# 7 Flashcards
Smallest cell Mycoplasma size
diameter between 0.1 and 1.0 μm
Typical bacteria size
1-5 μm in diameter.
Ten times the size of the mycloplasms .
Eukaryotic cell size
10-100 μm in diameter
In order to stay alive, cells exchange resources, waste, and energy with their environments. This exchange happens across the cell membrane. As the volume of a cell increases, the ratio of surface area to volume decreases, making these exchanges less efficient. Some cells have folds in their membranes, which increase their surface area to volume ratio.
As a cell grows in size, the surface area gets bigger, but the volume gets bigger faster.
Surface area of volume is critical.
Why does smaller cell has grater ratio of surface area to volume?
As a cell increases in size,its surface area grows proportionately less than its volume .
(Area is proportional to a linear dimension squared,whereas volume is proportional to the linear dimension cubed)
Microvilli
increases surface area without an appreciable increase in volume.
Nucleus from in to out ….
Nucleolus
Chromatin
Nuclear Envelope
Nucleolus
non-membranous structure involved in production of ribosomes; a nucleus has one or more nucleoli.
Chromatin
material consisting of DNA and proteins;visible in a dividing cell as individual condensed chromosome.
Nucleus Envelope
double membrane enclosing the nucleus perforated by pores continuous with ER
Ribosomes
Bound in nuclear envelope
Golgi Apparatus
Organelle active in synthesis,modification ,sorting ,and secretion of cell products.
Centrosome
Region where microtubules are initiated ;contains a pair of centrioles.
Cell wall
Outer layer that maintains cells shape and protects from mechanical damage . made of cellulose ,other polysaccharides and proteins
Plasmodesmata
Cytoplasmic channels through cell walls that connects the cytoplasm of adjacent cells
Chloroplast
photosynthetic organelle,converts energy of sunlight to chemical energy stored in sugar molecules
Central vacuole
Prominent organelle in older plants cells;functions include storage ,breakdown of the waste products, and hydrolysis of macromolecules;enlargement of the vacuole is a major mechanism of plant growth.
Most of the genes are located in Nucleus
Yes some are in mitochondria and chloroplast
Nucleus size
5 μm in diameter
Nuclear envelope is a double membrane .The two membrane ,each lipid bilayer with associated proteins are separated by the space
20-40 nm.
Envelope pore structure
100 nm in diameter
Pore complex
An intricate protein structure lines each pore and plays an important role in the cell by regulating the entry and exit of proteins and RNA’s,as well large complexes of macromolecules
except the pores the nuclear side of the envelope is line by the nuclear lamina[net like array of proteins filaments in animal cells called as intermediate filaments that helps in maitaining shape of the nucleus by mechanically supporting the nuclear envelope]
The nuclear lamina with its nuclear pores forms the outer boundary of the nuclear matrix
Nuclear matrix
a framework of proteins fibers extending throughout the nuclear the nuclear interior .
Function of nuclear envelope and matix
may help organize the genetic material so it function efficiently.
A prominent structure within the Non dividing nucleus is
Nucleolus which appears as a mass of densely stained granules and fibers adjoining part of chromatin.
rRNA is synthesised in
Nucleolus
No of nucleoli depends on
The species and the stage in cell’s reproductive cycle.
Functions of the nucleoli
controlling cell division
the life span of the cell
Is ribosomes considered as organelle
No since it is not double membrane
Chromatin
DNA associated with proteins
Ribosomes synthesis and assembly
NUCLEOLUS
REFER PG NO 173
REFER PG NO 173
Is bound and free ribosomes are structurally identical
YES
Most of the proteins are made up of
free ribosomes function within cytosol.
Eg: enzymes that catalyze the first step of sugar breakdown
Bound ribosomes
generally makes up proteins that are destined for insertion into membranes,for packaging within certain organelles such as lysosomes or for the export from the cell[secretion]
Pancreases that secrete digestive enzymes has bound ribosomes.
Ribosomes
complexes of rRNAs and proteins
Does ER has cisterna and lumen
Yes
Functions of Smooth ER
Functions in the diverse metabolic processes,which varies in cell type.These process includes
1.synthesis of lipids
2.metabolism of carbohydrates
3.detoxification of drugs & poisons
4.Storage of calcium ions
Functions of enzymes of SER
1.Synthesis of lipids
2.oils,Steroids New membrane phospholipids
Among steroids in animals the SER produces sex hormones and adrenal glands.
