Cell Structure & Transport Flashcards
(102 cards)
1
Q
What is the function of the nucleus?
A
- Contains the organisms hereditary material called chromatin
- Controls cell activities through production of mRNA
2
Q
What is the function of the mitochondrion?
A
To carry out aerobic respiration
-also can produce its own proteins
3
Q
Describe structural features of a chloroplast.
A
- The chloroplast envelope: (membranes) allows substances to enter and leave.
- Thylakoids: disks containing chlorophyll, arranged in stacks called Grana.
- Stroma: the fluid filled matrix.
4
Q
What is the structure of a nucleus?
A
- Nuclear envelope: a double membrane with lots of nuclear pores allowing molecules out, e.g RNA.
- Nucleoplasm: granular jelly like material.
- Nucleolus: manufactures RNA.
- Membrane can be continuous with the endoplasmic reticulum.
5
Q
What are the structural features of the mitochondrion?
A
- Double membrane: entry and exit of substances.
- The inner membrane is folded as Cristae, providing a larger SA for enzymes and proteins during respiration.
- Matrix: rest of the space, containing proteins, ribosomes, enzymes, lipids, and DNA so it can produce its own proteins.
- Rod like shape.
6
Q
What is the function of chloroplasts?
A
To carry out photosynthesis.
- also contain DNA and ribosomes.
7
Q
What is the function of the smooth endoplasmic reticulum?
A
Involved in the production, processing, and storage of carbohydrates, steroids, and mainly lipids.
8
Q
What is the structure of the smooth endoplasmic reticulum?
A
It has no ribosomes on its surface.
9
Q
What are lysosomes?
A
Vesicles which contain hydrolytic enzymes that break biological molecules down.
10
Q
What is the function of lysosomes?
A
Used to break down waste material e.g worn out organelles.
11
Q
Lysosome structure?
A
- Membrane
- Hydrolytic enzymes
- Transport proteins on the surface
12
Q
What is the function of the rough endoplasmic reticulum?
A
Processes proteins and glycoproteins made by ribosomes.
13
Q
Describe the structure of the rough endoplasmic reticulum.
A
- Covered in ribosomes.
- In places it’s continuous with the nuclear envelope.
14
Q
What is the structure of the Golgi Apparatus?
A
- Made up of flattened sacs of membrane called Cisternae.
- Similar to smooth ER but more compact.
15
Q
Describe the process of the Golgi Apparatus?
A
- Receives proteins (made in the rough ER) and other molecules in vesicles.
- Molecules become modified, make their way up through the Golgi and eventually packaged up into vesicles.
- The vesicles take the molecules to where they need to go e.g other membrane bound organelles.
16
Q
Where are ribosomes formed, found, and made up of?
A
- Found freely in the cytoplasm, or on the surface of the rough ER.
- Formed in the nucleolus.
- Composed of almost equal amounts of RNA and proteins.
17
Q
What is the function of ribosomes?
A
The site of protein synthesis
18
Q
How many subunits of ribosomes do Eukaryotic cells have?
A
80s ribosomes: made up of 60s and 40s subunits.
19
Q
How many subunits of ribosomes do Prokaryotic cells, mitochondria, and chloroplasts have?
A
70s ribosomes: made up of 50s and 30s subunits.
20
Q
What is the function of cell walls?
A
To give structural support to the cell as it is made up of a strong polysaccharide called cellulose, or chitin in fungi.
21
Q
Describe the structural features of the cell wall (cellulose)
A
- Cellulose forms larger molecules called microfibrils, which form a mesh like structure.
- In between plant cell walls is the middle lamella made of mineral ions and polysaccharides, acts as a glue.
- Plasmodesmata are small channels in the cell wall used for exchange of substances with other cells.
22
Q
What is the structure of the cell membrane?
A
-A partially permeable surface that allows substances to enter and leave the cell.
- Has receptor molecules to respond to hormones.
- Formed from a phospholipid bilayer.
23
Q
Structure of the vacuole
A
- Fluid filled sac bound by a single membrane called tonoplast.
- In mature plant cells, there may be a large central vacuole containing a solution of mineral salts, sugars, amino acids, wastes and pigments.
24
Q
What is the function of the vacuole?
A
- Act as a temporary food source
- Supports plants by making cells turgid
- Pigments may colour petals to attract pollinators.
25
What is the function of microtubules?
Part of the cytoskeleton of a cell, providing support and cellular locomotion, determines shape.
26
Describe the structure of microtubules.
Made up of alpha and beta tubulin dimers which join to form protofilaments.
27
What is pinocytosis?
The ingestion of extracellular fluids (fluid surrounding the cell)
28
How do pinocytotic vesicles work?
