Cell Biology 3 & Cell Biology 4 Flashcards
define diffusion
• Movement of atoms or small molecules from area of high concentration to low area
Such that equal and uniform concentration is achieved
define osmosis
• Diffusion of water (shows net change of water amount)
define hypertonic + consequences
greater solute concentration than starting)= shrivels (crenate)
define hypotonic + consequences
(lower concentration than starting)= water putting on= swollen cells (lyse)
what molecules using simple diffusion concentration gradient movement
all driven by concentration gradient)
what substances move through bilayer with simple diffusion
o Small lipid soluble solutes
• Gases
• Steroids
what substances move through channel proteins with simple diffusion
o water, small lipid-insoluble solute
• electrolytes
what types of substances are transported by facilitated diffusion
• Small hydrophilic
explain facilitated diffusion
• Carrier mediated - has its own dedicated carrier (shapes match)
• No extra energy
• Saturable (but initially driven by concentration gradient)
what types of substances are transported by factive transport
amino acids, ions
explain active transport
•
Carrier mediated
• Energy required (from ATP) (against concentration gradient)
• Enables transport against a concentration gradient
describe active transport of Na K pump
• Transports two molecules in different directions
- Na need to be transported out cell + taken up by pump (triggers requirement for ATP)
- Releases P causing protein to change shape (forcing Na out to extra
cellular + enabling intake of K ions) - K ions don’t require extra energy to enter
- Once K ions into cell triggers restart of protein
if active transport only moves one molecule at a time, which moves multiple
vesicular transport
what are the four types of vesicular transport
- Exocytosis (release from cell)
- Endocytosis (intake into cell)
a. Phagocytosis (eat, engulfing particles)
b. Pinocytosis (drinking)
what hormones do not enter cell + have to communicate outside
ones not made of lipid, not steroid
define ligand
hormones
what ligands bind to membrane + intracellular recent
o Bind membrane receptors or intracellular receptor (steroid/lipid base)
• Peptide hormones bind membrane receptors (e.g. insulin, oxytocin, GH)
transition of message to cell steps
- G proteins (primary proteins) are relays b/w 1st and second messengers
- When ligand binds: g proteins altered (changes confirmation and releases G proteins)
- G proteins then active and modify many other proteins
Second Messenger (Cyclic AMP)
describe polarisation of membrane
- Inside membrane has negative electrical charge compared to outside
o Extracellular Fluid: high concentration of NaCl // Na + and Cl-
o Intracellular Fluid: high concentration of K+ and negative ions - Maintain potential difference in two ways:
1.
Actively moves ions across membrane (sodium potassium pump)
o Transports Na+ out of cell and K+ inside
2. Cell membrane not equally permeable to all ions
o // large number of neg ions trapped inside
o although Na+ and K+ both +ve, not enough to counteract effect of large –ve ions
what occurs for an action potential to happen
- When sodium ions move inside membrane
- Stimulus reaches neuron > membrane becomes more permeable to Na+
- Depolarisation occurs when threshold exceeded (15Mv)
o inward movement= too great to be balanced by outward movement of K+ // membrane > depolarised
o then movement of Na+ proceeds independently of stimulus (size of response not related to strength of stimulus (all-or-none response)
what are the phases of cell cycle
- Interphase (G1, S, G2)
2. Mitosis (prophase, metaphase, anaphase, telophase)
how many chromosomes in human cell
• Normal human cell= 46 (23 pairs)
what is hap/diploid cell
• A DIPLOID cell has the full complement of chromosomes, a HAPLOID cell has half
what occurs at s phase
• In a cell in S phase, each chromosome doubles it’s DNA, forming 2 chromatids, joined by a centromere
Describe what occurs at Interphase G1
• Growth and normal cellular activity
Describe what occurs at Interphase S
- DNA replication
* 6-8 hours
Describe what occurs at Interphase G2
- Brief final preparation for cell division
- 3-4 hours
+ centriole duplicates
what occurs at prophase
- Chromosomes condense and become visible
- Nuclear membrane disappears
- Mitotic spindle starts to form from centrioles
what occurs at metaphase
- Chromosomes line up on equator
* Spindle is fully formed
what occurs at anaphase
- Chromosomes split at centromere
* Chromatids move to each poles
what occurs at telophase
- Decondensation of chromatin
- Cytokinesis (cytoplasm pinch off into two separate entities)
- Reform of nuclear membrane and envelope
2 steps of translation
- Enzyme RNA polymerase binds to DNA unwinding it + assembles RNA,
- Enzymes splice the exons and introns to form mRNA
why is U not T
U= easier to make (one more step to turn U to T)
• Why is u not in DNA?
• Most common mutation = C to U
• No naturally U // is recognised as mutation and corrected
• If Ts were Us then would not know which is mutated or not
what is the preRNA parts
a. Sense portions (exons= translated into protein)
b. Nonsense portions (introns= must be removed before translation)
describe translation
- mRNA carries code to ribosome
2. tRNA binds to free amino acid, + tRNA anticodon binds to complementary codon