Hence testes or ovaries are more in SER
Functions of RER
secretes proteins that are produced mainly by ribosomes attached to RER.
As a polypeptide chain grows from the bound ribosomes,the chain is threaded into the ER lumen through a pore formed by the protein complex in the ER membrane.
The new polypeptide folds into its functional shape as it enters the ER lumen.
Most secretory proteins are Glycoproteins,proteins with carbohydrates covalently bonded to them.
Carbohydrates are attached to the proteins in the ER lumen by enzymes built into the ER membrane.
Additional Functions
In addition to making secretory proteins, RER is a membrane factory for the cell ;it grown by adding membrane proteins and phospholipids to its own membrane.As polypeptides destined to be membrane proteins grow from the ribosomes,they are inserted into the ER membrane itself and anchored their by their hydrophobic portions.
Like the SER, the RER also makes membrane phospholipids;enzymes built into the ER memorandum assemble phospholipids from precursor cells in the cytosol. The ER membrane expands,and portions of it are transferred in the form of transport vesicles to other components of the endomembrane system.
Functions of golgi apparatus
Warehouse of receiving ,sorting,shipping,and even some manufacturing.Products of the ER such as proteins are modified and stored and then sent to other destinations.
extensive in cells specialized for secretions.
Lysosomal enzymes works best in
The acidic environment found in lyzozomes
What happens if lysosomes leaks its content
Nothing happens as cytosol is neutral pH.
[BUT EXCESSIVE LEAKAGE CAN DIGEST WHOLE CELL]
Hydrolytic enzymes and lysosomal membrane are made by
RER and transferred to the Golgi apparatus for further processing
How does lysosomes protect themselves from destruction ?
The 3D shape of the proteins protect the vulnerable bonds of the enzymatic attack.
Lysosomes carry intracellular digestion
Phagocytosis
Autophagy
lysosomes use their own hydrolytic enzymes to recycle the cells’s own organic material.This helps in renew the cells into new cells .eg.human liver cells recycles half of its macromolecules each week.
Vacuoles
Large vesicle derived from ER and GA thus they are integral part of the endomembrane system
Is vacuole and cytoplasm has the same solution composition
NO since vacuole is selective in transport
Food vacuoles
Contractile vacuoles
phagocytosis
pumps excess water out of the cell thus maintaining a suitable concentration of ions and molecules inside the cell.
Central vacuoles
Solution inside the central vacuoles is cell sap stores inorganic ions including potassium and chlorine.
Central vacuole function
plant growth as it absorbs water
Chloroplasts and mitochondria
Double membrane
evolutionary relations
contains ribosomes and circular dna[inner membrane]
autonomous
Mitochondria outer membrane is _____ and inner membrane is convoluted
Smooth
convoluted called cristae
Matrix of mitochondria contains
DNA and enzymes
Folding of cristae helps in
More surface area hence enhancing the productivity of cellular respiration
Size of the mitochondria
1-10 μm long
Mitochondria is also called as
power grid in skeleton muscles
Chloroplasts size
3-6 μm in length
Inner-membranous system contains
flattened interconnected sacs called thylakoids
Granum
thylakoids stacked
Stroma
Fluid outside thylakoids
Stroma contains
chlroplasts dna
robosomes
enzymes
Three compartments of chloroplast are
inter membrane space
stroma
thylakoid space
Compartmentelisation helps in
This organisation helps in converting light energy into chemical energy
Do mitochondria and chloroplast mobile
Yes they can change shapes and move inthe tracks of cytoskelton
Plastids
The chloroplast is specialized member of a family of closely related plant organelle
amyloplast
chromoplast
colorless;stores starch[particularly roots and tubes]
pigment[orange and yellow hues]
Peroxisomes
specialized metabolic compartment;single membrane
Function of peroxisomes
contains enzymes that removes hydrogen atoms from various substrate and transfer them to oxygen producing hydrogen peroxide[H2O2] as by-product.
