Cell Organelles and transport

Question 1

What are DNA triplets and codans??

Answer 1

DNA triplets are genetic codes that are sets of 3 letter combinations of nucleotides called codans. Condan corresponds with a specific amino acid or signals to start and stop coding.

Question 2

What is a gene?

Where are gene produced? In other words, the process of gene expression.

Answer 2

The portion of the DNA that contains the information necessary to produce one protein is referred to as a gene.

Individual genes are transcribed in the mucleus to messenger ribonucleic acid (mRNA), which is translated into protein in the cytoplasm.

Question 3

what are genetic codes?

Answer 3

Genetic code is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into amino acid sequences by living cells.

The genetic code contains sequences of 3 nucleotides referred to as triplets. Each DNA triplet encodes for one amino acid. However, the gentic code is degenerate or reduntant because some amino acids can be coded by more than one codan (A DNA triplet)

Question 4

Describe the process of translation

Answer 4

Once mRNA is coded from DNA in the nucleus, mRNa exit the nucleus and binds with ribosome in the cytosol, initiating the first step of translation. mRNA is “translated” into proteins refers to the codon or DNA triplets that is translated into a specific amino acid for example: Glutamine, cysteine, threonine….

Question 5

What is a Ribosome and it’s role?

Answer 5

Are composed of protein and nucleic acid and are involved in protein synthesis

Question 6

mRNA is translated into a protein at different ribosome sites. This depends on the type of protein is to be made.

Where is mRNA translated when making non-cytosolic proteins?

Answer 6

Depending on whether the protein is designated or “signalled” to be a cytosolic protein or non-cytosolic protein, mRNA is translated into protein at different structures.

non-cytosolic protein: the making of lysosomal, membrane or secretory protein will have mRNA being translated at the ribosome that’s attached to RER

Question 7

Non-cytosolic proteins are further modified in the RER, SER and Golgi complex, where they are sorted and assessed for quality.

How are non-cytosolic proteins further modified post translation?

Answer 7

Because non-cytosolic proteins aren’t quite completed into its final functional form, they require further modification post translation

• Cleavage of signal sequence of plasma membrane proteins
• Cleavage to smaller proteins, (some proteins are formed longer and need to be shortened)
• Proteins folding: ribosomes translate proteins into long AA chains and needs to be arranged in globular structures.

Glycosylation: add carbohydrates to plasma membrane proteins.

eg, glycosylation on plasma membrane proteins identifies the red blood cell as A B AB or O t ype

Question 8

Describe:

1) diffusional equilibrium (steady state)?

Versus

2) Net diffusion or net flux (one way flux)

Answer 8

Diffusional equilibrium refers to the movement of molecules across a permeable membrane in one direction is equal to the movement in the opposite direction, a diffusional equilibrium (steady state)

A net flux exists when the movement of molecules across a permeable membrane in one direction is greater that in the opposite direction. This larger movement of ions in one direction creats a net flux in the direction of the greatest movement.

Question 9

Describe the structure and function of the Golgi complex

Answer 9

Structure

• Sets of stacked, flattened membranous sacs

Function:

-Receives proteins that ribosomes have made, and then modifies, sorts, and package them into transport vesicles

It also renew and modify the plasma membrane

For example, the Golgi complex completes glycosylation (addition of carbohydrates on the cell plasma membrane)

Question 10

Describe the structure and function of lysosomes.

Answer 10

Lysosomes are membranous sacs containing hydrolytic enzymes. They Break down food–proteins that are taken into cells and break them down into amino acids

They serve as the digestive system of the cell, destroying pathogens and cellular debris

Question 11

Describe the structure and function of peroxisomes

Answer 11

Structure: a small membrane bound organelle.

Function: performs detoxification activities, break down lipids, produce Hydrogen peroxide which is further degraded by the enzyme catalase into H2o and o2

Question 12

describe structure and function of Nuclear pores

Answer 12

Each nuclear pore are transport proteins on the nuclear membrane that allows selective movement of small molecules and ions to pass, or diffuse, into or out of the nucleus.

