Chapter 4 Flashcards
What was the statement in the very first published cell theory?
“All living things are composed of living cells”
3 principles of complete cell theory
- all living things are made of cells
- a cell is the smallest unit in a living thing
- all cells come from other cells
Magnification
The increase in apparent size of an object. Said using #x
Ex. Saying we viewed something at 100x means that the objects was magnified at 100x its original size
Resolution
A measure of clarity of an image.
The ability of an optical instrument to show to nearby objects as separate.
Light microscopes
Can effectively magnify objects at about 1000x.
Typically used for live specimens in order to see movement.
Cannot achieve great resolution on these microscopes.
Electron microscopes
Focus a beam of electrons through a specimen (transmission electron microscopy), or onto its surface (scanning electron microscopy).
The beam of electrons excites electrons on the surface of the sample, and these electrons are detected by a device that translates their pattern into an image
2 principle types of cells
Prokaryotic cell: archaea and bacteria
- no membrane bound organelles
- 1/10 size of eukaryotic cell
- reproduce via binary fission
- capsule exterior helps evade from antibiotics/ being consumed by predators.
Eukaryotic cell: plants and animals
- membrane bound organelles
- nucleus holding DNA/RNA
Nucleus
Control center of the cell, holding the DNA. The DNA is coded with instructions which know how to produce proteins, hormones, and other things facilitating the cell.
Nuclear envelope / membrane
A tightly attached double-layered membrane surrounding the nucleus. It helps protect the DNA inside.
Nuclear pores
Small channels along the nuclear envelope that allow certain molecules to go in or out of the nucleus. (Semipermeable)
Nucleoplasm
A jelly like matrix that all other materials in the nucleus “float” in.
Chromatin
The material in the nucleus which composes chromosomes. It is composed of DNA, RNA, and the protein histone
Nucleolus
(Note: “nucleoli” = plural)
Dark stained circle-like structures in the nucleus. They are full of RNA.
Function to produce ribosomes.
Ribosomes
Protein making machines.
Can either be floating around in the cell (which means the proteins will be used for cellular purpose)
Or
Attached the the rough ER (which means the proteins will be exported for use outside of the cell)
Rough endoplasmic reticulum
Contains many ribosomes on the outside of its surface. It will help in the protein synthesis of ribosomes and export the proteins to the Golgi apparatus. It will also make more membrane.
(Shares the nuclear envelope membrane with the nucleus)
Smooth endoplasmic reticulum
Lacks ribosomes.
Is involved in the synthesis of steroid hormones and lipids. Can also detoxify drugs, alcohol…etc (in liver cells)
(Shares the nuclear envelope membrane with the nucleus)
Golgi apparatus
Contain several flattened “sacs” called cisternae
Receive proteins from the rough ER and modifies them if needed. Then it will ship it through one of its transport vesicles.
Lysosomes
Made by the rough ER, processed in the GA.
Contain digestive enzymes that are able to digest toxic material lying within a cell, or digest old cellular debris that isn’t useful anymore.
Vacuoles
In animals:
Water containing vesicles that help eliminate excess water.
In plants:
Have digestive functions or contain poisons to protect the plant
Peroxisomes
Will break down fatty acids. And in the liver it will detoxify alcohol into hydrogen peroxide, which enzymes will further convert into water.
Mitochondria
Site of cellular respiration: the conversion of energy from sugars to ATP.
Contain several small folds within that are called cristae which increase the surface areas for cellular respiration.
Within these folds is the mitochondrial matrix which contains DNA and ribosomes.
Chloroplasts
(Only in plant cells)
Function to convert light energy into chemical energy via photosynthesis.
The inner membrane has thick fluid called stroma which holds DNA, ribosomes, and enzymes.
In the stroma is thylakoids which contains pigment called chlorophyll.
(Note: a stack of thylakoids = granum
What is the endosymbiont theory?
States that mitochondria and chloroplasts were originally small prokaryotes or undigested bacteria in eukaryotic cells.
This is because they have their own DNA, their ribosomes are similar to prokaryotic ones, and they have double membranes
Cytoskeleton
A network of small protein fibres found throughout the cytoplasm.
Provides structural support for cells.
3 kinds of fibres making up the cytoskeleton:
1) microfilaments
2) intermediate filaments
3) microtubules
Microfilaments
Made from twisted rods of actin protein.
Function: form a 3D network in the plasma membrane that will support the cells shape.
Intermediate filaments
Bigger than microfilaments;
Made from several fibrous proteins that coil together to make a thick cable.
Function: reinforce cell shape and anchor certain organelles such as the nucleus.
Microtubules
Bigger than intermediate filaments;
Made from tubulin protein which forms a hollow tube.
Function: help maintain cell shape and combine with motor proteins to act as a track that helps organelles move in the cell.
Centrioles
Small clusters of microtubules arranged in a bundle.
Function: help in cell division
Cilia and flagella
Both serve to move the cell through any environment OR move fluid over the surface of the cell.
Cilia : short and numerous
Flagella : long and few in number
Extracellular matrix
In animal cells, there is an excretion of an extracellular matrix of proteins and collagen that helps hold tissues together and support the plasma membrane .
Cell junctions
Allow cells to interact with each other
3 types:
1) Tight junctions
2) Anchoring junctions
3) Gap junctions
Tight junctions
Bind cells together using proteins and form a leak-proof barrier between the cells.
Anchoring junctions
Attach cells together with cytoskeleton fibres, still allowing some material to pass between the cells.
Gap junctions
Protein-lined pores that connect cells allowing certain ions (such as water) to flow through
Cell wall
(Only in plants)
Not only do they hold the contents of the plant cell, but it has small holes which allow communication between plant cells.
The Biogenic Law
“All living cells arise from pre-existing cells”
- Rudolf Virchow
The endomembrane system
Consists of organelles that work together in at the synthesis, distribution, storage and export of molecules.
Organelles: nuclear envelope, both endoplasmic reticulums, Golgi, lysosomes, vacuoles, plasma membrane
Which organelles have double membranes?
Nucleus, Mitochondria, and Chloroplasts
