1
Q
What are Prokaryotes?
A
Unicellular
- No membrane bound organelles
- DNA not in nucleus
- Eg Bacteria
2
Q
What are Eukaryotes?
A
Unicellular or Multicellular
- membrane bound organelles
- DNA found in the nucleus
- Eg Animals, Plants, Fungi and Protoctists
3
Q
What are all the organelles ?
A
- nucleus
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum
- Golgi apparatus
- Lysosome
- Mitochondria
- Chloroplast
- Vacuole
4
Q
What is the function of the nucleus?
A
- Contains the cellular DNA and controls the cellular activities through the production of mRNA, tRNA and rRNA.
- Also assembles ribosomes
5
Q
What is the structure of the nucleus ?
A
- Surrounded by a nuclear envelope which is a double membrane. Outer membrane is continuous with the endoplasmic reticulum.
- nuclear pores are small channels that span the nuclear envelope and let substances enter and exit the nucleus. Eg mRNA out of the nucleus
- Each pore is lined by a set of proteins called the nuclear pore complex that control what molecules can go in and out.
- Chromatin is DNA wrapped around proteins called histones. Chromatin is found in the nucleoplasm, the jelly-like material that makes up the inside of the nucleus.
- the Nucleolus is a small spherical region which manufactures ribosomal RNA and assembles ribosomes. It holds genetic material for protein synthesis.
6
Q
What is the structure of ribosomes?
A
- May be found free in the cytoplasm or associated with the rough endoplasmic reticulum
- 80S ribosomes -> found in eukaryotic cells
- 70S ribosomes -> found in prokaryotic cells and sometimes in mitochondria
- Ribosomes have two subunits, one large, one small.
- Both units are made of protein and rRNA.
7
Q
What is the function of ribosomes
A
- protein Synthesis
- ribosomes has enzymatic properties that catalyse the formation of peptide bonds between amino acids
- between its two sub-units mRNA is held in place by the rRNA and proteins in the large subunit.
8
Q
What is the structure of the Rough Endoplasmic Reticulum ?
A
- It is continuous with the Outer membrane of the nucleus
- Forms an interconnected network of flattened membrane-enclosed sacs called cisternae.
- has ribosomes present on the Outer surfaces of the membrane
9
Q
What is the function of the rough endoplasmic reticulum?
A
protein Synthesis
10
Q
What is the structure of the smooth endoplasmic reticulum?
A
- Lacks ribosomes on the surface
- Tubular form
11
Q
What is the function of the smooth endoplasmic reticulum?
A
- Synthesises, stores and transports lipids and carbohydrates
12
Q
What is the structure of the Golgi Apparatus?
A
- Consists of a stack of membranes that make up flattened sacs called cisternae
- not connected
13
Q
What is the function of the Golgi Apparatus?
A
- proteins and lipids produced by the endoplasmic reticulum are passed through the Golgi apparatus
- the Golgi modifies these proteins, by either folding them into a specific shape or by adding a compound. Eg by the addition of carbohydrates to form glycoproteins
- Also labels them to be sorted and sent to their correct destinations
- Once sorted, the modified proteins and lipids are transported in vesicles which are regularly pinched off the Golgi cisternae. these vesicles May move to the cell surface where they fuse with the membrane and release their contents outside.
14
Q
What is the structure of the Lysosome?
A
- Contain enzymes such as protease and lipases and lysozymes (enzymes which hydralise the cell wall of certain Bacteria)
- Lysosomes isolate these enzymes from the rest of the cell before releasing them either to the outside of the cell or into a phagocytic vesicle.
15
Q
What is the function of the Lysosome ?
A
- Lysosomes fuse with vesicles
- they release hydrolytic enzymes
16
Q
What is the structure of Mitochondria?
A
- Usually rod-shaped
- Surrounded by a double membrane that controls the entry and exit of material
- The inner membrane is folded to form extensions called cristae. This provided a large surface area for the attachment of enzymes and proteins involved in respiration.