1. The cell membrane will pinch inwards, trapping some extracellular fluid and forming a pinocytotic vesicle.
2. The pouch is pinched off at the membrane and can then travel into the cytosol of the cell.
29
What does Eukaryotic mean?
The cell has a nucleus
30
What does prokaryotic mean?
The cell does NOT have a nucleus e.g a bacterial cell
31
What is Pili and why do bacterial cells have them?
Hair like projections on the surface of the cell that can attach to other surfaces and transfer genetic material
32
What is function of the Slime Capsule in a bacterial cell and where is it?
It is the outer most layer that protects the bacteria and is capable of producing toxins (makes us feel sick)
33
What type of ribosomes are in prokaryotic cells like bacteria?
70s ribosomes that are free in the cytoplasm
34
What is the smaller cell: Prokaryotic or Eukaryotic?
Prokaryotic
35
What does the cell wall do and where is it found in a bacterial cell?
The cell wall, made of murein, is between the slime capsule and cell membrane. Gives structure and prevents damage against osmotic lysis.
36
Where is the genetic material in a prokaryotic cell?
In the nucleoid, which is a circular loop
37
What are plasmids?
Small rings of DNA that aid the survival of the bacteria e.g producing enzymes that beak down antibiotics
38
Why do some bacterial cells have flagella?
In order to move
39
How do prokaryotic cells respire if they don't have mitochondria?
They have infolds of the cell membrane called mesosomes which provide large surface are for enzymes to attach for respiration.
40
How do some prokaryotic cells photosynthesise?
A chlorophyll pigment attached to the cell surface membrane.
41
What is step one of 'Cell Fractionation' and how is it carried out?
Homogenisation:
1. Cut a sample of tissue
2. Place in an ice-cold, buffered, isotonic solution
3. Break open the plasma membrane to release organelles, either by a blender or homogeniser- where you are then left with 'homogenate'
42
What is step two of 'Cell Fractionation' and how is it carried out?
Filtration:
- The homogenate is filtered through a gauze to separate any large cell debris e.g connective tissue or the cell wall
- Organelles are small enough to pass through the gauze
43
What is step three of 'Cell Fractionation' and how is it carried out?
Ultracentrifugation:
1. The homogenate is poured into a tube which is put into a 'Centrifuge' and spun at a low speed
2. The heaviest organelles (Nuclei) are flung to the bottom where it forms a thick sediment called a 'pellet', and the rest of the organelles are in the liquid above called the 'supernatant'.
3. The supernatant is drained off into another tube and spun at a higher speed, where, again, the heaviest organelles will form a pellet, this time the mitochondria.
4. This process is repeated until you get to the lightest organelle, by increasing the speed each time.
*Keep the pellets on ice so enzymes don't denature.
44
How does a Transmission Electron Microscope work?
-An electron gun fires a beam focused on the specimen by a condenser electromagnet.
-The beam passes through a thin section of specimen and into a vacuum below.
-Denser parts of the specimen absorb more electrons, appearing darker on the image.
*Specimen has to dead
45
How does a Scanning Electron Microscope work?
-Focuses a beam of electrons onto the surface of the specimen from above, this does not penetrate.
-The electrons scatter, creating a 3D image.
*specimen has to be dead
46
How does an Optical (light) Microscope work?
They use light to form an image :)
47
+ and - of the transmission electron microscope
+High res
+High mag
+Short wavelength
+Internal cell structures can be seen
-Electrons may damage specimen
-Image may contain artefacts
-Has to be really thin
-Black and white image
-Needs a vacuum
-Large and expensive
48
+ and - of the scanning electron microscope
+Does not have to be thin
+Can see 3D structures
-Electrons may damage specimen
-Image may contain artefacts
-Black and white image
-Large and expensive
-Slightly lower res than TEM
49
+ and - of the Optical (light) Microscope
+Living specimen
+Colour
+Smaller
+Cheaper
-Low res
-Low mag
-Can't see smaller organelles e.g ribosomes, lysosomes
50
What is the resolving power of an optical microscope (nm)?
500-600nm
51
What is the resolving power of a scanning electron microscope (nm)?
20nm
52
What is the resolving power of a transmission electron microscope (nm)?
0.1nm
53
Name the order of units (biggest to smallest) and what you times and divide by for microscopes.
Biggest: Centimetre (cm)
➗10↑ ↓x10
Millimetre (mm)
➗1000↑ ↓x1000
Micrometre (um)
➗1000↑ ↓x1000
Nanometre (nm)
Smallest:
54
Name the 4 structures of a virus and their role
- Capsid: a protein structure that holds the genetics
- Attachment Proteins: stick out of the sides and attach to host cell in order to enter
- Genetic material: of DNA or RNA that are in a string sort of form
- Lipid Envelope: formed by the host cell membrane, not all have one, around the capsid.
