2 Cells And Membranes

Question 1

Name all the 6 organelles

Answer 1

Nucleus
Endoplasmic reticulum (ER)
Golgi apparatus 
Ribosomes
Mitochondrion
Chloroplast

Question 2

Function of Nucleus

Answer 2

Storage of genetic information

Question 3

Function of rough Endoplasmic reticulum

Answer 3

Folding and modification of polypeptide chains, packaged into transport vesicles

Question 4

Function of smooth endoplasmic reticulum

Answer 4

Synthesis of lipids, carbohydrate metabolism, detoxification of drugs and poison

Question 5

Function of Golgi apparatus cis face?

Answer 5

Received materials from transport vesicles from ER for further modification of proteins

Question 6

Function of Golgi apparatus trans face?

Answer 6

Packages protein into secretory vesicles

Question 7

Function of ribosomes?

Answer 7

Site of polypeptide synthesis.

Bound ribosomes (rough ER) synthesis polypeptides to use outside cell, incorporated in plasma membrane or as lysosomal enzymes

Free ribosomes (cytosol) synthesize polypeptides that forms protein to be used in the cell

Question 8

Function of the mitochondrion?

Answer 8

Site of cellular respiration to produce energy to form a high energy compound adenosine triphosphate (ATP)

Question 9

Function of chloroplast?

Answer 9

Photosynthesis

Question 10

Structure of nucleus?

Answer 10

1. Double membrane bound nuclear envelope that contains nuclear pores
2. Aqueous matrix and dense region called nucleolus

Question 11

Structure of ER? (Smooth and rough)

Answer 11

Smooth: extensive network of membranous tubules

Rough: membrane bound sacs

Question 12

Structure of Golgi apparatus?

Answer 12

Flattened membranous sacs

Membrane bound

Question 13

Structure of ribosomes

Answer 13

Bound ribosomes are on the rough ER

they are not membrane bound

Question 14

Structure of mitochondrion?

Answer 14

Elongated/spherical
Double membrane bound outer and inner (high folded)
Contains own circular DNA, ribosomes and enzymes

Question 15

Structure of chloroplasts

Answer 15

Lens-shaped
Double membrane bound outer and inner (no folding)
Third membrane system consisting of flattened sacs called thylakoids
Contains own circular DNA, ribosomes and enzymes

Question 16

PROTEIN SYNTHESIS PATHWAY

Answer 16

1) DNA transcripts into mRNA
2) mRNA transported to rough ER
3) ribosomes on rough ER translate the mRNA into a polypeptide chain, which enters lumen of rough ER for folding and modification
4) folded protein packaged into a transport vesicle that buds off the rough ER
5) transport vesicle enters the vid face of the Golgi apparatus and releases the protein into the Golgi apparatus for further modification and folding
6) product packaged into secretory vesicles that bud off the trans face of Golgi
7) secretory vesicle fuses with cell membrane and secretes folded protein out of cell/ embeds it in the cell membrane/ allow formation of lysosomes

Question 17

What is phagocytosis (formation of lysosomes)

Answer 17

Fuses the newly formed vesicles to break down ingested materials

Question 18

What is the ‘fluid mosaic model’ of membranes

Answer 18

Mosaic: collage of different proteins randomly embedded in phospholipid bilayer

Fluid: phospholipid are mobile, they move around through rotation, lateral diffusion, flexion and flip flop

Question 19

What are integral proteins

Answer 19

Proteins deeply embedded in the hydrophobic core of the bilayer. Embedded in membrane and might be modified

Question 20

What is steroid cholesterol in the phospholipid bilayer

Answer 20

It is a major determinant of membrane fluidity and regulates membrane fluidity by restricting movements of phospholipids

Question 21

Functions of membrane proteins?

Answer 21

Transport
Enzymatic activity
Signal transduction
Cell-cell recognition

Question 22

Two types of vesicle transport across membrane

Answer 22

Endocytosis

Exocytosis

Question 23

Three types of transport protein with membrane protein

Answer 23

Diffusion (passive/facilitated)
Osmosis
Active transport

Question 24

What is diffusion across phospholipid bilayer

Answer 24

Net movement of molecule from region of higher concentration to a region of lower concentration, down the concentration gradient

Question 25

What molecules can cross through the phospholipid bilayer through passive diffusion

Answer 25

Small and relatively hydrophobic molecules

Question 26

What molecules can cross through the phospholipid bilayer through facilitated diffusion

Answer 26

Allows polar and charged molecules and ions to cross without interacting directly with the hydrophobic core

Question 27

Describe facilitated diffusion carrier proteins

Answer 27

Bind to molecule on one side Undergo conformational changes Releases molecule on other side

Question 28

Describe facilitated diffusion channel proteins

Answer 28

Form open pores for small particles of appropriate size and change to pass through freely Gates open to selective stimuli

Question 29

Describe osmosis

Answer 29

Net movement of water molecules from a region of higher water potential to a lower … through a partially permeable membrane

Question 30

Describe active transport

Answer 30

Movement of ions or molecules across membrane from region of concentration to lower … *against* concentration gradient

Question 31

What are the two parts of endocytosis

Answer 31

Phagocytosis and pinocytosis

Question 32

What is phagocytosis?

Answer 32

Ingestion of *large* particles -particles bind to surface of phagocyte (receptor), which triggers pseudopod to engulf particle and form a vesicle to transport it.

Question 33

What is pinocytosis?

Answer 33

Uptake of fluids/ macromolecules through small vesicles. It is non-selective - particles bind to plasma membrane, it folds inwards to form a channel

Question 34

Describe exocytosis

Answer 34

Movement of substances out of cell into extra cellular space/ vice versa - vesicle containing material transported to cell membrane - vesicle membrane fuses with cell membrane and releases contents

Question 35

What factors affect rate of movement?

Answer 35

- size - polarity - concentration gradient - temperature