1
Q
What is the structure of the Nucleus?
A
- Double membrane called nuclear envelope which contains pores
- Nucleolus does not have membrane but contains RNA
- Chromatin is genetic material wound around histone proteins. It is stretched out when cell not dividing but when dividing it condenses and coils into chromosomes.
2
Q
What makes a cell a eukaryote?
A
- Jelly-like cytoplasm which contains organelles.
- Membrane-bound organelles such as mitochondria, golgi apparatus and endoplasmic reticulum.
- Ribosomes where proteins are assembled.
- Vesicles.
- Cytoskeleton- network of protein filaments (actin & microtubules) which allow organelles to move from one point to another, allow cells (amoeba & lymphocytes) to move, allows muscles to contract.
- Nucleus, surrounded by nuclear envelope, with DNA organised and wound into linear chromosomes.
- Plasma membrane
- Nucleolus which contains RNA; where chromosomes unwind; ribosomes are formed.
3
Q
Advantage of Optical microscope?
A
- Relatively cheap
- Easy to use
- Portable (lab or field)
- Can study whole living organisms
4
Q
What is the magnification of Optical microscope?
A
1500-2000x
5
Q
Describe an Optical microscope.
A
-Uses visible light with a wavelength 400-700nm, meaning objects closer to each other than 200nm will be seen as one object.
6
Q
Define Magnification.
A
How many times an image is bigger an image is in comparison to its actual size.
7
Q
Define Resolution.
A
How clear an image is, higher the resolution, the greater the detail.
8
Q
What is the image under a Optical microscope called?
A
Photo micrograph.
9
Q
What is the image under a Electron microscope called?
A
Electron micrograph.
10
Q
Describe how a Scanning microscope works.
A
A light beam scans an object point to point and assemble the image on a computer using pixel information.
11
Q
Advantages of Scanning microscope.
A
- High resolution
- High contrast.
- Depth selectivity allows both whole organisms and cells to be observed.
12
Q
Use of Scanning microscope.
A
Used to examine the fungal filaments in the cornea of the eye in order to diagnose fungal corneal infection.
13
Q
Describe an Electron microscope.
A
- Use electrons with wavelength to 0.04nm to create an image.
- Electrons fired from cathode and focused onto specimen to screen/photographic plate using magnets.
14
Q
Describe a Transmission electron microscope.
A
- Specimen has to be chemically fixed, -> dehydrated and stained with metal salts.
- Electrons move through specimen and focused onto photographic plate.
- 2D greyscale image produced.
15
Q
What is the magnification of TEM?
A
500,000x
16
Q
Describe SEM.
A
- Electrons bounce off specimen and focused onto screen.
- Produces 3D greyscale image, false colour added.
- Specimen in vacuum and stained with fine metals.
17
Q
What is the magnification of SEM?
A
100,000x
18
Q
What do electron microscopes have in common?
A
- Large and expensive
- Require lots of skill
- Specimens in vacuum
- Stained with metal salts can be hazardous to user
19
Q
What is the function of a nucleus?
A
- Nuclear envelope separates contents of nucleus from the rest of the cell.
- Nucleolus produces ribosomes.
- Most of organisms DNA found here.
- Inner and outer membrane of nuclear envelope fuse to allow dissolved substances and ribosomes to diffuse through.
- Pores allow larger substances such as mRNA to leave and steroid hormones from cytoplasm to enter.
20
Q
Describe the structure of the RER.
A
- System of membranes containing fluid-filled matrix (cisternae) continuous from the nucleus membrane.
- Coated with ribosomes.
21
Q
What is the function of the RER?
A
- Large surface area for ribosomes to assemble amino acids into proteins, proteins pass through membrane into cisternae and transported to Gogli Apparatus for modification and packaging.
- Intracellular transport system of channels allowing substances to move from one place to another.
22
Q
What is the structure of the SER?
A
- Intracellular transport system of membranes containing fluid filled cavities allowing substances to move from one place to another.
- Not coated with ribosomes.
23
Q
What is the function of SER?
A
- Contains enzymes that catalyse lipid metabolism.
- Synthesis of lipid/phospholipid for the cell
- Synthesis of cholesterol
- Synthesis of steroid hormones
-Absorbs, synthesises and transports lipids from the gut.
24
Q
Describe the structure of the Golgi Apparatus.
A
- Stack of membrane bound flattened sacs.
- Vesicles bring material to and from Golgi.
25
What is the function of the Golgi Apparatus?
- Lipid modification
- Adding lipids to make lipoproteins.
- Adding sugar to make glycoproteins.
- Folding into 3D shape.
-Packaging into vesicles that are pinched to be stored inc cell or incorporated into plasma membrane or to be exported out of the cell.
26
Describe the structure of Mitochondria.
- Spherical, rod-shaped or branches and 2-5micrometers.
- Two membranes, in-between is a fluid filled space. Inner membrane folded into cristae.
- Inner mitochondrion has a fluid filled matrix.
27
What is the function of the mitochondrion?
- Site of ATP production for aerobic respiration.
- Self-replicating.
- Abundant in high metabolic rate cells (Liver, synapses).
