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Cells Flashcards

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1
Q

Cell-Surface Membrane Structure

A

Encloses a semi-solid substance called cytosol, which is made of proteins and other dissolved substances, within it are many organelles (Cytoplasm)

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2
Q

Cell-Surface Membrane Function

A

Allows the creation and maintenance of a particular internal environment,

It separates the cell from its surroundings by controlling what moves in and out,

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3
Q

Nucleus Structure

A

Contains most of the cells DNA, Chromosomes extend throughout the nucleus as chromatin,

Nuclei have one or more nucleoli,

The nucleus is bound by a nuclear envelope made of two membranes,

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4
Q

Nucleus Function

A

Has the information required to make a new copy of a cell and control the cell,

Nucleoli produce RNA to make ribosomes,

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5
Q

Mitochondria Structure

A

Surrounded by an enveloped of two membranes, an outer one and a highly folded inner one,

Has a matrix that contains free enzymes that catalyse respiration reactions,

Contain their own DNA,

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6
Q

Mitochondria Function

A

The site of aerobic respiration,

ATP is synthesised in the matrix,

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7
Q

Endoplasmic reticulum Structure

A

A Network of membrane-bound channels that run throughout the cytosol of every cell.

They link up with the nuclear envelope

The membranes sometimes have ribosomes on the outer surface, those that have are rough and those without are smooth,

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8
Q

Endoplasmic reticulum Function

A

The SER are where many lipids are synthesised,

Proteins made on the ribosomes move into the lumen between the membranes so they can be moved to other parts of the cell,

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9
Q

The SER are where many lipids are synthesised,

Proteins made on the ribosomes move into the lumen between the membranes so they can be moved to other parts of the cell,

A

The smallest organelles made of RNA and protein

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10
Q

Ribosome Function

A

They synthesise proteins

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11
Q

They synthesise proteins

A

A group of flattened membrane-bound cavities,

It constantly changes as material comes in one side from the ER and is lost from the other as vesicles ‘buff off’,

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12
Q

Golgi apparatus Function

A

It takes enzymes and other proteins that have been synthesised in the ER and packages them into membrane-bound vesicles,

They are often processed, for example adding short carbohydrate chains,

Vesicles transport materials to other part of the cell or fuse with the membrane to release their contents outside of the cell (secretion)

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13
Q

Lysosome Structure

A

Vesicles produced by the Golgi apparatus that contain digestive enzymes called lysozymes,

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14
Q

Lysosome Function

A

The lysozymes enzymes can destroy (by hydrolysis), old or surplus organelles inside the cell,

Whole cells and tissues that are no longer needed can be destroyed if cells nearby allow lysosomes to release their contents,

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15
Q

Chloroplast Structure

A

Surrounded by two membranes that control what enters and leaves,

It encloses a mixture of water, enzymes and other substances (the stroma) which contain and intricate series of membranes, creating spaces called thylakoids, in which theses membranes form stacks called grana,

They also contain their own circular DNA and starch granules,

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16
Q

Chloroplast Function

A

Chlorophyll harvests light energy in the grana,

The arrangement of the grana and thylakoids maximises the absorption of light energy,

Then the energy is used to convert carbon dioxide to carbohydrates in the stroma,

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17
Q

Cell Wall Structure

A

Made of cellulose (polysaccharides that lie side by side), In cell wall these are embedded in a background material (matrix) made of pectin,

The wall is built up in layers with the orientation of the cellulose microfibrils being different in each, creating a material that in immensely strong for its weight,

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18
Q

Cell Wall Function

A

It is fully permeable,

It provides support to the cell, when a plant cell absorbs water the cell wall resists the expansion and the cell becomes firm and strong,

Where plant cells lie side by side their cell walls are physically linked together through a layer of pectin,

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19
Q

Vacuole Structure

A

A liquid-filled space inside a cell, surrounded by a membrane,

All cells have vacuoles but many are very small and called vesicles,

They are very large in plant cells,

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20
Q

Vacuole Function

A

It contains many different substances in solution, such as sucrose and amino acids, It can be used for storage and to isolate substances that may be harmful to the rest of the cell,

It also helps maintain cell turgidity,

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21
Q

What are the two prokaryotic cell domains?

