Life at cellular level IA%%+(+ Flashcards
Prokaryotic cells
- Lack Nuclear membrane
- No Mitochondria
- No membrane bound structures
- e.g Bacteria
Eukaryotic cells
- Multicellular animals and plants
- Nucleus with membrane
- Membrane bound structures
- e.g Human cells
Multipotent cell
•Cells that can differentiate into many cell type
Pluripotent
Cells that can differentiate into all cell types
Apoptosis
- Is a process of programmed cell death
- Is a central mechanism controlling multicellular development
Cell membrane
- Selective barrier
- Detects chemical messengers and signalling molecules from surrounding cells or other organs
- Membrane lipids are amphipathic (hydrophilic head and hydrophobic tail)
- Membrane proteins (some span the membrane, others are embedded in the membrane)
Diffusion
Passive diffusion
- Concentration gradient needed
- Lipid-soluble molecules pass freely (non-polar)
Facilitated diffusion
- Concentration gradient needed
- Requires carrier molecules
endocytosis
Mechanisms for moving macromolecules across membranes without disrupting them.
There is an invagination (turned inside out) of the membrane to form a vesicle which eventually separates on the cytoplasmic (inside) surface of the membrane and migrates within the cell to its destination.
Exocytosis
The merging of vesicles with the plasma membrane to release materials from the cell.
Mitochondria
- Outer membrane contains pores (porin protein)
- Inner membrane has cristae
- Matrix contains binding sites for calcium and also most of the enzymes for oxidation of food molecules (e.g. Krebs cycle)
They also have:
- Their own circular DNA
- Ribosomes – similar to bacterial ribosomes
- Synthesise most of their own proteins
- Self-replicate
Nucleus
- Contains DNA, nucleoprotein and some RNA
- Nucleoli are sites of ribosomal RNA synthesis and ribosomal assembly
- DNA tends to be one of two forms:Heterochromatin, Euchromatin
Nuclear Membrane (Envelope)
- Phospholipid bilayer
- Encloses the nucleus
- Contains pores
- Closely associated with the endoplasmic reticulum
Endoplasmic reticulum and golgi apparatus
- Membrane bound
- Rough ER has ribosomes attached
- Protein modifications and transport coordinated by the RER and Golgi
- Smooth ER used mainly to breakdown compounds (e.g. drugs and glycogen) or synthesise some compounds (e.g. lipids)
Lysosomes
- Used to separate enzymes from the rest of the cell
- Used in autophagy (digestion of cells own materials) or digestion of engulfed particles (e.g. bacteria)
Cytoskeleton
- Supports and maintains cell shape
- Holds organelles in position
- Moves organelles
- Involved in cytoplasmic streaming (cytosol movement)
- Interacts with extracellular structures to hold cell in place
Cell surface projections
Cilia and eukaryotic flagella are made of microtubules
Cilia
- short
- many present
- move with stiff power stroke and flexible recovery stroke
Flagella
- Longer
- usually one or two present
- movement is snakelike
Nucleic acid
- They are polymers of nucleotide monomers linked by 3’,5’-phosphodiester bonds
- There are 2 kinds of base in nucleic acids
–Pyrimidines (flat, single rings CUT) – cytosine (C), uracil (U) and thymine (T)
–Purines (flat, double rings AG) – adenine (A) and guanine (G)
D-glucose
- Reducing sugar
- The linear form (but not cyclic form) has an aldehyde group, which can be oxidised
- If this is oxidised then the other reactant would be reduced
Triglycerides
- Storage lipids
- Non-polar
- 3 fatty acid chains linked to glycerol
1st energy law
Energy can be converted from one form to another but the total energy of the universe remains constant
2nd energy law
- All energy transformations ultimately lead to more disorder in the universe, i.e. increase the entropy
- As usable energy decreases and unusable energy increases, entropy increases
- Entropy is a gauge of randomness or chaos within a closed system. As usable energy is irretrievably lost, disorganization, randomness and chaos increase.
Gibbs free energy
- Free energy change can be used to define the spontaneity of a reaction
- Spontaneous reactions can occur if a system:
-Gives up energy (water runs downhill spontaneously, giving up potential energy as it goes)
And/or
-Becomes more random and increases in entropy (complex structures decay spontaneously giving up potential energy)
Reaction coupling
- Cells use a process called “energy coupling” to carry out thermodynamically unfavourable reactions
- Reaction coupled to energy-releasing reaction e.g catabolic ones
Facts about certain Molecules
- Charged molecules are also water soluble (hydrophilic)
- Non-polar (uncharged) molecules are hydrophobic
- Amphipathic molecules contain both hydrophobic and hydrophilic parts e.g phospholopid
- CO2 and O2 are non-polar and poorly water soluble
Water dissociation
- [H2O] is very high in pure water, so it is essentially constant
- Kw is the ion product of water. Kw = 1 × 10-14 (mol/L)2
Strong and weak acids
- Hydrochloric acid (HCl; produced in the stomach) fully dissociates into H+ and Cl- (chloride ion)
- Strong acids and bases fully dissociates
- Weak acids and bases are far more important in biological systems as they are only partially dissociated, which gives them some unique properties
- Lots of biomolecules (proteins, DNA) are affected by pH changes as their shape is often dictated by the pH of their environment
Buffers
- Acids are defined as proton donors and bases as proton acceptors
- The stronger the acid the greater its tendency to lose its proton in (an aqueous environment) and vice versa
- A buffer is a mixture of a week acid and its conjugate base
Buffers in the body
- In cells, the phosphate buffer system is important:
- And, in plasma, the bicarbonate buffer system is important:
Metabolism, Catabolism and Anaobilism►
Metabolism
- Metabolism refers to the biochemical reactions that take place in an organism. It consists of two processes – Catabolism and Anabolism
Catabolism
- Catabolism deals with energy releasing processes.
- It breaks things and releases energy
Anabolism
- Anabolism is related to energy-using processes.
- It builds things and consumes energy
Peroxisome
A major function of the peroxisome is the breakdown of very long chain fatty acids through beta-oxidation.
5 chemical reactions►
–Redox reactions
–Making and breaking C-C bonds
–Internal rearrangements (isomers)
–Group transfers
–Condensation and hydrolysis reactions
