week 2 and additional quiz notes Flashcards
Explain Cell Theory ( 5 rules)
Cells are the basic building block of living things and the smallest unit of the living entity.
- All living things are made up of cells.
- Cells are the basic unit of structure and function in living things
- Cell structure is correlated to cellular function.
- All cells are produced from other cells (we all start if as cells, which differentiate and multiply)
- All cells are related by their descent from earlier cells
why do cells need a large surface area?
Cells need a large surface area of plasma membrane to adequately exchange materials.
why is it best that cells are small?
The surface‐area‐to‐volume ratio requires that cells be small. Small size = large SA:volume ratio and vice versa.
why is a large surface area in cells necessary ?
If cell is small the surface area relative to volume increases, making transportation easier and quicker. Cells need a large surface area of membrane to adequately exchange materials. As cell size increases, it takes longer for material to diffuse into or out of the cell.
what is Surface area-to-volume ratio?
Surface area-to-volume ratio: as a cell increases in size, the volume increases 10x faster than the surface area requiring that cells be small. the smaller the cell the better as it = large surface are easy for transport.
why is it difficult when a cell size becomes larger?
As a cell becomes larger, adequate transport of materials through the membrane becomes more difficult. As the size of a cell increases, the amount of living material (the cell’s volume) increases more quickly than the size of quickly than the size of the outer membrane (the cell’s surface area)
what does a cell use to greatly increase surface area?
Cells specialized in absorption utilize membrane modifications such as microvilli to greatly increase surface area per unit volume
why are most cells microscopic?
Most cells are microscopic. Only a few are visible to the human eye. Cells are so small because they need to maintain a membrane size large enough relative to their volume, so the membrane can work effectively to pass nutrients and information to and from the cell. A mouse and an elephant have cells of similar kinds and sizes. The only difference is how many cells are present. Large cells-surface area relative to volume decreases. Volume is living cytoplasm, which demands nutrients and produces wastes. Cells specialised in absorption utilise membrane modifications such as microvilli to greatly increase surface area per unit volume.
Distinguish between prokaryotic & eukaryotic cells (single cells, unicellular and multicellular)
There are 2 types of cells: eukaryotes and prokaryotes.
Pro- means “before” and karyon means “nucleus” hence the term prokaryotic meaning “before the nucleus” i.e. lacks a nucleus.
Prokaryotic cells lack internal membranes, they are smaller and simpler, no nucleus, DNA is present in the nucleoid, Cell wall outside of plasma membrane, Do contain ribosomes (but don’t contain membrane-bound organelles) Eg: bacteria and archae
Eukaryotic cells are larger, more complex, have a nucleus that houses DNA and other membrane enclosed organelles, plasma membrane and plant cells have a cell wall Eg: protists, plants, fungi and animals, humans
What might be some advantages of having distinct compartments (organelles)?
Protection from foreign substances like bacteria that may invade organelle and take over the organelles function, if there is diversity the other organelles will keep cell running.
Complexity allows not all organelles to be vulnerable to an attack
Specialisation (every organelle has a different function which creates complexity).
Why is DNA only found in nucleus?
Protection: protecting DNA. If there were bits of DNA in in cytoplasm n different organelles the body might think its bacteria and attack the other organelles and destroy them.
what is a plasma membrane and phospholipid bilayer?
Eukaryotic cells have a plasma membrane as well as various compartments each with a membrane. Basically, it is a semi permeable barrier, to allow nutrients to enter cell and waste to exit out.
The semi permeable barrier is made up of a phospholipid bilayer composed of various phospholipids, and various types of proteins: channel, transport, integral, receptor and marker (identity) proteins
how does DNA turn into proteins
DNA through transcription turns into mRNA, mRNA goes through translation to give protein
what is mitochondria
powerhouse of a cell. All the process and activities within a cell require energy, organelles called mitochondria provide energy by breaking down nutrients from foods.
What is the most prominent cell organelle, explain what it is?
The nucleus is often the most prominent cell organelle. It contains the genome, the cells database, which is encoded in molecules of the nucleic acid, DNA. The dominant feature of eukaryotic cells is the nucleus, which contains most of the cell’s DNA.
what is a double membrane, and what does it contain?
