Cell ultrastructure
What is the main function of the mitochondria?
Produce energy
Which organelle is responsible for protein synthesis?
Ribosomes
Which organelle contains digestive enzymes?
Lysosomes
What is the function of the endoplasmic reticulum?
Protein synthesis
Which organelle is responsible for detoxifying harmful substances in the cell?
Smooth endoplasmic reticulum
What is the main function of the vacuole?
Store water and nutrients
Which organelle is responsible for photosynthesis in plant cells?
Chloroplasts
What is the function of the cytoskeleton?
Maintain cell shape and structure
Which organelle is responsible for storing and modifying proteins?
Golgi apparatus
What is the function of the cell membrane?
Control the movement of substances in and out of the cell
What is the equation for magnification?
image/real
What is resolution?
The minimum distance apart that two objects can be in order for them to appear as separate items.
What is cell fractionation used for?
To obtain large numbers of isolated organelles
Describe two factors of the solution that the sample is placed in before cell fractionation begins
- Cold, to reduce enzyme activity that could break down the organelles
- Same water potential as the tissue, to prevent organelles bursting/shrinking
- Buffered, so that the pH does not fluctuate. A change in pH could alter the structures of the organelles
What is homogenation?
Cells are broken up by a homogeniser which releases the organelles from the cell.
What are the two stages of cell fractionation?
1) Homogenation
2) Ultracentrifugation
What is ultracentrifugation?
The process by which the fragments in the filtered homogenate are separated in a centrifuge. The tubes of the homogenate spin at very high speeds to create a centrifugal force.
Describe the process of centrifugation for animal cells (6 steps) (The tube of filtrate, The heaviest organelles, The supernatant is removed, The supernatant is transferred, The next heaviest organelles, The process is continued
1) The tube of filtrate is placed in the centrifuge and spun at a slow speed
2) The heaviest organelles, the nuclei, are forced to the bottom of the tube where they form a thin sediment/pellet.
3) The supernatant is removed, leaving just the sediment of the nuclei
4) The supernatant is transferred to another tube and spun in the centrifuge at a higher speed than before.
5) The next heaviest organelles, the mitochondria, are forced to the bottom of the tube
6) The process is continued in this way so that, at each increase in speed, the next heaviest organelle is sedimented and separated out.
How many times better is an electron microscope than a light microscope?
2000
What are the two different types of electron microscope?
- Transmission electron microscope
- Scanning electron microscope
Describe 5 parts of the nucleus
- Nuclear envelope, double membrane that has ribosomes on its surface and controls what enters/exits the nucleus
- Nuclear pores, allow the passage of large molecules
- Nucleoplasm, jelly-like material that makes up the bulk of the nucleus
- Chromosomes, consist of protein-bound, linear DNA
- Nucleolus, manufactures RNA and assembles the ribosomes
Name 3 functions of the nucleus
- Control centre of the cell through the production of mRNA and tRNA
- Retain the genetic material of the cell in the form of DNA and chromosomes
- Manufacture RNA and ribosomes
Name 3 parts of the mitochondrion's structure
- Double membrane, controls what enters/exits the cell
- Cristae, extensions of the inner membrane which provide a large SA for the attachment of enzymes and other proteins involved in respiration
- Matrix, contains proteins, lipids, enzymes, ribosomes and DNA that allows the mitochondria to control the production of some of their own proteins
Name 3 key parts of the structure of chloroplasts
- Chrloroplast envelope, double plasma membrane that controls what enters/exits
- Grana, stacks of up to 100 thylakoids which contain chlorophyll and is where the first stage of photosynthesis begins
- Stroma, fluid-filled matrix that contains starch grains and is where the second stage of photosynthesis begins
Name 3 ways that the choroplast is adapted to its functions
- Granal membranes provide a large SA for the attachment of chlorophyll, electron carriers and enzymes that carry out the 1st stage of photosynthesis
- The fluid of the stroma contains all the enzymes needed to make sugars in the second stage of photosynthesis
- Chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis
Describe the general structure of the endoplasmic reticulum
A 3D system of sheet-like membranes , spreading through the cytoplasm of the cells.
Describe 2 key functional points for the structure of the RER
- Provides a large SA for the synthesis of proteins and glycoproteins
- Provide a pathway for the transport of materials
Describe 2 key functional points for the structure of the SER
- Synthesise, store and transport lipids
- Synthesise, store and transport carbohydrates
Describe the structure of the golgi apparatus
Consists of a stack of membranes that make up cisternae with vesicles
Name 5 functions of the GA (Add carb, Produce secretory, Secrete carbohydrates, Transport, modify, Form lysosomes)
- Add carbohydrate to proteins to form glycoproteins
- Produce secretory enzymes
- Secrete carbohydrates
- Transport, modify, and store lipids
- Form lysosomes
Where are GAs developed?
In secretory cells, such as epithelial cells.
Describe the structure of lysosomes
Lysosomes are small cell organelles in eukaryotic cells that contain hydrolytic enzymes for intracellular digestion
What are the 4 main functions of lysososmes?
- Hydrolyse material ingested by phagocytic cells
- Exocytosis in order to destroy the material around the cell
- Digest worn out organells so that the useful chemicals they are made of can be re-used
- Autolysis
Name the two types of ribosomes and briefly describe them
- 80S, found in eukaryotic cells, around 25nm in diameter
- 70S, found in prokaryotic cells, mitochondria and chloroplasts, slighty smaller than 80S
Name 2 features of the cell wall
- Consist of a number of polysaccharides, such as cellulose
- Middle lamella, marks the boundary between adjacent cell walls and cements adjacent cells together
Name 3 functions of the cell wall (mech. strength 2x)
- Provide mechanical strength in order to prevent cell lysis
- To allow water to pass along it, so contributes to movement of water through the plant
- Provide mechanical strength to the plant as a whole
Describe the structure of a vacuole
A fluid-filled sac surrounded by a membrane
Name 3 functions of the vacuoles
- Make cells turgid
- Sugars and amino acids act as a temporary food store
- Pigments may colour petals to attract insects