Cell Biology 3 & Cell Biology 4

Question 1

define diffusion

Answer 1

• Movement of atoms or small molecules from area of high concentration to low area
Such that equal and uniform concentration is achieved

Question 2

define osmosis

Answer 2

• Diffusion of water (shows net change of water amount)

Question 3

define hypertonic + consequences

Answer 3

greater solute concentration than starting)= shrivels (crenate)

Question 4

define hypotonic + consequences

Answer 4

(lower concentration than starting)= water putting on= swollen cells (lyse)

Question 5

what molecules using simple diffusion concentration gradient movement

Answer 5

all driven by concentration gradient)

Question 6

what substances move through bilayer with simple diffusion

Answer 6

o Small lipid soluble solutes
• Gases
• Steroids

Question 7

what substances move through channel proteins with simple diffusion

Answer 7

o water, small lipid-insoluble solute

• electrolytes

Question 8

what types of substances are transported by facilitated diffusion

Answer 8

• Small hydrophilic

Question 9

explain facilitated diffusion

Answer 9

• Carrier mediated - has its own dedicated carrier (shapes match)
• No extra energy
• Saturable (but initially driven by concentration gradient)

Question 10

what types of substances are transported by factive transport

Answer 10

amino acids, ions

Question 11

explain active transport

Answer 11

•

Carrier mediated
• Energy required (from ATP) (against concentration gradient)
• Enables transport against a concentration gradient

Question 12

describe active transport of Na K pump

Answer 12

• Transports two molecules in different directions

1. Na need to be transported out cell + taken up by pump (triggers requirement for ATP)
2. Releases P causing protein to change shape (forcing Na out to extra
   cellular + enabling intake of K ions)
3. K ions don’t require extra energy to enter
4. Once K ions into cell triggers restart of protein

Question 13

if active transport only moves one molecule at a time, which moves multiple

Answer 13

vesicular transport

Question 14

what are the four types of vesicular transport

Answer 14

1. Exocytosis (release from cell)
2. Endocytosis (intake into cell)
   a. Phagocytosis (eat, engulfing particles)
   b. Pinocytosis (drinking)

Question 15

what hormones do not enter cell + have to communicate outside

Answer 15

ones not made of lipid, not steroid

Question 16

define ligand

Answer 16

hormones

Question 17

what ligands bind to membrane + intracellular recent

Answer 17

o Bind membrane receptors or intracellular receptor (steroid/lipid base)
• Peptide hormones bind membrane receptors (e.g. insulin, oxytocin, GH)

Question 18

transition of message to cell steps

Answer 18

1. G proteins (primary proteins) are relays b/w 1st and second messengers
2. When ligand binds: g proteins altered (changes confirmation and releases G proteins)
3. G proteins then active and modify many other proteins

Second Messenger (Cyclic AMP)

Question 19

describe polarisation of membrane

Answer 19

• 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

Question 20

what occurs for an action potential to happen

Answer 20

• 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)

Question 21

what are the phases of cell cycle

Answer 21

1. Interphase (G1, S, G2)

2. Mitosis (prophase, metaphase, anaphase, telophase)

Question 22

how many chromosomes in human cell

Answer 22

• Normal human cell= 46 (23 pairs)

Question 23

what is hap/diploid cell

Answer 23

• A DIPLOID cell has the full complement of chromosomes, a HAPLOID cell has half

Question 24

what occurs at s phase

Answer 24

• In a cell in S phase, each chromosome doubles it’s DNA, forming 2 chromatids, joined by a centromere

Question 25

Describe what occurs at Interphase G1

Answer 25

• Growth and normal cellular activity

Question 26

Describe what occurs at Interphase S

Answer 26

• DNA replication

* 6-8 hours

Question 27

Describe what occurs at Interphase G2

Answer 27

• Brief final preparation for cell division
• 3-4 hours

+ centriole duplicates

Question 28

what occurs at prophase

Answer 28

• Chromosomes condense and become visible
• Nuclear membrane disappears
• Mitotic spindle starts to form from centrioles

Question 29

what occurs at metaphase

Answer 29

• Chromosomes line up on equator

* Spindle is fully formed

Question 30

what occurs at anaphase

Answer 30

• Chromosomes split at centromere

* Chromatids move to each poles

Question 31

what occurs at telophase

Answer 31

• Decondensation of chromatin
• Cytokinesis (cytoplasm pinch off into two separate entities)
• Reform of nuclear membrane and envelope

Question 32

2 steps of translation

Answer 32

1. Enzyme RNA polymerase binds to DNA unwinding it + assembles RNA,
2. Enzymes splice the exons and introns to form mRNA

Question 33

why is U not T

Answer 33

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

Question 34

what is the preRNA parts

Answer 34

a. Sense portions (exons= translated into protein)

b. Nonsense portions (introns= must be removed before translation)

Question 35

describe translation

Answer 35

1. mRNA carries code to ribosome

2. tRNA binds to free amino acid, + tRNA anticodon binds to complementary codon