A

Archaea and Bacteria

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22
Q

Similarities between prokaryotic and eukaryotic cells

A

Surrounded by a cell-surface membrane and contains cytosol

Also both have ribosomes but the prokaryotic cells have smaller ones (70s)

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23
Q

Do prokaryotic cells have a nucleus?

A

No but they do have DNA in the form of a single circular DNA molecule,

The DNA is also not associated with protein like it is in eukaryotic cells and do not have chromosomes,

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24
Q

What are Plasmids,

A

Much smaller loops of DNA in prokaryotic cells than can be easily exchanged between bacteria as a way of passing genes,

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25
What is the prokaryotic cell wall made of?
Murein, a polymer with amino acids and sugars, (a glycoprotein)
26
What is a capsule?
An extra layer outside of the cell wall of prokaryotic cells, it is made of polysaccharide and provides as extra protection,
27
How to prokaryotic cells move,
Flagella, they are long protein structures that are attached to the cell membrane and propel the flagellum along by twisting,
28
What a viruses?
Tiny particles of nucleic acid, either DNA or RNA, enclosed in a protein coat called a capsid, They are not made of cells (acellular) and therefore not a living organism,
29
How to viruses replicate?
They invade a living cell by attaching the protein molecules on the capsid to the cell surface membrane of the cell, the virus then enters the cell and its DNA/RNA hijacks the machinery of the cell, The cell copies the virus's RNA/DNA, makes new protein coats and assembles new viruses, They eventually burst out of the cell and destroy it.
30
How do optical microscopes work?
They use rays of light to pass through the specimen and produce an image on the retina of your eye.
31
Pros and cons of optical microscopes
Pros: Relatively inexpensive and easy to maintain, Easy to prepare specimens to view them, Can view living organisms through them, Cons: You can only see the larger organelles in them d
32
What is resolution?
The ability to distinguish between two objects
33
What is magnification?
The number of times larger an image is than the original object
34
How do transmission electron microscopes work?
Very thing slices of a specimen are embedded in resin then cut even thinner, They are then stained using heavy metals which are taken up by some parts of the specimen which will then not allow electrons to pass through and appear darker, It is then placed in a chamber which is sealed to produce a vacuum, electromagnets act as lenses and focus a beam of electrons that pass through the specimen and onto a viewing screen.
35
How do scanning electron microscopes work?
The beam is produced in the same way as the tem but the beam is them focused by one or two condenser lenses into a beam with a very fine focal spot, the beam passes through pairs of scanning coils in the objective lense, The beam is deflected vertically and horizontally and produces a 3d image
36
Pros and cons of the TEM
Not possible to view living specimens, Its difficult to make the very thin sections for viewing, Do not produce images in colour but you can use a computer to help distinguish areas, Higher resolution and magnification due to shorter electron wavelength,
37
Pros and cons of the SEM
Can produce a 3d image, Higher resolution and magnification than optical but not as high an TEM, Can scan a relatively large area of the specimen, Can image bulk materials,
38
What is cell fractionation?
Breaking open cells to view their organelles without damaging them
39
How do you separate different organelles in fractionated cells?
Spin them in a centrifuge so the larger, heavier particles accumulate at the bottom (the pellet) and everything else stays in liquid form (the supernatant), The pellet can be removed and the process is repeted to slowly separate all the organelles, speeding the centrifuge up more each time.
40
What liquid is used in a homogeniser?
Ice cold to prevent enzyme activity, Same water concentration to prevent cells bursting/shrinking, Same pH to prevent enzymes/proteins denaturing,
41
What is mitosis?
The part of the cell cycle where the cell divides.
42
What is Interphase?
Most time is spent in this phase, This is when DNA replicates, Individual chromosomes are not visible but just before the cell is about to start mitosis the DNA coils up to form thick, visible chromosomes, this makes it less likely DNA will break away and get lost, Each chromosome is made of two chromatids joined by an centromere,
43
What is prophase?
The two membranes of the nuclear envelope break, Spindle fibres made from microtubules for a set of radiating strands from each end of the cell, Two spindle fibres, one from each end of the cell, attach to each of the centromeres.
