Cell specialisation and differentiation

What if the function of a muscle cell?

They contract for movement

How is a muscle cell adapted for its function?

They have lots of **mitochondria** which provides energy / ATP for contraction

Describe how the xylem is adapted for carrying water and mineral ions around a plant.

• Cells are dead- allows water to move through freely

• they have no organelles- creates more space for water to flow through/ more water can go through

• form hollow tubes- continuous flow of water

• walls are strengthened (with ligning) / thickened - prevents the vessels from collapsing undress high pressure/stress

Describe the process by which bacterial cells divide.

* the process is called **binary fission**
* organelles double
* cytoplasm divides'/ cell walls form around each cell
* two genetically identical daughters are produced

One bacterium divides 5 times. How many bacteria are there now?

32

How is the nucleus of a mucle cell is different from the nucleus of a sperm cell ?

* the nucleus of a sperm cell contains half the number of chromosomes /contains one set of chromosomes
* sperm cell contains 23 chromosomes/muscle cell contains 46 chromosomes
* sperm cell is haploid and a muscle cell is diploid

Adaptations of a sperm cell that enables it to carry out its function

• Has a tail/ flagellum that enables it to swim (toward the egg)

• Contains many mitochondria to release energy for movement

• Contains enzymes (the acrosome) to penetrate/ enter the egg

• Haploid nucleus/ 23 chromosomes so chromosome number doesnt double at fertilisation

• has a streamlined shape for faster movement towards the egg

What happens when a cell differentiates?

* It develops different sub-cellular structures / a particular shape/ makes the proteins it needs
* It becomes specialized which enables it to carry out its certain function

Compare the process of differentiation in plants and animals

Differentiation in animals occurs early in development/ at an early stage

Plants retain the ability to differentiate/have unspecialised cells capable of forming any cells required to mature

Why does procaryotic/bacterium cells not have mithochondria?

Mithochondria is larger than bacteria cells

bacteria cells are small so aerobic respiration can occur in the cytoplasm/cell membrane

Why would the failure to development of root hair cell of a plant root could be catastrophic?

* The purpose / function of the root hair is to increase surface area;
* For absorption of water (by osmosis);
* (And) for absorption of mineral ions (e.g. magnesium ions, nitrate ions);
* Less root hairs would reduce absorption;
* Water is essential for photosynthesis / maintaining pressure / as a solvent;
* (Reduced absorption) could lead to mineral deficiencies, causing stunted growth

Describe how cell specialisation reasults in a zygote developing into a baby

* The single cell / fertilized egg divides by mitosis
* different cells are required to form different tissues
* cells in the embryo differentiate or develop/synthesize different organelles/shapes (for their function)

Explain the role of diferentiation in the development of root hair cells which allows them to carry out their specific function in plants

• Differentiation determines cell shape and the development of specific organelles (to allow them to carry out a particular function)

• Root har cells uptake water and mineral nutrients for the plant which is passed through the xylem.

• Root cells grow extensions / root hairs to give a large surface area to colume ratio which allows to maximise uptake of water by osmosis

• THey also develop many mithochondria to provide energy for active transport of mineral ions

• a large vacuole for storage of water and minerals to maintain a concentration gradient (for continious uptake of water by osmosis

• root hairs cells do not have chloroplasts as they do not photosynthesize

How does starch found in the roots of grass support growth?

* Glucose is stored as starch in plants
* Energy is released from glucose in respiration
* Energy is required for growth / building of new molecules **or** energy is required for active transport of mineral ions and nitrates into the roots