Specialised cells – Cancer cells and stem cells

Cancer cells

Description

Mutated, invasive cells
Malignant/ Benign
Found in places where cells are constantly dividing

  • stomach lining
  • skin
  • bone marrow (RBC)

Specialisation for survival
They are able to be dislodged and carried around the body through the blood/ lymph (plasma)

Can multiply at an uncontrolled rate
–> compete with healthy cells for survival needs
–> kills off healthy cells

∴ This increases their survival rate

Stem cells

Description

Not specialized

Can be changed to any specialised/ differentiated cell in the body under special conditions
Found in:

  • cord blood (in placenta, umbilical cord)
  • various parts of the adult body (e.g. bone marrow, small intestine’s lining)

Function:

  • The beginning of life  –> Stem cells multiply and change into specialised cells to become a foetus
  • Helps in growth
  • Replaces cells that die off in the body

Under certain conditions, these cells can develop into new organs. This can solve the shortage of organs for transplants and save many lives.

However, they can also be used to “make” a baby artificially. Naturally, this leads to controversy.

For more information: http://learn.genetics.utah.edu/content/tech/stemcells/scintro/

Pictures:

Tumour forming
Formation of cancer cells
Stem cells

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Specialisation in cells

Main idea:

All cells are specialised in order to carry out their functions effectively.

Terms:

Surface area to volume ratio –> not surface area!

Red Blood Cells

Description

Red
Biconcave disc (both sides are concave)
Round
No nucleus
Contains haemoglobin (the oxygen-carrying protein)
Function: Transport oxygen

Specialisation:

Does not have a nucleus and organelles
– Maximises the amount of haemoglobin it can accommodate
– Short lifespan (unable to undergo cell division)

Shaped like a biconcave disc to increase the surface area to volume ratio
– allows more oxygen and carbon dioxide to diffuse into the haemoglobin
∴ Allow the RBC to transport oxygen and remove carbon dioxide from all parts of the body effectively

Root hair cell

Description

No chloroplasts
Large surface area to volume ratio
Long protrusion
Large vacuole –> filled with cell sap
Thin cellulose cell wall
Function: absorb water and mineral salts

Specialization:

(Water and nutrients = WN)

Long protrusion increases the surface area to volume ratio of the cell
– more WN can be absorbed through osmosis.

Narrow protrusion also allows the root hair to absorb WN from hard-to-reach areas.

The large central vacuole and thin cell wall help to draw more water from the soil into the cell through osmosis.

∴ Increase the efficiency and amount of WN absorbed by the cell.

Xylem

Description

empty (hollow)
composed of a thickened wall and lignin
Function: transport water

Specialization:

Hollow, walls thickened and waterproofed with lignin
– Strengthens the vessels
– Allows water to pass through freely
– Strong walls give rigidity and support to the plant’s stems

The pits in the walls allow water to diffuse out of the xylem and into surrounding cells.

∴ Allow for quick and efficient transportation of water to all parts of plant

Ciliated cells

Description:

Finger-like extensions (microvilli) at the top of the cell
Intercellular junction
Function: Allows absorption to take place
Specialization:

Microvilli increase the surface area to volume ratio of the cell

∴ Maximises the amount of digested food absorbed by the small intestine

References:

Structure and Function of red blood cells
http://en.wikipedia.org/wiki/Root_hair
Root hair – large central vacuole’s function
Transport in plants – functions of xylem and phloem
Function of xylem – look at comments section as well
What are ciliated cells?

Functions of ciliated cells – why plants don’t have them

http://en.wikipedia.org/wiki/Microvillus

Revision 1 – Cell quiz

Plant cells –> 1, 5, 8, 9
Animal cells –> 2, 3, 4, 6, 7

Reason: Only cells 1, 5, 8 and 9 have a cell wall, which is found only in plant cells.

Random observations
I think I recognize some of the cells!

No.

Name

1 Guard cells for stomata
2 Red blood cell
3 Sperm
4 Nerve cell
5 (Usual plant cell you see in textbooks)
6 ?
7 Muscle cell
8 Root hair cell
9 The cells surrounding the xylem and phloem

Cells – Scientific terms

Reproduction

Binary fission(Asexual) the cell replicates its DNA and splits into 2 genetically identical daughter cells. Takes place in prokaryotes and certain organelles (e.g. mitochondria)

Budding (Asexual) a new organism develops from an outgrowth of the parent organism and breaks away when mature. It is genetically identical to the parent organism.

————————————————

Mitosis(Asexual) Eukaryotes separating its chromosomes into 2 separate nuclei, and dividing into 2 genetically identical cells with almost the same number of organelles. Similar to binary fission.

Meiosis – (Sexual) The 2 sets of chromosomes in the eukaryote form different combinations of genes; and the eukaryote separates into 4 genetically unique cells.

