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BIOLOGY > CELLS > Flashcards

CELLS Flashcards

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1
Q

What is the cell surface membrane and what is it’s function?

A
  • Semi-permeable boundary between the cell and it’s environment.
  • Regulates what goes in and out of the cell
  • Structure is mainly made of phospholipids
  • It’s flexible and self-sealing
  • Has a width of 7-10 nm
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2
Q

What does the nucleus contain?

A
  • The nucleus contains DNA which is present as linear chromosomes and has proteins called histones attached.
  • Contains one or more nucleolus
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3
Q

What does the nucleus control?

A

Cell functions and cell division

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4
Q

What is a gene and it’s function in the nucleus?

A

A gene is a short section of DNA that codes for protein.
An mRNA copy of the gene moves out of the DNA and attaches to the ribosomes which is called chromatin.
At cell division it condenses and individual chromosomes become visible.

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5
Q

How large is the nucleus?

A

6 micrometers in diameter surrounded by a nuclear envelope which has nuclear pores of 40 nm

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6
Q

What is transcription?

A

The process of turning DNA into RNA.

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7
Q

What is RNA?

A

It’s like DNA but is single stranded instead of double stranded.

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8
Q

What is the nucleolus?

A
  • Changes rDNA to rRNA
  • rRNA associates with protein in the nucleolus to form ribosomes
  • Looks like a dark circular structure in the nucleus
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9
Q

What is the structure of the ribosomes?

A
  • Made of a large and small subunit
  • 60% is ribosomal RNA
  • 40% ribosomal proteins
  • 25 nm or 80s
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10
Q

What is the function of the ribosomes?

A

It’s function is to synthesize proteins.

The mRNA copy of this gene is associated with ribosomes and ribosomes decodes it when making proteins.

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11
Q

Where are ribosomes located?

A
  • In the cytoplasm where it makes cytoplasmic proteins.
  • In the rough endoplasmic reticulum where ribosomes make proteins which can be secreted from the cell or used for other organelles
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12
Q

What is the rough endoplasmic reticulum?

A
  • Flattened membranous sacs that extends from the nuclear envelope.
  • It is abundant in cells which secrete proteins or which are growing rapidly and the ribosomes attached make proteins
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13
Q

What is the function of the smooth endoplasmic reticulum?

A

To make lipids and steroids eg sex hormones like testosterone and oestregen.

It is abundant in cells producing lipid secretions eg sebaceous glands in skin, liver and testis

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14
Q

What happens in the golgi?

A

Proteins and lipids from the smooth endoplasmic reticulum pass through the golgi and some proteins are folded at the golgi.

Some proteins are modified and sorted in the golgi.

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15
Q

What are the two different types of cell division and what’s the difference between the two?

A

Mitosis produces two daughter cells with the same number of chromosomes as the parent cells whereas meoisis produces four daughter cells with half the number of chromosomes as the parent cells.

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16
Q

What are triglycerides?

A

Tryglycerides are a type of lipid that are mainly used in energy storage molecules.

17
Q

How are tryglycerides formed?

A

Triglycerides are formed by the condensation reaction of one glycerol and three molecules of fatty acids

18
Q

What type of bond is formed within tryglcerides?

A

Ester bonds are formed between the glycerol and fatty acid chains. One water molecule is released per ester bond. So three water molecules are released per tryglyceride formed.

19
Q

What is the difference between mono-unsaturated, saturated and polyunsaturated?

A

If there is no double carbon-carbon bond the fatty acid is saturated, if there is one double bond between the carbons it’s mono-unsaturated and if more than one double bond is present it’s polyunsaturated.

20
Q

Why is the fatty acid saturated with no double carbon bonds?

A

Because all the carbon atoms are linked to as many possible number of hydrogen atoms, so they are saturated with hydrogen atoms.

21
Q

How are triglycerides structured for their purpose?

A
  • They are an excellent source of energy
  • They have a low mass to energy ratio meaning they can be stored in a small volume which reduces the mass animals have to carry as they move around.
  • Their insoluble in water so their storage doesn’t affect osmosis in cells
  • When they are oxidised they provide an important source of water especially in organisms in dry deserts
22
Q

What are the two different types of lipids?

A

Triglycerides and phospholipids.

23
Q

What is the structure of a phospholipid?

A

Phospholipids have two fatty acid molecules and one phosphate molecule. The fatty acid molecules are hydrophobic whereas the phosphate molecule is hydrophillic ( it attracts to water) this means it’s made up of two parts:

Hydrophollic head and the hydrophobic tail.

24
Q

Why are phospholipids polar?

A

Because they have two ends that behave differently.

25
Q

How is the structure of phospholipids related to it’s properties?

A
  • In aqueos environments, phospholipids form a bi-layer within cell-surface membranes which results in a hydrophobic barrier between the inside and outside of the cell.
  • The hydrophilic phosphate heads help to hold the surface of the cell surface membrane
  • The phospholipid structure allows it to form glycolipids by binding with carbohydrates within the cell-surface membrane which are important in cell recognition.
25
Q

How is the structure of phospholipids related to it’s properties?

A
  • In aqueos environments, phospholipids form a bi-layer within cell-surface membranes which results in a hydrophobic barrier between the inside and outside of the cell.
  • The hydrophilic phosphate heads help to hold the surface of the cell surface membrane
  • The phospholipid structure allows it to form glycolipids by binding with carbohydrates within the cell-surface membrane which are important in cell recognition.
26
Q

What is the test for lipids and how is it carried out?

A

The emulsion test:

  • Take a completely dry, grease free tube and add 2cm^3 of the sample being tested and 5cm^3 of ethanol
  • Shake the tube thoroughly to dissolve any lipid in the sample.
  • Add 5cm^3 of water and shake thoroughly

A milky white emulision becomes visible if lipid is present. As a control use water instead of the sample.

BIOLOGY (8 decks)

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