Cells

Question 1

What is the role of the plasma membrane?

Answer 1

• controls exchange between cell and environments

Question 2

What are the functions of the plasma membrane?

Answer 2

• Has receptors for cell recognition

- selectively permeable

Question 3

What is the role of the cytoplasm?

Answer 3

• suspended in the cytoplasm are number out specialised membrane-bound structures called organelles
• THE CYTOPLASM IS NOT AN ORGANELLE IT JUST CONTAINS ORGANELLES

Question 4

What is the role of the nucleus ?

Answer 4

• the nucleus contains DNA and controls the activities of the cell

Question 5

What are the functions of the nucleus ?

Answer 5

• the nucleus is the largest organelle surrounded by a double membrane called the nuclear envelope

Question 6

What is the nuclear envelope (the double membrane) perforated with?

Answer 6

The nuclear envelope is perforated with nuclear pores.

Question 7

What is the nucleolus? And what is its function?

Answer 7

• the nucleolus is a small densely staining disk within the nucleus
  ALWAYS APPEARS DARKER THAN THE NUCLEUS
• the nucleolus makes RNA and ribosomes

Question 8

What is the nuclear envelope?

Answer 8

• the nuclear envelope is a double layered structure consisting of two adjacent membranes
  The membranes are 40-70 nm apart

Question 9

What is the diameter of the nuclear pores?

Answer 9

50-70nm

Question 10

What is the function of the nuclear pores?

Answer 10

• the nuclear pore allows movement of substances in or out of the membrane such as RNA or ribosomes

Question 11

What are often found attached to the Nuclear membrane?

Answer 11

Ribosomes cover the outer layer of the nuclear membrane

Question 12

What are chromatin?

Answer 12

• when a cell is not dividing no chromosomes can be seen this is because DNA is unwound in the nucleus
• unwound DNA = chromatin

Question 13

What are mitochondria ?

Answer 13

• mitochondria are rod-shaped organelles
• outer smooth membrane
• inner folded membrane
• the folds of mitochondria are called Cristae

Question 14

What is the function of mitochondria ?

Answer 14

• they are concerned with energy production through making an energy storage molecule called ATP
• much of the process of aerobic respiration occurs within the mitochondria

Question 15

Why do mitochondria look different?

Answer 15

• mitochondria vary in shape
• cut in different planes and angles
• or deformed during preparation of section

Question 16

What is the ROUGH ENDOPLASMIC RETICULUM?

Answer 16

• the rough ENDOPLASMIC reticulum extends front the nucleus and is continuous with it

Question 17

What is the function of the Rough ENDOPLASMIC reticulum?

Answer 17

The rough endoplasmic reticulum is responsible in transporting proteins which have been made in the ribosomes to where they are needed:

• some proteins may be secreted from the cell e.g. Hormones or enzymes
• some proteins may be placed on the cell surface membrane e.g. Antigen

Question 18

What are on the surface of the RER?

Answer 18

• ribosomes
  Which are the sites of protein synthesis

Nb: free ribosomes are also found within the cytoplasm

Question 19

What is the function of the SMOOTH ENDOPLASMIC RETICULUM?

Answer 19

• the smooth endoplasmic reticulum is important in synthesising and transporting lipids/steroid based hormones/hormones

Question 20

Are there any ribosomes on the surface of the smooth ENDOPLASMIC reticulum?

Answer 20

NO

Question 21

What is the Golgi apparatus/ body ?

Answer 21

The Golgi apparatus is a stack if of 4 to 8 membrane bound sacks located close to the nucleus.

Question 22

What is the function of the Golgi body?

Answer 22

1. Receives proteins from rough endoplasmic reticulum/ribosomes
2. The Golgi body MODIFIES and PROCESSES proteins e.g. Carbohydrate chain makes glycoproteins
3. Protein is packaged –> vesicle to be released from the cell
   SECRETION FROM THE CELL
4. Also the Golgi body can make lysosomes
5. And is involved in lipid synthesising as well as the smooth endoplasmic reticulum

Question 23

What are lysosomes ?

Answer 23

Lysosomes are membrane bound organelles that contain digestive enzymes known as acid hydrolases

Question 24

What are the functions of lysosomes?

Answer 24

• involved in apoptosis - destruction of entire cell when damaged or diseased
• destruction of pathogens
• destruction of ageing, redundant cell organelles
• release of digestive enzymes from the cell to degrade other cells

Question 25

What is the cytoskeleton ?

Answer 25

Cells contain a network of fibres made of Protein

These fibres keep the cell’s shape stable by providing an internal frame work known as the cytoskeleton

Question 26

What are the two types of protein fibres:

Answer 26

1. Microtubules = help move organelles and other cell contents e.g. Chromosomes
2. Microfilaments = these are smaller than microtubules and act as a ‘Skeleton’ helping to support the cell
   Microfilaments are also responsible for cell movement

Question 27

What is the role of the cytoskeleton:

Answer 27

• provide STRENGTH and SUPPORT to cell
• determines cell SHAPE
• involved in MOVEMENT of ORGANELLES
• helps HOLD organelles in place
• make up CENTRIOLES And spindle fibres

Question 28

What are centrioles?

Answer 28

Centrioles are small tubes of protein fibres microtubules
They come in a pair next to the nucleus
ONLY IN ANIMAL CELLS
Centrioles are at right angles to each other

Question 29

What is the function of centrioles ?

Answer 29

• Centrioles are involved in cell division as they generate spindle fibres
• Spindle fibres are responsible for the separation of chromosomes

Question 30

What is the difference between flagella and cilia?

Answer 30

• cilia and flagella are structurally the same
• they are HAIRLIKE extensions that stick out from the surface of cells are often involved in movement
• however, cilia are used for relatively short structures e.g. Ciliated epithelial cells
• whereas, flagella is used for relatively long structures which are often found in ones or twos e.g. Sperm cells