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4 years ago

Discuss cell surface transport in the structure of constituents

Biology

1 answer:

nika2105 [10]4 years ago

3 0

Cell surface or membrane is made of phospholipid bilayer with embedded proteins and sugars. Cell membrane acts as a barrier between cell and its external environment but it is also responsible for the communication with other cells and transport of molecules inside and outside the cell. It is selectively permeable to ions and molecules (some of them pass through the membrane easily, while others require transport proteins or channels). There are 4 ways of molecule transport:

1. Diffusion – no energy required

2. Facilitated transport – transport proteins included

3. Active and co-transport – energy required

4. Vesicle transport (exocytosis and endocytosis)

Microvilli are extensions of cell membrane that increase its surface for diffusion.

Different types of cell junctions have a different influence on the membrane transport. For example, tight junctions are a barrier and the molecules are unable to pass through.

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Which of the following hypotheses might Dr Julian make to help answer this question ?

iogann1982 [59]

the choices are Mice live longer lives in the laboratory than in their natural habitats. The lifespan of a mouse is longer if it is a female. or

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3 years ago

Which of the following is a type of technology that can be used at a coal-burning power plant to remove both particulate matter

Gnesinka [82]

The answer is electrostatic precipitator

hope this helps :)

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3 years ago

What must be true in order for individuals best suited for growth and reproduction in a particular environment to contribute dis

11111nata11111 [884]

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4 years ago

For this assignment you will complete an illustration(s) (by hand) of how the lac operon works. You should be sure to include de

Fantom [35]

<h2>Lac operon </h2>

Explanation:

Lac operon present in prokaryotic chromosomes whose product involves in transportation and catabolism of lactose

Lac operon consists of three structural genes called Lac Z,Lac Y and Lac A and a regulatory element(promoter and operator)
Lac I gene is present outside the Lac operon,act as regulatory gene and control the expression of Lac operon genes
Lac Z codes for β galactosidase which converts lactose into allolactose
Lac Y codes for Lac permease which act as a membrane transporter and transport lactose into the cells
Lac A codes for transacetylase which neutralize the toxic effects of lactose

Lac operon in absence of lactose

In absence of lactose Lac operon exists in switch off state
Lac I gene produces Lac repressor which binds to operator region and prevent binding of RNA Polymerase thus blocks transcription

Lac operon in presence of lactose

In presence of lactose Lac operon exists in switch on state
In presence of lactose few molecules of Lac operon enzyme catalyse conversion of lactose to allolactose
Allolactose act as an inducer,binds to the Lac repressor and induce conformational changes causing dissociation of Lac repressor from operator
In absence of Lac repressor RNA Polymerase binds to the promoter and starts transcription of genes which catabolize lactose

Lac promoter is a weak promoter and direct transcription of Lac operon genes in very low level in presence of lactose

For higher level expression of Lac operon genes,operon system require conversion of weak promoter to strong promoter which is always mediated by catabolite protein-cAMP complex(CAP-cAMP complex)
CAP cAMP complex binds to the upstream of promoter called CAP binding site and stimulate expression of Lac operon genes by facilitating binding of RNA Polymerase
Catabolite activator protein(CAP) or cAMP receptor protein(CRP) activate when cAMP binds
cAMP is a secondary messenger synthesized from ATP and act as co-activator of CRP
With respect to CAP cAMP complex Lac operon system is positively controlled
In prokaryotic cell cAMP is very low when glucose concentration is relatively high and vice versa
At high concentration of glucose the growth rate is maximum and lactose catabolism is repressed called catabolite repression

6 0

3 years ago

Which of the following best describes gene flow?

Dimas [21]

I have no straight answer with ABDE as of your lack there-of. But here.

Gene flow is the introduction of genes/alleles between populations. An example is a flower having it´s pollen carried by a bee. The bee then introduces it (intentional or not.) to other flowers.

Another example is a pack of gray wolves suddenly having a different wolf introduced. *As long as it can breed, that is* They will slowly incorporate the new alleles/genes into the pack.

I wish you luck young lad.

7 0

3 years ago