55
Is a virus a living organism, and is it a cell?
No and no: cannot reproduce without a host cell so is not living, and is just made of nucleic acid surrounded by a protein so not a cell.
56
Briefly describe virus reproduction
1. Attachment proteins bind to the complementary receptor proteins of the host cell to attach.
2. The virus enter the host cell and injects their DNA or RNA.
3. The virus uses the host cells enzymes to produce copies of itself.
4. Virus particles leave the cell
* viruses can only enter certain cells based on their different attachment proteins and the host cells complementary receptors.
57
What is an eyepiece graticule and how do you work out the the length of one eyepiece division?
An eyepiece graticule is a scale in the lens why we have to calibrate.
One eyepiece division= stage micrometer/eyepiece
58
What are the 3 stages of the cell cycle?
1. Interphase
2. Mitosis
3. Cytokinesis
59
In interphase there are 2 checkpoints to look for DNA errors- when are they and what may occur if errors are/not found?
-One before and after Synthesis phase
Damage detected: p53 protein production is activated to stop progression of cell cycle and to repair.
If the DNA cannot be repaired, the cell will go under programmed death- apoptosis.
60
What is the longest stage of the cell cycle?
Interphase
61
What is the structure of a chromosome?
-2 sister chromatids
-A centromere joining them
62
Describe Prophase
-DNA condenses and chromosomes become visible
-Nuclear envelope breaks down and chromosomes are free in the cytoplasm.
-Centrioles move to opposite poles and form spinal fibres made of microtubules- the spindle apparatus
63
Describe metaphase
-Chromosomes are pulled along by the spindle fibres, attached at the centromere
- Arrange themselves along the equator of the cell
64
Describe anaphase
-Centromere splits and chromatids are pulled towards opposite poles
- Chromatids are now chromosomes
- The energy for this process is provided by mitochondria which gather at the spindle apparatus
65
Describe telophase
-Chromosomes reach poles and lengthen to become chromatin.
-Spindle fibres disintegrate
-Nuclear envelope reforms
66
What happens in cytokinesis?
The cytoplasm divides and 2 genetically identical cells are produced.
67
Describe the steps of binary fission (asexual reproduction in prokaryotic cells)
1. DNA and plasmids replicate
2. Septum begins to form and segregates the DNA
3. Cells splits into 2 to form identical daughter cells
68
What is the mitotic index calculation?
Mitotic index = number of cells in stages of mitosis/ total number of cells
(in an image)
69
Describe interphase
G1 to S to G2 phases
-Check points
-Organelles replicate
-Cell grows
-DNA is synthesised in S phase
70
What is a micelle?
Spheres of phospholipids that occur when phospholipids are shaken,
used to deliver drugs in medicine.
71
What 3 types of molecule is the cell membrane made up of?
-Phospholipids
-Proteins
-Carbohydrates
(all in different quantities)
72
How are the phospholipids arranged in a cell membrane (amphipathic molecules)?
With the hydrophilic phosphate head facing outwards, and the hydrophobic fatty acid tails facing inwards
73
What is the function of the phospholipids within a cell membrane?
To allow lipid-soluble substances in and out, and prevent water-soluble substances doing the same
74
Depending on the location of a protein they have different names, what are they?
Intrinsic proteins - within the membrane and span the whole bilayer.
Extrinsic proteins - give mechanical support or act as receptors, on the surface of the membrane.
75
Describe the function of a glycolipid, what it is, and where it is found
-Acts as a recognition site, a chemical receptor, and attach to each other to form tissues.
-Made from a carbohydrate covalently bonded to a lipid.
-Extends from the bilayer like a tree shape.
76
Define Hypotonic
A less concentrated solution outside the cell compared with inside
Cell will look lysed, swell and burst
77
Define Isotonic
The solution outside of the cell has the same solute concentration as inside
Cell will look normal
78
Define Hypertonic
There is more concentrated solution outside the cell compared with inside
Cell will look shrivelled
79
What is facilitated diffusion?
a process that uses channel proteins and carrier proteins to transport substances from an area of high conc to low conc
80
What is a channel protein?
-Water filled pores that allow charged substances to diffuse through the cell membrane.
-Most are gated
81
What is a carrier protein?
-Can switch between two shapes: the binding site will be open on one side at first, and then the other side when it changes shape
-Any ion specific to that protein can get through
82
Define Simple Diffusion
The net movement of molecules or ions from a region of high conc to low, until evenly distributed
83
What is the Ficks Law equation?
(rate of diffusion)
Rate of diffusion =
surface area x conc difference/
thickness of membrane
84
What factors may effect the rate of diffusion?
