BIOSC 130 CELL STRUCTURE PART 1

What is the analogy given to plasma membranes? What is the significance in compartmentalizing the interior of the cell? [this is for all cells]

- the plasma membrane are like the walls of a building such as the lab building. - the walls would be like our membrane, it makes the insides separate from what's going on outside - it can be hot or cold or rainy or windy but we could have a different environment inside our building. - the lab building also allows for subdivisions in that building, we have different rooms in there such as our lab, the lab next door, and the prep room. - there could be conflicting things going on in those rooms, for instance we could be giving a midterm, a presentation, someone else could be doing experiments, while someone else could be setting up lab for next week - this will be hard to do that all in the same space because we could get in each others way and interfere - it's the same thing with the chemical reactions that happen inside the cell, there is a lot going on inside cells, compartmentalizing the interior allows things to occur unimpeded or unaffected by these other potentially disruptive reactions. - to keep them separate and in different places - the plasma membrane allows things to come in and out. it wouldn't be useful just like your building wouldn't be useful if you could not get in and out of it. students and supplies have to come in and out, it regulates that, there's doorways here. an elephant's not going to walk through the door if we need to we can lock the door when we want to close up and we can unlock it and allow students to come in - the membrane is also the gate keeper and because of its properties, it controls what can get in and what can get out of the cell so it does provide this environment that is different from the outside environment but there are exchanges that are made which is great because we need energy, we need to get rid of waste products - it also contains just like the walls in this room and the lab room, there's duct work in there, there is electrical wiring, there's plumbing, there's sensors and these are within the walls you could have a security camera, an alarm system, a handicap door opener button... - membranes have those analogous structures as well, they have receptors that allow to see or scent what's going on outside of the cell, they have proteins that allow messages to be transmitted through, pumps channels these are all integrated or embedded into that membrane whether its the plasma membrane on the outside or in some cases these inner membranes as well

Name the four functions of plasma membrane function.

1) boundary between inside and outside of the cell 2) subdivides the cytoplasm into compartments 3) regulates entry and exit of substances 4) contains proteins which serve as channels, pumps, and receptors

These observations and others have been boiled down to what we know refer to as "cell theory." Name the three components of cell theory.

1. All organisms are composed of one or more cells 2) The cell is the smallest unit having the properties of life 3) The continuity of life (generation and generation) arises from the growth and division of single cells

Name the other limitations to cell size. [Other reasons why cells can't be too big] Explain.

1. Nucleus-to-cytoplasm ratio the nucleus is like the head of a small start up company and you got a couple of employees, you can be quick and respond to a few changes, so it is very efficient and very easy and you are super successful imagine if you grow and you grow and now you have 10,000 employees and you [nucleus] is still the one boss, you can't even talk to all your employees in a day or a month or a year. it gets too hard to have one manager try to control a vast empire, its that same thing in a cell. the nucleus controls what goes on in the cell, if the cell gets too big you still just have that one nucleus, if can't control what happens that is so far away. its very difficult, it becomes inefficient so the nucleus-to-cytoplasm ratio makes it difficult for cells to get too big because that control from the nucleus becomes less and less, there not very responsive 2. Gravitational effects a recent study showed that gravity started to matter too. fluid starts to act different when you get down to microscopic level where cells live, they start to act more viscous we look at water and we think that its an easily movable fluid solution, we can walk or swim through it if you took that same size water and you were a bacterium, it would be like swimming through jelly/honey or worse. they have those little flagella, they don't use them like we do. they use them like a screw to pull themselves through this very viscous liquid and this just happens at those small scales. its the same liquid gravity is kind of negligible. imagine if this room were filled with honey instead of air, stuff will stick where you put it, you don't really have to worry about it falling to the ground so easily the smaller you are, the less you have to worry about gravity playing a big role as you get bigger to like our scale, if we want to have stuff up on the ceilings or walls we have to use equipment you have to tie it, fasten it, glue it, hold it spend energy to utilize that space cells operate on the brink or right on that edge of where gravity matters or doesn't matter if you want to be big, here is an extra tax, you are going to have to use some energy to fight gravity larger cells have to spend a lot more energy tying things down, holding things up, suspending things, wasting energy building support structures to counteract gravity while smaller cells don't

There are subdivisions within the smooth ER and its functions vary with cell type. What are the four functions of the smooth endoplasmic reticulum?

1. enzymes of the smooth ER are important in the synthesis of or helps make lipids including oils, new membrane phospholipids, and steroids 2. helps with carbohydrate metabolism 3. other enzymes of the smooth ER detoxifies drugs and poisons 4. stores calcium ions needed for muscle contraction

What are the two sites of the rough endoplasmic reticulum for?

1. site of synthesis and modification of proteins since ribosomes are on the rough ER, this means we are making proteins here, so the rough ER is where the proteins get built 2. site of membrane production so, it is also a place where membrane is built, the rough ER is a membrane factory for the cell. As the cell grows, it has to produce membrane because it doesn't just stretch as it keeps growing. You need more of these molecules to make up the membrane. the key is that all membranes is produced in the rough ER and they keep making wall material and they can distribute it to all the membranous organelles that need it because its all interchangeable bits of membrane, its all just phospholipids. it grows in place by adding membrane proteins and phospholipids to its own membrane. the rough ER makes membrane phospholipids; enzymes built into the ER membrane assemble phospholipids from precursors in the cytosol. The ER membrane expands, and portions of it are transferred in the form of transport vesicles to other components of the endomembrane system

To summarize, what are the three reasons why cells can't be too big?

1. surface area-to volume ratio 2. nucleus has to control it all 3. you have to waste some of your precious energy fighting gravity, that's another tax on larger cells that small cells don't have to pay

Give some examples of prokaryotes.

Bacteria and Archaea

How are free ribosomes and bound ribosomes similar?

Bound and free ribosomes are structurally identical and they both make proteins

What does the word eukaryotic mean?

Eu = true karyo = kernel [referring to nucleus] true nucleus

A lot of what we know about cells comes from looking at microscopes. Who made the first observations through a microscope and in what year?

Galileo; 1590

Who was Antony Van Leeuwenhoek?

In 1674, he saw live cells, including sperm he visualized living cells, microorganisms in which he called "very little animalcules" he scraped the gunk off his teeth and put it under a microscope and saw movement and things crawling around. This is the 1600s so dentistry did not really come to its prime.

What did M. Schleiden and T.Schwann state?

In 1839, he states "all life is composed of cells"

What did Rudolf Virchow state?

In 1849, he states "cells come from [other] cells"

Give some examples of eukaryotes.

Protista, Fungi, Plantae, Animalia

Remember in biology and science, the word "theory" means what?

Remember in biology and science, the word "theory" doesn't mean doubt, it is not a guess. theory in this case means its a very very strongly well supported synthesis of a whole bunch of data with no evidence to the contrary

Where did the name "cell" come from? What year?

Robert Hooke; In 1665 he saw a sample of "cells" in cork and observed box-shaped structures in plant cells, which he called "cells" as they reminded him of the cells, or rooms in monasteries. like [jail] cells, so like little living areas Now, we know that not all cells are shaped like that.

Who was the first to see cell walls?

Robert Hooke; cell walls were first seen by Robert Hooke as he looked through a microscope at dead plant cells from the bark of an oak tree

Where are bound ribosomes located?

