Seminar 4: Exploring Eukaryotes

Question 1

How did the nucleus originate?

Answer 1

Invaginations of plasma membrane around nucleoid of ancient prokaryote.

Question 2

what is primary endosymbiosis?

Answer 2

when a eukaryotic cell engulfs a prokaryote, creating new organelles.

Question 3

describe the process of primary endosymbiosis

Answer 3

• eukaryotic cell engulfs prokaryote via phagocytosis
• vacuole forms around the prokaryote (endosymbiont)
• mutations either in vacuole or bacteria causes vacuole membrane to come apart
• causes endosymbiont to transfer its genetic info to host cell (part of it now)
• more endosymbionts can be made now

Question 4

what is secondary endosymbiosis

Answer 4

product of primary symbiosis is engulfed by another eukaryotic cell & retained by it

Question 5

benefits of cell compartmentalisation

Answer 5

• increase efficiency (many processes can occur at same time)
• increase cell specialisation
• able to concentrate metabolites in defined space

Question 6

what is part of the endomembrane system?

Answer 6

• cell membrane
• nuclear envelope
• ER
• golgi apparatus
• lysosome

Question 7

function of vesicles

Answer 7

shuttle substances b/w components of endomembrane system

Question 8

functions of nucleus (3)

Answer 8

• contain most of cells DNA, site of DNA replication
• where gene transcription is turned on/off
• nucleolus: where ribosomes are assembled from RNA & proteins

Question 9

functions of cytoskeleton (4)

Answer 9

• controls & maintain cell shape
• facilitates cell movement
• maintains intracellular organisation
• interacts w/ extracellular structures

Question 10

SER function (4)

Answer 10

• chemically modifies small molecules taken in by cell that may be toxic (make them more polar to be easily removed)
• site for glycogen degradation (animals)
• site where lipids & steroids are synthesised (+ some polysacc in plants)
• stores Ca2+, trigger cell responses when released

Question 11

RER function (3)

Answer 11

• prod most membrane bound proteins
• chemically mod & alter protein func, “tag” for delivery in/out of cell
• transport proteins > golgi (cis face)

Question 12

golgi apparatus func (5)

Answer 12

• receives protein (in vesicles) from RER
• mod, concentrates, sorts & packages proteins to their destination
• adds carbs to proteins, mods other carbs attached to them
• synthesis of SOME polysacc in plants
• cuts large precursor proteins from RER > smaller, func, fragments

Question 13

order of transport from ER

Answer 13

ER>cis-Golgi>medial-Golgi>trans-Golgi>cell membrane OR lysosome

Question 14

lysosome func (2)

Answer 14

• breakdown waste & foreign materials, engulf via phagocytosis
• contain digestive enzymes

Question 15

autophagy is the…

Answer 15

programmed destruction of cell components

Question 16

describe the structure of mitochondria (3)

Answer 16

• smooth outer membrane
• folded inner membrane, cristae (increases SA)
• mitochondrial matrix (enclosed by inner)

Question 17

desc chloroplast struc (2)

Answer 17

• 2 membranes
• stacks of granum (thylakoid, contain chlorophyll)

Question 18

peroxisomes function (2)

Answer 18

• accumulate toxic products (hydrogen peroxide)
• break it down without mixing w/ other parts of cell

Question 19

vacuoles function (4)

Answer 19

• contain pigments for reproduction (flowering plants)
• contain molecules for digestion
• store toxic molecules & waste prod
• give cell its structure

Question 20

list the components of the cytoskeleton (3)

Answer 20

• microfilaments
• intermediate filaments
• microtubules

Question 21

role of microfilaments (2)

Answer 21

• help entire cell/parts of it move
• determine & stabilise cell shape

Question 22

role of intermediate filaments (2)

Answer 22

• anchor cell structure in place (help maintain position of nucleus & other organelles)
• resist tension, maintains rigidity in body surface tissues (stretch cytoplasm, connect desmosomes)

Question 23

role of microtubules (2)

Answer 23

• form rigid internal skeleton for some cells
• act as framework, motor proteins move structures w/in cell

Question 24

what are microfilaments made of?

Answer 24

actin protein subunits

Question 25

what are microtubules made of?

Answer 25

alpha tubulin & beta tubulin

Question 26

what are intermediate-filaments made of?

Answer 26

diverse grp of proteins (depends on cell type, e.g keratin - epithelial cells, neurofilaments - nerve cells)