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Biology > Chapter 2.1 Basic components of living systems > Flashcards

Chapter 2.1 Basic components of living systems Flashcards

1
Q

What is a microscope

A

A microscope is an instrument that enables you to magnify and observe an object which are not visible by the naked eye.

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2
Q

What makes up the cell theory

A

Both plant and animal tissue are composed of cells.
Cells are the basic unit of life
Cells only develop from existing cells.

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3
Q

What is a light microscope/ optical microscope?

A

Type of microscope that uses visible light and a system of lenses to generate magnified images of small objects

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4
Q

How to prepare a light microscope (6 marker)?

A
  1. Specimens are prepared on a microscope slide therefore, a stain is used to highlight structures within the cells and this is typically methylene blue
    2.Clip the microscope slide onto the stage
  2. Ensure that the lowest-powered objective lens is over the slide.
  3. Use coarse adjusting knob to bring the stage up just below the lens.
  4. Look down the eyepiece and move stage downwards using coarse adjusting knob then stop when image is roughly in focus.
  5. To ring image into focus, use fine-adjusting knob until clear image is obtained.
  6. Observe image at a higher magnification by changing objective lens to a higher power therefore, readjust the stage using the coarse and fine adjusting knobs.
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5
Q

What are the 4 types of sample preperation in OCR biology?

A

Dry Mount, Wet Mount, Squash Slides and Smear Slides.

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6
Q

What is Dry Mount?

A

In a dry mount, the specimen is placed directly on the slide. A cover slip may be used to keep the specimen in place and to help protect the objective lens. Dry mounts are suitable for specimens such as samples of pollen, hair, feathers or plant materials

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7
Q

What is Wet Mount?

A

Specimens are suspended in a liquid such as water or an immersion oil. A cover slip placed at an angle so that aquatic samples are viewed this way.

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8
Q

What is a Squash Slide?

A

Squash slide is where an entire cells are pressed flat on a piece of glass and observed through a microscope technique.

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9
Q

Why is staining used within microscopy? (2 marks)

A

Staining is used to enhance visualization of the cell or certain cellular components under a microscope. As well as this some organelles absorb the stain and can increase contrast between components therefore, can identify organelles structure and function more easily.

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10
Q

What is a gram staining technique?

A

Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet.

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11
Q

What is the difference between Gram positive and Gram negative bacteria? (2 marker)

A

Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane whilst Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane.

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12
Q

What is the difference between magnification and resolution? (2 marker)

A

Resolution is the ability to distinguish two seperate points from being seperate entities whereas, magnification is the Magnification is how many times bigger the image of a specimen observed is in compared to the actual (real-life) size of the specimen.

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13
Q

What is the formula for manification? (2 marker)

A

magnification = imge size/ actual size.

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14
Q

What is the metric conversion? for example how do you get from metres to mm?

A

1m - 1000mm
1mm - 1000micrometers
1micrometers-1000nanometers.

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15
Q

What is an eyepiece graticule?

A

An eyepiece graticule and stage micrometer are used to measure the size of the object when viewed under a microscope.

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16
Q

What is the stage micrometer?

A

A ​stage graticule is a microscope slide with an accurate measuring scale – this is used to calibrate the value of the eyepiece divisions at different magnifications.

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17
Q

What is a laser confocal microscope?

A

Confocal laser scanning microscopy is a technique for obtaining high-resolution optical images with depth selectivity and allows protein localisation in specific cellular compartments.

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18
Q

How is a specimen viewed under a laser scanning confocal microscope?

A

The cells being viewed must be stained with fluorescent dyes
A thick section of tissue or small living organisms are scanned with a laser beam
The laser beam is reflected by the fluorescent dyes
Multiple depths of the tissue section/organisms are scanned to produce an image
Think of it like the laser beam is building up the image layer by layer

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19
Q

Advantages of a laser scanning confocal microscope?

A

They can be used on thick or 3-D specimens
They allow the external, 3-D structure of specimens to be observed
Very clear images are produced. The high resolution is due to the fact that the laser beam can be focused at a very specific depth
You can even see the structure of the cytoskeleton in cells

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20
Q

Disadvantages of a laser scanning confocal microscope?

