Cells (2.1 and 2.2) Flashcards

Question

What does the nucleoplasm do?

Answer 1

- contains molecules such as nucleotides and enzymes which are needed for DNA and RNA synthesis

Answer 2

- to allow entry of pruvic acid and oxygen - allow exit of ATP and carbon dioxide

Answer 3

- greatly increases surface area for the attachment of enzymes -To increase the capacity of the mitochondrion to synthesize ATP, the inner membrane is folded to form cristae. These folds allow a much greater amount of electron transport chain enzymes and ATP synthase to be packed into the mitochondrion.

Answer 4

Ultrastructure is the architecture of cells and biomaterials that is visible at higher magnifications than found on a standard light microscope.

Answer 5

- They facilitate cell movement, cell division, and transportation of materials within the cells. -Makes up the cytoskeleton of the cell

Answer 6

- Chromatin refers to a mixture of DNA and proteins that form the chromosomes found in the cells of humans and other organisms. - euchromatin = loosely packed DNA, available for transcription

Answer 7

- Transfer genetic code found in DNA out of nucleus and carry it into ribosomes within the cytoplasm.

Answer 8

Cilia - Made of microtubules. Numerous hairlike short, thin extensions of plasma membrane involved in movement i.e. allows movement of substances over cell surface. Flagella - Singular long, thin extensions of plasma membrane involved in movement i.e contract in sperm cells for cell movement. Flagella is made of longer microtubules

Answer 9

Tightly packed DNA , generally unavailable for transcription

Answer 10

Strong, flexible protein filaments that can elongate and contract. These are involved in moving organelles and controlling the shape of the cell.

Answer 11

Supports, strengthens and structures a cell

Answer 12

Long stranded molecule carrying the developmental and functional instructions for life

Answer 13

how many times bigger the image of a specimen observed is in compared to the actual (real-life) size of the specimen

Answer 14

Resolution is the ability to distinguish between two objects as seperate from one another. -The resolution of a light microscope is limited by the wavelength of light. As light passes through the specimen, it will be diffracted The longer the wavelength of light, the more it is diffracted and the more that this diffraction will overlap as the points get closer together

Answer 15

An eyepiece lens, which often has a magnification of x10 A series of (usually 3) objective lenses, each with a different magnification

Answer 16

eyepiece lens magnification x objective lens magnification = total magnification

Answer 17

Electron microscopes have a much higher resolution and magnification than a light microscope as electrons have a much smaller wavelength than visible light. This means that they can be much closer before the diffracted beams overlap

Answer 18

magnification = image size / actual size of object

Answer 19

- Optical microscopes use light to form an image - This limits the resolution of optical microscopes Using light, it is impossible to resolve (distinguish between) two objects that are closer than half the wavelength of light - Optical microscopes have a maximum resolution of around 0.2 micrometres (µm) or 200 nm - magnification of x 1500 This means optical microscopes can be used to observe eukaryotic cells, their nuclei and possibly mitochondria and chloroplasts but cannot be used to observe smaller organelles such as ribosomes, the endoplasmic reticulum or lysosomes

Answer 20

- 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. A beam of electrons has a much smaller wavelength than light, so an electron microscope can resolve (distinguish between) two objects that are extremely close together - magnification of x 1500000 -resolution of 0.0002 micrometers - electron microscopes can be used to observe small organelles such as ribosomes, the endoplasmic reticulum or lysosomes

Answer 21

Light microscopes are used for specimens above 200 nm. Light microscopes shine light through the specimen, this light is then passed through an objective lens (which can be changed) and an eyepiece lens (x10) which magnify the specimen to give an image that can be seen by the naked eye. The specimens can be living (and therefore can be moving), or dead Light microscopes are useful for looking at whole cells, small plant and animal organisms, tissues within organs such as in leaves or skin Electron microscopes, both scanning and transmission, are used for specimens above 0.5 nm Electron microscopes fire a beam of electrons at the specimen either a broad static beam (transmission) or a small beam that moves across the specimen (scanning) The electrons are picked up by an electromagnetic lens which then shows the image Due to the higher frequency of electron waves (a much shorter wavelength) compared to visible light, the magnification and resolution of an electron microscope is much better than a light microscope Electron microscopes are useful for looking at organelles, viruses and DNA as well as looking at whole cells in more detail Electron microscopy requires the specimen to be dead

Answer 22

- Transmission electron microscopes - Scanning electron microscopes.

