Topic 1.2 Cell Structure Flashcards
Why is compartmentalization needed? (prob not tested)
Each organelle has its own particular function which needs different specific internal conditions
Advantages of Compartmentalization (cells divided into organelles)
- Enzymes and substrates for a particular process can be much more concentrated than if spread throughout the cytoplasm
- Substances that cause damage to the cell can be kept inside the membrane of an organelle (digestive enzymes of lysosome
can be stored inside lysosome membrane) - Conditions such as pH can be maintained at an ideal level for a particular process, which may be different to the levels needed for other processes in a cell.
- Organelles can be moved around the cell
Exocrine Gland
- Exocrine gland cells in the pancreas secrete digestive enzymes into a duct that carries them to the small intestine
- Exocrine gland cells have many organelles which synthesize proteins–> process them to make them ready for secretion –> transport them to the plasma membrane –> release them
Structure and Function of the nucleus
- Surrounded by the nuclear envelope (double-membrane)
- Presence of many pores (have to draw)
- Contains chromosome which is visible during prophase; at other times it is not visible as chromatin threads
- One or more nucleoli are present in the nucleus
- Function: Regulate the synthesis of proteins including enzymes –> control chemical reactions –> control the cell activities
Structure and Function of Nucleolus
- Not membrane-bound; darkly-stained region
- Functions to transcribe ribosomal RNA (rRNA)
- rRNA associated with proteins imported from cytoplasm to subunits of ribosomes which exit the nucleus through nuclear pores to the cytoplasm
- Site of ribosome manufacture.
Structure and Function of Rough Endoplasmic Reticulum
Structure
- Double Membrane
- Between the membrane are fluid-filled spaces called cisternae –> allow materials to be transported throughout the cell
- Ribosomes studded on outer surface –> Ribosomes are the sites of protein synthesis
Function:
o Site of Protein Synthesis
o Packages and transport proteins made by the ribosomes in vesicles to the Golgi Apparatus
o Membrane factory for the cell
Structure and Function of Smooth Endoplasmic Reticulum
Structure
No ribosomes on its surface
Function
o Synthesizes fats and steroids – rich in cells of glands and organs which produce hormones
o Detoxification of poisons and drugs – rich in liver cells
o Stores Ca in lumen, released back to the cytoplasm when stimulated – Rich in muscle cells
Structure and Function of Ribosomes
Structure
- Small, non-membrane-bound organelles
- Made of 2 subunits, one small and one large subunit
- Each subunit is a complex of rRNA and ribosomal proteins
- 80s: Eukaryotic, 70s: Prokaryotic
Function 5. Sites of protein synthesis 6. Types of Ribosomes o Free Ribosomes - Proteins functioning within the cell/cytosol/cytoplasm o Bound Ribosomes - Membrane Proteins - Proteins packaged within organelles (lysosomes) - Proteins secreted outside cells
Structure and Function of Golgi Apparatus
Structure
- Stacks of flattened sacs
- One side of the stack is formed by the fusion of membranes of vesicles from SER
Function: o Modification and packaging of proteins o Transporting and storing lipids o Formation of lysosomes o Production of digestive enzymes o Secretion of carbohydrates for the formation of plant cell walls (pectin) and insect exoskeleton (cuticle)
The Secretory Pathway/exocytosis
- Secretory proteins synthesized from ribosomes from RER are packaged and transported in vesicles.
- Vesicles pinch off the RER which travel to the Golgi Apparatus
- The vesicles fuse with the cis face of the GA and the protein travels through the cisternae of the GA where it is modified and packaged into secretory vesicles.
- The secretory vesicles pinch off the Golgi Apparatus and fuse with the cell membrane, releasing the proteins outside the cell
Structure and Function of Lysosomes
Structure:
- Only in animal cells
- They are small vacuoles formed when
small pieces of GA are pinched off the
end
Functions:
o Lysosomes release enzymes to the outside of the cell to digest other cells – exocytosis
o Digestion is carried out in a membrane-bound vacuole in which the lysosomes fuse –> at low pH, enzymes break down large molecules
o Destroy worn-out organelles within the cell
o Resulting molecules from destroyed organelles are recycled
o Lysosome membrane breaks down –> release enzymes and digest entire cell –> autolysis
Structure and Function of Mitochondrion
Structure:
o Double Membrane
o Outer membrane controls the entry and exit of materials
o Enzymes involved in respiration are located in the matrix and on the cristae
o Inner membrane forms many folds called cristae
- Surface of crista covered with
stalked particles where ATP is made
by oxidative phosphorylation –>
Increase SA for ATP production
- Where ETC is located
o Space between the membranes –> Intermembrane space
o Space inside the mitochondria is called the matrix – filled with jelly-like fluid
- Site of Krebs Cycle
- Contains ribosomes and loops of
DNA
Function:
- Sites of aerobic cellular respiration
- Can replicate themselves when the
cell divides. (G1 Phase)
- Where the electron Transport chain is
located
Structure and Function of Centrioles
Structure:
- Two groups of 9 triple microtubules
- Anchor point for microtubules during cell division and also for microtubules inside cilia and flagella
- Centrioles replicate before cell division
Function:
o Grow the spindle fibres
o Spindle is responsible for the movement of chromosomes during nuclear division
Structure and Function of Chloroplast
- Site of Photosynthesis
- Double membrane (narrow intermembrane space)
- Thylakoids
o Membranous sacs, stacked to form a
granum (area of light-dependent
reactions)
o Light trapped in the pigments within
the membrane - Stroma
o Site of light-independent reactions
o Fluid contains
- Photosynthetic enzymes
- Circular DNA molecules
- 70 ribosomes
- Starch grains and lipid droplets
Similarities between Chloroplast and Mitochondrion
- Double membrane
- Transform energy
- Possess own DNA and 70 ribosomes
- Membrane proteins synthesized by free cytoplasmic ribosomes and own ribosomes
- Cytoplasmic ribosomes and own ribosomes
- Can grow and reproduce within the cell
