Biology Midterm 1 Review
All about Cells
1665: Robert Hooke discovers cells, Leeuwenhoek observes cells such as Paramecium
1838: Schwann and Schleiden formulate the cell theory:
1. Cell is the unit of structure, physiology and organization in living things
2. Cell is a distinct entity and building block in construction of organisms
3. Spontaneous generation(Virchow 1858) NOT TRUE
4. Cells pass hereditary information from one generation to another(modern)
5. All cells are based on the same chemistry(modern)
6. Cells trap and use energy to build molecules that make them up(modern)
Louis Pasteur disproved spontaneous generation using broth and a swan-necked flask
Eukaryotic Cells Prokaryotic Cells
Nucleus in center of cell No nucleus
Have ER and mitochondria No ER or mitochondria
Means ‘before nucleus’
Larger in size Smaller in size(with exceptions)
C, H, O, N, P and S make [lipids, polysaccharides](CHO), [nucleic acids](nucleotides),
[proteins](amino acids). All these are dry weight of the cell or macromolecules. Make up
20-30% of cell.
Water(wet weight of the cell) makes up 70-80%.
Surface area squares, volume cubes each time the cell divides
Limiting factor to cell growth is SA to Volume ratio, inability to transport quickly or
Cells’ Population Growth
Cells replicate through budding(daughter cells are smaller) or binary fission(divides into
2 equal-sized daughter cells) following the cell cycle:
1. Cell mass doubles, DNA replicates 2. DNA separate, septum forms
3. Septum or cell wall is complete.
4. Cells separate
5. Repeat process
Bacteria replicate in four general phases:
1. Lag phase: cells adapt to the medium. May be shortened if cells come from a
previously identical condition
2. Exponential/log phase: cells divide quickly or slowly(depends on number, or
type of energy cell) for an amount of time
3. Stationary phase: cells still divide, but more slowly. Some die, and growth and
death rate level out
4. Death phase: cell death rate increases and most cells die. Some adapt and use
During log growth,
=population at the time t g=time taken for population to double
=initial population size =number of generation per unit time
t=time allowed for growth unit time
N=# of times for population to double
Phospholipids and Lipid Bilayers
Phospholipids compose vesicles, micelles and the cytoplasmic membrane
Are amphipathic(dual-sympathy); have hydrophobic(water-hating) tails and
Micelles Lipid Bilayers/Vesicles
Created by hydrophilic heads facing water and hydrophobic tails facing each other
Slender tails Stalky tails
Plain surface Have transport proteins etc. on leaflet(surface
of a bilayer)
Single-layered Bilayered Nucleic Acids
Polymers of nucleotides. Either RNA(ribonucleotides) or DNA(deoxyribonucleotides).
Deoxy means lacking oxygen.
Purines: A, G. Pyrimidines: T, U, C(T in DNA only, U in RNA only)
Contain a sugar-phosphate backbone.
Discovered by James Watson and Francis Crick in 1953. They also discovered
complementary base pairing(G-C is stronger than A-T due to 1 more H-bond), or
Shape of double helix with major(large) grooves and minor(small) grooves was
Needs a template strand to copy itself into a complementary strand.
More reactive than DNA due to an extra hydroxyl group on 2’ side. Also less degrading.
Possibly the first life-form on Earth.
RNA only has 1 strand, so it H-bonds with itself in a hairpin model. This formation is
Made by ribosomes, then pushed into bilyaers for energy generation, transport etc.
Transport proteins have three classes
Channel: uses facilitated diffusion. Examples are aquaporin(moves water ten times
faster than normal), gated proteins(change shape using ATP)…these are also called ion
channels. Transport ions and water
Carrier: also called transporters or permeases since their reactions with substrates
seem like enzymes’
Pumps: use ATP or an electrochemical gradient. However, transport is ONE-WAY
ONLY(unidirectional). An example is the sodium-potassium pump. Pumps allow cells to
uptake nutrients despite the concentration gradient, remove waste and maintain
constant/non-equilibrium concentrations of inorganic ions.
Depends on hypertonic(outside more concentrated) or hypotonic(inside more
concentrated) concentration. Happens when a large concentration of cells want to go
through the membrane but can’t. If unprotected, cell bursts. Movement is spontaneous and continues until equilibrium due to entropy.
Particles spreading out in a solvent to minimize entropy. No membrane involved.
One of the 3 mechanisms for crossing the cell membrane. They are
1. Simple diffusion: this
2. Facilitated/passive diffusion: involves a channel or carrier protein and a
3. Active transport: pumps are involved.
Requires kinetic energy and a medium(solutions or empty spaces for gases)
Bond energies are listed from strongest to weakest
o Covalent(polar/non-polar)……share electrons
o Ionic(ions)……………………..transfer electrons
o Permanent dipole-permanent dipole(PDPD)…..H-bond