-Temperature
-Surface area
-Steepness of concentration gradient
-Properties of molecules (e.g polar or large)
85
Describe the function of a glycoprotein, what is it, and where is it found?
-Recognition site, helps cells attach to each other and form tissues, allows cells to recognise each other
-A carbohydrate chain attached to extrinsic proteins on the outer surface
-Cell surface receptors for hormones
86
What is the function of Cholesterol, where is it, and what is it?
-They reduce lateral movement of other molecules including phospholipids, makes the membrane less fluid at high temps, and prevents leaking of water and ions from cell
-Within the phospholipid bilayer
A small hydroxyl group that is hydrophilic, the rest is hydrophobic
87
Define Osmosis
Passage of water from a region of high to low water potential through a selectively permeable membrane
88
What is an aquaporin?
Protein channels that allow water through the membrane.
89
What is water potential?
Created by the pressure of water molecules. Standard conditions water is said to be 0
90
Define active transport
The movement of molecules in or out of a cell from low to high concentration using ATP and carrier proteins.
91
What does active transport allow for cells?
Build up stores of soluble substances that would otherwise spread out by diffusion
92
Describe the process of active transport
1. A molecule/ion binds to a receptor complementary in shape on the carrier protein.
2. ATP binds to the carrier protein from the onside of the cell and is hydrolysed to ADP + Pi
3. The Pi (Phosphate ion) attaches to the protein causing it to change shape and release the molecule to the other side.
4. The Pi is released and protein returns to original shape.
93
Why do we need co-tansport?
In order to absorb glucose into the blood, from the lumen of the ileum to the blood. (or amino acids)
This cannot happen directly by facilitated diffusion because once a certain amount of glucose has diffused into the epithelial and into the blood, there is no longer a conc gradient, so an active process is required.
94
What is the Fluid Mosaic Model and why is it called that?
The arrangement of molecules in a membrane.
Fluid: The arrangement of phospholipid molecules, constantly moving and flexible
Mosaic: Proteins are scattered through the bilayer in random shapes and patterns like tiles in a mosaic
95
Describe the process of Co-transport
1) Sodium (Na) ions are actively transported out of the epithelial cell and into the bloodstream via the sodium-potassium pump (K ions go the other way).
2) A conc gradient has now been created for Na ions, low in the epithelial cell, high in lumen of ileum.
3) The sodium-glucose co-transport protein allows the Na ions to diffuse down their conc gradient into the cell, and glucose molecules along with it via active transport against conc gradient.
4) Glucose now diffuses down conc gradient from cell to blood.
96
What factors may effect the rate of transport across membrane?
-Surface area
-Number of channel/carrier proteins
-Concentration gradient
97
What is cytosis used for and what are the 2 types?
To transport large molecules such as proteins across a membrane.
Exocytosis
Endocytosis
Energy released by the hydrolysis of ATP to ADP is used.
98
What is exocytosis?
Exiting the cell: A vesicle containing molecules of substance fuses with inside of the cell surface membrane and molecules are secreted from the cell (removed).
99
What is endocytosis?
Into the cell: The cell surface membrane binds to molecules: a vesicle sac forms and the sac enters the cell.
e.g phagocytosis (solids) and pinocytosis (liquids)
100
Describe the 'beetroot practical'
-The effect of alcohol concentration on the leakage of pigment from beetroot cells
1. Make colour standards: extract + water to make 6 test tubes containing 5cm^3 of different conc extracts, label 0, 2, 4 ,6 ,8, 10
2. Put data in table
3. Set up a 30℃ water bath
4. With a 2nd set of test tubes, add 2cm^3 of 100, 80, 60 ,40, 20 percent alcohol, add a bung, put in water bath.
4. Blot 10 discs of beetroot with paper towel and gently put 2 discs each into the alcohol test tubes, immediately replace bung.
5. Leave in water bath for 5 minutes and shake every minute.
6. pour each solution into new labelled test tubes and compare these with your colour standards.
7. Record in a table
101
Describe the 'potato practical'
-Determining the water potential of potato tuber cells
1. Label 6 boiling tubes 0, 0.2, 0.4 , 0.6, 0.8, 1.0 mol/dm3 of sucrose.
2. Find the ratio solution:water using the concs to maker up 20cm^3 , write in table.
3. But the boiling tubes in a water bath at 30℃ and use thermometer.
4. Cut 6 potato tubes to the same length, no skin, dry.
5. Weigh each initial mass
6. Leave potato in tubes for 20 mins
7. Take out and dry, weigh the final mass.
8. Calculate mass difference.
102
How do you find percentage change?
Difference/ original x 100