Question 13

Describe the structure and function of Cytoskeleton and the three types.

Answer 13

is the “bone and muscle” of the cell and contains three types of cytoskeletal filaments: microtubules, intermeditate filaments, and microfilaments

Microtubules are the largest in diameter of the three and are composed of protein tubulin. It add shape and structure to the cell. It also serve as an anchor for the movement of organelles like cilia and flagella.

Intermediate filaments: acts as the intermediary between microtubules and microfilaments, it is composed of various proteins

Microfilaments are the smallest in diamenter and is composed of protein actin. They serve to anchor the cytoskleton to the plasma membrane. In addition to having contractile ability, they also form the microvilli of the cell.

Question 14

Describe the strucutre and function of the Mitochondria

Answer 14

Rod or oval shaped bodies enclosed by two membranes. It acts as an energy producing organelles; major sites of ATP production; contain enzymes for citric acid cycle and electron transport chain.

Question 15

Endoplasmic Reticulum

Describe the difference between the rough vs smooth ER

Answer 15

RER has ribosomes studded to its membrane and is important for protein synthesis, it specifically process non cytosolic proteins

The SER lacks ribosomes on its membrane, functions in in lipid synthesis and detoxification.

It function as calcium storage site (muscle cells), and detoxification (liver cells)

Question 16

Describe the structure and function of ribosomes

Answer 16

Granules of RNA and proteins - some attached to rough ER and some free in the cytoplasm.

Serve as workbenches for protein synthesis

Question 17

Chaperones proteins are proteins that assists other proteins assembly, folding and unfolding and etc….

Give me an example of when chaperone proteins are used

Answer 17

Ex, Amino acid chains needs to be arranged in to a globular structure in order form in order to be functional. So, chaperones proteins help with this folding process.

Question 18

Cells require energy, aka ATP. Energy is obtained via nutrient (CHO, PROTEIN, FAT), and broken down intot their chemical constituents, absorbed, stored for usage. There are 3 metabolic pathways in which ATP can be produced for cellular processes.

The first one is glycolysis. Outline the events of glycolysis (describe the overall chemical reactions)

Answer 18

Under the glycolysis pathway, 1 glucose molecule could yield 2 NADH + 2 H+ 2 ATP + 2 pyruvic molecules from 2 NAD+ + 2ADP + Pi

Question 19

Describe the citric acid cycle aka Krebs Cycle aka Tricarboxylic acid (TCA) cycle

Answer 19

In the TCA cycle, acetyl CoA is converted from 2 pyruvic acid in the matrix of the mitochondrion.

Eight sequential chemical reactions occurs

2 pyruvate + 8 NAD+ + 2 FAD + 2 ADP + 2 Pi + 6 H2o

yields

6 Co2 + 8 NADH + 8 H+ + 2 FADH + 2 ATP

Question 20

Groups of cells form tissues and organs. How do they do that.

What are cell adhesion molecules?

Answer 20

CAMs are membrane proteins located on the cell surface involved in binding with other cells or with extracellular matrix. They help adjacent cells “stick” to each other and to their surroundings.

Question 21

Describe desmosomes

Function? What type of tissues are they most prevalant?

Answer 21

• is a specialized cell structure by which the two plasma membrane of two adjacent cells are attached. It is formed from protein plaques in the cell membranes linked by filaments.
• Provide a strong anchor for cells
• Desmosomes are prevalent between adjacent cells of skin and heart tissues

Question 22

What are tight junctions? functions? found?

Answer 22

Tight junctions connectors between cells and are formed near the luminal borders of adjacent epithelial cells. They limit the passage of molecules and ions through the space between cells.

Question 23

The cells in our body communicates with each other either directly or indirectly. The cells in our body can communicate directly via gap junctions.

What are gap junctions ?

Where are they most abundant?