Surrounded by a double membrane, the nuclear envelope, and usually contains one or several nucleoi, which are darkly staining regions that contain high concentrations of RNA and protein as well as DNA. The membrane contains nuclear pores, which are channels to allow the movement of certain molecules between the cytoplasm and the nucleoplasm.
The outer membrane of the nuclear envelope is continuous with……
The outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum. The nuclear pores are not simply holes perforating the double membrane. Each nuclear pore is a precisely organised complex containing multiple copies of about 30 different proteins which some of which delimit the size and shape of the pore. Small molecules can diffuse relatively quickly and freely through the nuclear pore but transport of large molecules is prevented, but these can be actively moved but need signal sequences.
Nucleus Function/Role:
Storage of genetic material
Regulation of development
Regulation of metabolism
Transcription of DNA into RNA.
Nucleolus contains rRNA and protein (site of ribosome assembly)
Nuclear Pores provide passageways for movement of materials
Double membrane: outer membrane is continuous with the endoplasmic reticulum
The nucleus contains DNA that specifies the recipe for protein production
Protein synthesis explained further
RNA is synthesized in the nucleus
Messenger RNA (mRNA) matches the sequence of DNA.
mRNA carries the “recipe” for making proteins through a nuclear pore in the two- layered nuclear envelope.
RNA binds to a ribosome; RNA moves from the nucleus out to a ribosome, where the protein is synthesized.
Some ribosomes float in the cytosol; others attach to the rough endoplasmic reticulum (RER)
what are Ribosomes and their function?
Are the site of protein synthesis (production) in the cell
Consists of a large subunit and a small subunit
Each subunit is composed of rRNA and proteins
Subunits are assembled in the nucleolus
Ribosomes translate some mRNA produced from transcription of DNA into protein
May be located on the endoplasmic reticulum (thereby making it the rough ER) or free in the cytosol. (Free floating in the cytoplasm and attached to endoplasmic reticulum)
Provides a large surface area for important chemical reactions Because it is folded, it fits into a small space
Cells that are actively producing protein (e.g. liver cells) have great numbers of free and attached ribosomes.
what is the endomembrane system and what does it include?
Network of membranes enclosing the nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles
Also includes plasma membrane
May be directly connected to each other or pass materials via vesicles
Some proteins are secreted from cells.
Endomembrane system’s process of secreting proteins(4 steps)
- The different parts of the endomembrane system work together to secrete proteins, moving them outside of the cell. Not all proteins that enter the RER leave the cells. Many stay and function in the various compartments and membranes of the endomembrane system.
- Proteins enter the RER; Secreted proteins move from ribosomes into the RER, where they are modified and folded into their appropriate 3D shape. The proteins exit the RER in bubbles of membrane called transport vesicles.
- Proteins are synthesized on ribosomes; Free floating ribosomes synthesize proteins that will function in the cytosol. Ribosomes attached to the RER synthesize proteins that function inside of the organelles of the endomembrane system or outside the cell.
- Proteins move from RER into the Golgi; The vesicles leaving the RER fuse with the Golgi apparatus— a stack of membrane sacs that acts as a “processing center.”
what is the Endoplasmic reticulum and what does it contain?
Network of membranes that form flattened, fluid-filled tubules or cisternae
ER membrane encloses a single compartment called the ER lumen
Includes both rough and smooth ER
Rough endoplasmic reticulum(rough ER): Studded with ribosomes, Involved in protein synthesis modification and sorting.
Smooth endoplasmic reticulum (smooth ER): Lacks ribosomes, Site of lipid synthesis, detoxification reactions, carbohydrate metabolism, calcium balance, synthesis (including fat), and modification of lipids.
Ribosomes are “protein manufacturing machines” therefore cells with an extensive amount of rough ER- for e.g. human pancreas cells- are capable of synthesizing large quantities of proteins.
Ribosomes are One of the most common organelles found in cells in the ER, consisting of folded membranes and tubes throughout the cell.