A

It is a slow process and takes a long time to obtain an image
The laser has the potential to cause photodamage to the cells

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21
Q

What is an electron microscope?

A

Electron microscopes use electrons to form an image
This greatly increases the resolution of electron microscopes compared to optical microscopes, giving a more detailed image. There are also two types of electron microscopes which are TEM and SEM.

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22
Q

What are TEM (Transmission electron microscope)?

A

TEMs use electromagnets to focus a beam of electrons
This beam of electrons is transmitted through the specimen
Denser parts of the specimen absorb more electrons
This makes these denser parts appear darker on the final image produced (produces contrast between different parts of the object being observed) as well as this, produces a 2D image.

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23
Q

Advantages of a TEM?

A

They give high-resolution images (more detail)
This allows the internal structures within cells (or even within organelles) to be seen

24
Q

Disadvantages of TEM?

A

They can only be used with very thin specimens or thin sections of the object being observed
They cannot be used to observe live specimens (as there is a vacuum inside a TEM, all the water must be removed from the specimen and so living cells cannot be observed, meaning that specimens must be dead, unlike optical microscopes that can be used to observe live specimens)
The lengthy treatment required to prepare specimens means that artefacts can be introduced (artefacts look like real structures but are actually the results of preserving and staining)
They do not produce a colour image (unlike optical microscopes that produce a colour image).

25
Q

What are SEM?

A

SEMs scan a beam of electrons across the specimen
This beam bounces off the surface of the specimen and the electrons are detected, forming an image
This means SEMs can produce three-dimensional images that show the surface of specimens

26
Q

Advantages of SEM?

A

They can be used on thick or 3-D specimens
They allow the external, 3-D structure of specimens to be observed

27
Q

Disadvantages of SEM

A

They cannot be used to observe live specimens (unlike optical microscopes that can be used to observe live specimens)
They do not produce a colour image (unlike optical microscopes that produce a colour image)

28
Q

What can and can’t be viewed under a light microscope?

A

Therefore optical microscopes can be used to observe eukaryotic cells, their nuclei and possibly mitochondria and chloroplasts
Optical microscopes cannot be used to observe smaller organelles such as ribosomes, the endoplasmic reticulum or lysosomes

29
Q

What can be viewed under an electron microscope?

A

Electron microscopes can be used to observe small organelles such as ribosomes, the endoplasmic reticulum or lysosomes

30
Q

What is the magnification and resolution of TEM?

A

500000X magnification
0.5Nm Resolution

31
Q

What is the magnification and resolution of a SEM?

A

100000X magnification
3-10Nm

32
Q

What is the magnification and resolution of a light microscope?

A

2000X magnification
200 Nm resolution

33
Q

Advantages of light microscopes over electron microscopes?

A

Inexpensive to buy and operate whereas electron is expensive. Small and portable and there is a simple sample preperation whereas Electron is large and complex sample preperation. Vaccum is not required whereas Electron a vaccum is required. Stains can be used therefore, color images are produced whereas Electron produce black and white images. Specimens can either be alive or dead whereas electron are all dead.

34
Q

Advantages of Electron over light microscope?

A

Light microscope has a limited magnification and resolution compared to electron microscopes.

35
Q

What is a eukaryotic cell?

A

A complex cell which contains membrane bound organelles and has genetic material enclosed in a nucleus.

36
Q

What is a prokaryotic cell?

A

A simple cell which doesn’t contain membrane bound organelles and has genetic material that is not enclosed in a nucleus.

37
Q

What is compartmentalization?

A

Where different cells are within distinct environments and conditions for the different cellular reactions therefore, increasing efficiency within the organism

38
Q

What is the nucleus and what is its structure and function?

A

The nucleus is responsible for contining the genetic material of the cell in the form of chromatin therefore, controls all the activities within the cell. Present in all eukaryotic cells, the nucleus 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, as well as allowing enzymes (eg. DNA polymerases) and signalling molecules to travel in
The nucleus contains chromatin (the material from which chromosomes are made)

39
Q

What is mitachondria, what is its structure and function?

A

Mitachondria is the site of aerobic respiration and the synthesis of ATP. Surrounded by double-membrane with the inner membrane folded to form cristae
The matrix formed by the cristae contains enzymes needed for aerobic respiration, producing ATP
Small circular pieces of DNA (mitochondrial DNA) and ribosomes are also found in the matrix

40
Q

What are vesicles and lysosomes and what is its structure and function?

