Longer answer questions Flashcards
Size, features present vs absent, DNA, ribosomes, reproduction
What are differences between a Prokaryotic cell and a Eukaryotic cell?
Tip if it asks you the difference between x and y, you start you sentence with x then y when you compare
If the questions asks you the difference between y and X you start your sentence with y and X
- PKs are small (1-10μM), simple cells e.g. bacteria…whereas…. ECs are larger (10-100μM) and more complex cells found in Plants, animals, fungi and some Protoctists (PRO TOC TISTS)
- PKs have NO… nucleus, membrane bound organelles e.g. Mitochondria, Golgi Body or Lysosomes (LY SO SOMES) however….ECs do
- The DNA in PKs is circular and not associated with proteins - plasmids can be present. In contrast…. the DNA in ECs is linear and associated with histone proteins. There are no plasmids.
- The ribosomes in PKs are smaller (70s) than ECs which are (80s)
- In PKs cells divide via binary fission and in ECs they divide by Mitosis. (MI TO SIS)
- In PKs there is no sexual reproduction however in ECs they reproduce via meiosis ( MEI O SIS)
What are the differences between animal and plant cells?
In contrast to plant cells, animal cells do not have:
- Cellulose cell walls
- Chloroplasts
- Plasmodesmata
Animal cells have centrioles and lysosomes present whereas plant cells do not.
Animal cells usually have a small temporary vacuole however plant cells have a large permanent vacuole surrounded by a tonoplast
Animal cells store food as glycogen whereas plant cells store food as starch grains
Plant cells create energy in the chloroplast by the proccess of Photosynthesis whereas in animal cells the energy is created in the mitochondria via aerobic respiration, when glycogen is converted into ATP
What is the structure of a Nucleus
- The nucleus is the Largest organelle in the cell, approximatly 10μM in diameter and can be seen by a light microscope.
- The outer layer of the Nucleus is called the Nuclear envelope, which has a number of gaps in it called Nuclear pores, through which large molecules (e.g. mRNA and Ribosomes) can pass.
- The outer Nuclear Membrane is attached to a number other membranes called the endoplasmic reticulum.
- The neucleus contains Nucleoplasm, which contains chromatin, that is made up of DNA attached to proteins called histones.
- The Nucleolus is a spherical structure, within the nucleus, where Ribonucleic acid (RNA) is produced
What cell does not have a nucleus?
Prokaryotes
What is the structure of a Mitochondria?
The mitochondria is a cylindrical shaped organelle between 1-10mM in diameter.
It has an outer layer which features a double membrane seperated by a fluid filled space.
The inner membrane is folded and called Cristae, which have stalked particles on their surface.
The mitochondria has a jelly like matrix which contains a number of compounds including small (70s) ribosomes, protiens, lipids and a circular strand of DNA
What is the function of chloroplasts
The role of the chloroplasts is to produce energy by the process of photosynthesis
The chlorophyll molecules, traps light energy in the Thylakoids of each granum
This light energy is converted into chemical energy and stored as starch granules
Summary - What are the functions of ER
There are two types of ER.
Rough ER has ribosomes on its surface which produce proteins that are packaged and stored ready for transport as needed
Smoth ER has NO ribosomes on its surface so does not produce proteins, however they do produce Lipids, Steroids and hormones which again are packaged and stored ready for transport as needed
Smooth ER also plays a part in detoxifying organic chemicals. (Lots in the liver)
A ribosome is
A ribosome is a small dense organelle found in large number in both prokaryotic and eukaryotic cells
The ribosomes found in prokaryotic cells are smaller (70s) than those found in Eukaryotic cells (80s)
Ribosomes are formed in the Nucleolus from RNA and Protein
The play an important part in protein synthesis as they are the site of translation, where mRNA is used to assemble polypeptide chains.