States

Turgidity – The state of being turgid or swollen, especially due to high fluid content. Turgidity is essential in plant cells to keep them firm.

Cells – Prokaryotes and Eukaryotes

Prokaryotes and Eukaryotes

Prokaryote

Eukaryote

Etymology:
Eukaryote = “good carrier bag” i.e. has a nucleus
Prokaryote = “before carrier bag” i.e. no nucleus

Differences

Prokaryotes

Eukaryotes

Bacteria, archaebacteria Protists (amoeba), plants, animals, fungi
Smaller (< 5μm) Larger ( > 10μm)
Always unicellular Often multicellular, can be unicellular
No nucleus and membrane-bound organelles*HAS organelles –> ribosomes and nucleoid Always has a nucleus and membrane-bound organelles
DNA is circular, without proteins DNA is linear, associated with proteins
Small ribosomes (70S) Large ribosomes (80S)
No cytoskeleton Always has a cytoskeleton
Reproduction by binary fission or budding (asexual) Reproduction by mitosis (sexual) or meiosis (asexual)
In general:Smaller and simpler In general:More advanced and complex

————————————————–

Plant and Animal cells

Similarities:

Both are present:

  •  Nucleus
  •  Cell membrane
  •  Cytoplasm
  •  Endoplasmic Reticulum (Both smooth and rough)
  •  Ribosomes
  •  Mitochondria
  •  Golgi Apparatus
  •  Microfilaments
  •  Flagella –> may be found in some cells

(those in bold are not found in the picture)

Differences:

Feature

Animal Cell

Plant Cell

Shape Irregular (round, elliptical) Fixed (rectangular)
Vacuole One or more small vacuoles (much smaller than plant cells) One large, central vacuole taking up 90% of cell volume
Function of vacuole Store water, ions and waste Store water and maintain turgidity of cell
Plasma membrane Cell membrane only Cell membrane and cell wall
Cell wall
Chloroplast
Plastids
Lysosomes Not confirmed (controversial)
Cilia ✖ (Rare)
Centrioles ✖ (only present in some lower plant forms – ferns, mosses)

—————————————————

Organelles and their functions

Organelle

Function

Nucleus Controls all activities of the cellProtects DNA from interference by separating it from cytoplasm’s activity
Nuclear membrane Allows transfer of material out of the nucleus to the cytoplasm
Chromatin(The contents of the nucleus, made up of DNA and proteins) Strengthen DNA to prevent damage during reproductionControl DNA replication
Cytoplasm A jelly-like substance where most cellular activities occur.Supports and protects organelles.
Cell membrane Separates and protects the interior of cell from the outside environmentSemi-permeable membrane that regulates the movement of substances in and out of cell
Vacuole(works with lysosomes) Stores nutrientsIsolates and exports harmful/unwanted materials in the cell

Plant cells -> contains cell sap

Regulates turgor pressure (i.e. plant’s rigidity) by regulating the amount of water in it

Animal cells

As animal cells are already in an aqueous environment, their vacuoles are not needed to store water and are small

Mitochondria Uses glucose and oxygen to produce energySite of aerobic cellular respiration
Endoplasmic Reticulum (ER) (Works with Golgi apparatus) Transports substances between and within cells.

(a layman’s definition and analogy: http://goo.gl/oS4Ds)

Smooth ER

Removes toxins from the cells

Rough ER

Supports the cell’s shape

Packs synthesized proteins from ribosomes and fats into vesicles and sends them to Golgi apparatus

Ribosomes Site of protein synthesis
Golgi apparatus(Works with ER) Packages proteins and other macromolecules for transport to other parts of the cell or for storage within the cell.
Lysosomes(Works with vacuole) Fuses with vacuole to digest the harmful/unwanted materials insideTransports undigested material to cell membrane for release
Choloroplast Contains chlorophyll for photosynthesis in plants
Cell wall Protects the cell and maintains its shapePrevents over-expansion due to turgor pressure when water enters the cell

References

Pictures:

http://yunzhenandbio.blogspot.sg/2010/02/cells.html
http://imcurious.wikispaces.com/Period+1+Midterm+Review+2009
http://evolution.berkeley.edu/evosite/lines/IIDmolecular.shtml

Information:
Difference between eukaryotes and prokaryotes – pdf file
Difference between eukaryotes and prokaryotes
Difference between eukaryotes and prokaryotes – Yahoo answers
What is Turgidity?
Functions of nuclear membrane
Function of vacuole in an animal cell
Function of endoplasmic reticulum

Interactive Websites about organelles:

http://www.cellsalive.com/cells/cell_model.htm

http://learn.genetics.utah.edu/content/begin/cells/insideacell/

http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm