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Biology > Cell Structure > Flashcards

Cell Structure Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the equation to work out magnification?

A

Size of image/ size of real object

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2
Q

What is the magnification of an object?

A

How many times bigger the image is when compared to the object.

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3
Q

What is the resolution of a microscope?

A

The minimum distance apart that the 2 objects can be in order for them to appear as separate items. Greater resolution means the image produced is more clear and precise.
Resolution of a microscope depends on the wavelength or form of radiation used. In a light microscope it is around 0.2 micrometers. This means that any 2 objects 0.2 micrometers apart will be seen separately but any closer then 0.2 micrometers will appear as a single object.
Increasing magnification increases the image size but not resolution as every microscope has a limit. It will appear large but be more blurred.

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4
Q

What is the process of cell fractionation used for?

A

To break up cells so the different organelles they contain are separated out.

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5
Q

What must occur before cell fractionation can begin?

A

The tissue is placed in a cold, buffered, isotonic solution.

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6
Q

Why is the solution used before cell fractionation begins buffered?

A

So the pH does not fluctuate as changes in pH could denature the enzymes.

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7
Q

Why is the solution used before cell fractionation used ice cold?

A

To decrease enzyme activity that might hydrolyse the organelles.

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8
Q

Why is the solution used before cell fractionation occurs isotonic?

A

To prevent organelles shrinking or bursting as a result of a loss of water or osmotic gain.

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9
Q

What is homogenisation?

A

Cells are broke up by a homogeniser. This releases the organelles from the cell. The resultant fluid (homogenate) is then filtered to remove any complete cells and large pieces of debris.

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10
Q

What happens in ultracentrifugation?

A

Tube of filtrate is placed in the centrifuge and spun at a slow speed.
The heaviest organelles (the nuclei) are forced to the bottom of the tube, where they form a thin pellet.
The fluid at the top of the tube (the supernatant) is removed leaving just the sediment of the nuclei.
Supernatant gets transferred to another tube and spun in the centrifuge at a faster speed then before.
The next heaviest organelles, the mitochondria, are forced to the bottom of the tube.
Process continues so that with each increase in speed the next heaviest organelle (lysosomes) is separated out.

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11
Q

How are the steps of cell fractionation ordered?

A
  1. Ice cold, isotonic, buffered solution
  2. Homogenisation
  3. Ultracentrifugation
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12
Q

Why do light microscopes have poor resolution?

A

Due to their relatively long wavelength of light.

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13
Q

Why do light microscopes have poor resolution?

A

Due to their relatively long wavelength of light.

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14
Q

What are the 2 main advantages of the electron microscope?

A
  1. Short wavelength so the microscope has a high resolving power
  2. As electrons are negatively charged the beam can be focused using electromagnets.
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15
Q

Why does a near vacuum have to be created within the chamber of an electron?

A

Because electrons are absorbed or deflected by the air molecules.

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16
Q

What is the scanning electron microscope? (SEM)

A

It directs a beam of electrons on to the surface of the specimen from above. The beam is then passed back and forth across a portion of the specimen in a regular pattern. The electrons are scattered by the specimen. Lower resolving power then a TEM (20nm).

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17
Q

What is the Transmission electron microscope? (TEM)

A

Consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet. The beam passes through a thin section of the specimen. Parts of the specimen absorb electrons and therefore appear dark. Other parts allow electrons to pass through and therefore appear bright. An image is produced on the screen and this can be photographed to give a photomicrograph. Resolution is 0.1nm.

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18
Q

Why can 0.1nm resolution of the TEM not always be achieved?

A

Due to difficulties preparing the specimen and a higher energy electron beam is re

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19
Q

What are the limitations of the TEM?

A

The whole system must be in vacuum and therefore living specimens cannot be observed.
Specimen must be extremely thin.
Image may contain artefacts which result from the specimens preparation. Artefacts may appear on the photomicrograph but not on the natural specimen.

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20
Q

Why when using a TEM must the specimens be very thin?

A

To allow electrons to penetrate through. The result is a flat 2D image.

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21
Q

How to measure cells?

A

When using a light microscope, we can measure the size of objects using an eyepiece graticule which in a glass disc played in the eyepiece. A scale is etched on the glass disc. This disc is usually 10mm long and divided into 100 sub-divisions. Graticule must be calibrated to for a particular objective lens.

22
Q

How to calibrate the eyepiece graticule?

A

Using a stage micrometer which has a scale etched onto it. The scale is usually 2mm long and its smallest sub divisions are 0.01mm.

23
Q

What is the function of the nucleus?

A

To act as the control of the cell through the production of mRNA and tRNA and hence protein synthesis.
Retain the genetic material of the cell in the form of DNA and chromosomes.
Manufacture ribosomal RNA and ribosomes.

24
Q

What are the components of the nucleus?

A

The nuclear envelope, nuclear pores, nucleoplasm, chromosomes and the nucleolus.

25
Q

What is the structure of the nuclear envelope?