Golgi body 5 functions
- Proteins are modified and packaged in the Golgi Body Produces secretory enzymes packaged into secretory vesicles
- Secrete Carbohydrates e.g. for the formation of plant walls
- Assembles glycoproteins, such as mucin, by combining carbohydrate and protein
- Transports and stores lipids
- Forms lysosomes containing digestive enzymes
What are the functions of a lysosome?
4
- The Lysosome releases hydorolytic digestive enzymes when the cell needs to recycle worn out organelles
- The Lysosome also releases these digestive hydrolytic enzymes when it wants to digest for example bacteria taken into a white blood cell via phagocytosis
- Lysosomes can release Lysozymes outside of the cell to digest other cells, (Exocytosis)
- Lysosomes can also force the cell to self destruct - Autolysis
What are the functions of a vacuole in a plant cell?
4
A plant cell vacuole:
- Allows water to enter the cell via osmosis
- Stores sugars, mineral salts and amino acids,
- Accumulates waste e.g. tanins (which in leaves are excreted when the leaves fall)
- Contains pigment which can give the cell colour, e.g. beetroot (betacyanin)
What is the structure of a plant cell wall?
A plant cell wall is mostly composed of cellulose
The cellulose molecules are polymers of beta glucose (polysacheride), which form 1,4 glycosidic bonds.
They form microfibrils which are then held together by many hydrogen bonds which provides strength to the cell wall.
(microfibrils which are aggregated into fibres embedded in a polysaccharide)
What are the 3 functions of a plant cell wall (introduction only)
Transport
Mechanical strength
Communication between cells
What are the 3 functions of a plant cell wall
A* answer”Transport”
There are gaps between the cellulose microfibres which makes the plant cell wall fully permeable to water, dissolved molecules and ions
The space outside the cell where solution moves is called the apoplast
The apoplast pathway is the main way water enters the root of a plant
What are the 3 functions of a plant cell wall
A* answer” Mechanical Strength”
The structure of cellulose microfibrils and their laminated arrangement make the cell wall very strong.
When the vacuole is full of solution, the cell contents push against the cell wall, which resists expansion and the cell become turgid supporting the plant.
What are the 3 functions of a plant cell wall
A* answer”Communication between cells”
- Cell walls have pores called pits through which strands of cytoplasm called plasmodesmata (SIngular - Plasmodesma) pass
- Each plant cell has approximately 100,000 plasmodesmata connecting them to other cells
- The plasmodesma are found where there is no cellulose thickening between two cells
- The strand of cytoplasm runs from one cell to the next
- The network of cytoplasm in connected cels is called the SYMPLAST.
- The symplast pathway is important in later transport through a plant.
What are the 6 structures of a cytoskeleton?
- Cell surface membrane
- Mitochondrion
- Microtubule 25nm diameter
- Microfilament 7-12nm diameter
- Endoplasmic reticulum
- Ribosome
What are the 4 functions of the cytoskeleton?
Provides internal framework to support the cell
Can move the whole cell or organises and move organelles within the cell
Construct the spindle during cell division
Provide the components of cilia and flagella
How are organelles interellated
(Protein Synthesis mainly)
The functions of organelles are often related.
- The nucleus contains chromosones in which the DNA encodes proteins
- Nuclear pores in the nuclear envelope allow mRNA molecules, transcribed off the DNA to leave the nucleus and attach to ribosomes in the cytoplasm of on the rough ER
- Ribosomes contain rRNA transcribed from DNA located at the nucleoulus
- Protein synthesis occurs on ribosomes producing proteins in their primary structure
- Polypeptides made on the ribosomes are moved through the ER and are packaged into vesicles
- The vesicles bud off the RER and carry the polypeptides to the golgi body where they are modified and folded.
- The Golgi body prodyces vesicles containing newly synthesised proteins.
- These maybe lysosomes, containing digestive enzymes used within the cell
- They may be secretory vesicles which carry the proteins to the cell membrane for exocytosis
- Phospholipids and triglycerides move through the soft ER to various destination in the cell
