Lecture 8: Cell Size and Endomembrane

Question 1

Why are cells so small?

Answer 1

-Just waving your arm requires many diffusion process, therefore they must occur on a millisecond scale
-Diffusion is only effective over ver small distances(distance traveled by a defusing molecule is proportional to the square root of time)
-Cells need to be small as it would take way to long for things to diffuse across the membrane

Question 2

How many cell are found in the human body?

Answer 2

Around 40 trillion

Question 3

Why can eggs be big?

Answer 3

Because all they do is store stuff

Question 4

What are prokaryotes?

Answer 4

-Single-celled organism
-Consists of archea and bacteria

Question 5

Characteristics of prokaryotes?(4)

Answer 5

1. Extremely small(same size as an organelle)
2. Prokaryotes can live in any environment(they can eat anything(plastic))
3. Their DNA sits in a nucleoid not surrounded by a membrane
4. Do not have a nucleus

Question 6

Characteristics of eukaryotes?(4)

Answer 6

1. Have a membrane enclosed nucleus that contains DNA (enclosed by a nuclear envelope that consists of two membranes)
2. Have organelles enclosed by membranes
3. Larger than prokaryotes
4. Compartmentalization

Question 7

Why are eukaryotes so much bigger than prokaryotes?

Answer 7

Due to compartmentalization

Question 8

What is compartmentalization and why does it make eukaryotes big?

Answer 8

Many internal membrane systems that create very small specialized spaces where diffusion can occur very quickly

Question 9

Parts found in prokaryotes(4)?

Answer 9

1. Plasmid(circular DNA)
2. Cell Wall: Provides stability and structure
3. Ribosomes: Translate proteins
4. Nucleoid: Filled with DNA and proteins

Question 10

Metabolism of prokaryotes

Answer 10

Prokaryotes can eat anything
- Can use all kinds of different final electron acceptors
Explains why bacteria are found EVERYWHERE

Question 11

Eukaryotes and metabolism

Answer 11

-Can only use oxygen as the final electron acceptor
-Must eat other plants/animals to survive

Question 12

Plant cell characteristics

Answer 12

1. Rigid cell wall made up of cellulose
2. No sodium potassium ATPase(it is unique to animals), plants don’t need osmolarity regulation because they have a rigid cell wall and water can just flow in.
3. Modified lysosome called a vacuole
4. Chloroplasts

Question 13

What is the endomembrane system?

Answer 13

Group of membranes and organelles within eukaryotic cells that work together

Question 14

Compartmentalization and the end-membrane system gives rise to organelles. Name some of the organelles.

Answer 14

1. Nucleus
2. ER
3. Golgi
4. Vesicles
5. Lysosomes

Question 15

What organelle does the outer membrane of the nucleus touch?

Answer 15

The ER

Question 16

Role of vesicles?

Answer 16

To communicate with the cell membrane and between the Golgi and ER

Question 17

What is the lumen(interior) of the Golgi, vesicles and ER made of?

Answer 17

Extracellular space

Question 18

Does every cell in the body have the same umber of each organelle?

Answer 18

NO, each cell type has a different ratio of these organelles depending the specialized function they have
ex. Pancreas cells have a lot of RER to make digestive enzymes

Question 19

What is found in the nucleus?

Answer 19

The nucleus contains DNA stored as chromosomes and it also contains proteins

Question 20

What is the nucleolus?

Answer 20

This is where ribosomes are assembled from rRNAs
-Assembled ribosomes are then transported through the nuclear port to the cytoplasm

Question 21

What occurs in the nucleus?

Answer 21

-DNA is replicated
- DNA is transcribed into mRNA or rRNA by RNA polymerase

Question 22

What are nuclear pores and their functions?

Answer 22

Holes in the nucleus that allow the transport of stuff in and out of the nucleus

Question 23

Where are ribosomes found in regards to the ER?

Answer 23

Ribosomes are found just on the outside of the ER, never on the inside

Question 24

Where is the rough endoplasmic reticulum?

Answer 24

Close to the nucleus, its membrane touches the nuclear envelope surrounding the nucleus

Question 25

Why is it called the rough ER?

Answer 25

Due to the ribosomes attached to the outside of the ER membrane

Question 26

How do ribosomes translate proteins on the RER?

Answer 26

Ribosomes bind to the outside of the RER when they start translating a membrane protein The first few amino acids of the protein encode a signal that tells the ribosome to bind to the RER -The freshly made protein is then inserted into the RER membrane and later into the lumen of the RER

Question 27

What occurs in the SER?

Answer 27

-All lipids are made in the SER -Detoxification also occurs in the SER (oxidation) ex. adding hydroxylgroups that make a molecule more hydrophilic, such that it can be excreted

Question 28

Who has a lot of SER?

Answer 28

DRUGGIES(need em to detoxify)

Question 29

What is the Golgi?

Answer 29

Stack of membranes that helps process and package proteins and lipid molecules

Question 30

What happens to proteins after they leave the ER?

Answer 30

Proteins are transported from the ER to the cis side of Golgi with the help of vesicles, the proteins then go through the Golgi (as they do so they are modified). After going through the Golgi the protein filled vesicles break off the Golgi on the trans side and are then moved to different destinations

Question 31

How do proteins and lipids flow through the Golgi?

Answer 31

From the cis side to the trans side

Question 32

What did the pulse chase experiment show?

Answer 32

How proteins travel through the end-membrane system

Question 33

How did the pulse-chase experiment work?

Answer 33

Radioactive amino acids are added to a culture and radioactive proteins will show up in the RER, later the Golgi, secretory vesicles and eventually the extracellular fluid

Question 34

What is the path of a protein through the endomembrane system?

Answer 34

RER -- Vesicles --- Golgi --- Vesicles -- Extracellular fluid

Question 35

What is phagocytosis?

Answer 35

Phagocytosis: Large particles such as microorganisms and dead cells are ingested via large endocytic vesicles called phagosomes

Question 36

What is endocytosis?

Answer 36

Process by which cells engulf large molecules. 1. Particles come in contact will cell 2. Cell membrane wraps around the particle 3. Once the particle is surrounded the vesicle break off into the cell(endosome) 4.This vesicle now may fuse with other vesicles 5. The endosome will then become a lysosome with a low pH its contents are digest and then released to the cytosol

Question 37

What is autophagy?

Answer 37

Self-eating - Lysosomal organelles can surround entire organelles and chunks of cytoskeleton and digest them

Question 38

What is a lysosome?

Answer 38

Organelle that contains digestive enzymes

Question 39

What makes sure that proteins end up in the correct spot after exiting the Golgi?

Answer 39

The primary amino acid sequences on proteins indicate where each one must go after it exists the Golgi in a vesicle