Cell Biology: Mitochondria and Centrioles

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Questions and Answers

What is a key disadvantage of using preparation and staining techniques in microscopy?

They are less complicated than light microscopy.

They are inexpensive and easy to use.

They require minimal training.

They can produce artefacts due to poor technique. (correct)

What is the correct formula to calculate the actual size of a cellular structure based on the image size and magnification?

Actual = Image x Magnification

Magnification = Actual x Image

Image = Actual + Magnification

Actual = Image / Magnification (correct)

Which unit conversion is often recommended to make calculations easier when measuring cellular structures?

Convert micrometres to millimetres.

Convert centimetres to metres.

Convert millimetres to micrometres. (correct)

Convert millimetres to centimetres.

What is the value of 1 micrometre in metres?

10^-6 metre Signup and view all the answers

Why is it important to convert measurements into the same units before calculations?

It ensures accurate measurement comparison. Signup and view all the answers

What is the primary function of the enzymes found in the matrix of mitochondria?

ATP production through oxidative phosphorylation Signup and view all the answers

Which process is primarily associated with the Krebs cycle found in the mitochondrial matrix?

Aerobic respiration Signup and view all the answers

What structural feature do centrioles consist of?

9 triplets of microtubules Signup and view all the answers

What role do ribosomes play in the cell?

Protein synthesis Signup and view all the answers

What type of proteins are primarily produced by the rough endoplasmic reticulum?

Secretory proteins Signup and view all the answers

During which phase do centrioles replicate and migrate to poles in animal cells?

Prophase Signup and view all the answers

How do ribosomes appear when present in the cytoplasm?

In polysomes or attached to the ER Signup and view all the answers

What is the primary role of the Golgi body in relation to proteins?

Modification and packaging of proteins Signup and view all the answers

What is the primary function of the smooth endoplasmic reticulum?

Production and transport of lipids Signup and view all the answers

What structural feature characterizes the Golgi body?

A stack of flattened, membrane-bound sacs Signup and view all the answers

How are enzymes within lysosomes synthesized and transported?

Synthesized on rough endoplasmic reticulum and transported to Golgi apparatus Signup and view all the answers

What is a primary function of lysosomes?

Digestion of proteins and other materials Signup and view all the answers

What occurs during autophagy?

Engulfment and digestion of unwanted structures within the cell Signup and view all the answers

What process do lysosomes perform when they fuse with endocytic vesicles?

Digestion of materials taken in by endocytosis Signup and view all the answers

Which type of cell would likely have large Golgi bodies?

Secretory cells Signup and view all the answers

What is the function of the enzymes found in lysosomes?

To break down complex biomolecules Signup and view all the answers

What is the conversion of 650 mm into micrometres (µm)?

650 000 µm Signup and view all the answers

According to the fluid-mosaic model, what primarily makes up the plasma membrane?

Proteins and phospholipids Signup and view all the answers

How is the actual size of an organelle calculated using the image size and magnification?

Actual size = Image size ÷ Magnification Signup and view all the answers

What does the selective permeability of the cell membrane signify?

It restricts passage based on size and charge Signup and view all the answers

If a lung cell measures 25.5 nm, what is its size in millimetres?

0.0000255 mm Signup and view all the answers

What does the term 'fluid' in the fluid-mosaic model refer to?

The ability of phospholipids to move laterally Signup and view all the answers

What happens to lipid-soluble molecules when they reach the cell membrane?

They pass rapidly through the membrane Signup and view all the answers

How many micrometres are in 1.5 meters?

1 500 000 µm Signup and view all the answers

What is the main characteristic of diffusion?

It occurs from high concentration to low concentration. Signup and view all the answers

Which factor does NOT increase the rate of diffusion?

Decreased temperature Signup and view all the answers

What distinguishes active transport from passive transport mechanisms?

Active transport uses ATP for energy. Signup and view all the answers

Which type of transport uses carrier proteins for polar molecules?

Facilitated diffusion Signup and view all the answers

What is the primary role of mitochondria in cells involved in active transport?

To produce ATP for energy. Signup and view all the answers

Which statement about osmosis is true?

It is the diffusion of water across a selectively permeable membrane. Signup and view all the answers

Which substance is transported via facilitated diffusion?

Glucose Signup and view all the answers

What effect do metabolic inhibitors have on active transport?

They decrease the rate of active transport. Signup and view all the answers

Study Notes

Mitochondria

Stalked particles are associated with ATP production via the electron carrier system (oxidative phosphorylation).
The matrix of mitochondria contains enzymes for the Krebs cycle (aerobic respiration), mitochondrial DNA, and ribosomes.
Mitochondrial DNA carries genetic information for mitochondrial replication.
Ribosomes in the mitochondria are responsible for protein synthesis.
Cells with high ATP demands, such as muscle cells, liver cells (for glycogen synthesis), and cells involved in active transport, possess numerous mitochondria.

