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Biology AS > Cells - Cell Structures > Flashcards

Cells - Cell Structures Flashcards

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1
Q
A
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2
Q

Define magnification

A

By how much an image is enlarged under a microscope. It is controlled by the power of the lens used

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3
Q

Define resolution

A

The minimum distance between 2 objects at which a microscope can distinguish them as separate entities

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4
Q

What are the 2 types of electron microscope?

A

Transmission Electron Microscope

Scanning Electron Microscope

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5
Q

What are the benefits of Transmission Electron Microscopes?

A

Higher magnification than scanning and light

High resolution due to shorter wavelength of electrons

Focuses using a condenser electromagnet

Produces a 2D photomicrograph

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6
Q

What are the limitations of a Transmission Electron Microscope?

A

Cannot look at living cells

Must be in a vacuum

Must be a thin specimen

Complicated preparation may create an artefact

Does not produce a colour image

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7
Q

What are the benefits of a Scanning Electron Microscope?

A

Higher magnification than light

Specimen doesn’t need to be thin

Focuses using a condenser electromagnet

Produces 3D images using computer analysis

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8
Q

What are the limitations of a Scanning Electron Microscope?

A

Cannot look at living cells

Must be in a vacuum

Complicated preparation may create an artefact

Does not produce a colour image

Lower resolution than a TEM

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9
Q

Explain the process of cell fractionation

A

Cells are placed in a cold, buffered, isotonic solution:

  • cold to reduce enzyme activity that could damage organelles
  • buffered to maintain constant pH and prevent protein damage
  • isotonic to prevent cell organelles bursting/shrinking
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10
Q

Explain the process of Homogenisation

A

Cells are broken up by a homogeniser to release organelles

Blended tissue is filtered through a sieve to remove insoluble material eg cell walls, connective tissue

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11
Q

Explain the process of centrifution

A

Filtrate is placed in a centrifuge and spun at a low speed

Heaviest organelles (eg nuclei) are forced to the bottom and form a thin pellet which is removed

Fluid at the top (supernatant) is removed

Supernatant re-spun at a faster speed to gain next heaviest organelles (eg chloroplasts)

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12
Q

What is used to measure objects with a microscope?

A

Eyepiece graticule and a stage micrometer

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13
Q

What is the process for calibrating an eyepiece graticule?

A

Line up the eyepiece graticule and stage micrometer under the desired magnification and calculate length of divisions

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14
Q

What are the 3 features of a mitochondria?

A

Double membrane

Cristae

Matrix

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15
Q

What is the double membrane in a mitochondria?

A

Outer membrane covers like skin

Inner membrane folded into layered structures -> increases surface area for respiration

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16
Q

What is the cristae in mitochondria?

A

Fold made by the inner membrane -> more space for chemical reactions to take place

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17
Q

What is the matrix in mitochondria?

A

The fluid within the organelle

It has its own ribosomes and DNA floating within it

Contains granules to help maintain ion concentration

18
Q

What are the 5 different features of the nucleus?

A

Nuclear Envelope

Nuclear Pores

Nucleoplasm

Chromosomes

Nucleolus

19
Q

What is the nuclear envelope?

A

Surrounds the nucleus and contains genetic info

Consists of 2 lipid bilayer membranes

20
Q

What are nuclear pores?

A

Gaps that allow the transport of molecules across the nuclear envelope

This includes the movement of RNA and proteins

21
Q

What is the nucleoplasm?

A

The substance of a cell’s nucleus

Includes chromosomes and nucleolus

22
Q

What is the nucleolus?

A

Largest structure within the nucleus

Makes ribosomes

23
Q

What are the 3 main components of a chloroplast?

A

Chloroplast envelope

Grana

Stroma

24
Q

What is the chloroplast envelope?

A

Double membrane

  • > outer membrane covers like skin
  • > inner folded into layered structure
25
Q

What is the grana?

A

Stacks of discs (individually known as thylakoids)

Site of light dependent photosynthesis

Connected by intergranal thylakoids

26
Q

What is the stroma?

A

Colourless fluid surrounded the grana

Contains enzymes required for photosynthesis

DNA and ribosomes also present

27
Q

What are the differences between the rough and smooth endoplasmic reticulum?

A

Rough is covered in ribosomes and makes proteins

Smooth isn’t covered in anything and makes lipids

28
Q

What is the golgi apparatus?

A

The organelle that ‘packages’ and secretes proteins

29
Q

What is the function of lysosomes?

A

to destroy unwanted / unneeded molecules (eg ribosomes that stop working)

contains very strong enzymes

30
Q

What organelles do prokaryotes have that eukaryotes don’t?

A

Pili

Flagella

Chromosomal / Plasmid DNA

Capsule

31
Q

What are pili?

A

Hair-like proteins surrounding a prokaryotic cell that help it attach itself to surfaces

32
Q

What is the function of the capsule on a prokaryotic cell?

A

To prevent desiccation and chemical attack

33
Q

What are the main structural features of a virus?

A

Attachment proteins OR a lipid envelope

DNA/RNA

Capsid

Matrix

Nucleoproteins

34
Q

Define attachment proteins

A

Proteins on the outside of a virus that allows the virus to force itself onto the membrane of the host cell

35
Q

Define a lipid envelope (viruses)

A

The outer membrane of a virus molecule that matches with the membrane of the host cell, allowing it to attach itself to a host undetected

36
Q

Why do viruses have a lipid envelope or attachment proteins - not both?

A

They both have the same function -> to allow the virus to attach itself to a host cell

37
Q

Define the capsid

A

The protein coat that encapsulates the DNA/RNA

38
Q

Define nucleoproteins

A

Accessory proteins eg enzymes

39
Q

Define the matrix (viruses)

A

Protein layer on the inside of the envelope

40
Q

Describe the process of virus replication

A
  1. Virus attaches to host cell and injects genetic material
  2. Genetic material used as code to synthesize proteins
  3. New viral proteins assembled into new viruses
  4. Viruses burst out of the host cell, destroying it

Biology AS (17 decks)

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