28
Describe the structure of chloroplasts?
- 4-10micrometers long.
- Double membrane or envelope, continuous inner membrane forming stacks of membrane-bound flattened sacs called thylakoids. Each stack called a granum.
- Fluid-filled matrix called stroma.
- Loops of DNA and starch grains.
- Found only in plant cells and protoctists.
29
Describe the function of chloroplasts.
- Site for photosynthesis.
- First part of photosynthesis where light trapped in chlorophyll and turned into ATP occurs in the Grana. Water is also split into hydrogen here.
- 2nd part of photosynthesis occurs in stroma where hydrogen reduces carbon dioxide using ATP to make carbohydrates.
- Abundant in leaf cells especially palisade mesophyll cell.
30
Describe the structure of a vacuole.
- Surrounded by membrane called a tonoplast.
| - Contains fluid.
31
What is the function of a vacuole?
- Only large permanent vacuole exists in plants.
- Contain water and solutes for cell stability as when full it pushes against cell wall making cell turgid.
- If many cells turgid it helps support plant structure especially in non-woody plants.
32
Describe the structure of lysosomes.
- Small bags, surrounded by single membrane, formed in the Golgi apparatus.
- Contain powerful hydrolytic digestive enzymes.
- Abundant in phagocytic cells such as macrophages and neutrophils which are types of white blood cells that ingest and digest invading pathogens.
33
What is the function of lysosomes?
- Separate hydrolytic enzymes from rest of cell.
| - Engulf old organelles and pathogens and return recycled components to cell for reuse.
34
Describe structure of Cilia and undulipodia.
- Formed from Centrioles.
- Contains microtubules.
- Protrusions from a cell surrounded by plasma membrane.
35
What is the function of the Cilia and undulipodia.
- Cilia line airways allowing mucous to move out of the airway.
- Nearly all cells have a cellium that is an antenna. It contains a receptor that can detect signals in its immediate environment.
- Spermatozoa has an undulipodium to allow it to move.
36
Describe the structure of Ribosomes.
- Small, spherical, 20nm in diameter.
- Made up of ribosomal RNA.
- Made in nucleus at two subunits that combine in the cytoplasm.
- Some are free in cytoplasm where as others attach to ER.
37
What is the function of Ribosomes?
- Bound to exterior of RER to assemble amino acids into proteins exported out the cell.
- Those free in cytoplasm assemble amino acids into proteins to be used in cell.
38
Describe the structure of Centrioles.
- It is made up of two bundles of microtubules at right angles to each other.
- Microtubules made up of tubulin protein subunits and from cylinder.
39
What is the function of centrioles?
- Before cell divides spindle made up of tubulin threads is formed from the centrioles.
- During division chromosomes attach to the middle of spindle and motor proteins walking along tubulin threads pull them to opposite poles of the cell.
- Cilia formation by many centrioles multiplying underneath cell surface membrane and then microtubules sprout out of each centriole forming cilium or undulipodia.
40
Describe the structure of the Cytoskeleton.
- Microfilaments which are polymers of actin and 7nm in diameter.
- Microtubules made up of tubulin and 18-30nm in diameter.
- Intermediate filaments 10nm in diameter.
- Cytoskeletal motor proteins(myosins, kinesins, dyneins) act as molecular motors which can also bind to and hydrolyse ATP for energy source.
41
What is the function of the Cytoskeleton?
- Microfilaments provide mechanical strength, cell shape stability and movement.
- Microtubules from spindle, centrioles, cilia, undulipodia. and also create a track allowing motor proteins to walk along dragging organelles along.
- Intermediate filaments allow nucleus to be anchored in cell, cells to adhere to basement membrane for stability and cell to cell signalling.
42
Describe the structure of a Cellulose Cell Wall.
-Made up of bundles of cellulose fibres.
43
What is the function of the Cell Wall?
- Mechanical strength
- Solutes to pass through
- Shape stability
44
How are prokaryotic and eukaryotic cells similar?
- Plamsa membrane
- Ribosomes
- Cytoplasm
- DNA & AMP; RNA
45
How are prokaryotic and eukaryotic cells different?
- Much smaller
- Less developed cytoskeleton (no centrioles)
- Do not have membrane-bound organelles
- Cell wall made up of peptidoglycan instead of cellulose
- Smaller ribosomes
- No nucleus
- Naked DNA
Some ALSO have:
- Protective waxy capsule surrounding cell wall
- Small loops of DNA called Plasmids
- Flagella
- Pili
46
How do prokaryotic cells divide?
Binary Fission
47
How is Insulin made?
1) Gene that codes for insulin found in the chromatin inside nucleus is transcribed into mRNA.
2) Many copies are made and passed out to ribosome.
3) Ribosomes translates mRNA and insulin molecules formed.
4) Molecules pass into cisternae and packaged into vesicles which are pinched off and pass to Golgi apparatus via motor proteins.
5) Vesicles fuse with Golgi apparatus and modified for release.
6) Inside vesicles pinched and move to plasma membrane.
7) Vesicles bind to plasma membrane and insulin released.