While bound ribosomes are attached to membrane organelles such as the outside of the endoplasmic reticulum or nuclear envelope and they make proteins that are going to be either further processed or packaged up for export and are excreted from the cell

Phospholipids form what?

a bilayer

Why is it inefficient if cells are too big?

a cell uses its whole surface area but it has the same basic problem... your volume dictates your need your surface dictates your ability to meet those needs, so it gets inefficient if it tries to get too big. It's a problem because as cells grow and try to get bigger, the volume increases faster than the surface area. mathematically = it increases by the cube where as surface area increases by the square so the problem is that the surface-to-volume decreases

State the definition of the endomembrane system.

a series of organelles in which lipids are made and protein chains are modified into their final form

What did a study find about the nucleolus?

a study found almost 300 proteins and enzymes within the nucleolus most of which we have no idea what they do, so it is more than a ribosome factory

The hydrophilic parts of phospholipids and membrane proteins are found in contact with what?

aqueous solutions on either side

Explain Figure 6.7 Geometric relationships between surface area and volume. What is the problem with what happened with the middle column?

balance of surface area and volume middle column our cell is going to grow its the same shape, its still a cube the volume got a lot bigger than the surface area did. the metabolic needs increased 125 times, but the surface area did not increase by nearly that much, so the surface to volume ratio decreased this becomes a problem at some point. our metabolic needs are met through how much food we can put in our mouth. imagine that you got bigger and bigger and then eventually you have a peanut hole size mouth you had to eat through, you could not do it at some point because it's just not big enough.

Why is the plasma membrane technically NOT an endomembrane? In other words, why is the plasma membrane not part of the endomembrane system?

because it is on the outside

Why is the smooth ER called smooth?

because its outer surface lacks ribosomes, so it does not have a bumpy appearance

Why does the rough ER look bumpy and why are they called rough?

because those bumps on the rough ER are ribosomes; the rough ER is studded with ribosomes on the outer surface of the membrane and thus appears rough through the electron microscope

What may be attached to the proteins or lipids on the outer surface of the plasma membrane?

carbohydrate side chains

State the definition of organelles.

compartmentalized portions within the cytoplasm that allow reactions to be separated in time and space

What do the cell's compartments provide?

different local environments that support specific metabolic functions, so incompatible processes can occur simultaneously in a single cell

Define nuclear envelope.

double membrane enclosing the nucleus; perforated by pores; continuous with ER

Does light or electrons have a smaller wavelength?

electrons

What does the word endomembrane system mean?

end = inside inside membrane

What are the two main types of cells?

eukaryotic cells and prokaryotic cells

Define nuclear lamina and why it is important.

except at the pores, the inner surface of the nuclear envelope is lined by the nuclear lamina, a netlike array of protein filaments (in animal cells, called intermediate filaments) that maintains the shape of the nucleus by mechanically supporting the nuclear envelope. this netting that maintains the structure of the shape of the nucleus, is important because it is one of the most permanent parts of the cell and it [the nucleus] contains important cargo, the DNA

Where are free ribosomes located?

free ribosomes are suspended or floating in the cytosol and they make proteins that are for the use of the cell right then and there after receiving instructions from the nucleus

State the characteristics of eukaryotic cells.

have a nucleus and organelles

The hydrophobic parts of phospholipids and membrane proteins are found where?

in the interior of the membrane

What does the endomembrane system include?

includes nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and vacuoles

Define cytosol.

inside all cells is a semifluid, jellylike substance called cytosol

What does the scanning electron microscopes allow you to see?

it gives you a view of the surface, so we can't see inside it but we can see a three-dimensional view

Why is a sufficiently high ratio of surface area to volume especially important in cells?

it is especially important in cells that exchange a lot of material with their surroundings

What is the analogy given to the nucleus?

it is the control center of the cell; like the boss of a company, one entity that control what goes on

What does transmission electron microscopy allow you to see?

it shows you see a cross-section the cross-section allows you to see internal structures

Figure 6.3

it's two views of the same thing it's cilia, which are hairlike extensions that cells use to swim around and are also lining your respiratory system

What are the microscopes that we use in the laboratory? How is it limited?

light microscopes; there is a limit to how much you can magnify light

Define microvilli.

long thin finger-like projections from their surface to absorb nutrients called microvili

A lot of what we learned about cells has come from what?

