2.1 - Cell Structure

Question 1

What is The Cell Theory?

Answer 1

A universally accepted theory about cells

Question 2

What statements are in The Cell Theory?

Answer 2

Cells are the structural and functional units of living things.

All living things are made of cells, or the product of cells.

Every cell arises from a pre-existing cell.

Cells contain hereditary material.

Question 3

What are the two exceptions to The Cell Theory?

Answer 3

Striated Muscle Fibres and Aseptate Fungal Hyphae

Question 4

How are striated muscles fibres an exception to The Cell Theory?

Answer 4

Challenges the idea that cells always function as autonomous units.

Question 5

How is Aseptate Fungal Hyphae an exception to The Cell Theory?

Answer 5

Challenges the idea that living structures are composed of discrete units.

Question 6

What are the two main types of cells?

Answer 6

Prokaryotic cells and Eukaryotic Cells

Question 7

What is the purpose of membrane-bound organelles in eukaryotic cells?

Answer 7

Allow the eukaryotic cell to perform functions including energy production and controlling cell growth.

Question 8

What organelles can be found in eukaryotic cells?

Answer 8

Some organelles are found in all eukaryotes.

Some organelles are only found in plant cells (chloroplasts and central vacuoles)

Some organelles are only found in animal cells (many, small vacuoles).

Question 9

How many membrane-bound organelles are there?

Answer 9

Nine

Question 10

Name the nine membrane-bound organelles:

Answer 10

1. Nucleus
2. Nucleolus
3. Mitochondria
4. Chloroplast
5. Vacuoles
6. Golgi Body
7. Endoplasmic Reticulum
8. Ribosomes
9. Lysosomes

Question 11

Membrane-Bound Organelle: Nucleus

Answer 11

Controls the activities of the cell by controlling the amount and type of proteins available inside the cell.

Contains DNA and is enclosed by a double membrane called a nuclear envelope.

There are nuclear pores in the nuclear envelope that allow mRNA to move into the cytoplasm.

Question 12

Membrane-Bound Organelle: Nucleolus

Answer 12

An area within the nucleus where ribosomal RNA (rRNA) is transcribed to produce ribosomal units.

Known as the site of ribosomal biogenesis.

Plays a vital role in making proteins.

Question 13

Membrane-Bound Organelle: Mitochondria

Answer 13

The site of aerobic respiration and the production of ATP (used for energy).

Known as the “Powerhouse of the Cell”.

Has two membranes: the outer membrane and the inner membrane (highly folded to form cristae and increase surface area for efficiency).

Question 14

Membrane-Bound Organelle: Chloroplast

Answer 14

PLANT CELLS ONLY (and other photosynthetic autotrophs).

Contain a system of flattened sacs (thylakoids) that contains the pigment chlorophyll (used to trap light energy for photosynthesis).

Thylakoids are arranged in stacks called grana lamella.

Stroma is the fluid that surrounds the grana.

Question 15

Membrane-Bound Organelle: Vacuoles

Answer 15

A membrane-bound, fluid-filled space that usually contains water and dissolved minerals.

They maintain water and salt balance.

PLANT CELLS: Usually contain one large, central vacuole.

ANIMALS CELLS: Usually contain multiple, small vacuoles.

Question 16

Membrane-Bound Organelle: Golgi Body

Answer 16

Layers of membranes with swellings at the ends, often positioned near vesicles (membrane bags).

Important in packaging and secretion of chemicals (a post office).

Produces secretory enzymes (eg: digestive enzymes in pancreas) and form lysosomes.

Transport and store lipids (fats).

Question 17

Membrane-Bound Organelle: Endoplasmic Reticulum

Answer 17

A system of membrane layers that extends from the nuclear membrane to the cell membrane.

Transports materials to different parts of the cell.

Rough ER: Has ribosomes on its surface and is involved in protein synthesis.

Smooth ER: Does not have ribosomes and is involved in producing lipids and steroids.

Question 18

Membrane-Bound Organelle: Ribosomes

Answer 18

Play a key role in protein production specifically in translation.

Found in both prokaryotes and eukaryotes.

Made up of two subunits: a small subunit and a large subunit.

Can be free-floating in the cytoplasm, or attached to the rough endoplasmic reticulum in eukaryotes.

Question 19

Membrane-Bound Organelle: Lysosomes

Answer 19

A membrane-bound organelle that contains digestive enzymes.

Functions to break down unwanted macromolecules.

Involved in digesting food and breaking down when it dies.

Question 20

What is the Cytoskeleton made up of?

Answer 20

Made of protein fibres of different sizes (microtubules, actin filaments and intermediate filaments).

Question 21

What are the functions of the cytoskeleton?

Answer 21

1. Maintain cell shape
2. Strengthen the cell
3. Anchors organelles in place
4. Assists with mitosis (the spindle is a microtubule structure)
5. Cell movement (flagella and cilia are composed of microtubules)

Question 22

What is the cell membrane?

Answer 22

A double layer (bilayer) of phospholipids that encloses the contents of a cell.

Question 23

Why is the cell membrane thin?

Answer 23

To allow for rapid exchange of materials and the semi-permeable membrane regulates what enters and exits the cell.

Question 24

How is the cell membrane dynamic?

Answer 24

The phospholipids are not fixed in position, but move around.

Question 25

Proteins which are embedded within the membrane are also what?

Answer 25

Mobile

Question 26

What do the different proteins in the membrane create?

Answer 26

A ‘mosaic’ appearance

Question 27

What does the cell membrane represent?

Answer 27

A Fluid Mosaic Model.