Answer 23

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) HOWEVER 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

Answer 24

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

Answer 25

A: They can be used on thick or 3-D specimens They allow the external, 3-D structure of specimens to be observed D:They give lower resolution images (less detail) than TEMs 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)

Answer 26

- things we see down a microscope that aren't part of the cell or specimen i.e dust, air bubbles, fingerprints. - common in electron micrographs because specimens need a lot of preparation before we view them under a microscope

Answer 27

Starch grains are large enough to be seen with a light microscope but they first require staining in order to be seen easily. Iodine in potassium iodide solution can be used to stain starch grains. This can be done by adding a drop of potassium iodide onto the specimen (mounted on a slide) before placing a coverslip over the top. This makes the starch grains darker in colour, making them easier to see. Remember, iodine in potassium iodide solution has a light orange-brown colour but turns blue-black in the presence of starch

Answer 28

- By repeatedly preparing specimen in different ways. If an object could be seen with one preparation technique and not another, it was most likely an artefact

Answer 29

- Much smaller than eukaryotic cells - Prokaryotic cells -They also differ from eukaryotic cells in having: cytoplasm that lacks membrane-bound organelles smaller ribosomes no nucleus; instead they have a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins a cell wall that contains murein, a glycoprotein. In addition, many prokaryotic cells have: cell surface membrane made of lipids and proteins and it controls the movement of substances into and out of the cell. They instead have: one or more plasmids a capsule surrounding the cell one or more flagella.

Answer 30

- small loops of DNA that are seperate from the main circular DNA molecule. - contains genes that can be passed between prokaryotes ( i.e AB resistance ) - not present in all prokaryotes

Answer 31

- a final outer layer that helps protect bacteria dying out and from attack by cells of the immune system of the host organism - not present in all prokaryotes

Answer 32

A long, hair -like structure that rotates, enabling the prokaryote to move (a bit Like a propeller). Some prokaryotes have more than one. Not present in all prokaryotes.

Answer 33

- Flagellum - Slime capsule - protects cell - Plasmid - a small loop of DNA - Pili - attaches bacterial cell to other cells/surfaces - involved in sexual reproduction because during the process of bacterial conjugation, conjugative pili allow the transfer of DNA between bacteria ( they allow for the exchange of genes via the formation of "mating pairs ) - Infolding of cell surface membrane - It helps in increasing the surface area and also helps in secreting enzymes and in respiration.

Answer 34

- cell wall containing peptidoglycan and murein - cell surface membrane - cytoplasm - circular DNA - ribosomes

Answer 35

the idea that all living organisms are made of cells The cell theory is a unifying concept in biology (it is universally accepted)

Answer 36

- All living organisms are made up of one or more cells - Cells are the basic functional unit (i.e. the basic unit of structure and organisation) in living organisms - New cells are produced from pre-existing cells

Answer 37

The nucleus of a cell contains chromatin (a complex of DNA and histone proteins) which is the genetic material of the cell

Answer 38

Sections of linear DNA tightly wound around proteins called histones

Answer 39

- 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

Answer 40

In complex multicellular organisms, eukaryotic cells become specialised for specific functions. Specialised cells are organised into tissues, tissues into organs and organs into systems.

Answer 41

The shape of the cell e.g. Red blood cells are biconcave and do not contain a nucleus. This makes more space inside the cell so that they can transport as much oxygen as possible The organelles the cell contains (or doesn’t contain) e.g. Cells that make large amounts of proteins will be adapted for this function by containing many ribosomes (the organelle responsible for protein production)

Answer 42

Function: Conduction of impulses Adaptations: Has a cell body where most of the cellular structures are located and most protein synthesis occurs Extensions of the cytoplasm from the cell body form dendrites (which receive signals) and axons (which transmit signals), allowing the neurone to communicate with other nerve cells, muscles and glands The axon (the main extension of cytoplasm away from the cell body) is covered with a fatty sheath, which speeds up nerve impulses. Axons can be up to 1m long in some animals and can therefore enable fast communication over long distances (from the brain all the way to the toes only using a few neurones!)