microscopy and the technological advances we made

What cell structure increases the surface area without an appreciable increase of volume?

microvilli

In a prokaryotic cell, is its DNA incapsulated in a nucleus?

no

State the characteristics of prokaryotic cells.

no nucleus or comparable organelles

Are cell walls and plasma membranes the same thing?

no, cell walls and plasma membranes are NOT the same thing

Do animals and humans have a cell wall?

no; animals and humans do NOT have a cell wall

Do viruses meet the criteria for being alive?

no; because by our definition of life, since viruses can't reproduce on their own, they need a live host to be alive but the teacher said that they are sure are more alive than a rock is

Do all eukaryotic cells have a cell wall?

no; not all eukaryotic cells have a cell wall

Are we limited to using light waves in microscopy?

no; other advances are using electrons, so electron microscopy and their smaller wavelength allows you to magnify that much further

Is there something holding the phospholipid bilayer together? How? Describe the plasma membrane structure.

no; there is nothing holding them together with their neighbors, the heads want to be dissolved in water while the tails don't so they make a sandwich-looking structure

Define nucleolus.

non-membranous structure involved in production of ribosomes; a nucleus has one or more nucleoli it is a dense region within the nucleus, where the parts of the ribosomes get built when cells are dividing, the nucleolus disappears, so the nucleolus is visible in a non-dividing cell

Are the light microscopes that we use in lab better than the ones in Galileo's time?

not really

What is the nuclear envelope lined by?

nuclear lamina

The surface of the nuclear envelope has what?

nuclear pores

Which cell structure makes ribosomes?

nucleolus

The plasma membrane and the membranes of organelles consist of what?

of a double layer (bilayer) of phospholipids with various proteins attached to or embedded in it

What is the word organelle come from?

organelle comes from the word organs like we as humans have organs such as kidney, lungs that do different jobs for you cells have analogous structures that do certain jobs within the cell

What do organelles allow in the cell?

organelles allow these reactions to be separated, so you are not trying to do all of the things that a cell has to do all at the same place and time that whole building is a cell, you got all these different rooms where you can have certain things be done without interference that is a much better way of operating so those individual rooms would be different organelles.

What is the cell enclosed by?

plasma membrane

What is the function of nuclear pores?

plays an important role in the cell by regulating the entry and exit of substances/molecules in the nucleus such as proteins and RNAs, the nuclear pores open and close this makes sense because the nucleus holds the DNA and the DNA has the instructions or recipes for making proteins, so those instructions have to be able to get out, so they come out of these little holes/pores and then they can go get made into proteins

What does the word prokaryotic mean?

pro = before karyo = kernel [referring to nucleus] before nucleus these are thought of existed before the development of a membrane-bound nucleus

Which type of cell is the more simple cells? Why?

prokaryotic cells; they are usually smaller, they don't have a nucleus and don't have a lot of the organelles

What is the function of the Golgi apparatus?

protein processing, sorting, packaging products of the ER, such as proteins, are modified and stored and then sent to other destinations

What is embedded in the plasma membrane? What is the analogy given to it?

proteins that drift around like big icebergs in the sea of phospholipids

Which cell structure makes proteins?

ribosomes

What are ribosomes the site for?

ribosomes are the site of protein synthesis

Ribosomes exist in two different forms. What are they?

ribosomes exist in two different forms, free and bound ribosomes.

Where is microvilli found?

small intestine

Does a smaller or larger wavelength allow you to magnify further in the microscope?

smaller wavelength

What is the function of a nucleus which are ONLY in eukaryotic cells? What is the function of the DNA?

the DNA is held in the nucleus, and the DNA holds the instructions for building proteins or the recipes for making proteins that the entire cell is going to need

The ability to meet your metabolic needs is determined by your what?

the ability to meet your metabolic demands is determined by your surface area

What was one of the very first things that Galileo saw when he looked through the microscope?

the facets on the eye of a fly

Define cytoplasm.

