electrons is condensed to the create the image
high resolving power as electrons have a short wavelength
higher magnification
black and white images
sample must be in a vacuum, and therefore non living
note: have a poor resolution due to the long wavelength of light. Small organelles in a cell are not visible using an electron microscope but living samples can be examined and a colour image is obtained
note: electrons are absorbed by air which is why samples must be in a vacuum. For this reason only non living specimens can be examined. The image is also black and white as the samples must be stained
How do transmission and scanning electron microscopes work?
TEM (Transmission Electron Microscope)
Goes through the specimen. Extremely thin specimens are stained and placed in a vacuum. An electron gun produces a beam of electrons that pass through the specimen. Some parts absorb the electrons and appear dark (denser psrts). The image produced is 2D and shows detail images on the internal structure of cells. Long prep time, only thin, only 2D, staining required
SEM (Scanning Electron Microscope)
Scans surface. The specimens do not need to be thin, as the electrons are not transmitting through. Instead, the electrons are beamed onto the surface and the electrons are scattered in different ways depending on the contours. This produces a 3D image
Light produces a 2D image
What is the difference between magnification and resolution?
The magnification of a microscope refers to how many times larger the image is compared to the object
The resolution of a microscope is the minimum distance between two objects in which they can still be viewed as separate (such that you can still see two parts of the cell as separate rather than being blurred to look like one single point). The resolution in an optical microscope is determined by the wavelength of light and the wavelength of the beam of electrons determines the resolution in electron microscope
What is the formula of magnification
magnification = size of image / size of real object
Describe process of cell fractionation
Steps:
Homogenisation
The cells must be broken open (homogenised) using a blender. These cells are blended in a cold, isotonic and buffered solution. The solution is filtered to remove large cell debris
Filtration
To remove large debris and tissue fragments that would interfere with the centrifugation process.
Ultracentrifugation
The filtered solution is spun at different speeds in a centrifuge
Organelles separate according to their densities
Differential centrifugation
The centrifuge spins and the centrifugal forces ( the forces cause organelles to form pellets) cause pellets of the most dense organelles to form at the bottom
The centrifuge spins and the centrifugal forces causes pellets of the most dense organelles to form at the bottom
The centrifuge is first spun at a low speed and the process is repeated at increasingly faster speeds
Each time the supernatant (liquid) is removed, leaving behind a pellet of organelles
The supernatant liquid is then spun again to remove the next pellet of organelles
Note: supernatant liquid is the liquid after like the most dense organelles sink to the bottom
Order at which they separate is due to their density
Nuclei
Chloroplasts (if using plant tissue)
Mitochondria / Lysosomes
Endoplasmic reticulum
Ribosomes
NCMLER
No Candy Make Lilly Exit Room
Nutella chocolate makes little easier rabbits
What are the conditions for cell fractionation and what is it used for
Used to isolate different organelles so they can be studied
This enables individual organelle structures and functions to be studied
cells are broken to release the contents and organelles are then separated
The cells must be prepared in a cold, isotonic and buffered solution
cold- to reduce enzyme activity. When the cell breaks open enzymes are released which could damage the organelles
Isotonic- must be the same water potential to prevent osmosis as this could cause the organelles to shrivel or burst
Buffered- the solution has a pH buffer to prevent damage to organelles
m —> mm —> μm —> nm
m —x10³—> mm —x10³—> μm —x10³ —> nm
Which organelles have a double membrane
Nucleus:
Surrounded by the nuclear envelope which has two membranes
Mitochondrion:
Has an outer membrane and a highly folded inner membrane (cristae)
Chloroplast:
Has an outer and an inner membrane
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Biological Molecules64
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Organisms exchange substances with their environment32
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B5 And B662
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Cell Membrane Structure And Transport32
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All Math Stuff In Bio27
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Mass Trabsport In Animaks8
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Cells21
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Z Cell Membranes29
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Immune System33
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Digestion4
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Z Digestion & Absorption10
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RNA nucleic Acid Structure And Function and DNA11
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Z Nucleic Acids 113
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ATP4
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Mass Transport In Plants12
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Immune System Z21
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Genetic Diversity Z18
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Z Nucleic Acids 212
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Protein Sythesis12
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Geneitc Diversity 213