Answer 23

Gap junctions are formed by connexions which form channels between adjacent cells that permit the movement of small molecules between the cells.

Cardiac and smooth muscles

Question 24

What is the extracellular matrix composed of?

Answer 24

The ECM is a gelatinous substance composed primarily of protein fibres and carbohydrates.

Question 25

Cells communicates directly with one another via gap junction or connexons.

What are the role of connexons?

Answer 25

connexion are protein that form the pores for gap junction, allowing small molecules to pass between the cytoplasms of two adjacent cells.

Gap junctions are structures that allow cells to communicate directly with each other.

Question 26

Why is it that glucose and amino acids and Na+, K+, and Ca2+ are unable to move freely across the cellular membranes?

Answer 26

The phospholipid bilayer of cellular membranes is selectively permeable and allows the passage of small and relatively lipid soluble molecules. Glucose and amino acids are large molecules while Na+ Ca2+. and K+ are lipid insoluble molecules which requires membrane transport proteins to help carry them across.

Question 27

Phosphorylated conformation Y of carrier

Answer 27

A transport protein that has a high affinity for the molecules to be transported. This molecules bind to carrier on the low-concentration side and pumps it out to the high concentration side)

Question 28

There are two types of protein found on the membrane of a cell which can facilitate diffusion. Channel proteins are one of them. What are channel-mediated facilitated diffusion?

Answer 28

Is a specific transport process for ions. Channels form a pore-like structure through the membrane and have a gating mechanisms responsible for opening and closing the channel.

These channels will provide net flux of an ion across a membrane according to the direction of the electrochemical gradient for that ion.

Eg, sodium channels allow for Na+ ions to gain entry into the ICF (cell) if there are greater concentration of Na+ outside of the cell

Eg, secondary active transport

Question 29

Carrier mediated transport can take two forms. It can be passive or active depending on whether energy is required for the transport process to occur.

When carrier protein transport molecules or ions across the cell membrane from high to low concentration gradient for that molecule. This is call ______ transport. Net flux of the molecule will continue until a steady state is reached.

An example of this is ________

Answer 29

the transport of glucose into cells using a glucose carrier molecule.

Question 30

What are the main types of passive transport?

Answer 30

Main types of passive transport

Simple diffusion: the movement of small or lipophilic molecules (eg, o2, co2, etc..)

Osmosis: movement of water molecules, dependent on solute concentrations

Facilitated diffusion: movement of large or charged molecules via membrane proteins

Question 31

In mediated transport, the rate of facilitated diffusion is:

Answer 31

limited by saturation of the carrier binding sites, unlike the rate of simple diffusion.

Question 32

The thyroid gland has 99 percent of the body’s iodine. To transport iodine into thyroid gland would mean to transport the iodine from an area of low concentrationn of iodine to an area of high concentration (thyroid). Going against the concentration gradient would require energy to drive the carrier protein.

The carrier protein has an ______ conformation (X) with binding sites that faces the extracellular fluid. Once iodine bound to the carrier protein, the comformation changes to face ______ (Y) and the binding sites are exposed to the ICF. Once iodine detaches, the molecule will change back to its originally comformation with both binding sites available and facing the ECF.

Answer 32

outward facing

Inward facing

Question 33

how many ATP is produced via oxidative phosphorylation ?

Answer 33

38 ATP

Question 34

T/F?

Under anaerobic conditions, the chemical reactions of both the citric acid cycle and the electron transport chain are inhibited.

Answer 34

True

the presence of NADH. esp when coupled with lactate from pyruvate by lactate dehydrogenase.

Question 35

True or False

In non dividing cells, DNA is stored as chromosomes and forms chromatin only during cell division

Answer 35

False

DNA is stored as chromatin and form chromosomes only during cell division.

Question 37

Tissue

Answer 37

In medicine, tissue mean the aggregate of various cellular and extracellular components that make up a particular organ

(eg, lung tissue or liver tissue)