Science Titbits
During centrifugation the bigger particles sediment faster and have higher
sedimentation coefficients (Svedberg, or S values) Sedimentation coefficients are,
however, not additive Sedimentation rate does not depend only on the mass or volume
of a particle, and when two particles bind together there is inevitably a loss of surface
area Thus when measured separately they will have Svedberg values that may not add
up to that of the bound particle This is notably the case With the ribosome. Ribosomes
are most often identified by their sedimentation coefficient For instance, the 70 S
ribosome that comes from bacteria has actually a sedimentation coefficient of 70
Svedberg, although it is composed of a 50 S subunit and a 30 S subunit
Teacher's Point
Teachers would demonstrate all the techniques used in cell biology or show
fiims/slldeshow on screen or monitor of computer.
QI- What are the major differences between animal cell and plant cell?
Ans.' Differences between Animal Cell and Plant Cell:
Animal Cell Plant Cell
, cell wall A cell membrane is the outer A cell wall IS the outer most
most boundary of an annal boundary & a plant cell.
cell Ceil wall is absent
Centrioles Centnoles are present In Centrioles are absent In
annal and lower plant cells higher plant cells
Vacuoles An animal cell may contain A plant cell has one or few
numerous small srzed large sized vacuole
vacuoles
Position of The position of nucleus IS Due to a large vacuole
Nucleus usually central nucleus is pressed aside
towards the cell membrane
Plastids There are no plastids In Plastids are present In plant
ansmal cet! and hence they cells and hence they can
cannot manufacture their manufacture their own food
own food material material.
OR Second Answer
Plant Cell Animal Cell
1. The are iar er In size I. The are smaller in size.
2. Cell wail 's present 2. Cell wall is absent
3. Lysosomes are absent or very few 3. Lysosomes are larger in number
in number
4. Plastids are present 4. Plasttds are absent
5. Subunits of Golgl bodes known as 5- Prominent Golg' bodies are present
dict osomes are present
6. are lar er In size 6 Vacuoles are smaller in Size
Q2. Draw the electron microscopic structure of both animal and plant
cells. Ans:
, Electron microscopic structure of an animal cell
Electron microscopic structure of a plant cell
Q3. What is the difference between cell wall and plasma membrane?
Ans: Difference between cell wall and plasma membrane:
, 1. Cell membrane is also known as plasma membrane or plasma lemma cell
wall IS not
2. Cell membrane IS found In annal cells and cell wall In plant cells
3. Cell wall covers the cell membrane and forms the outer covering
4. Cell membrane IS partially permeable but cell wall IS completely permeable
5. Cell membrane do not contain cellulose cell wall does
6. Cell wall is elastic, cell membrane IS not
7. Cell wall controls turgidity of a cell, plasma membrane does not.
8. Cell wall made up of peptidoglygan is present tn bacteria
9. Celi wall made up of chitin is present in fungi
10. Cell wall is metabolically inactive but cell membrane is metabolically active
Cell wall protects the shape of the cell ang maintains it while cell
membrane protects the cytoplasm and osmotic balance In a cell
OR Second Answer
Basis for Plasma Membrane Cell Wall
Com arison
Meaning Plasma Membrane IS a Cell Wall is a thick r191d
delicate. thin structure of structure of around 4-
around 5-1 Onm Wide and ts 20um Wide and ES VISIble
vtslble under electron under light microscope, it
microscope and it IS present IS present In plant cell
In all types of cell helps In bacterial and fungal cell
the passage of molecules helps in providing sha e
and rotects the roto lasm and rl Idit to the
cell
Presence Plasma Membrane IS present Cell Wall IS present In the
In all types of ceils plant cell, bactena, fungi
and al ae
Composition Made up of lipids and Made up of cellulose (plant
proteins and carbohydrates cell) chitin (fungi) and e tido
I can bacterta
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