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OCR A level Biology > 2.1 Basic components of living > Flashcards

2.1 Basic components of living Flashcards

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1
Q

What are the 2 lenses called on a compound light microscope?

A

Objective lens and eyepiece lens

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2
Q

What are the 4 types of sample preparation?

A

Dry mount
Wet mount
Squash slides
Smear slides

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3
Q

Name 2 positively charged dyes and what they are attracted to

A

Methylene blue and Crystal violet

attracted to negatively charged materials in the cytoplasm

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4
Q

Name 2 negatively charged dyes and what they are repelled by

A

Nigrosine and Congo red

repelled by the negatively charged cytosol

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5
Q

What happens to gram positive bacteria when stained with crystal violet?

A

The gram positive bacteria retain the pain and appear blue/purple under a microscope

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6
Q

What happens to gram negative bacteria when stained with crystal violet?

A

Gram negative bacteria lose the stain due to thinner cell walls. They are then stained with a counterstain, safranin dye which makes them appear red.

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7
Q

Which type of bacteria is susceptible to penicillin?

A

Gram positive - it inhibits the formation of cell walls

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8
Q

What are the 4 stages in the production of pre-prepared slides?

A
  1. Fixing
  2. Sectioning
  3. Staining
  4. Mounting
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9
Q

What are the rules for producing good scientific drawings?

A
  • include a title
  • state magnification
  • use a sharp pencil
  • use white unlined paper
  • use as much paper as possible
  • draw smooth continuous lines
  • do not shade
  • label lines should not cross and should be parallel to the top of the page and drawn with a ruler
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10
Q

How is magnification calculated?

A

Magnification (no units) = size of image/actual size

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11
Q

What is magnification?

A

How many times larger the image is than the actual size of the object being viewed

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12
Q

What is resolution?

A

the shortest distance between 2 objects that can be seen as separate objects

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13
Q

What is resolution limited by?

A

Diffraction

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14
Q

What is diffraction?

A

Diffraction is the tendency of light waves to spread as they pass close to physical structures

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15
Q

How can resolution be increased?

A

by using beams of electrons

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16
Q

What do you use to calibrate a light microscope?

A

an eyepiece graticule

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17
Q

Name 4 disadvantages of electron microscopy

A
  • expensive
  • can only be used inside a carefully controlled environment in a dedicated space
  • specimens can be damaged by the electron beam
  • problem with artefacts
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18
Q

What are the 2 types of electron microscope?

A
  • Transmission electron microscope

- Scanning electron microscope

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19
Q

What is the difference between TEM and SEM?

A

In TEM a beam of electrons is transmitted through a specimen whereas in SEM a beam of electrons is sent across the surface of the specimen

20
Q

How is a sample prepared for electron microscopes?

A

fixation using chemicals/freezing
staining with heavy metals
dehydration with solvents

21
Q

Name 4 differences between light microscopes and electron microscopes

A
  • light microscopes are inexpensive to buy and operate
  • electron microscopes are large and need to be installed
  • electron microscopes require complex sample preparation
  • in light microscopy samples can be living or dead
22
Q

What is an artefact?

A

A visible structural detail caused by processing the specimen and not a feature of the specimen

23
Q

How does a laser scanning confocal microscope work?

A

It moves a single spot of focused light across a specimen which causes fluorescence from components labelled with a fluorescent dye. This emitted light is filtered through a pinhole aperture and is detected. A 2D image is produced.

24
Q

Name a use of laser scanning confocal microscopy

A

used in the diagnosis of diseases

25
Q

What is the function of the nucleus?

A

It contains the coded genetic information in the form of DNA

26
Q

What is the function of the nucleolus?

A

responsible for producing ribosomes. It is composed of proteins and RNA.

27
Q

What is the function of mitochondria?

A

They are the site of the final stages of cellular respiration

28
Q

What are vesicles?

A

membranous sacs that have storage and transport roles

29
Q

What are lysosomes?

A

Specialised forms of vesicles that contain hydrolytic enzymes, responsible for breaking down waste material in cells

30
Q

What are the 2 important roles of lysosomes?

A
  • in the immune system they break down pathogens

- in programmed cell death/apoptosis

31
Q

What is the function of the cytoskeleton?

A

A network of fibres necessary for the shape and stability of a cell

32
Q

What are the 3 components of the cytoskeleton?

A
  • Microfilaments
  • Microtubules
  • Intermediate fibres
33
Q

What are centrioles?

A

component of the cytoskeleton composed of microtubules involved in the positioning of flagella/cilia and form the centrosome which is involved in the assembly and organisation of the spindle fibres during cell division

34
Q

What are flagella?

A

whip like extensions that enable cell’s motility

35
Q

What are cilia?

A

hair like extensions that can be mobile or stationary and can move fluids/objects adjacent to cells

36
Q

What is the endoplasmic reticulum?

A

a network of membranes enclosing cisternae

37
Q

What are the 2 types of endoplasmic reticulum and their functions?

A
  • Smooth ER - lipid and carb synthesis and storage

- Rough ER - synthesis and transport of proteins

38
Q

What are ribosomes?

A

site of protein synthesis

39
Q

What is the Golgi apparatus?

A

compact structure formed of cisternae, does not contain ribosomes and has a role in modifying and ‘packaging’ proteins into vesicles.

40
Q

What is the function of the cell wall?

A

gives the plant cell shape and acts as a defence mechanism

41
Q

What are plant cell walls made of?

A

Cellulose

42
Q

What are vacuoles?

A

membrane lined sacs in the cytoplasm containing cell sap, they are important in the maintenance of turgor

43
Q

What is the membrane of a vacuole called?

A

tonoplast

44
Q

What is the function of chloroplasts?

A

responsible for photosynthesis

45
Q

Name 4 differences between prokaryotic and eukaryotic cells?

A
  • prokaryotic cells do not have a nucleus
  • prokaryotic DNA is circular
  • non-membrane bound organelles in prokaryotic cells
  • smaller ribosomes (70S) in prokaryotic cells

OCR A level Biology (8 decks)

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