cells and organelles 1

Question 1

origin of cells

Answer 1

cells originate from preexisting cells.

Question 2

definition of cells

Answer 2

smallest structural and functional unit of an organism.
All organisms are made of one or multiple cells.
Cells are derived from other cells through cell division.

Question 3

advanced cell theory

Answer 3

Capability to generate Energy (metabolism and biochemistry) occurs within cells
=> like glucose being created through glycolysis
Cells carry hereditary materials (DNA)
DNA is transferred from one cell to another.
Cells possesses same basic chemical compositions - same inorganic/ organic molecules

Question 4

cell plasma membrane

Answer 4

• protective sheath that encloses the cell as an independent reaction container.
• separates the intracellular fluid (ICF) from the extracellular fluid (ECF).
• semipermeable membrane
• regulates the exchange of molecules between the ICF and ECF.
• composed of a bilayer of lipid molecules with associated protein molecules.

Question 5

properties of cells

Answer 5

they grow and reproduce (replicate).
Cells have a finite lifespan – they die (by design, age or disease). - red cells = 90 days
Cells internal processes allow them to change, adapt, or respond - cells respond to you taking coke for example increasing glucose levels (different cells performance different function).

Question 6

plasma mobility

Answer 6

restrictive and not uniform
molecules or nutrients get transfered from the intestinal lumen to the basolateral domain to the connective tissue area and into the blood

Question 7

5 major phospholipids

Answer 7

(phosphatidylcholine and sphingomyelin) = outer leaflet of membrane; (phosphatidylethanolamine, phosphatidylserine & phosphatidylinositol) = inner leaflet of membrane.

Question 8

DNA

Answer 8

deoxyribonucleic acid.
chromosomes are carriers of DNA which are wrapped around a particular proteins that are called histones

Question 9

gene

Answer 9

carriers of identity materials

Question 10

when used electronic microscope

Answer 10

100 nm - 1 mm

Question 11

cell membrane= amphipatic molecules

Answer 11

phosphate group = hydrophilic head = water loving on outside and
two hydrophobic fatty acid chains= embedded into cell membrane

Question 12

what is embedded in the cell membrane - fluid mosaic model

Answer 12

not just fluid, proteins
cholesterol.
integral proteins, the phospholipid bilayer and the glycoproteins

Question 13

cholesterol role

Answer 13

cholesterol is embedded into membrane with a polar hydroxyl
to give it rigidity and its therefore not so fluid
1. rigidity
2. fluidity = no stifness

Question 14

phosphatidylserine

Answer 14

phospholipid translocates from the inner cell to the outer cell of the plasma membrane.
And that sends a signal for a dying cell and then a process known as phagocytosis eliminates cell

Question 15

membrane protein groups/ function

Answer 15

integral = transmembrane
peripheral
=> diff functions = receptors/ transporters/ signalling/ adhesion

Question 16

how do molecules get through the cell membrane

Answer 16

=> diffusion = hydrophobic molecules / small uncharged molecules

vs large polar molecules and ions
= membrane transport protein => channel = passive transport => based on concentration/ electrochemical gradient

vs carrier protein => molecules bind to protein, experience transformational change when on receptor binding site and enter => often powered by hydrolysis of AATP

Question 17

types of membrane protein activities

Answer 17

Cell identity markers: membrane proteins that identify the cells of an individual. They are person specific

Linking proteins: gives structure to the plasma membrane, they also hold the cells together and participate in movement.

Enzymes: some membrane proteins are enzymes that drives biochemical reactions at the cell surface level.

Receptors protein: certain proteins on the surface function as receptor for the attachment of specific molecules e.g., hormones or neurotransmitters. Receptors are key in diseases e.g., antibodies and antigens.

Question 18

prokaryotes

Answer 18

• simple, single-celled organism without a nucleus and membrane-bound organelles (e.g., mitochondria).
• spherical, rod-shaped, or spiral
• Simple cell division.
• The genetic materials in the central region = nucleoid -> consists of a single chromosome of a circular DNA.
• Prokaryotes = Bacteria
• Up to a few thousandths of mm (few microns) in size (1 – 10µm).
• Amongst oldest and most abundant type of life on earth (preceded complex cells).

Question 19

membrane bound organelles

Answer 19

have their own membrane
mitochondria, the Golgi apparatus, endoplasmic reticulum

Question 20

eukaryotes

Answer 20

Eukaryotes possesses more complex internal structure and with several chromosomes (DNA molecules) in the nucleus.
Consists of multiple liner DNA molecules.
They have a true nuclear membrane and often contain several specialised organelles e.g., Golgi apparatus, mitochondria, endoplasmic reticulum etc.
They are multicellular organisms.
Most complex eukaryotes are found in human, animals, plants (cytoplasm divided by membrane to enclose compartments/organelles, has a nucleus).
Up to a 10 thousandths of mm in size (10 microns or much more).
Amongst more recent cells to evolve, representing complex cells in multicellular organisms.