Centrioles

Small hollow cylinders (0.3 – 0.5μm long, 0.2μm diameter) containing 9 microtubule triplets.
Occur in pairs in most animal cells.
Replicate and migrate to opposite poles of the spindle during nuclear division.
Spindle fibers (microtubules) control chromosome separation.

Ribosomes

Tiny organelles (20nm diameter) composed of two subunits (large and small) made of protein and ribosomal RNA.
Found individually in cytoplasm, in chains called polysomes, or attached to the endoplasmic reticulum.
Function in protein synthesis by joining amino acids.

Endoplasmic Reticulum (ER)

Network of flattened membrane sacs called cisternae serving as an internal transport system.

Rough Endoplasmic Reticulum (RER)

Has ribosomes attached to its surface.
Produces proteins that are transported through the cisternae often for secretion out of the cell.
Secretory proteins are often directed to the Golgi body for packaging.

Smooth Endoplasmic Reticulum (SER)

Lacks ribosomes.
Involved in the production and transport of lipids.

Golgi Body

Stack of flattened, membrane-bound sacs called cisternae.
Cisternae are continuously formed at one end and pinched off as vesicles at the other.
Secretory cells have large Golgi bodies.
Functions as an internal processing and transport system:
- Production of glycoproteins.
- Packaging and secretion of proteins (e.g., enzymes).
- Formation of lysosomes.

Lysosomes

Spherical organelles (0.2-0.5μm) found in most eukaryotic cells.
Single-membrane-bound sacs containing digestive (hydrolytic) enzymes:
- Proteases break down proteins.
- Nucleases break down nucleic acids.
- Lipases break down lipids.
Lysosomal enzymes are kept separate from the rest of the cell to prevent destruction.
The enzymes are synthesized on the RER, transported to the Golgi apparatus, and packaged into Golgi vesicles that bud off to become lysosomes.

Lysosome Functions

Digestion of material taken in by endocytosis: Lysosomes fuse with endocytic vesicles/vacuoles, releasing enzymes to digest the contents. Products are absorbed by the cytoplasm, leaving undigested remains which are released through exocytosis.
Autophagy: Unwanted structures in the cell are engulfed and digested within lysosomes. These structures are enclosed in a single membrane (usually from smooth ER) and fuse with a lysosome, forming an "autophagic vacuole" for digestion. This is part of the regular turnover of cellular organelles (old ones replaced by new ones).

Calculating the Size of Cellular Structures

Use the formula: Image size = Actual size x Magnification.
Convert measurements to micrometres (µm) for cellular structures.

Cell Membrane

Also known as the plasma membrane.
Surrounds the cytoplasm of a cell.
Controls the entry and exit of substances.
Structure is described by the fluid-mosaic model.

Components of Cell Membrane

Phospholipids form a bilayer that is constantly moving.
Protein molecules are unevenly distributed throughout the membrane, creating a mosaic pattern.

Selective Permeability

The type and distribution of proteins and phospholipids determine the selective permeability of the membrane.
The phospholipid bilayer allows for rapid passage of lipid-soluble molecules but restricts the movement of ions and polar molecules.

Transport Across Membranes

Movement of substances into or out of cells can occur through:
- Diffusion
- Facilitated diffusion
- Osmosis
- Active transport

Diffusion

Net movement of molecules from high to low concentration until they are equally distributed.
Passive process (i.e., doesn't require energy from respiration).
Gaseous exchange occurs through diffusion.

Factors Affecting Diffusion Rate

Higher concentration gradient increases the rate.
Large surface area (e.g., microvilli) increases the rate.
Shorter distance (e.g., single cell layer) increases the rate.

Facilitated Diffusion

Transport of polar molecules (e.g., glucose, amino acids) across membranes.
Involves channel proteins and carrier proteins.
Passive process (i.e., doesn't require energy).
Not inhibited by respiratory inhibitors (e.g., cyanide).

Active Transport

Movement of molecules or ions against the concentration gradient (low to high concentration).
Requires energy in the form of ATP produced by respiration.
Involves carrier proteins.

Factors Affecting Active Transport

Lowering temperature decreases the rate.
Lack of oxygen decreases the rate.
Metabolic and respiratory inhibitors (e.g., cyanide) decrease the rate.
Cells involved in active transport have numerous mitochondria to provide ATP.

Osmosis

Net movement of water molecules across a partially permeable membrane from a region of high water potential to a region of low water potential.
Essentially diffusion of water molecules.

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Description

This quiz covers essential information about mitochondria, centrioles, and ribosomes. It highlights the roles of these organelles in cellular respiration, protein synthesis, and cell division. Test your knowledge on their structure and functions in various cell types.