Anatomy of the cell

Question 1

Define what a cell is

Answer 1

A cell is the basic structural unit of all living organisms

Question 2

True or false - embryonic cells have less water than old cells?

Answer 2

False - embryonic cells actually have more water than old cells

Question 3

Name the 5 components of a cell and the % of each component

Answer 3

1. Water (80%)
2. Proteins (15%)
3. Lipids (2.5%)
4. Carbohydrate (1.5%)
5. Inorganic (1%)

Question 4

What is the plasmalemma?

Answer 4

It is the cell membrane which separates the cytoplasm from the outside environment. It is a biomolecular layer of amphipathic phospholipid molecules

Question 5

What is endocytosis and exocytosis?

Answer 5

Endocytosis is the movement of material into the cell and exocytosis is the movement of material out of the cell

Question 6

What does a cytoskeleton do?

Answer 6

It determines the shape and fluidity of the cell

Question 7

What are cytoskeletal proteins?

Answer 7

A set of filamentous cytosolic proteins that maintain several functions of the cell

Question 8

Name the 3 classes of filaments in a cytoskeleton and what composes them

Answer 8

1. Microfilaments (composed of protein actin)
2. Intermediate filaments (composed of 6 main proteins)
3. Microtubules (composed of 2 tubulin proteins - alpha and beta tubulin)

Question 9

Describe the structures around the nucleus

Answer 9

The nucleus is enclosed by a nuclear envelope which is made up of an inner nuclear membrane (smooth) and outer nuclear membrane (studded with ribosomes)

Question 10

Name the 2 types of DNA that the nucleus contains

Answer 10

1. Euchromatin which is dispersed DNA that is active

2. Heterochromatin which is condensed DNA that is not undergoing transcription

Question 11

What are nucleolus?

Answer 11

Nucleolus are where ribosomes are constructed

Question 12

What is each ribosome made up of?

Answer 12

A small subunit which binds RNA and a large subunit which catalyses formation of peptide bonds.

Question 13

What is the endoplasmic reticulum?

Answer 13

A network of interconnecting membrane-bound compartments in the cell. Made up of the Rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER)

Question 14

What is the purpose of the RER?

Answer 14

RER is studded with ribosomes so it plays a key role in the synthesis of proteins for insertion into membrane or secretion

Question 15

What is the purpose of the SER?

Answer 15

SER continues processing the proteins from the RER and also plays a key role in the synthesis of lipids

Question 16

What is the golgi apparatus and what does it do?

Answer 16

The golgi apparatus is made up of a group of flattened, membrane bound cisternae. Transport vessicles arrive at the golgi apparatus from the RER and SER. The modification and packaging of macromolecules from the endoplasmic reticulum also occurs here (e.g adding of sugars, cleaving of proteins etc.)

Question 17

What is the function of the mitochondria?

Answer 17

It is the powerhouse of the cell as it generates ATP.

Question 18

Why is the inner cristae of the mitochondria folded?

Answer 18

To increase the surface area to make more energy

Question 19

What are intercellular junctions?

Answer 19

These are specialised structures which link individual cells together into a functional unit

Question 20

Name the 3 types of intercellular junctions and their different functions

Answer 20

1. Occluding junctions (AKA tight junctions) - prevent diffusion by sealing off two cells
2. Anchoring junctions (AKA zonula adherens) - provide strength by linking cells together in an intercellular space
3. Communicating junctions (AKA gap junctions) - Allows movement of molecules between cells

Question 21

Name 3 ways that material can move across the cell membrane

Answer 21

1. Diffusion
2. By transport proteins (e.g pumps, channels)
3. Vesicular transport

Question 22

Explain the steps that occur in endocytosis and exocytosis

Answer 22

In endocytosis, material from the extracellular space is incorporated into the cell and invaginated to form a new endocytotic vessicle which then buds into the cell. The mechanism for exocytosis is the same but in reverse, so the material is released out of the cell

Question 23

What is phagocytosis?

Answer 23

This is when bacterium etc is taken into the cell from the extracellular space and binds to the cell surface receptors causing the cell to engulf it forming a phagosome which can then be destroyed using a lysosome