Topic 2.1 - Cells and Microcopes Flashcards
The production and secretion of proteins
Synthesis: Proteins are made in ribosomes on the rough endoplasmic reticulum (RER) from mRNA.
Modification: In the RER, proteins fold and may undergo glycosylation (addition of carbohydrates).
Transport to Golgi: Proteins are packaged into vesicles and transported to the Golgi apparatus for further modification.
Packaging and Sorting: The Golgi apparatus modifies, and packages proteins into new vesicles.
Vesicle Transport: Proteins are transported in vesicles either to the cell membrane (for secretion via exocytosis) or to other parts of the cell (e.g., mitochondria, nucleus).
Explain Exocytosis
Vesicle Formation: A vesicle containing the substance to be secreted buds off from the Golgi apparatus or endoplasmic reticulum (ER).
Vesicle Transport: The vesicle is transported towards the cell membrane along the cytoskeleton, using motor proteins.
Fusion with the Cell Membrane: The vesicle fuses with the plasma membrane, driven by changes in the membrane’s structure.
Release of Contents: The contents of the vesicle (such as proteins) are released into the extracellular space or outside the cell.
Ultrastructure of nucleus
Nucleoplasm
Nucleolus
Nuclear pores
Nuclear membrane/envelope
Chromatin
Ultrastructure of Mitochondria
Cristine - describes the fold of the membrane
Outer membrane
Inner membrane
Mitochondrial DNA
Matrix
Ultrastructure of Chloroplasts
Outer membrane
Inner membrane
Chloroplast DNA
Starch grains
Thylakoid
Chlorophyll
Granum
Stoma
Stoma - Chloroplasts
Fluid with dissolved solids
Granum - Chloroplasts
A basic structural unit of the thylakoid membrane network, it is also the site of light reactions of photosynthesis
Thylakoid - Chloroplast
Tiny compartments found inside chloroplasts that help absorb sunlight for photosynthesis
Chlorophyll - Chloroplast
Located inside thylakoids, where photosynthesis occurs.
Matrix - Mitochondria
the inner space surrounded by the mitochondrial inner membrane
Cristine - Mitochondria
The inner mitochondrial membrane is folded into invaginations called cristae.
Nucleoplasm - Nucleus
Fluid consisting of other molecules
Nucleolus - Nucleus
A spherical structure found in the cell’s nucleus whose primary function is to produce and assemble the cell’s ribosomes.
Chromatin - Nucleus
Made from DNA (linear) and Histone (protein).
Ultrastructure of Ribosomes
RNA
Protein
Ultrastructure of Cytoskeleton
Microfilament
Microtubules
Microfilament - Cytoskeleton
Structure and Function
- Made from actin
- Solid strands
- Involved in movement of the whole cell
- Causes the membrane to fold during endocytosis
Microtubule - Cytoskeleton
Structure and Function
- Made from tubulin
- Tube structure
- Allows organelles and vesicles to be transported around the cell, facilitated by motor proteins.
- In structures like flagella and Cilia it helps with movement.
- Help support shape of cell
Centrioles (only in animal cells)
Structure and Function
- Cylindrical structures made up of microtubules
- During mitosis and meiosis, centrioles play a key role in forming the spindle fibres, which are responsible for separating chromosomes.
- Centrioles are involved in the formation of basal bodies, which give rise to cilia and flagella, helping with cell movement and the movement of substances across the cell surface.
Lysosomes
- Membrane-bound organelles containing hydrolytic enzymes.
- Spherical shape and have a single lipid bilayer membrane that maintains an acidic environment inside.
- Enzymes within lysosomes include proteases, lipases, and nucleases.
Rough endoplasmic reticulum (RER)
Structure and Function
- Network of membrane-bound sacs and tubules.
- Ribosomes placed on the surface
- The membrane is continuous with the nuclear envelope, linking it to the nucleus.
- Ribosomes on the RER synthesize proteins that are either secreted from the cell, incorporated into the cell membrane, or sent to lysosomes.
- Involved in the folding of proteins into their correct 3D shape -
- Transports synthesised proteins in vesicles to the Golgi apparatus for further modification and sorting.
Smooth endoplasmic reticulum (SER)
Structure and Function
- A system of membrane-bound tubules and cisternae.
- Does not have ribosomes on its surface, making it smooth in appearance.
- It is continuous with the rough endoplasmic reticulum (RER) and the nuclear envelope.
- Involved in the synthesis of lipids, including phospholipids and steroid hormones.
- Helps detoxify harmful substances, especially in liver cells, by modifying drugs and toxins.
- It is involved in the conversion of glycogen to glucose in liver and muscle cells.