Smooth ER: Fat metabolism and detoxification reactions involved in the destruction of toxic substances, such as alcohol and drugs occur on this surface. Human liver cells are responsible for detoxification reactions and contain extensive smooth ER.
what are Centrioles and their function ?
Two sets of microtubules arranged at right angles to each other
Located in a region called the centrosome (Microtubule-organizing centre near nucleus)
Organize microtubules into spindles used in cell division
During cell division, centrioles are responsible for organizing microtubes into a complex of Fibers known as the spindle, ensuring proper separation of chromosomes during division.
what are Cytoskeleton and their function?
Provides shape support and movement of e.g. macromolecules/ organelles
Fibers that extend through cytoplasm
Anchors organelles
what are Peroxisomes?
Membrane-bound
Active in lipid metabolism (e.g. fatty acid breakdown)
Enzymes in peroxisomes are synthesized by free ribosomes in the cytoplasm (instead of rough ER)
function of peroxisomes
Another organelle that consists of many kinds of enzymes. First identified by the presence of an enzyme catalase, that breaks down hydrogen peroxide. Not formed from Golgi membrane, but from ER membrane and contains different enzymes that imported. Involved in the breakdown of long-chain fatty acids, the synthesis of cholesterol, and the synthesis of plasma membrane lipids used in nerve cells.
Contain the enzyme catalase; Breaks down hydrogen peroxide, breaks down long-chain fatty acids, synthesizes cholesterol and bile salts and synthesizes some lipids
Contain enzymes involved which function to catalyse certain reactions that break down molecules by removing hydrogen or adding oxygen
Peroxisomes are abundant in liver cells
Catalase breaks down H2O2 into water and oxygen
what is Endosymbiosis:
-one cell engulfed a second cell and a symbiotic relationship developed
-mitochondria and chloroplasts are thought to have evolved this way
Mitochondria and chloroplasts similarities
-have 2 membranes
-possess DNA and ribosomes
-divide by a process similar to bacteria
Mitochondria role (during aerobic cellular respiration)
organelles present in all types of eukaryotic cells
contain oxidative metabolism enzymes for transferring the energy within macromolecules to ATP (the cell’s energy currency)
found in all types of eukaryotic cells
Mitochondria are unusual in that they contain DNA. This information resides on small circular DNA molecules that are similar to the chromosomes of bacteria but very different to those found in the nucleus. This provides strong evidence for the endosymbiont theory for the origin of mitochondria. The also contain free ribosomes in their cytoplasm just like bacteria, again more like the ribosome found in bacteria than the ribsomes found in the cell cytoplasm.
how does Mitochondria provide Energy:
Outer and inner membrane; Intermembrane space and mitochondrial matrix
Primary role is to make ATP which is used by the cell
Also involved in the synthesis, modification, and breakdown of several types of cellular molecules (carbohydrates)
Contain their own DNA and ribosomes, divide by binary fission
Mitochondrion functions
Double membrane
Respiration
carbohydrate metabolism
ATP generation
(many other functions not covered in this unit)
what are Vacuoles and their function
e.g. plants and fungi. Similar to lysosomes- but for storage as well as degradation.
Vacuoles have diverse functions in cell maintenance.
Vesicles and vacuoles (larger versions) are membrane-bound sacs with varied functions.
Food vacuoles are formed by phagocytosis and fuse with lysosomes.
Contractile vacuoles, found in freshwater protists, pump excess water out of the cell to maintain the appropriate concentration of salts.
A large central vacuole is found in many mature plant cells.
The membrane surrounding the central vacuole, the tonoplast, is selective in its transport of solutes into the central vacuole.
what are Lysosomes and their function?
contain hydrolytic enzymes
Some transport vesicles leaving the Golgi carry enzymes that catalyze hydrolysis reactions.
