Euk and prok cell features and functions Flashcards
Includes the nucleus features.
Where is the DNA found in a eukaryotic cell?
Enclosed in a membrane bound nucleus
What are chromosomes formed by?
DNA tightly wrapped around by proteins called histones, together this forms chromosomes
Give the main characteristic of the DNA in a eukaryotic cell
The DNA is linear meaning that the ends of the DNA molecule in the chromosome is not coiled to form a loop
Name the membrane bound organelles in a eukaryotic cell
Mitochondria, golgi apparatus, and the endoplasmic recticulum. in plant cells chloroplast and vacuole is also membrane bound.
Name the organelles in a eukaryotic cell that are not membrane bound
Ribsomes
Give the different types of ribosomes found in cells
80s ribosomes found in eukaryotic cells
70s ribosomes found in prokaryotic cells which is smaller
Give the function of the cell surface membrane, and what type of cell has this
Helps control the molecules that pass in and out of a cell in animal cells, plant cells have this surrounded by a cell wall.
What is the cell wall in plant cells made from?
Polysaccharide cellulose
Give 3 uses of proteins
Enzymes for chemical reactions, Structural proteins e.g organelle movement and transport molecules e.g heamoglobin
This means protein synthesis is one of the most important processes that takes place in cells.
Describe the role of the nucleus in protein synthesis
The instructions for encoding the amino acid sequence of a protein are contained within the gene for that protein. These genes are made up into chromosomes which are found in the nucleus.
- When a protein is being synthesised, the genetic information encoded by that gene is converted into mRNA which is called transcription
- This mRNA then leaves the nucleus, and a ribosome reads the information contained and then synthesises the protein molecule, which is called translation.
- If a protein remains in the cytoplasm, translation will take place on a free ribosome in the cytoplasm, however some are secreted by cells so they make their way through the rough ER and the golgi apparatus before leaving the cell.
What is the nucleoplasm?
A material in the nucleus containing nucleotides and enzymes, which is needed for DNA and RNA synthesis.
What is the function of nuclear pores?
Found in the nuclear envelope, these allow passage of large molecules and allows molecules to enter and leave the nucleus.
What is the nuclear envelope?
The double membrane on the outside of the nucleus which contains 2 phospholipid bilayers
Give the characteristic of the outer membrane of the nuclear envelope
This is continuous with the rough endoplasmic reticulum, forming flattened sacs called cisternae.
Describe the function of the RER
Has a large surface area with ribosomes present on the outer surface for synthesising proteins and is a pathway of transport.
What is a chromatin?
Found in the nucleus, these consist of DNA coiled around proteins called histones, these paired together create chromosomes.
When can we see chromosomes in a nucleus?
Only when the cell is undergoing mitosis or meiosis
What is the function of the nucleolus?
rRNA is assembled
rRbosomal subunits are assembled.
Give the 2 key features of lysosomes
They contain powerful digestive enzymes such as proteases, which digest large molecules into smaller soluble molecules
They also have an acidic internal fluid because lysosomal enzymes have an optimum PH of acidic
Give the functions of lysosomes
They play a key role in phagocytosis, when a WBC forms a vacuole around a bacteria, called a phagosome, lysosomes will now fuse with this besicleand the lysosomal enzymes ( hyrdolytic enzymes) will digest the bacteria.
-They also can destroy organelles that are damaged or no longer functional. This happens when the organelle is wrapped in a vacuole so the vacuole fuses to the membrane and uses its enzymes to digest the organelle.
- Lysosomes can also transfer their enzymes to out of the cell in exocytosis to digest and remove unwanted proteins or dead cells.
Describe the structure of a mitochondria
-A double membrane with inter-membrane space.
-Has a fluid called the matrix where enzymes for the Krebs cycle are found.
- There is also a loop of DNA there containing the genes needed for enzymes found in mitochondrial respiration
- There are also mitochondrial l ribsomes which synthesise proteins encoded by mitochondrial DNA.
- Inner membrane is folded to form cristae, gives a larger surface area for attachment of enzymes and proteins involved in respiration
Give an adaptation of mitochondria
They have large amounts of cristae which provide a large surface area for enzymes needed for oxidation phosphloryiation.
