Cell: Eukaryotes

Question 1

who all are the eukaryotes? how are they different from prokaryotes

Answer 1

The eukaryotes include all the protists, plants, animals and fungi. In
eukaryotic cells there is an extensive compartmentalisation of cytoplasm
through the presence of membrane bound organelles. Eukaryotic cells
possess an organised nucleus with a nuclear envelope. In addition,
eukaryotic cells have a variety of complex locomotory and cytoskeletal
structures. Their genetic material is organised into chromosomes.

Question 2

when was the cell membrance studied

Answer 2

The detailed structure of the membrane was studied only after the advent
of the electron microscope in the 1950s. Meanwhile, chemical studies on
the cell membrane, especially in human red blood cells (RBCs), enabled
the scientists to deduce the possible structure of plasma membrane.

Question 3

what is the cell memrance composed of?

Answer 3

phospholipids
proteins
cholestrol
carbohydrates

Question 4

how are phospholipids present

Answer 4

The major lipids are phospholipids that are arranged
in a bilayer. Also, the lipids are arranged within the membrane with the
polar head towards the outer sides and the hydrophobic tails towards
the inner part.This ensures that the nonpolar tail of saturated
hydrocarbons is protected from the aqueous environment

Question 5

what is the composition of cell membrance in eryhtrocyte

Answer 5

The ratio of protein and lipid varies
considerably in different cell types. In human beings, the membrane of the
erythrocyte has approximately 52 per cent protein and 40 per cent lipids

Question 6

how are protiends classified in cell membrance

Answer 6

Depending on the ease of extraction, membrane proteins can be
classified as integral(intrinsic)and peripheral(extrinsic). Peripheral proteins lie on the surface
of membrane while the integral proteins are partially or totally buried in
the membrane.

integral/intrinsic:
fully buried: completely integralted into the cell membrance
partially buried: partially integrated into cell membrane

peripheral extrinsic:
they are lying loosely on the surface of cell memebrane, cn be removed easily.
have enzymatic activity

Question 7

when was the improved cell membrance structure made?

Answer 7

An improved model of the structure of cell membrane was proposed
by Singer and Nicolson (1972) widely accepted as fluid mosaic model
protien icebergs floating in a sea of phospholipids

Question 8

what is fluidity of the membrane? what are its functiosn

Answer 8

According to this, the quasi-fluid nature of lipid enables
lateral movement of proteins within the overall bilayer. This ability to move
within the membrane is measured as its fluidity.
The fluid nature of the membrane is also important from the point of
view of functions like cell growth, formation of intercellular junctions,
secretion, endocytosis, cell division etc.

Question 9

what are carbohydrates

Answer 9

oligosaccharides(chain life structure)
when present on lipids they are called glycolipids
when present of protiens they are called glycoproteins
they act as surface markers on the cell memebrance for cell-tocell recognition
ex: sperm and egg recognition for fertilization
blood groups

Question 10

what are cholestrols

Answer 10

fat molecules intermittent throughout the bilayer
they confer stability to the cell membrance

Question 11

how does plasma membrance allow transpot of molecules

Answer 11

One of the most important functions of the plasma membrane is the
transport of the molecules across it. The membrane is selectively permeable
to some molecules present on either side of it.

Question 12

types of transport

Answer 12

passive transport:
-movement of molecules from high concetration to low concentration along the concentration gradient
-does not require atp

active transport:
-movement of molecules from low to high concentration against the concentration gradient
-requires energy in the form of atp
- na_/k+ pump

Question 13

what are polar and non polar molecules

Answer 13

polar molecules: have an accumulation of charge( glucose/h20)
non polar molecules: do not have charge( vsrbon dioxide and oxygen)

Question 14

how do non polar soluted move across the memebrance?

Answer 14

non polar solutes/neutral solutes move from one side of the membrane to the other via diffusion, since they are small and non polar they face no challenge while moving through the hydrophobic layer

Question 15

how does water move across the membrane?

Answer 15

water is a polar molecule but its extremely small in size and can easily pass through the hydrophobic bilayer through osmosis.
in cells where water permeability is high, water is transported htoruhg specialised protiens called aquaporins

Question 16

how is glucos transported

Answer 16

being large in size and polar molecule, glucose is transported through transport protien embedded in the cell membrane calle GLUT-4

Question 17

why do polar molecules need a protien

Answer 17

As the polar molecules cannot pass
through the nonpolar lipid bilayer, they require a carrier protein of the
membrane to facilitate their transport across the membrane.

Question 18

what are the types of passive transport

Answer 18

diffusion: net movement of substance from a region of high conc to low conc. do not require membrane

osmosis: movement of water molecules from a region of high ocnc to low conc across a semipermeable memebrance

facilittated diffusion: movement of substance from a region of high conc to low conc via protein channel. type ofdiffusion

Question 20

what is arm ratio? who has max?

Answer 20

The ratio of length of the long arm(q) to the short arm(p) of a chromosome is called arm
ratio. Arm ratio is maximum in acrocentric chromosome.