44
What is metaphase?
The spindle fibres pull the chromosomes so they end up in a line across the centre of the cell.
45
What is anaphase?
The spindle fibres shorten and pull the two chromatids of each chromosome apart, the fibres continue to shorten dragging the chromatids to each end of the cell, This ensures one copy of each DNA goes to each daughter cell
46
What is telophase?
When the sets of chromatids arrive at the poles they start to unravel and become invisible long strands of DNA, The nuclear envelope reforms, Now mitosis has finished and the rest of the cell splits in half in cytokinesis,
47
What is a tumour?
When a group of cell divide uncontrollably, usually forming a lump and can shed cells that form secondary tumours in other parts of the body,
48
How do prokaryotes divide?
By binary fission; First the circular DNA molecule replicated (and any plasmids), The identical DNA molecules are moved to opposite ends of the cell and the cell splits, The two new cells have an identical copy of the circular DNA molecule but may have different numbers of plasmids, Mitochondria and chloroplasts also divide by binary fission.
49
How do phospholipids form a bilayer?
They have hydrophilic heads and hydrophobic tails so when they are in water they orientate themselves so their heads face into the water and their tails away- naturally forming a bilayer
50
How to proteins behave in a membrane?
They are embedded in the phospholipid layers, Some span from one side to the other, Some appear on one face only, Some form passageways through,
51
Why is it said to be a fluid-mosaic structure?
The phospholipid and protein molecules fit together to form a continuous pattern like tiles in a mosaic, however not all molecules are fixed in place - they can move around so it is described as fluid
52
What are glycoproteins and glycolipids?
Some protein and lipid molecules in the bilayer have 'branches' attached which are little chains of sugar molecules. These are composite molecules, part protein or lipid and part carbohydrate, They interact with molecules that arrive at the cell surface from its environment
53
What is the role of cholesterol in the bilayer?
It provides stability by placing itself between the phospholipids, It is found in small quantities in plant cells and large quantities in animal cells
54
Factors that affect the rate of diffusion
The concentration gradient (difference in concentration between two volumes) The length of the diffusion pathway between two volumes, The size of the molecules/ ions that are diffusing, The temperature- higher means more kinetic energy so the particles move faster
55
How does diffusion work?
All particles are in constant random motion which results in the net movement of particles from a region of high concentration to lower concentration
56
What is simple diffusion?
When small, non-polar, lipid-soluble molecules can diffuse through the cell surface membrane easily
57
What is facilitated diffusion
When larger molecules and substances with significant charges cannot diffuse through the cell surface membrane and require proteins to help them
58
What are the proteins involved in facilitated diffusion?
Channel proteins- Channels that are a specific size for particular ions, so they can slip through to the other side Gated Channel proteins- The cell can decide whether it is open or closed, Carrier proteins- The molecule binds temporarily with the protein which then changes shape so the molecule passes through it to the other side
59
What is osmosis?
Water molecules are very small so are able to slip through the phospholipid bilayer- and because water it on both sides of the membrane and so many substances are dissolved in it cannot dissolve through the bilayer so it is given its own name due to its importance
60
What is water potential?
A term for the amount of water in a solution, It is also the tendency of water to move out of a solution When water moves from an area of high water potential to low water potential it has moved down the water potential gradient, A dilute solution has a higher water potential than a concentrated solution
61
What is active transport?
Sometimes cells need to move substances into the cell that are in a smaller concentration than outside, the cell has to use energy which almost always comes from the hydrolysis of ATP,
62
How are carrier proteins used in active transport?
The phosphate group of ATP attaches to the carrier protein so it accepts the particle, energy is transferred to the carrier protein and it changes shape which transports the particle across the membrane
63
What is co-transport?
When the movement of one substance along its gradient provides the energy for the movement of another substance against its concentration gradient

Biology (11 decks)

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