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OCR A level Biology > 2.1 Cell Biology > Flashcards

2.1 Cell Biology Flashcards

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1
Q

What’s the use of Microscopes?

A

Microscopes can be used to observe and investigate cell structure

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2
Q

Types of Microscopes?

A

Different types of microscope can be used to study cells at different levels of detail
- Light microscopes
- Electron microscopes

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3
Q

What are light microscopes?

A

Light microscopes use light to form an image
- Maximum resolution is 0.2 micrometres (µm)
- Maximum useful magnification is ×1500
- used to observe larger structures:
= entire cells
= nuclei
= mitochondria and chloroplasts

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4
Q

Light Microscopes : Positives

A
  • they are small and relatively cheap
  • they can be used to produce colour images
  • they allow the observation of living specimens
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5
Q

Light Microscope : Negatives

A
  • they’re resolution is lower
  • they’re magnification is also lower
  • aren’t capable of seeing specific small structure
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6
Q

What are Electron Microscopes?

A

Electron microscopes use electrons to form an image
- Maximum resolution of 0.2 nm
- Maximum magnification from around ×1,000,000 up
Electron microscopes can be used to observe small structures inside cells:
= cell membranes
= ribosomes
- there are two types:
= transmission electron microscopes (TEMs)
= scanning electron microscopes (SEMs)

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7
Q

Electron Microscopes : Positives

A
  • produces very high resolution therefore the specimen can be well investigated
  • also has a very high magnification to identify certain parts
  • images can be artificially coloured during processing
  • helps validate studies and has 2 different types
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8
Q

Electron Microscope : Negatives

A
  • they are very large and expensive
  • specimens must be prepared using a highly complex process
  • live specimens cannot be observed
  • images are always produced as black and white
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9
Q

EM : Transmission Electron Microscopes

A
  • Use electromagnets to transmit a beam of electrons through a specimen; denser parts appear darker on the final image
  • TEMs produce images that:
    = are high-resolution
    = allow the internal structures within cells
    = are two-dimensional
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10
Q

EM : Scanning Electron Microscope

A
  • pass a beam of electrons across the surface of a specimen and then detect the rate at which the electrons bounce back
  • SEMs produce images that:
    = are three-dimensional
    = show the surface of specimens
    = lower maximum resolution than TEMs
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11
Q

What’s the Magnification Formula?

A

Magnification = size of Image ÷ size of Actual object

The magnification formula can be rearranged to allow the calculation of:
- magnification (M)
- size of image (I)
- size of actual size (A)

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12
Q

Describe conversion units in Magnification:

A

Units of measurement relate to each other as follows:
- 1000 nm = 1 µm
- 1000 µm = 1 mm
- 1000 mm = 1 m
- 10 mm = 1 cm

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13
Q

What is magnification?

A

Magnification:
The number of times larger an image is than the actual object

The ability of a microscope to magnify an object depends on the type of microscope, and on the features of the microscope itself

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14
Q

What is resolution?

A

Resolution:
The ability to distinguish separate points on an image as two separate objects

The higher the resolution, the shorter the distance at which the two objects can be clearly distinguished

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15
Q

What’s a Eukaryotic cell?

A
  • Eukaryotic cells are larger than other cells
  • their DNA is contained in a nucleus
  • are complex multicellular organisms containing a range of specialized cells
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16
Q

EC : Cell Membrane

A
  • cells are surrounded by a cell surface membrane
  • it controls the exchange of materials between the internal cell environment and the external environment; involved in osmosis
  • membrane is ‘partially permeable’
  • in control of what goes inside and outside of the cell
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17
Q

EC : Cell Wall

A
  • found in plant cells but not in animal cells
  • cell walls are formed outside of the cell membrane
  • provide structural support to the cell
  • is thick and also provides protection for the cell
18
Q

EC : Nucleus

A
  • present in all eukaryotic cells
  • is relatively large and separated from the cytoplasm by a double membrane
  • the nuclear envelope: which has many pores
  • nuclear pores: are important channels for allowing mRNA and ribosomes to travel out of the nucleus
  • nucleolus: are the sites of ribosome production
19
Q

EC : Mitochondria

A
  • the site of aerobic respiration (the powerhouse of the cell)
  • are just visible with a light microscope
  • surrounded by double-membrane with the inner membrane
20
Q

EC: Chloroplast

A
  • Chloroplasts are found in plant cells
  • Larger than mitochondria, also surrounded by a double-membrane
  • Chloroplasts are the site of photosynthesis
  • Also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
  • the green colour a result of a pigment, chlorophyll
21
Q

