Cell and Molecular Bio- Intro to Cell theory and Membranes

Question 1

Organisms may be of two types:
Unicellular
Multicellular
Define these terms:

Answer 1

Unicellular-any life for that consists of just a single cell
Multicellular-organisms that consists of more than 1 cell

Question 2

There are two types of cells
Eukaryotes
Prokaryotes

Define and give examples of these:

Answer 2

Prokaryotes-cells with no membrane bound organelles (nucleus)
Bacteria
Archaea

Eukaryotes-cells with membrane bound organelles, more complex structure (has nucleus).
Animal cell 
Plant cell 
Fungal cell 
Protist cell

Question 3

What is the function of the nucleus?

Answer 3

• control center
• contains DNA (genetic material that code hereditary information and controls the cell’s growth and reproduction)
• largest organelle

Question 4

Cell size:

Answer 4

• smaller cells have larger amount of surface area compared to volume
• An increase in surface area allows for more nutrients to pass into the cell and waste to exit the cell

Question 5

What are the 5 components of the nucleus?

Answer 5

1. Nuclear envelope
2. Nuclear pore
3. Nucleolus
4. Chromatin
5. Nucleoplasm

Question 6

What is function of the Nuclear envelope?

Answer 6

Prevent the substances from moving freely into and out of a nucleus

Question 7

What is function of the Nucleolus?

Answer 7

• spherical dense mass of material

- Site for the synthesis of ribosomal RNA and for the formation of ribosomal sub units

Question 8

What is function of the Nuclear Pores?

Answer 8

Permit the selective transport of substances across the nuclear envelope.

Question 9

What is function of the Chromatin?

Answer 9

Diffuse DNA (DNA compacts into chromosomes before cell division)

The primary function is to package long DNA molecules into more compact, denser structures

Question 10

What is function of the Nucleoplasm (nuclear plasm)?

Answer 10

• nucleus sap, similar to the cytoplasm

- Maintains the structure

Question 11

Describe the structure of the cell membrane:

Answer 11

• composed of a double layer of phospholipids (phospholipid bilayer) and proteins
• Flexible boundary between a cell and its environment
• Controls what enters or leaves the cell
• Selectively permeable-some substances pass freely, some transported, some prohibited

Question 12

Semi-permeability of cell membrane:

Answer 12

Impermeable to:
large and polar molecules such as ions, proteins and polysaccharides

Permeable to:
non polar and hydrophobic molecules like lipids as well as to small molecules like O2, CO2, N2

Permeability: depends on solubility, charge, chemistry and solute size

Question 13

Why are cell membranes selectively permeable?

Answer 13

> Essential molecules enter
Metabolic intermediates remain
Waste products exit

Question 14

What is the role of Cytoplasm?

Answer 14

• In eukaryotic cells, includes all of the material inside the cell and outside the nucleus.
• contains organelles to carry out specific jobs

Question 15

What is Cytosol?

Answer 15

jelly like substance of cytoplasm where the other parts of the cytoplasm such as various organelles and particles remain suspended

Question 16

What is the function of Ribosome?

Answer 16

protein factory

Question 17

Explain the process of how ribosomes are made:

Answer 17

1. Built in nucleolus-> 2. shipped out of nucleolus -> 3. through nuclear pores -> 4. to cytoplasm in eukaryotic cells

Question 18

Characteristics of Ribosomes:

Answer 18

• exists in eukaryotes and prokaryotes
• Non-membrane bound structure
• Numerous non-soluble particles in the cytoplasm of cells either free or attached to the endoplasmic reticulum
• contain RNA and protein-> the site of manufacturing proteins

Question 19

What is the function of cytoskeleton?

Name the 3 types of cytoskeletons:

Answer 19

help maintain a cell’s shape and either anchors the organelles or assists in their movement

1. Microtubules
2. Actin filaments
3. Intermediate filaments

Question 20

Characteristic of cytoskeleton:

Answer 20

A network of filaments or fibres that is present in the cytoplasm of eukaryotic cell.

Question 21

Characteristic of the Endoplasmic reticulum:

Answer 21

• network of membranes
• attached to the nuclear membrane
• 2 forms:
• smooth
• rough (they are usually interconnected)

Question 22

Characteristic and role of the Rough Endoplasmic Reticulum (RER):

Answer 22

• Has ribosomes attached to the outer surface
• Makes proteins
• Also has enzymes that can add glucose to protein= glycoproteins (exported by the cell)

Question 23

Characteristic and role of the Rough Endoplasmic Reticulum (RER):

Answer 23

• No attached ribosomes

- RER and SER are interconnected

Question 24

Characteristic and role of the Golgi Apparatus:

Answer 24

(postmen)

• stacks of flattened membrane-bound sacs
• receives, modify and packages proteins or lipids from ER to export from cells
• packed with enzymes that complete the processing of modifying proteins

Question 25

How does the Golgi Apparatus modify proteins?

