Module 2.1.1 : Cell Structure And Microscopy: Cell Ultrastructure Flashcards
What is Chromatin?
is the DNA (with associated histone proteins). Contains the genetic code which controls the activity of the cell.
Function of Cilia
- Sensory function, beat creating a current to waft fluid/mucous
- For locomotion
Structure of the Large Permanent Vacuole:
- Single membrane bound (membrane is called a tonoplast)
- Contains a fluid called cell sap
- Selectively permeable barrier
Function of Chloroplasts:
For photosynthetic reactions
Structure of Golgi apparatus/body:
- Stacks of flattened, membrane-bound sacs (cisternae).
These are continuously formed from the ER at one end and budding off as Golgi vesicles at the other.
Function of Smooth Endoplasmic Reticulum:
Responsible for lipid, carbohydrate, and steroid synthesis and storage.
Function of Golgi apparatus/body
- Allows internal transport
- Recieves proteins from RER
- Modifies and processes molecules and packages them into vesicles
- These may be secretory vesicles or lysosomes
- Makes lysosomes
- Lipid synthesis
Function of the Rough Endoplasmic Reticulum:
Site of protein synthesis
Function of Cellulose Cell Wall:
- Gives the plant mechanical strength
- Gives the plant cell support and it’s shape
- Contents of plant cell can ‘push’ against the cell wall. This gives the cell (and whole plant) good support.
Structure of lysosomes:
Spherical sacs surrounded by a single membrane
Function of Cell Surface Membrane
- Regulates the movement of substances into and out of the cell
- Contains receptor molecules which allow it to respond to chemical like hormones
What is the Double Nuclear Envelope?
A double membrane which compartmentalises the nucleus and prevents damage. Protects the DNA.
Structure of Mitochondria:
- Surrounded by two membranes
- The inner membrane forms finger-like structures called cristae which increases surface area.
- The solution inside is called a matrix which contains enzymes for respiration.
- Mitochondrial DNA - small amounts of DNA, enable mitochondrion to reproduce and create enzymes.
What do intermediate fibres do?
They give strength to cells and help maintain integrity.
Structure of Flagella
- Similar to Cilia but longer
- They protrude from the cell surface and are surrounded by the plasma membrane
- Like cilia they have a 9 +2 arrangement.
Function of Cell Surface Membrane
- Regulates the movement of substances into and out of the cell
- Contains receptor molecules which allow it to respond to chemical like hormones
Structure of Centrioles:
- 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.
Function of Nucleus:
- Controls all the activity of the cell
- Where the DNA of the cell is stored, replicated and copied into RNA (transcribed)
- The nucleus is attached to the Rough ER so the mRNA can easily get to ribosomes.
Structure of Cell Surface Membrane:
- The membrane found on the surface of animal cells and inside the cell wall of plant and prokaryotic cells.
- A phospholipid bilayer
- Composed of proteins and lipids
What are microtubules?
Formed by the globular protein tubulin. They polymerise to form tubes that determine the shape of the cell. They also act as tracks for organelles moving around the cell.
Function of the Ribosomes:
These are where proteins are made and they assemble amino acids into proteins in chains using mRNA.
Function of Large Permanent Vacuole
- Stores cell sap
- Support herbaceous plants by making cells turgid
- Helps maintain shape and gives support by maintaining turgor pressure
- Sugars and amino acids act as a temporary food store
Structure of Cellulose Cell Wall:
- Made of B-cellulose microfibrils - complex carbohydrate
- Cell wall is fully permeable to substances
- Thin layer called the middle lamella which marks the boundary between adjacent cell walls and ‘cements’ adjacent cells together.
Structure of Cell Surface Membrane:
- The membrane found on the surface of animal cells and inside the cell wall of plant and prokaryotic cells.
- A phospholipid bilayer
- Composed of proteins and lipids
Structure of Chloroplasts
- Double membrane which encloses the stroma
- Series of membrane-bound flattened sacs called thylakoids in the stroma. Thylakoids stacked together are called grana.
- Grana are linked together by lamellae
- The grana contain chlorophyll
Function of Flagella:
- (whip-like) enables a cells mobility
- The microtubules contract to make the flagellum move
- Propel cells forward e.g. sperm cells
Structure of Cilia:
- ‘Hair-like’ extensions that protrude from some animal cell types.
- In cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside with two microtubules in the middle (known as the 9 +2 arrangement)
- Arrangement allows movement
Function of Centrioles:
Makes a copy of itself during cell division and then helps to form the spindle in cell division.
Function of lysosomes:
- They contain powerful hydrolytic digestive enzymes called lysozymes
- They break down worn out components of the cell or digest invading cells
Function of Mitochondria
- Site of aerobic respiration
- As a result of respiration, they release ATP (source of energy for use at cellular level)
Function of the Ribosomes:
These are where proteins are made and they assemble amino acids into proteins in chains using mRNA.
Structure of Ribosomes:
- Made from RNA and protein
- Not membrane bound
- Very small organelles: 22nm in diameter
- Found free floating in the cytoplasm or attached to the Rough ER
Structure of the Smooth Endoplasmic Reticulum:
Similar to RER but lacks ribosomes - it’s a system of interconnected tubules.
Structure of the Rough Endoplasmic Reticulum:
Stacks of membrane bound sacs which form sheets called cisternae. Attached to the nucleus and covered in ribosomes. It consists of an interconnected system of flattened sacs.
Function of Nucleus:
- Controls all the activity of the cell
- Where the DNA of the cell is stored, replicated and copied into RNA (transcribed)
- The nucleus is attached to the Rough ER so the mRNA can easily get to ribosomes.
Parts of the nucleus:
- Double Nuclear Envelope
- Nuclear Pores
- Nucleolus
- Chromatin
What is the nucleolus?
Part of the nucleus - Site of ribosome production. Composed of RNA and proteins.
What are microfilaments?
Fibres made from the protein actin. They are responsible for movement of the cell and cytoplasm during cytokinesis.
What are the Nuclear Pores?
Part of the nucleus that allows molecules to enter (e.g. nucleotides for DNA replication) and leave the cell e.g. mRNA leaves the cell.
What are microtubules?
Formed by the globular protein tubulin. They polymerise to form tubes that determine the shape of the cell. They also act as tracks for organelles moving around the cell.
Function of the Cytoskeleton
- Provides mechanical strength to cells
- Aiding transport within cells
- Enabling cell movement
The 3 structural components of the cytoskeleton:
- Microfilaments
- Microtubules
- Intermediate fibres
In protein synthesis, what happens in the nucleus?
DNA in the nucleus contains the code to make proteins
In protein synthesis, what occurs in the cytoplasm?
mRNA leaves the nucleus through a nuclear pore
In protein synthesis, what occurs at the cell surface membrane?
The vesicles fuses with cell surface membrane
Cells with many mitochondria…
Typically undertake energy-consuming processes (e.g. neurones, muscle cells)
Cells with extensive ER…
Undertake secretory activities (e.g. plasma cells, exocrine gland cells)
Cells rich in lysosomes tend to..
Undertake digestive processes (e.g. phagocytes)
What is a photo-micrograph?
A photo taken through a microscope to show a magnified image of a specimen
