Mitochondria Structure and Function

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the smooth endoplasmic reticulum (sER)?

Production of ATP

Transport of RNA molecules

Synthesis and storage of lipids and cholesterol (correct)

Synthesis and storage of proteins

Which of the following statements about the endoplasmic reticulum (ER) is true?

The smooth ER contains numerous ribosomes on its surface.

Transfer vesicles bud off from the ER to deliver proteins to the Golgi apparatus. (correct)

The rough ER is responsible for lipid synthesis.

The interconnected cavities of the ER do not facilitate intracellular transport.

What role does the smooth ER play in muscle cells?

Acting as a calcium pump for muscle contraction (correct)

Synthesis of neurotransmitters

Storage and breakdown of glycogen

Production of red blood cells

Which of the following is NOT a function of the smooth endoplasmic reticulum?

Translation of mRNA Signup and view all the answers

What feature distinguishes the smooth endoplasmic reticulum from the rough endoplasmic reticulum?

Morphology of membrane-bound tubules and vesicles Signup and view all the answers

What is the primary function of mitochondria in cells?

Energy release through oxidation of foodstuffs Signup and view all the answers

Which statement about the number of mitochondria per cell type is correct?

Mitochondria are more numerous in specialized cells such as kidney and liver. Signup and view all the answers

What is the thickness of the mitochondrial membranes?

5 to 6 nm Signup and view all the answers

What term is used to describe the folded extensions of the inner mitochondrial membrane?

Cristae Signup and view all the answers

What additional space is created by the inner and outer mitochondrial membranes?

Intermembrane space Signup and view all the answers

In which type of organism can mitochondria be found?

In both unicellular and multicellular organisms Signup and view all the answers

Which part of the mitochondria is rich in enzymes?

Matrix space Signup and view all the answers

What is the shape variation of mitochondria?

Spherical or filamentous Signup and view all the answers

What is the shape of mitochondrial cristae in most cells?

Flat and shelf-like Signup and view all the answers

Which of the following is NOT a function of mitochondria?

Producing proteins from amino acids Signup and view all the answers

What type of RNA is a component of ribosomes?

Ribosomal RNA (rRNA) Signup and view all the answers

Where are ribosomes formed within the cell?

Nucleolus Signup and view all the answers

Which statement about mitochondrial cristae is true?

Their shape can vary based on cell function. Signup and view all the answers

What is the primary function of ribosomes?

Protein synthesis Signup and view all the answers

How do mitochondria contribute to spermatozoa?

By forming the tail sheath Signup and view all the answers

Which of the following statements about ribosomal subunits is true?

They consist of a small subunit and a large subunit. Signup and view all the answers

What type of ribosomes are involved in the synthesis of proteins for secretion?

Attached ribosomes Signup and view all the answers

Which site on the ribosome is the binding site for the aminoacylated tRNA?

A site Signup and view all the answers

Which of the following characterizes free ribosomes in a cell?

Synthesize proteins for organelle regeneration Signup and view all the answers

During protein biosynthesis, how many sites are occupied at any one time?

Two Signup and view all the answers

What is the primary function of ribosomes in the context of protein synthesis?

Facilitating peptide bond formation Signup and view all the answers

What are clusters of ribosomes connected by mRNA called?

Polysomes Signup and view all the answers

Which type of cells primarily contain ribosomes that are arranged on the membrane surface of the rER?

Pancreatic secretory cells Signup and view all the answers

What role does the E site play in ribosome function?

Releasing deacylated tRNA Signup and view all the answers

Who first discovered the endoplasmic reticulum (ER)?

Emilio Veratti Signup and view all the answers

What best describes the structure of the endoplasmic reticulum?

A network of membranes called cisternae Signup and view all the answers

What is a defining feature of the rough endoplasmic reticulum (rER)?

It appears as membrane-bound sheets with ribosomes attached Signup and view all the answers

Which function is associated with the rough endoplasmic reticulum (rER)?

Synthesis of proteins Signup and view all the answers

Which component is essential for ribosomes to bind to the rough endoplasmic reticulum?

Ribophorins Signup and view all the answers

What is the main difference between rough ER and smooth ER?

Rough ER has ribosomes on its surface, while smooth ER does not Signup and view all the answers

What is the type of ribosome associated with the rough endoplasmic reticulum?

80S ribosomes Signup and view all the answers

The endoplasmic reticulum is considered the largest organelle in the cell; what does it primarily contain?

