cell structure and CSM

Question 1

which are the membrane bound organelles

Answer 1

Nucleus, (nucleolus, chromatin,) RER SER , GA, mitochondrion, chloroplast, lysosome)

Question 2

descriptions of the nucleus and nucleolus

Answer 2

Nucleus: spherical organelle surrounded by a double membrane( nuclear envelope) perforated with pores and continuous with RER, contains nucleolus and chromatin
nucleolus: contains large amounts of DNA rRNA and protein

Question 3

describe RER and SER

Answer 3

RER: network of membranous flattened sacs called cisternae, has ribosomes on the outer surface; continuous with outer membrane of the nuclear envelope
SER: network of membranous tubular sacs called cisternae, no ribosomes

Question 4

describe golgi apparatus

Answer 4

membrane bound flattened sacs called cisternae

Question 5

describe lysosome

Answer 5

membranous sac containing hydrolytic enzymes

Question 6

desc ribosomes

Answer 6

consists of a large and small subunit. each subunit is made up of protein and rRNA is assembled in the nucleolus, may be found either bound to ER or freely floating in cytosol

Question 7

describe mitochondrion

Answer 7

spherical/rod shaped structure surrounded by a double membrane; inner membrane is highly convoluted with infoldings called cristae; between the membranes is the intermembrane space; cristae project into semi-fluid matriz containing circular DNA, 70s ribosomes, phosphate granules and enzymes for aerobic respiration. atp synthase complex on inner membrane projects into matrix

Question 7

which are the non membrane bound organelles

Answer 7

ribosomes and centrioles

Question 7

`describe chloroplast

Answer 7

lens shaped structure surrounded by a double membrane; internal membrane system consists of flattened sacs called thylakoids and intergranal lamella. fluid within the chloroplast surrounding the grana is called stroma; contains circular DNA, 70s ribosomes, enzymes and starch grains. chlorophyll molecules are located on the thylakoid membrane
atp synthase complex on thylakoid membrane project into stroma

Question 8

desc centrioles

Answer 8

pair of hollow cylinders made up of 9 triplets of microtubules; two rod like cylinders are positioned at right engles to each other; is found in a region called the centrosome

Question 9

what is cell theory

Answer 9

cells are the smallest unit of life, all cells come from pre-existing cells and living organisms are composed of cells

Question 10

what is the endo membrane system

Answer 10

it consists of the nuclear envelope, RER SER GA lysosomes, vesicles and the plasme membrane (its the cellular pathway of the protein synthesis)

Question 10

what is chromatin

Answer 10

hereditary material of the cell; thin elongated threads of DNA coiled around histone proteins
euchromatin is lightly stained and is transcriptionally active
heterochromatin in darkly stained and transcriptionally inactive.

Question 11

what are the functions of the membrane bound organelles (9pts) total

Answer 11

nucleus: To contain the hereditary material ; to control cell activities by regulating protein synthesis; contains enzymes for DNA replication, transcription and RNA processing
(nucleolus: to synthesise rRNA; site of assembly of rRNA and proteins into large and small ribosomal subunits
chromatin: DNA contains genes which undergo transcription in nucleus to form mRNA which then undergo translation at ribosomes to form ppts
RER: to transport proteins which are synthesised on its surface to the GA via transport vesicles; to allow proteins to fold into their native conformation
to glycosylate proteins hence forming glycoproteins
SER: to synthesise lipids and carbohydrates ; to detoxify drugs and poisons; store ca2+ ions
Chloroplast: see more in photosyn
mitochondrion: acts as the site for certain stages of aerobic respiration to generate energy in the form of atp –> see more in respiration
lysosome: to digest material taken in by the cell by endocytosis; to release enzymes from cells by exocytosis for extracellular digestion; to digest unwanted or worn-out organelles ; to induce apoptosis

Question 12

what are the functions of the non-membrane bound organelles

Answer 12

ribosome: act as the site for protein synthesis
centrioles: organise spindle fibres during nuclear division; determine polarity of the cell

Question 13

explain the fluid mosaic model

Answer 13

fluid because the membrane is a dynamic structure where both the ppl and membrane proteins are able to move, mosaic because of the random arrangement of proteins embedded in the ppl bilayer

Question 14

list components of the CSM

Answer 14

ppl bilayer, cholesterol, proteins, glycoproteins and glycolipids,

Question 15

characteristics and functions of ppl bilayer

Answer 15

amphipathic –> hydrophilic interacts with the aq medium and hydrophobic core
it regulates movement of substances by acting as a barrier to charged ions, polar and large molecules
allows compartmentalisation
acts as a boundary

Question 16

characteristics and functions of cholesterol

Answer 16

slightly amphipathic, 4 ring structure –> regulates membrane fluidity; prevents the membrane from being overly fluid at warmer temps by restricting ppl movement and vice versa for lower temps + helps to anchor proteins in the membrane

Question 17

characteristics and functions of proteins

Answer 17

also amphipathic –> function as channels/carrier for facilitated diffusion and AT.
channel proteins have a hydrophilic channel for direct diffusion of ions or molecules across the membrane e.g aquaporins
carrier proteins bind the solute on one side of teh membrane and as a result the protein undergoes a conformational change that allows the access of the solute to the opp side of the membrane e.g glucose transporter ; others are pumps to use ATP to move solutes against a conc gradient
they also function as enzymes, receptor proteins, and stabilise membrane structure

Question 18

outline the function of membranes ate the surface of the cell/ inside the cell

Answer 18

regulate movement of substances as they are a selectively permeable barrier
allow for compartmentalisation
1) unique environments to be formed; spatial separation and accumulation of ions to high concs
surface for chemical reactions
increase SA
enable communication between the cell and its surroundings

Question 18

characteristics and functions of glycoproteins and glycolipids

Answer 18

function as marker sites in cell-cell recognition and adhesion / receptors

Question 19

compare the different types of transport

Answer 19

simple vs facilitate diffusion ; active vs bulk transport
atp requirement: no no yes yes
transport protein requirement no yes yes no
movement across conc gradient down down up anytg

Question 20

definition of simple diffusion

Answer 20

net movement of molecules from a region of high concentration to a region of low concentration down a concentration gradient

Question 21

definition of facilitated diffusion

Answer 21

net movement of molecules from a region of high concentration to a region of low concentration down a concentration gradient through a transport protein

Question 22

definition of active transport

Answer 22

energy consuming transport of molecules or ions across a membrane thru transmembrane carrier proteins called pumps against a conc gradient.

Question 23

how does bulk transport occur

Answer 23

requires ATP –> exocytosis endocytosis; phagocytosis or pinocytosis or receptor mediated endocytosis

Question 24

osmosis is what

Answer 24

diffusion of water thru a selectively permeable membrane