EC: Ribosomes

A
  • found in all cells
  • found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells
  • each ribosome is a complex of ribosomal RNA (rRNA) and proteins
    80S ribosomes are found in eukaryotic cells
  • Site of translation
22
Q

EC : Endoplasmic Reticulum (Rough)

A
  • found in plant and animal cells
  • their surface is covered in ribosomes
  • formed from continuous folds of membrane continuous with the nuclear envelope
  • processes proteins made by the ribosomes
  • RER - site of protein synthesis and glycoprotein synthesis
  • the proteins can then be transported through the RER
23
Q

EC : Endoplasmic Reticulum (Smooth)

A
  • found in plant and animal cells
  • does not have ribosomes on the surface
  • involved in the production, processing and storage of lipids, carbohydrates and steroids
  • SER – create, store, and transport lipids and carbohydrates.
24
Q

EC : Golgi Apparatus

A
  • found in plant and animal cells
  • stacks of membranes creating flattened sacs, surrounded by small round hollow vesicles.
  • modifies proteins and lipids before packaging them into Golgi vesicles
  • proteins that go through the Golgi apparatus are usually exported put into lysosomes or delivered to membrane-bound organelles
25
Q

EC : Vesicles

A
  • found in plant and animal cells
  • a membrane-bound sac for transport and storage
  • proteins and lipids are transported in the Golgi vesicles
26
Q

EC : Lysosomes

A
  • formed when the Golgi apparatus contains enzymes
  • its a specialist forms of vesicles which contain enzymes (enzymes that break biological molecules down)
  • break down waste materials such as worn-out organelles
27
Q

EC : Centriole

A
  • hollow fibres made of microtubules
  • two centrioles at right angles to each other form a centrosome, which organises the spindle fibres during cell division
28
Q

EC : Microtubles

A
  • found in all eukaryotic cells
  • makes up the cytoskeleton of the cell
  • the cytoskeleton is used to provide support and movement of the cell
29
Q

EC : Microvilli

A
  • found in specialised animal cells
  • cell membrane projections
  • used to increase the surface area of the cell surface membrane in order to increase the rate of exchange of substances
30
Q

What’s a Prokaryotic cell?

A
  • Prokaryotic cells are simple cells that lack a nucleus and other membrane-bound organelles
  • they are found in single-celled organisms such as bacteria.
31
Q

PC : Plasmids

A
  • small loops of DNA that are separate from the main circular molecule
  • plasmids contain genes that can be passed between prokaryotes
  • not present in all prokaryotes
32
Q

PC : Capsule

A
  • a final outer layer
  • helps protect bacteria from drying out and from attack by cells of the immune system of the host organism
  • not present in all prokaryotes
33
Q

PC : Cilia

A
  • hair-like projections made from microtubules
  • allows the movement of substances over the cell surface
34
Q

PC : Flagella

A
  • a long, hair-like structure that rotates, enabling the Prokaryote to move
  • contract to provide cell movement for example in Bacteria
  • similar in structure to cilia, made of longer microtubules
35
Q

PC : Pili

A
  • for attachment to other cells or surfaces
  • involved in the cells sexual reproduction
36
Q

Comparison of PC and EC : Size

A

PC = 0.5-5 micrometres DIAMETER
EC = can be upto 100 micrometres DIAMETER

37
Q

Comparison of PC and EC : Genome

A

PC = DNA is circular with no proteins, free in the cytoplasm
EC = DNA codes for proteins, formed into chromosomes

38
Q

Comparison of PC and EC : Cell Division

A

PC = occurs by binary division, no spindles
EC = occurs by mitosis or meiosis and involves spindle fibres to separate chromosomes

39
Q

Comparison of PC and EC : Ribosomes

A

PC = 70s ribosomes
EC = 80s ribosomes

40
Q

Comparison of PC and EC : Organelles

A

PC = very few
= has no membrane-bound organelles
EC = has numerous types of mem-bound organelles
= single membrane ( Lysosomes, Golgi Complex and Vacuoles)
= double membranes ( Nucleus, Mitochondria, Chloroplast)
= no membrane ( Ribosomes, Centrioles, Microtubules)

41
Q

Comparison of PC and EC : Cell Wall

A

PC = made up of Peptidoglycan (Polysaccharide and amino acids)
= as well as Murein
EC = present in plants (made up of cellulose) and fungi (made up of chitin)

42
Q
A

OCR A level Biology (2 decks)

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