the interior of either type of cell is called the cytoplasm

The more surface area you have, the easier or harder it is for substances/molecules to come in and for waste products to go out?

the more surface area you have, easier it is for stuff to come in and for waste products to go out

How is the nuclear envelope different than the plasma membrane?

the nuclear envelope and plasma membrane are both lipid bilayers, but the nuclear envelope is special because it is a double membrane. These two membranes, each a lipid bilayer with associated proteins, so there is an inner membrane layer and an outer membrane layer

Is the plasma membrane in motion constantly or is it still? How is it different than the analogy we had of the cell membrane being the walls of a building?

the plasma membrane is in motion constantly, but the walls of our buildings are not because when we put a brick in the wall it's going to stay there. However, if this was a phospholipid membrane, it would be like having brick that are all moving around constantly in your wall

What is the common analogy given to the Golgi apparatus?

the post office of the cell; this is the receiving and shipping center, busy

In eukaryotic cells, the cytoplasm is the region between what? What does it contain?

the region between the nucleus and the plasma membrane; it holds the cell's components such as membrane-bound organelles, particles, and filaments.

What is the surface area of a cell?

the total area covered by the plasma membrane; if you are a cell, everything has to go in and out of through that membrane, thats your surface area

Does the rough ER and smooth ER have the same or different jobs?

they both have different jobs

True/False: the smooth ER is an organelle that grows with repeated use.

true; if you are constantly taking in drugs, poisons, alcohol, and other chemicals that your body tries to get rid of, you will develop more and more smooth ER and it will get better at excreting them or getting rid of it Real-life application: if you never have had caffeine before and you give someone a cup of coffee, they are going to get slammed by that other people drink a cup of coffee a day and feel nothing the affect that you feel have to do with your biology and prior history a tolerance or resistance can build up even to things you have not experienced yet because you may have a lot of smooth ER that is really good at handling the stuff that you put into your body everyday if were your a doctor/physician and i were to prescribe medication to you, i might need to tweak the doses because maybe your body is going to be really good at getting rid of this, while someone elses is not it is not a same size fits all, it does not work the more you know about your patients history and other medical issues, the better you can treat them

What determines your metabolic demands/needs? Why?

volume; because the bigger you are, the more metabolic demands/needs you have. a small child does not have to eat as much as a giant adult the bigger you are, the more needs you have. the bigger the cell is, the more action is going on inside the more energy its going to need

What is the solution for not having big cells?

well the solution to that is that instead of one big cell, we have a bunch of little cells same total volume, but we chop it up into all these tiny cubes, so we have an enormous amount of surface area now. so the solution is if you want to grow, you don't make bigger cells, you make more cells and keep them small. you want lots of smaller cubes than one big cube Surface area increases while total volume remains constant from the second to third column

When cells are dividing, you can't see chromosomes. What can you see?

when cells are not dividing, you can't see chromosomes, but you can see this mass of DNA called chromatin

Are membranes interchangeable parts?

yes

Does different types of microscopes allow you to look at different things?

yes

In a prokaryotic cell, does it have a pile of DNA that sits off to the side?

yes

Are most cells very small? Is it too small to see with a naked eye?

yes; a typical cell is about 2,000 cells of them across your thumbnail; it is too small to see with a naked eye

Do all eukaryotic cells have a nucleus?

yes; all eukaryotic cells have a nucleus

Is the plasma membrane also interchangeable parts [they can swap parts of it] and a phospholipid bilayer?

yes; so we have all these organelles inside the plasma membrane that are interchangeable parts

Is the endoplasmic reticulum membranous organelles?

yes; the endoplasmic reticulum are membranous organelles, made out of membrane

What are other solutions that gives you a greater surface-to-volume ratio without having to have more cells?

you change the shape a cube is not a very good shape for this, a sphere is worse What kind of shape would be better? a rectangle, flat, concave, wavy, make it long or skinny, make it concave or wavy, those are all good ways to raise surface area