Chapter 2.4 - Eukaryotic Cell Structure

Question 1

Definition of cells

Answer 1

Basic unit of all living things

Question 2

Two fundamental types of cell

Answer 2

Prokaryotic
Prokaryotes are single celled organisms with a simple structure of just a single undivided internal area called cytoplasm (made up of salts, water and organic molecules)
Eukaryotic
These cells make up multicellular organisms (animals, plants and fungi)
Complicated internal structure containing nucleoplasm and cytoplasm
Contains many membrane bound cellular components

Question 3

What are chemical reactions

Answer 3

Fundamental processes of liye and in feuds requires enzymes and specific reaction conditions

Question 4

Definition of metabolism

Answer 4

synthesis and breaking down of molecules. Different sets of reactions take place in different regions of the ultrastructure of a cell.

Question 5

where do reactions take place

Answer 5

Cytoplasm

Question 6

Purpose of cell surface membrane

Answer 6

Separates cell cytoplasm from external environment

Question 7

Definition of organelles

Answer 7

Different membrane bound compartments divided in cell cytoplasm

Question 8

Purpose of membrane bound compartments

Answer 8

Provide distinct environments and conditions for different cellular reactions

Question 9

Features of membranes

Answer 9

Selectively permeable - control movement of substances (cells and organelles)
Effective barriers
Fragile

Question 10

Nucleus

Answer 10

Contains coded genetic information in the form of DNA molecules
DNA directs synthesis of all proteins required by the cell
Controls metabolic activities
Often biggest organelle

Question 11

DNA

Answer 11

Contained within double membrane - nuclear envelope (protects DNA from damage in cytoplasm)
Envelope has nuclear pores for molecules to move through nucleus
DNA too large to leave to site of protein synthesis
Transcribed into RNA
Associates with histones to form chromatin
Chromatin coils and condenses to form chromosomes
Become visible when cells are about to divide

Question 12

Nucleolus

Answer 12

Produces ribosomes
Composed of proteins and RNA
RNA produces rRNA
rRNA combines with proteins to form ribosomes

Question 13

Mitochondria

Answer 13

Small amount of DNA
Site of final stage of cellular respiration
Produces ATP so energy stored in bonds of complex organic molecules is made available for cell to use
Double membrane
Inner membrane folds to form cristae. Contains enzymes for aerobic respiration
Fluid interior is matrix
Produces own enzymes and reproduce themselves

Question 14

Vesicles

Answer 14

Membranous says
Storage and transport
Single membrane with fluid inside

Question 15

Lysosomes

Answer 15

Specialised vesicles
Hydrolytic enzymes
Break down waste material
Break down pathogens that have been ingested by pathogens
Cell death or apoptosis

Question 16

Definition of cytoplasm

Answer 16

Network of fibres necessary for shape and stability of cell.

Controls cell movement and movement of organelles within the cell

Question 17

Microfilaments

Answer 17

Formed by protein actin
Contractile fibres
Cell movement and cell contraction
Cytokinesis

Question 18

Microtubules

Answer 18

Globular tubulin proteins polymerise. Form tubes that form scaffold like structure that shape cell
Tracks for movement
Spindle fibres made up of microtubules have role in physical segregation of chromosomes

Question 19

Intermediate fibres

Answer 19

Mechanical strength

Help maintain integrity

Question 20

Centrioles

Answer 20

Not present in flowering plants and most fungi
Composed of microtubules
2 associated centrioles form centrosome - involved in assembly and organisation of spindle fibres during cell division
Position flagella and cilia

Question 21

Flagella

Answer 21

Whip like
Protrude from some cell types
Longer than cilia
Enable cells motility
Sensory organelle detecting chemical changes in cells environment

Question 22

Cilia

Answer 22

Stationary - present on cell surface. Sensory (nose)
Mobile - beat in rhythmic manner creating current
Cause fluids or objects adjacent to move (trachea moving mucus away from lungs keeping airways clean)
Fallopian tubes to move egg cells from ovary to uterus
Contains two central microtubules surrounded by 9 pairs
Pairs of parallel microtubules slide over each other causing cilia to move in beating motion

Question 23

Endoplasmic reticulum

Answer 23

Network of membranes enclosing flattened sacs called cisternae
Connected to outer membrane of nucleus

Question 24

Smooth Endoplasmic Reticulum

Answer 24

Lipid and carbohydrate synthesis

Storage

Question 25

Rough endoplasmic reticulum

Answer 25

Ribosomes bound to the surface

Responsible for synthesis and transport of proteins

Question 26

Secretory cells

Answer 26

Releases hormones or enzymes

More Rough Er than cells that don’t release proteins

Question 27

Ribosomes

Answer 27

Site of protein synthesis
Either free floating or attached to endoplasmic reticulum
Not surrounded by membrane
Constructed of RNA molecules made in nucleolus

Question 28

Golgi apparatus

Answer 28

Modified and packages proteins into vesicles (e.g. secretory vesicles if leaving or lysosomes if staying)
Similar in structure to smooth ER
Compact structure formed of cisternae
No ribosomes

Question 29

Steps of protein production

Answer 29

Synthesised on ribosomes bound to ER
Pass into ERs cisternae and packaged into transport vesicles
Vesicle goes to Golgi apparatus via cytoskeleton
Vesicle fuses with cis face of Golgi apparatus
Protein enters Golgi apparatus
Protein is structurally modified
Leaves through trans face after being packaged into vesicle
Vesicle fuses with cell - exocytosis
Some form lysosomes - contain enzymes for use in the cell