Cisternae and vesicles Signup and view all the answers

Study Notes

Mitochondria

Mitochondria are thread-like organelles found in unicellular and multicellular organisms.
They are known as the "powerhouses" of cells as oxidation of food and energy release occur within them.
Mitochondria are membrane-bound organelles.
They are spherical or filamentous, approximately 0.5-1 µm wide and up to 12 µm long.
The number of mitochondria is roughly consistent per cell type.
More specialized cells, like those in the kidney and liver have more.
Amoeba cells can have up to 500,000.
Liver cells have between 500-2500 per cell.
Sperm cells have as few as 20.
Some oocytes can have up to 300,000.

Mitochondrial Structure

Mitochondria are sac-like structures.
They have an outer and inner membrane.
Each membrane is approximately 5-6 nanometers thick.
The outer membrane is smooth and continuous.
The inner membrane folds inward, forming cristae.
The inner membrane is similar in appearance to the outer membrane but is folded.
The folds are called cristae.
The space between the outer and inner membranes is called the intermembrane space.
The space enclosed by the inner membrane is called the matrix (intercristae space).
Cristae shape varies depending on the cell the mitochondria are located in.
Most mitochondria have flat shelf-like cristae, whereas steroid-secreting cell mitochondria are tubular.

Mitochondrial Functions

Mitochondria degrade metabolites.
They contain tricarboxylic cycle enzymes that generate nucleotides from citric acid.
They assist in steroid and nucleic acid synthesis.
They are greatly involved in cell metabolism, especially of fats and amino acids.
They are responsible for forming the tail sheath of spermatozoa.

Ribosomes

Ribosomes are complex molecular machines in living cells that produce proteins from amino acids during a process called protein synthesis or translation.
All living cells synthesise proteins in this way.
Ribosomes are made of RNA and protein, a ribonucleoprotein.
Ribosomes are composed of two subunits.
Ribosomes are non-membrane-bound organelles.
Ribosomes are formed from nucleolus proteins and pass through the nuclear pores to the cytoplasm.

Ribosomes: Structure & Types

Ribosomes consist of two subunits: small and large.
Small ribosomal RNA reads RNA.
Large ribosomal RNA links amino acids to form a polypeptide chain.
Ribosomes can be:
- Free in the cytoplasm (e.g., embryonic cells)
- Attached to areas of the cell (e.g., endoplasmic reticulum).
- Appear as minute basophilic granules (light-microscopy).
- Appear as dense granules in electron microscopy.
Ribosomes can be clustered (polyribosome/polysome).

Ribosomes Functions

Free ribosomes produce proteins for cell growth and organelle regeneration.
Attached ribosomes create proteins for secretory granules and secretions.
Help create peptidyl transfer and peptidyl hydrolysis.
During protein synthesis, tRNA moves through three primary binding spots on the ribosome:
- A site (aminoacylated tRNA)
- P site (peptidyl tRNA)
- E site (exit site for deacylated tRNA)

Endoplasmic Reticulum (ER)

ER is the largest organelle in the cell, and is a network of membranes.
It's present in the cell's cytoplasm.
Organelles have a network of tubules, vesicles, and flattened cisternae.
There are two main types: rough and smooth ER.

Rough ER (rER) Structure and Function

Present in protein-producing cells, such as those of the plasma cell.
Its surface has glycoprotein receptors called ribophorins.
These receptors attach ribosome subunits to the cell's surface.
Light microscopy shows it as basophilic areas (darker areas)
Electron microscopy shows flattened cisternae with ribosomes on the surface

Rough ER (rER) Functions

Protein synthesis occurs on the surface.
The formed protein accumulates within the cavities.
Transfer vesicles bud off the ER move proteins to the Golgi apparatus.

Smooth ER (sER) Structure and Function

Found in lipid and steroid-hormone producing cells.
The structure cannot be observed through light microscopy. (Not basophilic)
Electron microscopy shows membrane-bound tubules and vesicles, lacking ribosomes.

Smooth ER (sER) Functions

Synthesizes and stores lipids and cholesterol.
Creates steroid hormones (testosterone, cortisone).
Aids muscular contraction by regulating calcium levels.
Stores and breaks down glycogen in liver and muscle cells.
Detoxifies some drugs and hormones.
Participates in intracellular transport connecting to the Golgi apparatus.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the structure and functions of mitochondria, often referred to as the powerhouses of cells. It covers their characteristics, variations in different cell types, and their membrane structure. Test your knowledge about these essential organelles and their role in energy production.