2.1.1a Cell Ultrastructure Flashcards
1
Q
What are prokaryotic organisms
A
- Single celled organisms
- Genetic material in prokaryotic cells are not enclosed by a nucleus
Smaller/simpler cells, eg. bacteria
2
Q
What are eukaryotic organisms
A
- Multi-cellular organisms
- Consist of one or more cells that contain DNA in a membrane-bound nucleus, separate from the cytoplasm
- All eukaryotic cells contain a large number of specialised, membrane-bound organelles
Complex cells, eg. animals, plants, fungi, protists
3
Q
3 structural components of the cytoskeleton
A
- Microfilaments
- Microtubules
- Intermediate fibres
4
Q
What is the cytoskeleton
A
- Organelles in cells are surrounded by the cytoplasm
- The cytoplasm has a network of protein threads running through it. These protein threads are called the cytoskeleton
5
Q
Functions of the cytoskeleton
A
- Providing mechanical strength, support & stability to the whole cell (maintaining cell shape)
- Allows movement of cilia/flagella
- Changing shape of cells (cytokinesis, phagocytosis)
- Organelles can be moved or held in place
- Movement of chromosomes, chromatids, mRNA
- Movement of vesicles along microtubules
6
Q
What are Microfilaments (in cytoskeleton)
A
Fibres made from the protein, actin. They are responsible for movement of the cell & cytoplasm during cytokinesis
7
Q
What are Microtubules (in cytoskeleton )
A
Formed by the globular protein, tubule. They polymerise to form tubes that determine the shape of the cell. They also act as tracks for organelles moving around the cell
8
Q
What are Intermediate Fibres (in cytoskeleton)
A
Gives strength to cells & helps maintain integrity
9
Q
What is the Nucleus
A
A large organelle surrounded by a nuclear envelope, which contains many nuclear pores. The nucleus contains chromatin & a structure called the nucleolus
10
Q
4 components of the Nucleus
A
- Double Nuclear Envelope
- Nuclear Pores
- Nucleolus
- Chromatin
11
Q
What are Double Nuclear Envelopes (in nucleus)
A
A double membrane which compartmentalises the nucleus & prevents damage. This protects the DNA
12
Q
What are Nuclear Pores (in nucleus)
A
Allows molecules to enter (eg. nucleotides for DNA replication) & leave the cell (eg. mRNA leaves the cell)
13
Q
What is the Nucleolus (in nucleus)
A
Site of ribosome production. Composed of RNA & proteins
14
Q
What is the Chromatin (in nucleus)
A
Chromatin is the DNA (with associated histone proteins). It contains the genetic code which controls the activity of the cell
15
Q
Functions of the Nucleus
A
- Controls all the activity of the cell
- Where the genetic code (DNA) of the cell is stored, replicated & copied into RNA (transcribed)
- The nucleus is attached to the Rough Endoplasmic Reticulum so the mRNA can easily get to ribosomes
16
Q
What does Rough ER stand for
A
Rough Endoplasmic Reticulum
17
Q
Structure of Rough ER
A
- Stacks of membrane bound (fluid filled) sacs which form sheets called cisternae
18
Q
What is the Rough ER
A
- The Rough ER is attached to the nucleus & is covered with ribosomes.
- It consists of an interconnected system of flattened sacs
19
Q
Function of the Rough ER
A
Site of protein synthesis (folds & processes proteins that have been made at the ribosomes)
20
Q
What does Smooth ER stand for
A
Smooth Endoplasmic Reticulum
21
Q
What is the Smooth ER
A
- Similar to Rough ER BUT lacks ribosomes.
- It is a system of interconnected tubules
22
Q
Function of the Smooth ER
A
Responsible for lipid, carbohydrate & steroid synthesis as well as storage
23
Q
Difference between Rough and Smooth ER
A
- Rough ER are studded with ribosomes WHILST Smooth ER does not have ribosomes
24
Q
Similarity between Rough and Smooth ER
A
- They BOTH have the same structure
25
Structure of Ribosomes
- A 2 subunit organelle
- Made from RNA & protein
- Not membrane bound
- Very small organelles (abt 22nm in diameter)
- Found free floating in the cytoplasm OR attached to the Rough ER
26
Function of Ribosomes
- Site of protein synthesis
- They assemble amino acids into proteins in chains using mRNA
27
Structure of Mitochondria
- Oval shaped
- Surrounded by 2 membranes (double membrane)
- The inner membrane form finger-like structure called **cristae**, which increases the SA
- The solution inside is called a **matrix**, which contains enzymes for respiration
- Mitochondrial DNA - small amounts of DNA, enable mitochondrion to reproduce & create enzymes
28
Function of Mitochondria
- Site of aerobic respiration
- As a result of respiration, they release ATP (energy carrier in cells)
- found in a large no. of cells that are very active & require lots of energy
29
Structure of Golgi Apparatus
- Stacks of flattened, membrane bound sacs (cisternae)
- These are continuously formed from the ER at one end & budding off as Golgi vesicles at the other
30
Function of Golgi Apparatus
- Allows internal transport
- Receives proteins from the Rough ER
- Modifies & processes molecules (sa. new lipids & proteins) & packages them into vesicles. These may be secretory vesicles (if the proteins need to leave the cell) or lysosomes (which stay in the cell)
- Makes lysosomes as well as lipid synthesis
31
Structure of Lysosomes
They are spherical sacs surrounded by a single membrane, w no clear internal structure
32
Function of Lysosomes