Question 21

protein expression eukaryotes

Answer 21

DNA (with its genes) packaged in a central store called a nucleus.
DNA (with its genes) transcribed to produce mRNA (transcription).
Nucleus is enclosed by a double membrane the nuclear envelope (nucleus is one of a number of cell compartments).
mRNA (message) passes from the nucleoplasm to the cytoplasm via holes called nuclear pores.
Nuclear pores are selective aqueous channels for transport between nucleus and cytosol (mRNA passage but also in both directions).

mRNA is decoded and proteins made (translation) on specialised factories called the ribosomes.

Question 22

prokaryotes expression

Answer 22

PROKARYOTES DNA is packaged but not enclosed by membrane.

Question 23

what allows binding of DNA around histones

Answer 23

two amino acids -> lysine + arginine => forms complex = chromatin

Question 24

Chromatin

Answer 24

Chromatin is packaged in two main ways – euchromatin; and more-dense heterochromatin = peripheric.
Most of the active genes are found in the euchromatin = scattered everywhere , inactive ones in heterochromatin.

Question 25

ribosomes

Answer 25

Proteins are made on specialised organelles called Ribosomes.

Ribosomes decode mRNA message and convert it to linear polypeptides (protein).

Many ribosomes remain “free” during protein translation.

Ribosomes have two subunits (small and large subunits).

Question 26

Proteins in the cytosol

Answer 26

bound ribosomes => some proteins have signal sequence which allows them to be recognised and sent to the RER = rough ER + properly folded => sent to golgi = post officer => sent to membrane bound organelle

free ribosomes => others are signal free and go to nucleus, mitochondria, chloroplaste,…

Question 27

Rough Endoplasmic Reticulum functions

Answer 27

Site of membrane synthesis (lipids and proteins)
Modifies proteins – adds sugar chains, trims them (proteolytic cleavage), disulfide bond formation
Quality control e.g., monitors correct folding (unregulated protein synthesis or misfolding - cystic fibrosis) => good protein = go to destination, bad proteins => destruction
Signals stress – e.g., when secretion is blocked/poorly folded proteins.

Question 28

smooth endoplasmic reticulum

Answer 28

lipid synthesis, they have several mechanisms that goes through that particular process along the trunk of the cell membrane.
The smooth endoplasmic reticulum (SER) is free of ribosomes hence smooth when viewed through a microscope. The SER is common in cell types active in lipid metabolism. The SER is involved in:
Lipid synthesis.
No protein synthesis.
Steroid synthesis.
Detoxification.

Question 29

secretion pathway

Answer 29

Vesicles carry “cargo” from RER to the Golgi.

Cargo proteins are processed and sorted in the Golgi.

Some vesicles can bud from Golgi containing packaged (stored) secretory proteins.

Other vesicles bud from Golgi with membrane for the PM (Constitutive vesicles).

Question 30

golgi compartments + rer to golgi

Answer 30

cis/ medal/ trans/ trans golgi network

RER makes membrane and is widely spread through most cells.
Cargo packaged into vesicles (e.g., proinsulin) sent along tracks to the central Golgi complex.
Golgi complex stacks of flattened sacs (found close to the nucleus).
Golgi receives these membrane vesicles + their content (cargo) from RER.

Question 31

golgi degradation role

Answer 31

protein release =late endosomes => lysosomes => protein degradation

Proteins destined for lysosomes are specifically identified and modified by the addition of a phosphate group to the mannose-6-phosphate residues.

Processes and sorts cargo into vesicles specific for the target organelle (plasma membrane, lysosome, outside of the cell (secretion)).

Receives output from RER.

Modifies lipids/proteins – grows sugar chains on proteins/adds phosphate to some proteins.

Sorts and packages cargo into distinct vesicles for export to other organelles (this happens at the exit face of the Golgi)..

Question 32

proteolytic processing of insulin secretory vesicles

Answer 32

pre pro insulin from the mRNA
this is going to be fed into the ER
lumen
cleave off that signal sequence that’s going to be characteristic of any protein in the ER

transported to the golgi - packaged into a vesicle and
then insulin can then be
released into the blood in proportion to
the amount of glucose in the blood
And once that signal is released, then they go into action.

pro insulin modified into insulin