Organelle, structure and functions Flashcards
What is the function of the cell surface membrane?
• Controls the exchange of materials between the internal cell environment and the external environment.
• It is partially permeable, allowing some substances to pass through while blocking others.
• Formed from a phospholipid bilayer approximately 10 nm thick.
• Also known as the plasma membrane
Describe the structure and role of the nucleus in eukaryotic cells
• Structure:
• Large and separated from the cytoplasm by a double membrane called the nuclear envelope.
• Contains nuclear pores for the transport of mRNA, ribosomes, and other molecules.
• Function:
• Houses chromatin (DNA and proteins) for genetic information.
• Responsible for the organization of linear DNA tightly wound around histones.
• Contains the nucleolus, which produces ribosomes
What is the nucleolus
• The nucleolus is a darkly stained region of the nucleus visible under a microscope.
Q: What is the primary structure and function of mitochondria?
S: Mitochondria have a double membrane structure, consisting of an outer membrane and a highly folded inner membrane, which forms structures known as cristae.
F : The matrix of mitochondria contains enzyme, needed for aerobic respiration, producing ATP
Also there is a small piece of DNA known as mitochondrial DNA and ribosomes are found in the matrix. These are needed for replication of mitochondria before cell division.
Ribosomes
S: ribosomes can be found as free organelles in the cytoplasm of all cells, or as part of rough endoplasmic reticulum
Ribosomes are complex of a ribosomal RNA and proteins
They are not surrounded by a membrane
F: Ribosomes are site of translation
Rough Endoplasmic reticulum RER
S: they are formed from folds of membrane continues with the nuclear envelope
The surface of RER is covered in ribosomes
F: The role of them is to process proteins made on the ribosome
Smooth Endoplasmic reticulum SER
they are also formed from folds of membrane, but its function is distinct from RER , they are involved in production, processing and storage of lipids, carbohydrates and steroids
Also SER does not have ribosomes on its surface
Golgi apparatus structure
Consist of flattened sacs of membrane similar in appearance to the smooth Endoplasmic reticulum
They also known as Golgi body
Can be Distinguished from SER by its regular stacked appearance (WiFi symbol)
Golgi apparatus role
They modify proteins and lipids before packaging them into Golgi vesicles
Vesicles then transport the protein and lipid to their required destination
Proteins that go through the Golgi apparatus can be :
1 exported from the cell, for example hormones, such as insulin 2 put into lysosomes ex hydrolytic enzymes 3 Deliverd to other membrane-bound organelles
Lysosomes
Lysosome are specialist form of vesicle that contain hydrolytic enzymes
Role : They break down waste materials, such as worn out organelles
They are also used extensively by cells of the immune system in programmed cell death known as apoptosis
Centrioles
Centrioles are made of hollow fibers known as microtubule
Microtubules Are filaments of proteins that can be used to move substances around inside a cell, as well as to support the shape of the cell from the inside
Two Centrioles at right angles to each other forms a centrosome which organizes the spindle fibers during cell division
Centrioles are not found in plants and fungi
Chloroplast
1 Chloroplast are larger than mitochondria
2 surrounded by a double membrane
3 within the chloroplast, there are membrane-bound components called
Thylakoid containing chlorophyll stack to form structure, called Grana
4 grana are joined together by lamellea
5 Chloroplast also contain small circular pieces of DNA and ribosomes used to synthesize proteins, needed in chloroplast, replication and photosynthesis