hydrolytic enzymes fuse with lysosomes, where cellular digestion of a range of molecules can occur including proteins from the secretory pathway and plasma membrane, small molecules, macromolecules, whole organelles and foreign cells and matter ingested from the cell exterior
The Golgi Apparatus location and appearance
Consists of a stack of 3-20 flattened, curved saccules
Resembles a stack of hollow pancakes
Modifies proteins and lipids: Receives vesicles from ER on the cis (inner) face, Prepares proteins for “shipment” in vesicles, Packages proteins into vesicles at the trans (outer), Vesicles have several destinations
Within cell (lysosomes, ER) – Export from cell (secretion,exocytosis)
The Golgi apparatus contents, role and function
The Golgi apparatus consists of stacks of 4 to 10 disc-shaped cisternae. Each Golgi stack has a distinct polarity. One side that faces a cisterna of ER. This is the cis face or entry face of the stack. The membrane of the ER that faces the cis face lacks ribosomes. The opposite side of the Golgi stack is the trans face or exit face. Proteins and glycoproteins are transferred from the ER is vesicles that bud off the ER and fuse with the cis membrane of the Golgi. As they pass through the stack they are modified in various ways. Sugars can be trimmed and other sugars are added on. The resulting sugars often have many sugar molecules added to them. Polysaccharides are also formed in the Golgi apparatus. Once mature they are sorted out and targeted to their correct destinations.
The Golgi apparatus is involved in the processing and packaging of glycoproteins and polysaccharides, Intracellular sorting and transport and the Golgi
Some molecules may be enzymes required for degradative processes within the cell. Some may be glycoproteins or polysaccharides for export across the plasma membrane. Vesicle formation is how these materials are sorted and distributed throughout the cell.
Sorting of proteins within the cisternae or trans-Golgi network lumen is achieved by their association with so-called “cargo” receptors on the inside face of the membrane.
Vesicles transport materials between stacks
Packaging and distribution of materials to different parts of the cell (involved in secretion, processing, and protein sorting)
Why use vesicles?
Transport vesicles help move materials, such as proteins and other molecules, from one part of a cell to another. When a cell makes proteins, transporter vesicles help move these proteins to the Golgi apparatus for further sorting and refining.
Secreted proteins leaving cell process:
Proteins leave the Golgi in transport vesicles.
The transport vesicles then fuse with the cell membrane.
The contents of the vesicle are expelled to the outside of the cell.
If you found a unicellular organism how
might you determined whether it is a
prokaryote or a eukaryote?
The primary distinction between these two types of organisms is that eukaryotic cells have a membrane-bound nucleus and prokaryotic cells do not. The nucleus is where eukaryotes store their genetic information.
How would you determine whether a unicellular organism was a prokaryote or eukaryote
Prokaryotes don’t have a nucleus in eukaryotes do
What are some basic things that all cells must have and are present in both prokaryotes and
eukaryotes?
All prokaryotic and eukaryotic cells have some similar features as they both contain ribosomes, genetic material, a cytoplasm, and plasma membranes.
Why are membranes
important?
The plasma membrane, or the cell membrane, provides protection for a cell. It also provides a fixed environment inside the cell, and that membrane has several different functions. One is to transport nutrients into the cell and also to transport toxic substances out of the cell.
What desirable characteristics
might you expect a membrane
to have?
Structure of the plasma membrane (article) | Khan Academy
The principal components of the plasma membrane are lipids (phospholipids and cholesterol), proteins, and carbohydrate groups that are attached to some of the lipids and proteins. A phospholipid is a lipid made of glycerol, two fatty acid tails, and a phosphate-linked head group
What is the role of ribosomes?
A ribosome is an intercellular structure made of both RNA and protein, and it is the site of protein synthesis in the cell. The ribosome reads the messenger RNA (mRNA) sequence and translates that genetic code into a specified string of amino acids, which grow into long chains that fold to form proteins
- Where are ribosomes synthesised?
in bacterial cells, ribosomes are synthesized in the cytoplasm through the transcription of multiple ribosome gene operons. In eukaryotes, the process takes place both in the cell cytoplasm and in the nucleolus, which is a region within the cell nucleus.
- Can a single ribosome perform slightly different tasks in its lifetime?
Yes, Ribosomes can interact with different types of RNA molecules, called messenger RNAs (mRNAs), which carry the instructions for building specific proteins. a single ribosome can bind to different mRNAs and synthesize different proteins based on the instructions encoded in those mRNAs. Furthermore, ribosomes themselves can undergo modifications or interactions with other cellular components that might influence their behavior
