fundamentals of cell biology and cell=cell interactions Flashcards
Cell Biology: Lysosome
A lysosome is a membranous sac of hydrolytic enzymes that an animal cell uses to digest macromolecules.
The inside of a lysosome is very acidic because lysosomal hydrolytic enzymes work effectively in acidic environments.
The hydrolytic enzymes and the lysosomal membrane are made by the rough ER and then transferred to the GA for further processing.
The membrane surrounding the lysosome prevents the digestive enzymes inside from destroying the cell.
Functions of a lysosome:
Lysosomes enzymes break down complex food molecules such as complex sugars and proteins.
Lysosomes also play a recycling role by digesting excessive or worn-out organelles, food particles, other unwanted material and engulfed viruses and bacteria. In certain circumstances, lysosomes will actually digest the cell’s functioning organelles for nutrients.
Vacuoles
Vacuoles are membrane-bound vesicles that serve a variety of functions.
Vacuoles are usually absent in animal cells. If found in some animal cells, then they are very small in size.
Vacuoles are found in all plant cells. They are the largest organelles in plant cells and are often referred to as a central vacuole.
Function of a vacuole:
Storage for proteins, potassium, chloride, etc.
Serves as disposal sites for waste material. This helps to prevent contamination of the cell.
Some vacuoles contain pigments, e.g. red and pink pigments of petals assist in attracting pollinating insects to flowers.
Some plant and fungi vacuoles carry out enzymatic hydrolysis, as animal lysosomes do.
Some vacuoles contain poisonous substances that protect the plant against predatory animals.
The vacuole can also store large amounts of water at any given time which is essential for the growth of the plant.
Cytoskeleton
The cytoskeleton is a network of fibres extending through the cytoplasm that provides mechanical support and maintains the cell’s shape.
There are three types of protein fibres based on their diameter and composition:
microtubules, microfilaments, and intermediate filaments.
Other functions of the cytoskeleton:
involved in cell motility.
Manipulates the plasma membrane to form food vacuoles during phagocytosis.
Plays a role in the regulation of biochemical activities.
The cytoskeleton is flexible, quickly dismantling in one part of the cell and reassembling in a new location, changing the shape of the cell.
The largest of the protein fibres, the microtubules, create three complex structures that are involved in some form of cell movement. These structures are centrioles, flagella and cilia.
Centrosome
Centrosomes are organelles which serve as the main microtubule organising centres for animal cells.
They are responsible for assembling tubulin proteins into microtubules.
A centrosome is made up of paired cylindrical structures called centrioles. The individual centrioles are located at right angles to one another.
Chloroplast
Chloroplasts capture solar energy and convert it to chemical energy (food).
They are lens-shaped organelles that are found in plants and algae.
Like mitochondria, chloroplasts contain their own DNA and can reproduce themselves.
Chloroplasts are the main site of photosynthesis
Structure of the chloroplast:
Chloroplasts have an inner and outer membrane with an empty intermediate space in between.
The dense fluid inside the chloroplast is called stroma.
Inside the chloroplasts are stacks of thylakoids, called grana (singular is granum).
These thylakoids contain a green pigment called chlorophyll that gives plants their green colour. This pigment is responsible for absorbing solar/light energy which is required in photosynthesis.
The space that the chlorophyll fills within the thylakoids is called the thylakoid space.
Lamellae connect the thylakoids and keep them at an optimal distance for energy production.
Similarities Between a Plant and Animal Cell
Nucleus
Cytoplasm
Plasma membrane
Golgi apparatus
Mitochondria
Endoplasmic reticulum
Ribosomes
Differences Between a Plant and Animal Cell
look at notes on mylms
