Lectures 2-14 Flashcards
What is a cell?
A cell is the simplest collection of matter that can be alive.
What are the 3 domains of cells?
- Bacteria
- Archaea
- Eukarya
What are the 4 kingdom of cells in the Eukarya domain?
- Plantae
- Fungi
- Animalia
- Protist (single cell)
What is the benefit of smaller cells?
A small cell has a greater surface area to volume ratio.
What are the 3 important parameters in microscopy? (explain)
- Magnification (ratio of image size to real size)
- Resolution (clarity of image)
- Contrast (difference between light and dark areas of the image) - can be enhanced by staining.
Talk about Light microscopy (LM).
- Magnification is about 1000x
- Further magnification is limited by resolution.
- Staining helps enhance LM
Talk about Scanning Electron microscopy (EM).
- Resolution is immensely proportional to wavelength.
- Shorter wavelengths of electrons increase the resolution.
- Used to examine the cell’s internal structure.
List the 4 types of building blocks.
- Amino Acids
- Nucleobases
- Simple Carbohydrates
- Lipids
List The 5 types of Macromolecules.
- Proteins
- DNA
- RNA
- Complex carbohydrates
- Lipids
List the 4 types of Carbohydrates and define them.
- Monosaccharides (simple) - single unit building blocks of carbohydrates (mono).
- Disaccharides (simple) - 2 monosaccharides joined together (Di).
- Oligosaccharides (complex) - 3 to approx 10 linked monosaccharides.
- Polysaccharides (complex) - Approx > 10 monosaccharides linked together. (poly for many)
What are the 3 functions of carbohydrates?
- Recognition of cells
- Energy
- Structure (Cellulose in plants)
Talk about Lipids.
- NOT Polymers.
- Heterogenous (many different variants)
- Hydrophobic (dislike water).
What are the 3 functions of Lipids?
- Structural (cholesterol and phospholipids in the cell membrane)
- Regulatory (Cholesterol -> Testosterone -> Esotrogen
- Energy (fats and oils)
What are the 2 types of nucleic acids, and what does their structure compose of?
-DNA & RNA - made up of a chain of nucleotides (polymers), each nucleotide consists of a sugar, a phosphate, and a base. (uracil replaces thymine in RNA)
What are proteins and what are they used for?
Proteins are polymers of amino acids and are molecules which cells use to perform their functions in the whole organism. Proteins perform a variety of functions within the body (structural, regulatory, contractile, transport etc).
Why are there only 20,000 protein coding DNA sequences (genes) but around 100,000 unique proteins?
Because some genes code for only one proteins, and some genes code for up to 5 slightly different proteins. (Hence 1:5 ratio).
Name 4 important structures on a prokaryote (bacteria) and their functions.
- Fimbriae (allows bacteria to stick to surfaces)
- Cell wall (Provides strength to the cell and prevents osmotic lysis/ cell bursting)
- Capsule (formed by either organised (capsule) or unorganised (slime layer) glycocalyx (a gelatinous polysaccharide (polypeptide outer covering). - helps prevent phagocytosis (digestion of bacterial cell by another cell) by making it hard to make contact with the cell, help bacteria stick to structures, can be used as a source of nutrients and prevents cell from drying out (desiccation).
- Flagella (long flexible appendages that provide motility by spinning like a propeller)
Describe the gram-stain test and explain how it is carried out and what it’s used to determine.
- Crystal violet dye is added to a sample of bacteria
- Cells will stain blue/purple.
- Alcohol is added to remove the dye.
- Some cells will retain there colour, where as some cells will lose all the dye.
- Pink dye is then added to the sample, staining the cells that lost their colour pink.
- Purple/Blue cells are gram-postive (thick cell wall, hence dye could not be washed out of the cell once it has enter)
- Pink cells are gram-negative (thin cell wall with thin layer of peptidoglycan, which is located between the outer and inner membrane, hence the dye was washed out easily)
Explain how bacteria cells use flagella to located attractants.
- The flagella are bundled and spin in a CCW direction to ‘run’
- Flagella spread out and rotate CW to ‘tumble’
During the tumble phase the bacteria are using receptors to detect the change in concentration of the attractant in the solution over time (temporal gradient) and responds by going in the direction of the attractant.
(Positive Chemotaxis - movement towards an attractant
Negative Chemotaxis - movement away from something harmful)
Explain the function of Fimbriae and their structure.
Fimbriae are hair like structures much shorter than flagella, that help bacteria cells stick to surfaces. This is done by the Adhesin protein, which detects key receptors on structures to attack to (lock and key). Fimbriae are either made up of fimbrin proteins or pili depending on the type of cell.