Name all the differences between prokaryotic and eukaryotic cells
P has no nucleus whereas E does in a nuclear envelope
P has no DNA associated with proteins whereas E has DNA associated with histone proteins
P has DNA in circular strands called plasmids whereas all DNA in E is linear
P has no membrane bound organelles whereas E does
P has no chloroplats whereas E does
In P ribosomes are smaller (70s) in E they are larger (80s)
In P cell wall is made up of murein whereas in E they are made up of cellulose
P has capsules whereas E doesnt
Give the role of the cell wall in prokaryotic cells
A physical barrier that excludes certain substances and protects against mechanical damage and osmotic lysis
Give the role of the capsule in prokaryotic cells
Protects bacterium from other cells and helps groups of bacteria stick together for future protection
Give the role of the cell surface membrane in prokaryotic cells
Acts as a differentially permeable layer that controls the entry and exit of materials
Contains 70s ribosomes
Give the role of the circular DNA in prokaryotic cells
Possesses the genetic material for the replication of bacterial cells
Give the role of plasmids in prokaryotic cells
Possesses genes that may aid the survival of the bacteria in adverse conditions e.g enzymes that may resist antibiotics
What is the range of size of virus particles?
20nm-300nm
Where do viruses reproduce?
In host cells only
How do viruses reproduce inside a host cell?
They attach to the surface of the host cell and they go in and use the host cells enzymes to make copies of themselves then leave
Describe the structure of viruses
They have genetic material, either DNA or RNA, and this is contained inside a protein structure called a capsid. On the surface of the virus we find attachment proteins, which allow viruses attach to and enter host cells
Sometimes the capsid is surrounded by a lipid envelope formed from the host cell membrane
Describe the structure of choroplasts
They have a double membrane controlling which molecules enter and leave the organelle.
They have grana which are stacks of disks called thylakoids and these are responsible for LDR as they contain chlorophyll
Thylakoids on different grana are connected to each-other by flattened membranes called lamellae which play a role in LDR and allows chemicals to pass through grana
The stroma is a fluid matrix where LIR in photosynthesis takes place such as sugar synthesis
They also have a loop of DNA which contains genes which code for proteins needed for photosynthesis
They also contain ribosomes synthesisng the proteins from the DNA
What does the chloroplast do with the product of photosynthesis?
Glucose can be converted into the polysaccarhide starch which is stored in chloroplast as starch granules
Describe the functions of the cellulose cell wall
-Provides mechanical strength to the cell which is important because water molecules have to enter the cell wall for photosynthesis inside the cell, and if water potential outside the cell is greater than on the inside where will be a net inflow of water in osmosis, creating a great deal of hydrostatic pressure inside the cell pushing outwards so the plant cell needs to be strong so resist this
-To allow water to pass along it and so contribute to the movement of water through the plant
What is the cell wall made up from?
Microfibrils of the polysaccharide cellulose embedded in a matrix. There is a thin layer in the middle called the middle lamella which marks the boundary between adjacent cell walls and cements adjacent cells together.
Give the structure and function of the cell wall in fungi and algae
In algae they are made up of cellulose or glycoproteins or a mixture of both and in fungi they are made up of chitinn, glycan and glycoproteins
Describe the function of vacuoles
They support herbaceous plants, and herbaceous parts of woody plants making the cells more turgid
The sugars and amino acids in these may be used as a temporary food store
The pigments may colour petals attracting pollinating insects
Describe the structure of the vacuole
These are fluid filled sacs that are filled with fluid. The single membranearound it is called the tonoplast which controls which chemicals enter and leave the vacuole.
The fluid in the vacuole is called cell sap containing dissolved sugars, amino acids and mineral salts
List all structural features of the nucleus
-Surrounded by a double membrane nuclear envelope
- Has nuclear pores in this envelope
- Contains chromosomes
-Contains protein bond, linear DNA
-One or more nucleolus
- Nucleoplasm
List the functions of the nucleus
- Acts as the control centre of the cell through the production of mrna and trna needed for protein synthesis
- Assembles trna and ribosomes
- Retains genetic material of the cell in the form of chromsomes and DNA
How is the structure of the chloroplast suited to its function?
- Granal membranes/ lamellae
provide a large SA for the attachment of chlorophyll, electron carriers and enzymes needed for first stage of photosynthesis - Stroma matrix contains all the enzymes needed for the production of sugars in P2
- Chloroplast contain DNA and ribosomes so they can easily manufacture proteins needed for photosynthesis
Summarise functions of lysosomes
- Hydrolyse material injested by phagocytic cells such as WBC and bacteria
-Release enzymes to the outside of the cell in order to destroy material outside of the cell
-Digest worn out organelles so the useful chemicals they are made of can be re used - Break down cells after they have died autolysis