A

Is a double membrane that surrounds the nucleus. Its outer membrane is continuous with the endoplasmes reticulum of the cell and often has ribosomes on its surface.

26
Q

What is the function of the nuclear envelope?

A

Controls the entry and exit of materials in and out of the nucleus and contains the reactions taking place within it.

27
Q

What is the function of the nuclear pores?

A

They allow the passage of large molecules such as mRNA, out of the nucleus.

28
Q

What is the function of the nucleolus?

A

To manafucture ribsomal RNA and assemble to ribosomes.

29
Q

What structures are mitochondrion made up of?

A

Around the organelle is a double membrane that controls the entry and exit of material. The inner of the two membranes is folded to form cristae.

Cristae are extensions of the inner membrane which provide a large surface area for the attachment of enzymes involved in respiration.

The matrix makes up the remainder of the mitochondrion. It contains proteins, lipids, ribosomes and DNA that allows the mitochondria to control the production of some of their proteins.

30
Q

What is the function of mitochondria?

A

The site of the aerobic stages of respiration eg the Krebs cycle. They are responsible for the production of ATP.

31
Q

What is the function of chloroplasts?

A

To carry out photosynthesis.

32
Q

What is the main features of chloroplasts?

A

The chloroplast envelope is a double plasma membrane that surrounds the organelle and is highly selective in what it allows to enter and exit the chloroplast.
The grana are stacks of disc structures called thylakoids. Within the thylakoids is chlorophyll.
The stroma is a fluid filled matrix where the second stage of photosynthesis (synthesis of sugars) takes place.

33
Q

Where does the first stage (light absorption) of photosynthesis take place?

A

Grana

34
Q

What are 3 ways that chloroplasts are adapted to their function?

A

The fluid in the strana possesses all the enzymes needed to make sugars in the second stage of photosynthesis.

Chloroplasts contain both DNA and ribosomes so they can quickly manufacture some proteins needed for photosynthesis.

The granal membranes provide a large surface area for the attachment of chlorophyll and enzymes that carry out the first stage of photosynthesis.

35
Q

What is the Rough Endoplasmic reticulum?

A

Has ribosomes present on the outer surfaces of the membranes.
It provides a large surface area for the synthesis of proteins to glycoproteins.
Provides a pathway for the transport of materials eg proteins throughout the cell.

36
Q

What is the Smooth Endoplasmic Reticulum?

A

Lacks ribosomes on its surface.
Synthesises, stores and transports lipids and carbohydrates.

37
Q

What are the functions of the Golgi apparatus?

A

Add carbohydrate to proteins to form glycoproteins.
Produce secretory enzymes
Secrete carbohydrates such as those used making plant cell walls.
Transport, modify and store lipids
Form lysosomes

38
Q

What are the functions of lysosomes?

A

To hydrolyze material ingested by phagocytic cells such as white blood cells and bacteria.
To release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell.
To digest worn out organelles so the useful chemicals they are made out of can be re-used.
To completely break down cells after they have died (autolysis).

39
Q

What are the two types of chloroplasts?

A

80S which are found in eukaryotic cells and 70S which are found in eukaryotic cells, mitochondria and chloroplasts.

40
Q

What is the function of ribosomes?

A

They are the site of protein synthesis.

41
Q

What are ribosomes made up of?

A

Protein and ribosomal RNA.

42
Q

What are the features of the cell wall?

A

They consist of a number of polysaccharides, such as cellulose.
There is a thin layer called the middle lamella which marks the boundary between adjacent cell walls and cements adjacent cells together.

43
Q

What are the functions of the cellulose cell wall?

A

To provide strength in order to prevent the cell wall bursting under the pressure created by the osmotic entry of water.
Give strength to the plant as a whole.
To allow water to pass along it and contribute to the movement of water through the plant.

44
Q

What are the cell walls of fungi made up of?

A

Chitin, glycan and glycoproteins

45
Q

What is the structure of a vacuole?

A

A fluid filled sac bound by a single membrane which is known as a tonoplast).

46
Q

What is the function of a plant vacuole?

A

Provide support by making cells turgid.
The sugars and amino acids it contains may act as a temporary food store.
The pigments it contains may colour petals to attract pollinating insects.

47
Q

What is cell specialisation?

A

In complex multicellular organisms, eukaryotic cells become specialised for specific functions
These specialised eukaryotic cells have specific adaptations to help them carry out their functions

Structural adaptations include:
The shape of the cell
The organelles the cell contains (or doesn’t contain)

48
Q

What are examples of cell specialisation?

A

Sperm with function of reproduction

The head contains a nucleus that contains half the normal number of chromosomes (haploid, no chromosome pairs)
The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus
The mid-piece is packed with mitochondria to release energy (via respiration) for the tail movement
The tail rotates, propelling the sperm cell forwards and allowing it to move towards the egg

49
Q

What is a tissue?

A

Cells grouped together to work efficiently.

50
Q

What are organs?

A

Tissues grouped together that are coordinated together to perform a variety of functions.

Biology (7 decks)

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