They contain powerful hydrolytic digestive enzymes known as lysozymes. Their role is to break down worn out components of the cell or digest invading cells
33
Structure of Centrioles
- A component of the cytoskeleton, composed of many microtubules
- Small, hollow cylinders that occur in pairs next to the nucleus in animal cells only
- Each centriole contains a ring of 9 triplet microtubules
34
Function of Centrioles
Makes a copy of itself during cell division & then helps to form the spindle in cell division
35
Structure of Cilia
- 'Hair like' extensions that protrude from some animal cell types
- In cross section, they have an outer membrane & a ring of 9 pairs of protein microtubules inside w 2 microtubules in the middle (known as a 9+2 arrangement). This arrangement allows movement
36
Function of Cilia
- Sensory function (eg. nose), create a current to move mucous/objects
- For locomotion - the microtubules allow the cilia to move, used by the cell to move substances along the cell surface
37
Structure of Flagella
- Similar to cilia but longer
- They protrude from the cell surface & are surrounded b y the plasma membrane
- Like cilia they have a 9+2 arrangement (2 microtubules in centre, 9 pairs around the edge)
38
Function of Flagella
- 'Whip like', enables a cells mobility
- The microtubules contract to make the flagellum move
- Propels cells forward (eg. sperm cells)
39
Are chloroplasts found in animal or plant cells
Plant cells
40
Structure of Chloroplasts
- Double membrane which encloses the stroma
- Stroma contains: starch grains, lipid stores, DNA, RNA, ribosomes
- They contain membrane-bound flattened sacs called, thylakoids in the stroma. Thylakoids stacked tg are called grana
- Grana are linked tg by lamellae
- The grana contains chlorophyll
41
Function of Chloroplasts
site of photosynthesis
- some parts of photosynthesis happen in the grana & others in the stroma
42
What is the Cell Surface Membrane (or Plasma Membrane)
- The membrane found on the surface of animal cells & inside the cell wall of plant & prokaryotic cells
43
Structure of the Cell Surface Membrane (or Plasma Membrane)
- A phospholipid bilayer composed of proteins & lipids
44
Function of the Cell Surface Membrane (or Plasma Membrane)
- Regulates the movement of substance into & out of the cell
- Contains receptor molecules which allow it to respond to chemicals like hormones
45
What is the Cellulose Cell Wall
A rigid structure that surrounds plant cells
46
Structure of the Cellulose Cell Wall
- Made of B-glucose microfibrils - complex carbohydrate
- Cell wall is fully permeable to substances
- Thin layer called the middle lamella which marks the boundary between adjacent cell walls & 'cements' adjacent cells tg
47
Function of the Cellulose Cell Wall
- Gives the plant mechanical strength, support & shape
- Contents of plant cells can 'push' against the cell wall (turgid cell). This gives the cell (and whole plant) good support
48
Where is the Large Permeable Vacuole found
Plant cells
49
Structure of the Large Permanent Vacuole
- Single membrane bound (membrane is called a tonoplast)
- Contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes, etc)
- Selectively permeable barrier
50
Function of the Large Permanent Vacuole
- Stores cell sap
- Support herbaceous plants by making cells turgid
- Helps maintain shape & gives support by maintaining turgor pressure
- Sugars & amino acids act as a temporary food store
51
Describe protein production
DNA in the nucleus contains the gene to make proteins. The particular gene is copied by mRNA, which takes the copy of the gene out of the nucleus via the nuclear pore to the ribosomes on the Rough ER. Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum. They then pass into the cisternae of the RER & are packaged into transport vesicles. Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the microtubules of the cytoskeleton. The vesicles fuse w the cis face of the Golgi apparatus & the proteins enter. The proteins are structurally modified before leaving the Golgi apparatus in vesicles from its trans face. Golgi repackages the protein into secretory vesicles. The vesicles move towards & fuse w the cell-surface membrane, releasing their contents by exocytosis. Some vesicles form lysosomes - these contain enzymes for use in the cell.
52
What are vesicles
Small fluid-filled, membrane bound sacs in the cytoplasm
53
Function of vesicles
- Transports substances in & out of the cell (via plasma membrane) & between organelles.
- Some are formed by the Golgi apparatus or the ER, while others are formed at the cell surface
54
What is the cytoskeleton
- The organelles in cells are surrounded by the cytoplasm.
- The cytoplasm is more than just a solution of chemicals
- It's got a network of protein threads (arranged as microfilaments & microtubules) running through it. These protein threads are called the cytoskeleton
55
See goodnotes for dia of animal cell (eukaryotic)
56
See goodnotes for dia of plant cell (eukaryotic)
57
How do plant cells differ to animal cells
Plants have all same organelles as animal cells, but a few added extras:
- **Cell wall** with plasmodesmata ('channels' for exchanging substances w adjacent cells)
- **Vacuole** (compartment that contains cell sap)
- **Chloroplasts**