A

Vescicles are membraneous sacs which have storage and transport roles within the cell as well as, containing membrane fluid. Lysosomes are specialised vesicles and they contain hydrolytic enzymes that are responsible for breaking down pathogens within the cell therefore, has important roles within the immune system and breaks down pathogens by engulfing via phagocytic cells.

41
Q

What are ribosomes and what is its structure and function?

A

Ribosomes are the site of protein synthesis within the translation phase.
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 (composed of 60S and 40S subunits) are found in eukaryotic cells
70S (composed of 50S and 30S subunits) ribosomes in prokaryotes, mitochondria and chloroplasts

42
Q

What is the endoplasmic reticulum?

A

Network of membranes enclosing in flattened sacs called cisternae and there are two types which are, smooth endoplasmic reticulum and rough endoplasmic reticulum.

43
Q

What is the structure and role of smooth ER?

A

Does not have ribosomes on the surface, its function is distinct to the RER
Involved in the production, processing and storage of lipids, carbohydrates and steroids

44
Q

What is the structure and function of RE?

A

Surface covered in ribosomes
Formed from continuous folds of membrane continuous with the nuclear envelope
Processes proteins made by the ribosomes

45
Q

What is the golgi apparatus?

A

Compact structure and is flattened to form cisternae.
Flattened sacs of membrane similar to the smooth endoplasmic reticulum
Modifies proteins and packages them into vesicles or lysosomes to either undergo exocytosis and leave the cell or be transported within the cell.
Undergoes endo and exocytosis.

46
Q

Structure and function of centrioles?

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
Not found in flowering plants and fungi

47
Q

Structure and function of microtubules?

A

Makes up the cytoskeleton of the cell about 25 nm in diameter
Made of α and β tubulin combined to form dimers, the dimers are then joined into protofilaments. Thirteen protofilaments in a cylinder make a microtubule
The cytoskeleton is used to provide support and movement of the cell

48
Q

Structure and function of flaggela?

A

Similar in structure to cilia, made of longer microtubules
Contract to provide cell movement for example in sperm cells
Moves molecules away from toxic substances and towards required molecules such as oxygen.

49
Q

What is the cytoskeleton?

A

Network of fibres that is necessary for the shape and stabllity of the cell. Can be in 3 forms which are microfilaments, microtubules and intermediate fibres.

50
Q

What is the role of microfilaments?

A

Contains the protein actin which is responsible for contraction and and cell movement especially within processes such as cytokinesis.

51
Q

What is the role of microfilaments?

A

Contains the protein actin which is responsible for contraction and and cell movement especially within processes such as cytokinesis.

52
Q

What is the role of microtubules?

A

Consists of globular tubulin proteins that polymerise to form tubules that determine the shape of the cell furthermore, responsible for the movement of organelles such as vesicles and spindle fibres.

53
Q

What is the role of intermediate fibres?

A

Fibres provide mechanical strength to cells and maintain integrity.

54
Q

What is the role of a cell wall?

A

Made of cellulose which means that it gives the plant strength and prevents pathogens from entering the plant cell therefore, acts as a primary defense mechanism.

55
Q

What is the structure and function of vacuoles?

A

Chloroplasts is involved within the process of photosynthesis.
The main functions of vacuoles include maintaining cell acidity and turgor pressure, regulating the storage and transport of substances, controlling the transport and localization of key proteins through the endocytic and lysosomal-vacuolar transport pathways, and responding to biotic and abiotic stresses
Sac in plant cells surrounded by the tonoplast, selectively permeable membrane
Vacuoles in animal cells are not permanent and small

56
Q

What is the structure and function of chloroplasts?

A

Larger than mitochondria, also surrounded by a double-membrane
Membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana
Grana are joined together by lamellae (thin and flat thylakoid membranes)
Chloroplasts are the site of photosynthesis:
The light-dependent stage takes place in the thylakoids
The light-independent stage (Calvin Cycle) takes place in the stroma

57
Q

What cells are found in animal cells but not found in plant cells?

A

Centrosomes, lysosomes and centriolles.

Biology (1 decks)

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