Cell Structure and Composition Flashcards
Definition of a cell
The basic unit from which living organisms are made, consisting of an aqueous solution of organic molecules enclosed by a membrane. All cells arise from existing cells, usually by a process of division.
Predominant types of molecules found in cells
Soluble proteins, ions, sugars, nucleotides, amino acids, mRNA, tRNA, lipids, cholesterol, peptides.
Size of cells
10-20 micrometres diameter
Mass of a cell
1 nanogram
Size of a virus
10 nanometres
Small protein
40 nanometres
Unit of measurement for cell volume
Nanolitres
Size of molecules
0.2 nanometres in diameter
Function of nucleus
Contain the genetic information for the cell, coordinate the activity of the cell
Function of nucleolus
Contains genes for rRNA production
Function of nuclear envelope
Contain the nucleus
Function of mitochondrion
ATP synthesis
Function of rough ER
Synthesis and packaging of proteins
Function of smooth ER
Synthesis of lipids
Function of ribosomes
Synthesis of protein
Function of golgi apparatus
Modification of proteins and packing into vesicles
Function of secretory granules
Contain and release contained molecules
Function of plasma membrane
Contain and define limits of the cell
Function of cytoskeletal components
Provide organisation and control of components of intracellular matrix
Essential characteristics of prokaryotic cells
- No membrane bound organelles
- No nucleus
- Some have flagella
- Lesser degree of organisation within cell
- Some have peptidoglycan cell walls
- 70s ribosomes
Essential characteristics of eukaryotic cells
- Membrane-bound organelles
- Nucleus
- Some have cilia/microvilli
- Cytoskeleton - high degree of organisation
- No cell wall, only cell membrane
- 80s ribosomes
Structural components of phospholipids (in descending order)
Hydrophilic choline head
Phosphate
Glycerol
Two fatty acid tails
Explain the formation of phospholipid bilayers in aqueous environments
Hydrophobic tails form hydrophobic core of bilayer, pointing towards the inside of the bilayer. Hydrophilic heads form the two hydrophilic surfaces of the bilayer, facing outwards from the inside of the bilayer. Form a micelle.
Permeability properties of phospholipid bilayer membrane
- Selectively permeable
- Impermeable to large molecules and charged molecules
- Permeable to water molecules and small uncharged molecules
Functions of membrane proteins
- Increase fluidity of membrane
- Transport of molecules
- Transmission of signals
- Anchors linking intracellular actin filaments to extracellular matrix
- Receptors for hormones
- Cell recognition and adhesion
- Electron carriers
- Enzymes
Simple diffusion
Movement of a particle down its concentration gradient
Facilitated diffusion
Movement of charged particles through channel proteins down their concentration gradient
Active transport
Movement of a particle against its concentration gradient, using ATP in the process.
Example of simple diffusion
O2/CO2 molecules through lipid bilayer
Example of facilitated diffusion
K+ diffusion through its gated channel protein
Example of active transport
Na+/K+ pump, both ions moving against their electrochemical gradients
