Unit 2 - Cells and Tissue Flashcards
Describe the difference in internal membranes between pro/eukaryotic cells
prokaryotic - internal membranes are not common, except for photosynthetic bacteria that have internal membranes specialised for harnessing light energy
eukaryotic - internal array of membranes that define the organelles that divide the cell into smaller spaces specialised for different functions
difference between cytosol and cytoplasm
cytoplasm - the entire contents of a cell other than the nucleus
cytosol - jelly like internal environment that surrounds the organelles
Difference in plant and animal organelles
Animal - nucleus, endoplasmic reticulum, golgi apparatus, lysosomes
Plant - cell wall, vacuoles for water uptake, chloroplasts for energy conversion, plasmodesmata (channels allowing the passage of large molecules such as mRNA and proteins between neighbouring cells)
are organelles isolated entities
no. the are either physically connected by membrane bridges or transiently connected by vesicles (small membrane enclosed scas that transport substances within a cell or from the interior to the exterior of the cell
how do vesicles form
by budding off an organelle, taking with them a piece of the membrane and internal contents of the organelle that they derived from. they then fuse with another organelle of the cell membrane, reforming a continuous membrane and unloading their contents
What does the endomembrane system consist of
the nuclear envelope, ER, golgi apparatus, lysosomes, cell membrane, vesicles
what is specific to plants concerning the endomembrane system
The endomembrane system is continuous between cells through plasmodesmata
Define 1. exocytosis and 2. endocytosis
- when a vesicle fuses with the cell membrane, providing the vesicle with a way to empty its contents to the extracellular matrix or deliver proteins embedded in the vesicle membrane to the cell membrane
- budding off from the cell membrane and bringing enclosed material from the outside of the cell into the cell interior
nuclear membrane
double membrane that surrounds the nucleus, containing nuclear pores
nuclear pores
openings in the nuclear envelope that transport proteins (transcription factors) into the nucleus and mRNA out of the nucleus to the cytosol - the mRNA binds to ribosomes or stay free in the cytosol -
where does protein synthesis occur
in the cytosol, free ribosomes in cytosol associated with the ER
Endoplasmic Reticulum
Physically continuous with the nuclear envelope, interior (lumen) is continuous throughout. very convoluted membrane for larger SA
involved in protein and lipid synthesis.
produces and transports many of the proteins and lipids used inside and outside the cell (including transmembrane proteins)
Rough ER
has ribosomes
synthesizes transmembrane proteins, proteins that end up in the interior of the organelles and proteins destined for secretion
cells that secrete large quantities of proteins have extensive rough ER (eg cells of the gut that secrete digestive enzymes, and cells of the pancreas that secrete insulin)
Smooth ER
lacks ribosomes
site of fatty acid and phospholipid biosynthesis
more common in cells that produce lipids (eg cells that synthesize steroid hormone, as they produce cholesterol)
Golgi Apparatus
three primary roles:
1. further modifying proteins (with enzymes) and lipids produced by the ER
2. acts as a sorting station as these proteins and lipids move to their final destinations
3. the major site where carbohydrates are added to proteins and lipids
made up of flattened membrane sacs called cisternae
vesicles are the primary way that proteins move through the golgi apparatus with to their final destination
Where do Lysosomes originate from
They are specialised vesicles derived from the golgi apparatus
What is the function of lysosomes
They degrade damaged or unneeded macromolecules. therefore playing a key role in intracellular digestion and the recycling of organic compounds. they’re also involved in apoptosis (programmed cell death)
How do lysosomes break down molecules
They contain a variety of hydrolytic enzymes that are packaged into lysosomes by the golgi apparatus. The golgi apparatus also packages the macromolecules that are destined for degradation
what is the optimal internal environment of proton pumps
pH 5 (acidic)
How does the cell protect the organelles from being degraded by the lysosomes
By having an environment of pH 7, in which the lysosomal enzymes cannot function
What do mitochondria do
harness energy from chemical compounds such as sugars and convert it into ATP. A proton electrochemical gradient is used to synthesize ATP for use by the cell
Describe the structure of mitochondria
Two membranes, an outer membrane and a highly convoluted inner membrane whose folds project into the interior.
These folds allow for a greater surface area available for the biochemical machinery that pumps protons and then synthesizes ATP
What do chloroplasts do
capture the energy of sunlight to synthesize simple sugars (this process is called photosynthesis) results in the release of O2
describe the structure of chloroplasts
surrounded by a double membrane, and have a third, internal membrane, called the thylakoid membrane
What does the thylakoid membrane do
it separates the internal compartment called the thylakoid, the membrane contains specialised light collecting molecules called pigments (chlorophyll)
describe the function of chlorophyll
collects light energy, which enzymes in the chloroplast then use CO2 as a carbon source for carbohydrates
What are the functions of vacuoles in animal and plant cells
animal - help get rid of waste products
plants - help maintain water balance
What roll does vacuoles play in homeostasis
They regulate the turgidity by regulating the amount of water in a cell. they will absorb water and diffuse it out of the cell if it is in excess, if the cells lacks water the vacuole tends to revert it back into the cell
What four types of tissue do animals have
- epithelial
- connective
- nervous
- muscle
they combine to form organs
What determines the shapes of cells in animals
Maintained and determined by structural protein networks in the cytoplasm called the cytoskeleton
What are cell junctions
complexes of proteins in the cell membrane where a cell makes contact with another cell or the extracellular matrix
what is the extracellular matrix and what is its importance
A meshwork of proteins and polysaccharides outside of many cells and tissues. It are important in maintaining a strong, properly shaped tissue or organ
What is endosymbiotic theory
The theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). This theory explains the origin of eukaryotic cells.
What is the main role of the cytoskeleton
Provides internal support for the cellsh
What two cytoskeletal elements do all eukaryotes have
microfilaments and microtubules (animals cells also have a third element, intermediate filaments)
