universal principles of life

Question 1

what are the basic functions of life?

Answer 1

• chemical reactions -> metabolism
• acquire and use energy
• reproduction
• homeostasis - constant maintenance of internal environment
• respond to external environment
• evolution

Question 2

properties of cells

Answer 2

smallest unit of life performing cycle of life

• composed mainly by water and macromolecules (proteins)
• store genetic information in the same chemical code: DNA (can be transferred an interpreted between organisms)
  
  • all DNA is copied through templated polymerisation
• all proteins are coded from RNA in organisms (RNA acts as intermediary)
• all cells use energy coming directly/indirectly from the sun (ATP)
• all cells are enclosed in plasma membrane - regulate movement of molecules inside/out, isolate the cell

Question 3

properties of membranes

Answer 3

• separate compartments
• regulate transport
• maintain ion gradients

Question 4

phospholipid bilayer

Answer 4

double layer of phospholipids and proteins held together by non-covalent bonds

- lipid provides impermeable barrier
- proteins mediate transport of molecules 
- phospholipids - amphiphilic (both hydrophobic and hydrophilic-spontaneously become double layer)
- polar, hydrophilic head (phosphate group)
- fatty acid chains (hydrophobic) - 1 has cis-double bond which creates bend and allows molecules to not be compacted (free to move)
- cholesterol  - asymmetric shape
- phosphotidylserine (contained in mammal plasma membrane) contained in internal layer of membrane 
- when the cell dies, it is flipped outside and acts as a signal

Question 5

eukaryotes vs prokaryotes

Answer 5

prokaryotes: no membrane bound proteins and genetic information is stored in plasmids free in cell
eukaryotes: contain nucleus which stores genetic information and membrane bound organelles

Question 6

structure of eukaryotic cell: nucleus

Answer 6

double membrane dotted with nuclear pores

- DNA replication molecular processes (transcription and translation)

Question 7

structure of eukaryotic cell: endoplasmic reticulum

Answer 7

tubules (smooth ER) and flattened stacks (rough ER-dotted with ribosomes)

• RER: synthesis of proteins - protein modification - membrane tagging
• SER: synthesis of lipids - synthesis of fatty acids/steroid hormones

Question 8

structure of eukaryotic cell: end-membrane structure

Answer 8

moving of macromolecules in/out cell

• secretory pathway
• endocytic pathway
• recycling pathway

Question 9

structure of eukaryotic cell: golgi apparatus

Answer 9

flattened sacks (cisternae)

• connected to vesicular networks arriving from ER (transport)
• synthesise carbohydrates

Question 10

structure of eukaryotic cell: lysosomes

Answer 10

digestive system of the cell

• connected to vesicular networks arriving from ER (transport)
• synthesise carbohydrates

Question 11

structure of eukaryotic cell: peroxisomes

Answer 11

use molecular oxygen to perform oxidation reactions

Question 12

structure of eukaryotic cell: mitochondria

Answer 12

cellular respiration

• retain DNA
• contain cristae - where chemiosmotic coupling takes place (ATP production)
• dynamic organelles: shape changes frequently, undergo fusion/fission mechanisms, interact with other organelles
• move in cell by sliding over cytoskeleton

Question 13

structure of eukaryotic cell: cytoskeleton

Answer 13

intracellular skeleton used for transporting organelles and provide physical structure
- composed of 3 main filaments