H2O2 is itself toxic but
converts it to water
specilized peroxisomes
glyoxysomes
found in fat storing tissues of plant seed ; converts fatty acids into sugar and carbon hence produce energy until it makes photosynthesis
Cytoskeleton
network of fibres that organizes structures and activities in the cell…..support and motility
Cytoskeleton is more dynamic than an animal skeleton . TRUE/FALSE
True
Three main fibres that makes cytoskeleton
Microtubules > intermediate filaments> microfilaments[actin filaments]
Microtubules [tubulin polymers]
Hollow tubes —–structure
25 nm with 15-nm lumen —-diameter
Tubulin,dimer consists of alpha tubulin and beta tubulin—–protein sub-units
Main function of microtubules
Maintenance of cell shape;
cell motility;
chromosome movement in cell division;
organelle movements
Microfilaments[actin]
Two intertwined strands of actin —structure
7 nm —-diameter;
Actin —-protein sub units
Main function of microfilaments
Maintenance of cell shape;
changes in the cell shape;
muscle contraction;
cytoplasmic streaming[plant cells] ;
cell motility;
cell division[animal cells]
Intermediate filaments
Fibrous proteins coiled into cables—-structure
8-12 nm—diameter;
one of several different proteins[including keratin]— protein subunits
Main function of Intermediate filaments
Maintenance of cell shape;
anchorage of nucleus and certain other cellular organelles;
formation of nuclear lamina;
All eukaryotic cells have microtubules
True
Microtubules,hollow rod constructed from_______
Globular proteins called Tubulins.
Tubulin
Each tubulin protein is a dimer, amolecule made up of two componenets.
a tubulin dimer consists of two slightly different polypeptides, alpha and beta tubulin.
can microtubules be dismantled
Yes and form elsewhere with the help of tubulin dimers
Why two ends of microtubules are different ?
one end can accumulate or release tubulin dimers at much higher rate than other,thus growing and shrinking significantly during cellular activities. this is called plus end,not because it can only add tubulin proteins but because it is the end where both’‘on’’ and ‘‘off’’ rated are much higher.
Main function of microtubules
shape and support the cell and also serves as tracks along which organelles equipped with motor proteins can move.
it guides vesicles from the ER to the golgi apparatus and from the golgi to plasma membrane.
involved in the separation of chromosomes during the cell division.
In animal cells, microtubules grow out from the
Centrosome[located near the nucleus]
Microtubules functions as
compression resisting girders of the cytoskeleton
Centrioles
Within centrosome there are pair of centrioles each composed of nine sets of triplets microtubules arranged in a ring .
Does every eukaryotic cells has centrosomes ?.
No even though animals has cells has many other eukaryotic cells lack centrosomes they organize microtubules by other means
cillium based signaling function
Brain function and embryonic development
What is common in cillia and falgellum
9+2 arrangements
if non-motile 9+0
Modified centrioles
Basal body 9+0 [sperm’s flagellum enters the egg and become centriole]
How does microtubules assembly produce the bending movements of flagella and motile cilia?
Bending involves larger motor proteins called dyneins.[use ATP]
Microfilaments are solid rods
made of actin,globular protein
Main function of microtubules are
bear tension [pulling force]
this network gives the outer cytoplasmic layer called cortex .
well known for cell’s motility
Is microfilaments and microtubules present in all eu cells
yes
thin actin and thick myosin helps in
muscle contraction
Intermediates filamnets
larger than microfilaments
smaller than microtubules
intermediate filaments are present in
only in cells of some animal esp vertebrates
function
Bearing tension
Proteins subunits in intermediate filaments include
Keratin
Intermediate filamnets are
consistent in diameter and composition
Intermediate filaments are
Permanent fixtures unlike micro-tubules & filaments which re-assemble and disassemble,
even after cells die this network often persists like skin dead cells keratin .
often considered ad permanent framework of the entire cells unlike other cytoskeleton components. eg nucleus sits in the cage made of intermediate filaments .
nuclear lamina made of Intermediate filaments.
Extracellular structure of plant cells is
Cell wall
Middle lamina rich in
pectin
The most abundant glycoprotein in extracellular matrix in animal cells is
Collagen…..strong fibres outside the cell
40 % of proteins are collagen
true
