Functions and Structures of Organelles

Question 1

Main function of the cell surface/plasma membrane?

Answer 1

To control which materials pass in and out of the cell.

Question 2

What is the structure of cell surface/plasma membrane?

Answer 2

Has a DOUBLE layer of phospholipids, arranged tail to tail with some protein molecules between which are either embedded in the membrane or penetrating the bilayer forming pores (channels).

Question 3

What are the proteins in cell surface/plasma membrane important for?

Answer 3

Proteins in the membrane or penetrating the bilayer are important for the transport of substances across the membrane and the proteins on the outside of the cell are often involved in cell recognition or as receptor sites for hormones.

Question 4

What is the space between the membranes termed?

Answer 4

The ‘fluid mosaic structure’

Question 5

What is the size of the nucleus?

Answer 5

It is the largest organelle in the cell and is about 10um.

Question 6

What is the function of the nucleus?

Answer 6

To control cell activities, contains instructions to make proteins.

Question 7

What is the structure of the nucleus?

Answer 7

Has a nucleolus which produces the RNA needed to make ribosomes, has nucleoplasm, is bound by a nuclear membrane/envelope/phospholipid bilayer and has nuclear pores to allow substances to move in and out of the nucleus eg. mRNA

Question 8

How is DNA stored in the nucleus?

Answer 8

When the cell isn’t dividing it is stored in the form of chromatin. In a dividing cell, the DNA molecules are condensed to chromosomes that become clearly visible. The DNA carries info that allows cells to divide and carry out cellular processes.

Question 9

In the nucleus what are the individual sections of DNA called and their function?

Answer 9

Genes - they contain the necessary information to make individual proteins.

Question 10

What does RER stand for?

Answer 10

Rough Endoplasmic Reticulum

Question 11

Where is the RER found?

Answer 11

It joins to the nuclear membrane (nucleus)

Question 12

Describe the RER.

Answer 12

A system of thin, intricate channels that spread throughout the cell. The channels are membranes enclosing a fluid-filled space. The surface is COVERED IN RIBOSOMES.

Question 13

What is the difference between RER and SER?

Answer 13

RER is covered in ribosomes, otherwise they are very similar.

Question 14

What is the function of the RER?

Answer 14

Fold and transport/(process) the proteins made on the ribosomes. The proteins made in the rough ER are secreted out of the cell. Can also store enzymes and other proteins.

Question 15

What type of cell has a large volume of rough ER?

Answer 15

Cells which make and secrete lots of protein.

Question 16

What do the small vesicles do? (RER)

Answer 16

Small vesicles containing newly made proteins pinch off from the ends of the rough ER and either fuse with the golgi complex or pass directly to the cell membrane. (Transport substances in and out of the cell/between organelles)

Question 17

What is the size of a ribosome?

Answer 17

About 20nm, small and dense.

Question 18

Where are ribosomes found?

Answer 18

Most are attached to the rough ER but some float freely in the cytoplasm.

Question 19

Function of ribosomes?

Answer 19

Carry out protein synthesis (assembling amino acids into the right order to produce new specific proteins using the code on the mRNA - messenger RNA). General proteins that are to be used inside the cell are made by free ribosomes.

Question 20

Structure of ribosomes?

Answer 20

Made up of proteins and RNA, not membrane bound.

Question 21

Where is the Smooth Endoplasmic Reticulum (SER) found/how can it be identified?

Answer 21

In small areas not continuous (not connected) to the nuclear membrane, contains folds all connected

Question 22

What is the function of the smooth ER?

Answer 22

The site of steroid (lipid hormone) production and processing. Also contains enzymes that detoxify a wide range of molecules and acts as a storage site for calcium in skeletal muscle cells.

Question 23

What is the structure of the Golgi complex/apparatus/(body)?

Answer 23

A tightly packed, group of flattened, fluid-filled, membrane-bound sacs. It is a shifting flexible structure. Identified because of its folds which are NOT connected.

Question 24

What is the function of the Golgi complex/apparatus/(body)?

Answer 24

To process and package proteins (and lipids) made in the Rough ER - PPP. Also makes lysosomes (Also thought to synthesise or modify the chemicals before they are secreted from the cell)

Question 25

What are Golgi vesicles?

Answer 25

A small fluid-filled sac in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus - are constantly being added at one side and lost by the other.

Question 26

What is the function of the Golgi vesicles?

Answer 26

Store proteins and lipids made by the Golgi apparatus and transport them around the cell (via the cell-surface membrane)

Question 27

What is the function of mitochondria?

Answer 27

The site of aerobic respiration to produce ATP - the energy currency of the cell.

Question 28

In what type of cell are mitochondria found?

Answer 28

All cell eukaryotic cells but specifically in large numbers in cells that are very active and require a lot of energy.

Question 29

Explain the structure of a mitochondrion.

Answer 29

Has a double membrane - the outer is smooth while the inner is folded. The inner folds to create a large SA, these folds are cristae and hold many of the enzymes concerned with the final stage of respiration. Has a central fluid filled space called the matrix which contains the free enzymes that are involved in the early stages of respiration.

Question 30

What is the function of a chloroplast?

Answer 30

To make sugars (glucose) via photosynthesis. Some parts occur in the grana others occur in the stroma.

Question 31

What is the structure of a chloroplast?

Answer 31

Small, flattened structure, has a double membrane - the inner one is folded creating thylakoids and inbetween this is fluid called stroma (a bit like cytoplasm), contains chlorophyll.

Question 32

What are grana (granum)? - in chloroplasts

Answer 32

In places, the thylakoid membrane is arranged in stacks called grana (granum). They are thought to maximise the absorption of light energy and transfer it into chemical energy.

Question 33

What does the stroma contain? - chloroplasts

Answer 33

Enzymes which fix CO2 into sugars.

Question 34

Function of chlorophyll? - chloroplasts

Answer 34

The first stage of photosynthesis is light being absorbed by chlorophyll.

Question 35

What are lamellae?

Answer 35

Thin, flat pieces of thylakoid membrane that link grana together.

Question 36

What are lysosomes?

Answer 36

A small, round organelle, are membrane-bound, no clear internal structure, type of golgi vesicle, contain lysozyme (hydrolitic) enzymes which are kept separate from the cytoplasm by membrane.

Question 37

What is the function of a lysosome?

Answer 37

The lysozyme enzymes are used to digest invading cells or break down worn out components of the cell.

Question 38

What is the function of the cellulose cell wall?

Answer 38

To support and strengthen the cell to prevent them from changing shape.

Question 39

What is the structure of the cellulose cell wall?

Answer 39

In plants and algae its made up of cellulose - a polysaccharide. About 2000 parallel cellulose molecules are packed together to form microfibrils, these bundle together to form fibrils which gives the cell wall strength and ridigity. In fungi its made of chitin.

Question 40

What are the four functions of the vacuole?

Answer 40

a) absorb water by osmosis and swell to keep the cell rigid (maintain pressure) and stop the plant wilting.
b) store food substances eg. sugars and mineral salts
c) store pigments that give colour eg. petals
d) can help isolate unwanted chemicals in the cell.

Question 41

What is the structure of the vacuole?

Answer 41

Membrane- bound organelle (membrane is called tonoplast) found in the cytoplasm, contains cell sap - a weak solution of sugar and salts.

Question 42

Where do the different types of respiration occur?

Answer 42

Aerobic - mitochondria

Anaerobic - cytoplasm