- Stores and releases calcium ions, which are crucial for muscle contraction and signalling.
Plasma Membrane
- Composed of a phospholipid bilayer with hydrophilic heads and hydrophobic tails.
- Contains proteins (e.g., channel, carrier, and receptor proteins) and carbohydrates (glycoproteins and glycolipids).
- Selective Permeability: Regulates entry and exit of substances.
- Cell Signalling: Receives signals from the environment.
- Protection: Provides structural support and acts as a barrier.
- Cell Communication: Involved in cell recognition and communication.
Cell wall
- A rigid outer layer found in plant, fungal, and bacterial cells.
- In plants, it is mainly composed of cellulose.
- In fungi, it is made of chitin, and in bacteria, it consists of peptidoglycan.
- Structural Support: Provides strength and rigidity to the cell.
- Protection: Protects the cell from mechanical damage and pathogens.
- Prevents Excessive Water Intake: In plant cells, the cell wall prevents the cell from bursting due to water uptake (osmosis).
Flagella
- Made of microtubules arranged in a 9+2 pattern (nine pairs of microtubules around two central microtubules).
- Covered by the plasma membrane.
- Typically long and usually one or a few per cell.
- Locomotion: Flagella enable cells (e.g., sperm cells) to move by rotating or waving.
- Movement: Helps propel cells through liquid environments
Cilia
- Made of microtubules arranged in a 9+2 pattern (nine pairs of microtubules around two central microtubules).
- Covered by the plasma membrane.
- Shorter and numerous, often covering the cell surface.
- Movement of substances: Cilia move fluid or mucus over the cell surface (e.g., in the respiratory tract).
- Locomotion: Cilia help in the movement of some cells, though less commonly than flagella.
Components in Prokaryotic cells
Ribosomes
Flagella
Slime Capsule
Circular DNA
Cell Wall
Cell Surface Membrane
Mesosomes
Pili
Glycogen Granules
Lipid Droplets
Describe how Light Microscopes work
- Lenses focus rays of light and magnify the view of a thin slice of the specimen
- Different structures absorb different amounts and wavelengths of light.
- Reflected light is transmitted to the observer via the objective lens and eyepiece
Describe how a transmission electron microscope (TEM) works
- Pass a high-energy beam of electrons through a thin slice of the specimen
- More dense structures appear darker since they absorb more electrons.
- Focus image onto fluorescent screen or photographic plate using magnetic lens
Describe how a scanning electron microscope (SEM) works.
- Focus a beam of electrons onto a specimens surface using electromagnetic lenses.
- Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
Describe how a laser-scanning confocal microscope works.
- Focus a laser beam onto a small area on a sample’s surface using objective lenses.
- Fluorophores in the sample emit photons.
- Photomultiplier tube amplifies the signal onto a detector. An image is produces pixel by pixel in the correct order
State the magnification and resolution of a compound light microscope
Magnification: x 2000
Resolution: 200 nm
State the magnification and resolution of a TEM
Magnification: x 500 000
Resolution: 0.5 nm
State the magnification of a SEM
Magnification: x 500 000
Resolution: 3 - 10 nm
Advantages of Light Microscopes
- Portable
- Can use living or dead specimens
- can be coloured
Disadvantages of Light Microscopes
- Low resolution of 200 nm
- Low magnification of x 2000
- Requires staining
- 2D image
Advantages of Scanning Electron Microscope (SEM)
- Very high magnification of x 100 000
- High resolution of 3-10 nm
- Produces 3D imaging
Disadvantages of Scanning Electron Microscope (SEM)
- Expensive
- Requires staining
- Only uses dead specimens
- Only produces black and white images
Advantages of Transmission Electron Microscope (TEM)
- Very high magnification of x 100 000
- Very high resolution of 0.5 nm
Disadvantages of Transmission Electron Microscope (TEM)
- Expensive
- Can only use dead specimens
- 2D images
- Only produces black and white images
Advantages of Laser Scanning Confocal
- Can view depths of thick specimens
- High resolution
- Much clearer images
- Specimens can be alive or dead
- Has both 2D & 3D imaging
- Can be coloured images
Disadvantages of Laser Scanning Confocal
- Low magnification
- Requires Staining
Formula for Magnification
Magnification = Image size / Real size
Explain Endocytosis
- Engulfing material: The cell membrane surrounds the material to be taken in, forming a pocket around it.
2.Formation of a vesicle: The pocket pinches off from the cell membrane, creating a vesicle inside the cytoplasm.
3.Energy requirement: Endocytosis is an active process, requiring energy in the form of ATP.
- Transport into the cell: The vesicle moves into the cytoplasm, where it may fuse with a lysosome for digestion.
