Cell Structure and Function

Question 1

Definition of prokaryote

Answer 1

DNA of the cell is not separated from the cytoplasm

Question 2

Definition of eukaryote

Answer 2

DNA is partitioned off in a membrane bound nucleus

Question 3

Compare the characteristics of prokaryotic and eukaryotic cells

Answer 3

Question 4

Properties of the plasma membrane

Answer 4

1. Surrounds the cell
2. Partially permeable
3. Highly permeable to water and oxygen
4. Charged ions do not pass through easily

Question 5

Components of the cell membrane

Answer 5

1. Phospholipids
2. Protein
3. Carbohydrates

Question 6

Function of the protein component of the cell membrane

Answer 6

Pass ions into and out of the cell
Receptors

Question 7

Structure of carbohydrate component of the cell membrane

Answer 7

Attached to proteins as glycoproteins or attached to lipids as glycolipids

Question 8

Functions of carbohydrate molecules in cell membrane

Answer 8

Cell-cell recognition
Communication
Intercellular adhesion

Question 9

Methods of transporting large molecules across plasma membrane

Answer 9

Exocytosis
Endocytosis (including pinocytosis and phagocytosis)

Question 10

Define exocytosis

Answer 10

Release of material from the cell cytoplasm across the cell membrane

Question 11

Define endocytosis

Answer 11

Uptake and transfer of molecules across the cell membrane into the cell interior

Question 12

Define pinocytosis

Answer 12

Cells ingest small molecules of extracellular liquids

Question 13

Define phagocytosis

Answer 13

Ingestion of large solid particles by the cells, e.g. bacteria

Question 14

What is the endoplasmic reticulum?

Answer 14

A network of interconnected tubules & vesicles

Question 15

What are the types of endoplasmic reticulum?

Answer 15

Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum

Question 16

Characteristics of the rough ER

Answer 16

Studded with ribosomes
Synthesizes proteins

Question 17

Characteristics of smooth ER

Answer 17

Lacks ribosomes
Segregates newly synthesized proteins from the cytoplasm
Detoxification of drugs in the liver
Lipid synthesis (in gonads, adrenal gland)
Ca²⁺ reservoir in skeletal muscle

Question 18

What are ribosomes formed from?

Answer 18

Made from 2 subunits formed from proteins

Question 19

Where can ribosomes be found?

Answer 19

In the rough ER
Free in the cytoplasm

Question 20

Functions of ribosomes

Answer 20

Translate mRNA into proteins

Question 21

What are polyribosomes?

Answer 21

Clusters of ribosomes held together by strand of mRNA

Question 22

What is the Golgi Apparatus?

Answer 22

Stacked and flattened membranous sacs which are closely associated with the rER

Question 23

Shape of the Golgi Apparatus

Answer 23

Concave side (cis side): Near the ER
Convex side (tras side)

Question 24

Function of the Golgi Apparatus

Answer 24

Modifies, packages and transports proteins and lipids secreted by the cells

Question 25

What is the function of lysosomes?

Answer 25

Break down waste materials and cellular debris

Question 26

How are lysosomes formed?

Answer 26

Vesicles produced by the Golgi Apparatus

Question 27

What do lysosomes contain?

Answer 27

Acid hydrolases

Question 28

What are phagosomes?

Answer 28

Vacuole that is formed by the fusion of the cell membrane around the particle

Question 29

What are peroxisomes?

Answer 29

Membrane-bound organelles Present in all cells but prominent in hepatocytes and proximal tubule cells Contain oxidative enzymes

Question 30

What are the functions of peroxisomes?

Answer 30

Hydrogen Peroxide Metabolism Fatty acid metabolism Alcohol degradation Formation of phospholipid needed for myelination of nerve cells

Question 31

What are mitochondria?

Answer 31

Oval or elongated structures which vary in number according to the cell function

Question 32

What is the structure of the mitochondria?

Answer 32

Contain an outer and inner membrane Inner membrane is folded into cristae Contains granular material called matrix

Question 33

What are the functions of the mitochondria?

Answer 33

Generation of ATP Control cell cycle and cell growth Apoptosis

Question 34

What is the nucleus?

Answer 34

Membrane bound organelle containing chromatin, nucleoli and surrounded by nuclear envelope

Question 35

What is the nuclear envelope?

Answer 35

Double layered membrane forming a selective barrier bewteen the cytoplasm and nucleus

Question 36

Outer membrane of the nuclear envelope is continuous with ...

Answer 36

Rough endoplasmic reticulum

Question 37

What is the inner nuclear membrane lined with?

Answer 37

Nuclear lamina (condensation of intermediate filaments)

Question 38

What is the function of the nuclear lamina?

Answer 38

Maintain the shape of the nucleus

Question 39

How are nuclear pores formed?

Answer 39

Fusion of the outer and inner membrane of the nuclear envelope

Question 40

Function of the nuclear pores

Answer 40

Control the movement of ribosomal subunits between the nucleus and cytoplasm

Question 41

Function of chromatin

Answer 41

Encodes cell structure and function

Question 42

Types of chromatin

Answer 42

**Heterochromatin**: Darkly staining and inactive **Euchromatin**: Lightly staining and active

Question 43

Characteristics of the nucleolus

Answer 43

Dark-staining spherical body Not bound by a membrane Contains lots of RNA and protein Site of ribosome synthesis

Question 44

Types of cytoskeletal structures divided according to thickness

Answer 44

**Microtubules** (composed of tubulin subunits): 25 nm thick **Intermediate filaments**: 10 nm thick **Microfilaments** (mostly actin): 7 nm thick

Question 45

What are microtubules?

Answer 45

Hollow tubes responsible for intracellular movement of cytoplasmic organelles

Question 46

What are microtubules formed from?

Answer 46

Spherical protein tubulin

Question 47

What structures are formed from microtubules?

Answer 47

Centrioles Cilia Flagella

Question 48

Which cells do not contain microtubules?

Answer 48

RBCs

Question 49

What are intermediate filaments?

Answer 49

Tough, insoluble protein fibers with high tensile strength

Question 50

Function of intermediate filaments

Answer 50

Resist pulling forces on the cell

Question 51

What are microfilaments?

Answer 51

Strands of actin protein Attached to the cytoplasmic side of the plasma membrane

Question 52

Function of microfilaments?

Answer 52

Braces and strengthens the cell surface

Question 53

What is the centrosome?

Answer 53

Area of the cytoplasm near the nucleus containing two small cylindrical structures called centrioles

Question 54

What are centrioles?

Answer 54

Small barrel-shaped organelles which are formed of pinwheel array of 9 triplets of microtubules

Question 55

Function of centrioles

Answer 55

Move to opposite poles of the cell during cell division Organize spindle that controls the distribution of chromosomes to the daughter cells

Question 56

Types of cellular extensions

Answer 56

Cilia Flagella Microvilli Sterocilia

Question 57

What are cilia?

Answer 57

Short cell projections composed of nine pairs of microtubules surrounding a central pair Move fluid in a single direction across the cell surface

Question 58

What are flagella?

Answer 58

Structures longer than cilia E.g. tail of sperm cell

Question 59

What are microvilli?

Answer 59

Tubular extensions of plasma membrane containing bundles of actin filaments Increase surface area for absorption

Question 60

What are sterocilia?

Answer 60

Modified microvilli seen on cells in the epididymis Length and bundle arrangement differentiate them from microvilli Increase surface area for absorption