A Level Biology - OCR A at University Of Cambridge | Flashcards & Summaries

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TESTE DEIN WISSEN

What is an enzyme?

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A biological catalyst that interacts with a substrate molecule to facilitate chemical reactions/increase their rates by lowering activation energy. 

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Describe the structure and function of the nucleolus. (2.1 g)

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TESTE DEIN WISSEN

Structure

  • Area inside the nucleus
  • Composed of proteins and RNA


Function

  • Ribosomes necessary for protein synthesis are produced here from RNA, which is used to produce rRNA.
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TESTE DEIN WISSEN

What is used to calibrate the eyepiece graticule and what is it? What is the scale usually?

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TESTE DEIN WISSEN
  • A stage micrometer - a glass slide with a scale on it that is placed onto the microscope stage
  • This scale is usually 2mm long with subdivisions of 10 micrometers apart. 
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TESTE DEIN WISSEN

Laser scanning/confocal microscope

  • Advantages
  • Uses
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TESTE DEIN WISSEN
  • Specimens can be whole and living
  • Depth selectivity
  • High resolution, high contrast


Therefore it is useful in the medical sector for easier diagnosis and quicker treatment, such as with corneal fungal filaments. 


Lösung ausblenden
TESTE DEIN WISSEN

Why stain samples?

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TESTE DEIN WISSEN
  • This helps scientists to distinguish between different cells and cell components - specimens are colourless when cut into thin sections. 


  • Live and dead cells, such as by using eosin, which only stains dead cells, such as sperm. 
Lösung ausblenden
TESTE DEIN WISSEN

Light microscopes

  • Magnification & resolution
  • Advantages
  • Disadvantages
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TESTE DEIN WISSEN
  • Up to x1500/x2000 magnification
  • Resolution of 200nm


Advantages

  • Easy to use, no skill required
  • Cheap 
  • Portable - small and light
  • Living samples

Disadvantages

  • Low magnification and resolution
Lösung ausblenden
TESTE DEIN WISSEN

How is magnification calculated?

Lösung anzeigen
TESTE DEIN WISSEN

Magnification = I/A

I = image size

A = actual size

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TESTE DEIN WISSEN

Which chemical elements make up carbohydrates, lipids, proteins and nucleic acids?

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TESTE DEIN WISSEN
  • Carbohydrates - C, H, O
  • Lipids - C, H, O, N, S, P
  • Proteins - C, H, O, N, S
  • Nucleic acids - C, H, O, N, P
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TESTE DEIN WISSEN

State the functions of membranes within cells. 

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TESTE DEIN WISSEN
  • The formation of vesicle or organelles like mitochondria.
  • Separating organelles from the cytoplasm, e.g. lysosomes separate hydrolytic enzymes from the cytoplasm. 
  • Providing a surface of attachment for ribosomes or enzymes.
  • Control what substances enter and leave organelles.
Lösung ausblenden
TESTE DEIN WISSEN

Define the term ultrastructure.

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TESTE DEIN WISSEN

The features of the cell that can be seen using an electron microscope.

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TESTE DEIN WISSEN

3.3 (a) - Why do plants need a transport system and specialised exchange surfaces?

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TESTE DEIN WISSEN
  • They have a high demand for water and sugars.
  • Sugars cannot be absorbed from the soil and water cannot be absorbed from the air.
  • Thus, they need a transport system to move water and minerals from the roots to the leaves.
  • They also need to move sugars from the leaves to the other areas of the plant.
Lösung ausblenden
TESTE DEIN WISSEN

3.3 (b) (i) - What is transported by the xylem?

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TESTE DEIN WISSEN

Water and minerals

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Q:

What is an enzyme?

A:

A biological catalyst that interacts with a substrate molecule to facilitate chemical reactions/increase their rates by lowering activation energy. 

Q:

Describe the structure and function of the nucleolus. (2.1 g)

A:

Structure

  • Area inside the nucleus
  • Composed of proteins and RNA


Function

  • Ribosomes necessary for protein synthesis are produced here from RNA, which is used to produce rRNA.
Q:

What is used to calibrate the eyepiece graticule and what is it? What is the scale usually?

A:
  • A stage micrometer - a glass slide with a scale on it that is placed onto the microscope stage
  • This scale is usually 2mm long with subdivisions of 10 micrometers apart. 
Q:

Laser scanning/confocal microscope

  • Advantages
  • Uses
A:
  • Specimens can be whole and living
  • Depth selectivity
  • High resolution, high contrast


Therefore it is useful in the medical sector for easier diagnosis and quicker treatment, such as with corneal fungal filaments. 


Q:

Why stain samples?

A:
  • This helps scientists to distinguish between different cells and cell components - specimens are colourless when cut into thin sections. 


  • Live and dead cells, such as by using eosin, which only stains dead cells, such as sperm. 
Mehr Karteikarten anzeigen
Q:

Light microscopes

  • Magnification & resolution
  • Advantages
  • Disadvantages
A:
  • Up to x1500/x2000 magnification
  • Resolution of 200nm


Advantages

  • Easy to use, no skill required
  • Cheap 
  • Portable - small and light
  • Living samples

Disadvantages

  • Low magnification and resolution
Q:

How is magnification calculated?

A:

Magnification = I/A

I = image size

A = actual size

Q:

Which chemical elements make up carbohydrates, lipids, proteins and nucleic acids?

A:
  • Carbohydrates - C, H, O
  • Lipids - C, H, O, N, S, P
  • Proteins - C, H, O, N, S
  • Nucleic acids - C, H, O, N, P
Q:

State the functions of membranes within cells. 

A:
  • The formation of vesicle or organelles like mitochondria.
  • Separating organelles from the cytoplasm, e.g. lysosomes separate hydrolytic enzymes from the cytoplasm. 
  • Providing a surface of attachment for ribosomes or enzymes.
  • Control what substances enter and leave organelles.
Q:

Define the term ultrastructure.

A:

The features of the cell that can be seen using an electron microscope.

Q:

3.3 (a) - Why do plants need a transport system and specialised exchange surfaces?

A:
  • They have a high demand for water and sugars.
  • Sugars cannot be absorbed from the soil and water cannot be absorbed from the air.
  • Thus, they need a transport system to move water and minerals from the roots to the leaves.
  • They also need to move sugars from the leaves to the other areas of the plant.
Q:

3.3 (b) (i) - What is transported by the xylem?

A:

Water and minerals

A Level Biology - OCR A

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