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).