- The matrix is found in the middle of the mitochondrion. This contains enzymes and proteins involved in respiration.
17
Q
What is the function of mitochondria?
A
- Site of respiration
- Responsible for the production of ATP
18
Q
What is the structure of Chloroplasts?
A
- ‘Disc-shaped’ organelles. 2-10 um + 1 um in diameter
- Surrounded by a double membrane called the chloroplast envelope
- The grana are stacks of thylakoids which contain chlorophyll. They provide a large surface area for the attachment of chlorophyll and enzymes that carry out the first stage of photosynthesis. This is where light absorption takes place.
- The stroma is a fluid-filled matrix. Contains enzymes and proteins needed to make sugars in the second stage of photosynthesis. Starch grains are found in the stroma.
- Chloroplasts contain DNA and ribosomes so can quickly manufacture proteins needed to photosynthesis
19
Q
What is the function of Chloroplasts?
A
Carry of photosynthesis
20
Q
What is the structure of the vacuole?
A
- Fluid filled sac bounded by a single membrane called a tonoplast
- Contains a solution of mineral salts, sugars, amino acids and sometimes pigments.
21
Q
What is the function of the vacuole?
A
- Support Plants by making them turgid
- Pigments May colour petals to attract pollinators.
22
Q
What is the structure of the Cell Wall?
A
- make of microfibris of cellulose
- There is a thin layer called the middle lamella, which marks the boundary between adjacent cell walls and cement adjacent cells together
23
Q
What is the function of the cell wall?
A
- to provide mechanical strength to plant
- to give mechanical strength in order to prevent the cell from bursting
- to allow water to pass along It
24
Q
Describe the Capsule
A
- protects bacterium from other cells and helps groups of Bacteria to stick together for further protection
25
Describe the Cell Wall
| Prokaryotic Cells
Physical barrier made of murein that excludes certain substances and protects against mechanical damage
26
Describe the role of the Cell membrane
Acts as a differentially permeable layer, which controls the entry and exit of chemicals.
27
Describe the Circular DNA
Possess the genetic information for the replication of bacterial cells. DNA is not associated with histones.
28
Describe the Plasmids
small circular pieces of DNA that passes genes that May aid the survival of Bacteria in adverse conditions e.g. produce enzymes that break down antibiotics
29
Function of 70s ribosomes
Synthesis of proteins
30
Describe the Flagellum
For motility
31
Function of Pili
to help bacterial cell to attach to surfaces
32
Describe the cell structure of a prokaryotic cell?
- Flagellum
- Pillus
- circular DNA
- 70S ribosomes
- slime capsule
- Cell Wall
- Cell membrane
- Cytoplasm
- Plasmid
33
Describe the structure of a virus
- envelope
- attachment proteins
- Capsid (protein coat)
- enzymes
- Viral Genome
34
How do viruses enter and replicate inside host cells?
- Viruses attach to the surface of host cell
- Viruses inject their DNA into cell
- Replication takes place -> viral DNA / RNA replicates and new viral proteins are made (forming new capsids)
- New viral particles are assembled
- Host cell lyses (bursts) releasing the newly made viruses or particles leave individually through cell membrane via ‘budding’, often taking sections of membrane with them, which is the envelope surrounding some viruses.
35
What do prokaryotic cells have that eukaryotic cells do not ?
- Smaller cells
- No nucleus
- DNA is not associated with proteins
- Plasmids present
- No membrane bound organelles
- Ribosomes are smaller (70s)
- Cell wall made of murein
- Capsule may be present
36
What do Eukaryotic cells have?
- larger cells
- nucleus present
- DNA is associated with proteins called histones
- no plasmid
- membrane bound organelles present
- ribosomes are larger (80s)
- Where present, cell wall is made of cellulose (or chitin in fungi)
- No capsule
AS-Level Biology
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