Answer 43

Function: Contraction for movement Adaptations: There are three different types of muscle in animals: skeletal, smooth and cardiac (heart) All muscle cells have layers of protein filaments in them, these layers can slide over each other causing muscle contraction Muscle cells have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction Skeletal muscle cells fuse together during development to form multinucleated cells that contract in unison

Answer 44

Function: Reproduction - to fuse with an egg, initiate the development of an embryo and pass on fathers genes Adaptations: 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

Answer 45

Function: Absorption of water and mineral ions from soil Adaptations: Root hair to increase surface area (SA) so the rate of water uptake by osmosis is greater (can absorb more water and ions than if SA were lower) Thinner walls than other plant cells so that water can move through easily (due to shorter diffusion distance) Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient Mitochondria for active transport of mineral ions Remember that chloroplasts are not found in these cells – there’s no light for photosynthesis underground!

Answer 46

Function: transport tissue for water and dissolved ions Adaptations: No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration Cells are essentially dead, without organelles or cytoplasm, to allow free movement of water Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant

Answer 47

Function: transport of dissolved sugars and amino acids Adaptations: Made of living cells (as opposed to xylem vessels which are made of dead cells) which are supported by companion cells Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through (by translocation) Cells also have very few subcellular structures to aid the flow of materials

Answer 48

Epithelial cells group together to form epithelial tissue (the function of which, in the small intestine, is to absorb food) Adaptations: - wall of small intestine has villi which are folds in cell surface membrane and increase surface area for absorption - epithelial cells = on the surface of villi have micro villi = increase surface area more - lots of mitochondria - provides energy for the transport of digested food molecules into the cell

Answer 49

- DNA for proteins is coded - Ribosomes on RER make the translation -Mitochondria releases ATP for the reaction/ process -Golgi apparatus modify the protein that get transported in the vesicular transport

Answer 50

Prokaryotic cells are much smaller than eukaryotic cells (between 100 - 1000 times smaller)

Answer 51

- no nucleus = more room for the oxygen carrying haemoglobin

Answer 52

- lots of mitochondria = provides large amounts of energy they need to move around

Answer 53

- how prokaryotic cells replicate. In binary fission, cells replicate its genetic material, before physically splitting into 2 daughter cells.

Answer 54

1) Circular DNA and plasmids replicate. Main DNA loop can only be replicated once but the plasmids can be replicated lots of times 2) Cells gets bigger and DNA loops move to opposite poles of the cell 3) Cytoplasm begins to divide and the new cell wall begins to form 4) Cytoplasm divides and 2 daughter cells are produced. Each daughter cell has one copy of the circular DNA but can have a variable number of plasmid copies.

Answer 55

Viruses are acellular and non living. They are essential just nucleic acid surrounded by protein. Examples are: Influenza, HIV, Rhinovirus, Coronavirus

Answer 56

Viruses replicate by injecting their nucleic acid into a host cell: First, a virus uses attachment proteins on its surface to bind to complementary receptor proteins on the surface of a host cell The virus then injects its DNA or RNA into the host cell The host cell then uses its nucleic acid and protein-building machinery (ribosomes) to produce new viral particles Eventually, the new viral particles are released. This may occur when: The host cell bursts open, releasing all the new viral particles at once Viral particles leave individually through the host cell membrane via a process known as ‘budding’

Answer 57

The exiting of viruses damages their host cells, causing disease For example, HIV infects cells of the immune system (such as helper T cells and macrophages) When the newly replicated HIV particles exit, these host cells are destroyed Over time, the immune system becomes severely compromised and this eventually leads to Acquired Immunodeficiency Syndrome (AIDS)

Answer 58

Viruses are acellular and non living. Much smaller than prokaryotic cells. They are essential just nucleic acid surrounded by protein. Examples are: Influenza, HIV, Rhinovirus, Coronavirus. Viruses invade and reproduce inside the cells of other organisms. The cells are called host cells

Answer 59

A nucleic acid core (their genomes are either DNA or RNA, and can be single or double-stranded). This so that the genome can be transcribed and translated into the host cell. A protein coat called a ‘capsid’ = a protective protein coat that sometimes is covered in a lipid layer called the envelope, formed usually from the membrane-phospholipids of a cell they were made in Attachment proteins - viruses use these to bind to host cells and infect them

Answer 60

All viruses are parasitic in that they can only reproduce by infecting living cells by injecting their DNA or RNA into the host cell. The hjjacked cell then uses its own machinery i.e ribosomes and enzymes to replicate the new viral particles.

