(02) Cell Structure and Function Intro Flashcards
Three principles of cell theory
- All living organisms are composed of one or more cells
- the cell is the basic unit of structure and organisation
- All cells arise only from pre-existing cells
prokaryotic and eukaryotic cells both have:
plasma membrane
cytosol
DNA
RNA
protein
ribosomes
difference between prokaryotic and eukaryotic cells
eukaryotic cells have Membrane-bound organelles
prokaryote cells lack a membrane- bound nucleus
define cytoplasm
everything inside the plasma membrane including organelles but NOT including the nucleus
define cytosol and its composition
the fluid portion of the cytoplasm
water + dissolved ions, ATP, protein, lipids
name the organelles in the endomembrane system
Nucleus
Endoplasmic Reticulum (smooth + rough)
Golgi apparatus
Lysosomes
name the six major organelles
nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Mitochondria
Ribosomes
define plasma membrane
a selectively permeable barrier controlling the passage of substances in and out of the cell
what makes up the plasma membrane
phospholipid bilayer with embedded proteins
parts of a phospholipid
hydrophilic polar heads (phosphate)
hydrophobic lipid tails (fatty acids)
define amphipathic
having both hydrophilic and hydrophobic regions
what are integral proteins
proteins embedded (partially or fully) into membrane
define transmembrane proteins
integral membrane proteins that fully span membrane
contact both extracellular and cytoplasmic areas
name the six cell specific dynamic repertoire of plasma membrane proteins
transport
enzymatic activity
signal transduction
cell-cell recognition
intercellular joining
attachment (to cytoskeleton and ECM)
define transduction
the process of moving genetic material
how does cell-cell recognition work?
use of glycoproteins (carb + plasma membrane protein) as molecular signature on extracellular side
how do PM proteins help attachment to cytoskeleton and ECM
eg. fibronectin mediates contact between cell surface integrals and ECM
define membrane
a mosaic of molecules in a fluid bilayer of phospholipids
(the fluid mosaic model)
structure of the nucleus
enclosed by double lipid bilayer = nuclear envelope
continuous with rough ER
nuclear pores - for entry / exit
Nucleolus in centre
network of chromatin
what is chromatin
a mixture of DNA and proteins that form chromosomes
functions of the nucleus
house/protect DNA
make rRNA and assemble ribosomes
pores regulate movement of substances (protein, mRNA)
molecule segregation allows temporal and spatial control of cell function
what are ribosomes
made of ribosomal RNA (rRNA) and proteins
the site of protein synthesis (translation) in the cell
reads messenger RNA
storing DNA in the nucleus - structure
DNA wrapped 2x around a group of 8 histones
–> nucleosomes
many nucleosomes –> chromatin
most of the time, DNA is present as chromatin and chromatin fibres
structure of chromosomes
as cell prepares for cell division, chromatin –> chromatin fibres –> loops –> chromosomes
comprises many genes
what is a gene
a DNA segment contributing to phenotype / function
describe the structure and location of ribosomes
two subunits - large and small
subunits assemble in nucleolus and leave through nuclear pores
either:
free in cytoplasm (making proteins for cytosol)
OR attached to RER
what is endoplasmic reticulum
an extensive network of tubes and tubules stretching out from the nuclear membrane
two types: rough / smooth
describe the structure / location of rough endoplasmic reticulum
continuous with nuclear envelope
dotted with RIBOSOMES
function + processes of rough endoplasmic reticulum
ribosomes –> production of secreted, membrane and organelle proteins
proteins enter lumen within RER for folding
RER membrane surrounds protein –> transport vesicles destined for the Golgi
structure and location of smooth endoplasmic reticulum
extends from the rough ER
LACKS ribosomes
I think it looks a bit like coral
functions of smooth ER
very cell/tissue type specific - hence functions vary greatly
housing unit for (cell specific) proteins and enzymes
synthesises lipids (incl steroids and phospholipids)
function of Golgi apparatus
modify, sort, package and transport proteins received from the rough ER using enzymes
formation of secretory, membrane and transport vesicles
structure of Golgi apparatus
made up of 3-20 flattened membranous sacs = cisternae
stacked on top of one another
cis face = receiving side
trans face = shipping side
what are lysosomes
vesicles formed from Golgi membrane
contains powerful digestive enzymes - hence VERY ACIDIC
main functions of lysosomes
digests / destroys substances that enter a cell, cell components, entire cells
define autophagy
digestion of cell components (by lysosomes)
(for removing damaged organelles or misfolded proteins)
define autolysis
cell self-destructs due to injury / dying tissue
(esp in lysosomes)
describe the structure of mitochondria
outer membrane
inner membrane, with folds called cristae
matrix = fluid filled interior cavity
mitochondria carry a separate ……
a separate small (37 genes) genome encoding mitochondrial specific products
ATP hydrolysis equation
ATP –> ADP (adenosine diphosphate) + phosphate
+ Energy (released)
name the three types of filaments in the cytoskeleton and their diameters
microfilaments - 7nm
intermediate filaments - 8-12nm
microtubules - 25nm
describe the structure of protein in microfilaments
actin molecules assembled in two long chains, twisted around each other
found in the periphery of interior cell
assembled and disassembled as required = DYNAMIC
function of microfilaments
bears tension + weight
anchors cytoskeleton to PM proteins
functions and features of intermediate filament
bears tension and weight throughout cell
scaffolds cellular organelles
keratin
MOST PERMANENT - less dynamic
describe the structure of microtubules
tubular structure - 25nm, centre lumen 15nm
made of coiled TUBULIN dimers (alpha and beta)
branched from centrosome
assembled and disassembled as required - DYNAMIC
functions of microtubules
supports cell shape / size
guides movement of organelles (eg. vesicles from Golgi to membrane)
chromosome organisation - cell division
movement of cilia / flagella