Answer 25

- Add sulphur or phosphorus atoms to certain regions of the protein - Cut off tiny pieces of the protein ends

Question 26

Describe the structure and function of a Lysosome:

Answer 26

structure: small spherical organelles enclosed by a single membrane (common in animal cells, rare in plant cells) - synthesized in the RER and matured in the Golgi Apparatus function: contains powerful digestive enzymes that break down worn out organelles and ship their building blocks to the cytoplasm where they are used to construct new organelles - also dismantle and recycle proteins, lipids and other molecules

Question 27

Describe the function and role of Peroxisomes:

Answer 27

structure: contain oxidative enzymes - resemble lysosome but DO NOT develop through Golgi A function: protective function, oxidation of biomolecules e. g found in liver cells contain the enzyme catalase which neutralizes dangerous peroxides such as H2O2

Question 28

Describe the structure and role of Mitochondria:

Answer 28

structure: bound by double membrane - outer membrane: faces the cytoplasm - inner membrane: folds into projections called cristae - Has their own DNA (mtDNA), genes code for enzymes proteins and other essential - Has their own ribosomes (similar to bacteria ribosomes) function: - make energy via cellular respiration - takes in nutrients from the cell, breaks it down and turns into energy

Question 29

What is cellular respiration?

Answer 29

The process of oxidizing food molecules e.g glucose using O2 and giving off CO2 & H2O The energy released is captured in the form of ATP for use by all energy-consuming activities of the cell

Question 30

Fluid mosaic model:

Answer 30

Membrane is considered a mosaic of lipid, protein and carbohydrate molecules membrane exhibits properties that resemble a fluid because lipids and proteins can move relative to each other within the membrane

Question 31

Plasma membrane:

Answer 31

also a phospholipid bilayer which is essentially a membrane that can cover a cell or a cell organelle

Question 32

Explain the function of the cell membrane?

Answer 32

1-Separate internal cellular environment from external environment -very thing 2. All cells must take in and release substances to survive, grow and reproduce 3. Controls movement of materials into and out of the cell - Allow certain molecules to cross freely -> selective permeability

Question 33

What are the 4 components of the cell membrane?

Answer 33

1. Phospholipids 2. Cholesterol 3. Membrane proteins 4. Membrane carbohydrates

Question 34

What are Phospholipids?

Answer 34

A class of amphipathic molecules. Possessing both hydrophilic (water loving, polar) and lipophilic (fat loving, non polar, hydrophobic) properties.

Question 35

What is the role of cholesterol in the cell membrane?

Answer 35

-Important for membrane fluidity and integrity In warm temp: cholesterol molecules interfere with phospholipid movement and reduce membrane fluidity In cool temp: cholesterol keeps the saturated fatty acid tails from packing and maintains adequate fluidity. Prevent it from being too rigid.

Question 36

Structure and characteristics of cholesterol in the cell membrane:

Answer 36

Amphipathic molecule >Hydrophilic: hydroxyl (OH) group aligns with the phosphate heads of phospholipids. >Hydrophobic: remaining portion which tucks itself into fatty acid portion of the membrane

Question 37

What are the two classes of membrane proteins?

Answer 37

1. Peripheral membrane proteins: adhere only temporarily to the cell membrane with which they are associated with - attach to integral proteins, or - penetrate the peripheral regions of the lipid bilayer 2. Integral Proteins: penetrate lipid bilayer across the whole membrane (transmembrane protein)

Question 38

What are the 6 major membrane protein functions?

Answer 38

1. Transport 2. Enzyme activity 3. Signal transduction 4. Attachment to cytoskeleton and extracellular matrix 5. Cell to cell recognition 6. Intracellular joining

Question 39

Characteristics of membrane carbohydrates:

Answer 39

(5-8%) of the cell membrane The extracellular surface of the cell membrane is decorated with carbohydrate groups attached to lipids and proteins, this occurs through glycosylation.

Question 40

Glycolipids and Glycoproteins

Answer 40

Glycogen and lipids | Glycogen and proteins

Question 41

What are the functions of membrane carbohydrates?

Answer 41

- cell recognition e.g A,B,O blood typing | - cell adhesion e.g cell-cell signaling or cell pathogen interactions

Question 42

More details on the 6 major functions of membrane proteins:

Answer 42

1. Transport: A protein that spans a membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute - other proteins may shuttle a substance from one side to the other by changing shape. Hydrolyze ATP as an energy source to actively pump substances across the membrane 2. Enzyme Activity: Carries out sequential steps of a metabolic pathway. Protein with active site exposed to substances. 3. Signal transduction: Membrane protein with binding site with a specific shape that fits the shape of a chemical messenger (hormone). The external messenger (signal) may cause a change in the protein (receptor) that relays the message to the inside of the cell 4. Cell-cell recognition: Some glyco-proteins serve as identification tags that are specifically recognized by other cells 5. Intercellular joining: Membrane proteins of adjacent cells may hook together in various kinds of junctions, such as gap junctions or tight junctions 6. Attachment to the cytoskeleton and extracellular matrix: Microfilaments or cytoskeleton may be bonded to membrane proteins, a function that helps maintain cell shape and stabilizes the location of certain membrane proteins. Proteins that adhere to the ECM can coordinate extracellular and intercellular changes

Question 43

What are the two types of transport in the membrane?

Answer 43

1. Active - bulk transport - pumps 2. Passive - facilitated diffusion - osmosis - diffusion

Question 44

Define Osmosis:

Answer 44

The net movement of water particles from a high water potential to low water potential through a semi-permeable membrane