Answer 61

To inject DNA/RNA, viruses first have to attach to the host cell surface. They do this by using attachment proteins to bind to complementary receptor proteins on cell surface membrane of host cell. As different viruses have different attachment proteins on host cells, some viruses can only infect one type of cell and some can infect many.

Answer 62

It is easier to find what you are looking for in the field of view This helps to prevent damage to the lens or coverslip incase the stage has been raised too high

Answer 63

A graticule is a small disc that has an engraved scale. It can be placed into the eyepiece of a microscope to act as a ruler in the field of view As a graticule has no fixed units it must be calibrated for the objective lens that is in use. This is done by using a scale engraved on a microscope slide (a stage micrometer) By using the two scales together the number of micrometers each graticule unit is worth can be worked out After this is known the graticule can be used as a ruler in the field of view

Answer 64

to find out how many micrometers each graticule unit represents

Answer 65

The drawing must have a title The magnification under which the observations shown by the drawing are made must be recorded A sharp HB pencil should be used (and a good eraser!) Drawings should be on plain white paper Lines should be clear, single lines (no thick shading) No shading The drawing should take up as much of the space on the page as possible Well-defined structures should be drawn The drawing should be made with proper proportions Label lines should not cross or have arrowheads and should connect directly to the part of the drawing being labelled Label lines should be kept to one side of the drawing (in parallel to the top of the page) and drawn with a ruler

Answer 66

An eyepiece lens, which often has a magnification of x10 A series of (usually 3) objective lenses, each with a different magnification

Answer 67

eyepiece lens magnification x objective lens magnification = total magnification

Answer 68

Electron microscopes have a much higher resolution and magnification than a light microscope as electrons have a much smaller wavelength than visible light. This means that they can be much closer before the diffracted beams overlap

Answer 69

Look at the appearance of the specific organelle under an electron microscope Conduct research on the specific organelle (for example, to learn more about its function)

Answer 70

M1: To do this, a pure sample is needed (containing only the specific organelle being studied) M2: The process of separating cell organelles from each other is known as cell fractionation and involves breaking up a suitable sample of tissue and then centrifuging the mixture at different speeds. M3: Cell fractionation can be split into three stages: Homogenisation Filtration Ultracentrifugation

Answer 71

Homogenisation = breaking up of cells. The sample of tissue (containing the cells to be broken up) must first be placed in a cold, isotonic buffer solution The solution must be: 1. Ice-cold to reduce the activity of enzymes that break down organelles 2. Isotonic (it must have the same water potential as the cells being broken up) to prevent water from moving into the organelles via osmosis, which would cause them to expand and eventually damage them 3. Buffered (have a buffer solution added) to prevent organelle proteins from becoming denatured The tissue-containing solution is then homogenised using a homogeniser. This is a blender-like machine that grinds the cells up (the cells can also be vibrated until they break up) and breaks the plasma membrane of the cells and releases the organelles into a solution called the homogenate.

Answer 72

The homogenate (containing the homogenised cells) is then filtered through a gauze. This is to separate out any large cell debris or tissue debris that were not broken up. The organelles are all much smaller than the debris and are not filtered out (they pass through the gauze). This leaves a solution (known as the filtrate) that contains a mixture of organelles

Answer 73

The filtrate is placed into a tube and the tube is placed in a centrifuge (a machine that separates materials by spinning). The filtrate is first spun at a low speed. This causes the largest, heaviest organelles (such as the nuclei) to settle at the bottom of the tube, where they form a thick sediment known as a pellet The rest of the organelles stay suspended in the solution above the pellet. This solution is known as the supernatant. The supernatant is drained off and placed into another tube, which is spun at a higher speed. Once again, this causes the heavier organelles (such as the mitochondria) to settle at the bottom of the tube, forming a new pellet and leaving a new supernatant. The new supernatant is drained off and placed into another tube, which is spun at an even higher speed This process is repeated at increasing speeds until all the different types of organelle present are separated out (or just until the desired organelle is separated out). Each new pellet formed contains a lighter organelle than the previous pellet

Answer 74

Nuclei Chloroplasts (if carrying out cell fractionation of plant tissue) Mitochondria Lysosomes Endoplasmic reticulum Ribosomes

Cells (2.1 and 2.2) Flashcards

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