Organelles

Question 1

describe the cell-surface (plasma) membrane

Answer 1

• the membrane found on the surface of animal cells and just inside the cell wall of other cells
• it’s mainly made of lipids and protein

Question 2

what’s the function of the cell-surface (plasma) membrane?

Answer 2

• regulates the movement of substances into and out of the cell
• also has receptor molecules on it which allow it to respond to chemicals like hormones

Question 3

describe the nucleus

Answer 3

• a large organelle surrounded by a nuclear envelope (double membrane) which contains many pores (nuclear pores)
• contains chromosomes (made from protein-bound linear DNA) and one or more nucleoli

Question 4

what’s the function of the nucleus?

Answer 4

• controls the cell’s activities (by controlling the transcription of DNA)
• DNA contains instructions to make proteins

Question 5

what is the function of the nuclear pores?

Answer 5

• nuclear pores allow substances (like RNA) to move between the nucleus and the cytoplasm

Question 6

what is the function of the nucleolus?

Answer 6

• makes ribosomes

Question 7

describe the mitochondria

Answer 7

• usually oval-shaped
• have a double membrane
• the innemembrane is folded to form structures called cristae
• between these folds is a fluid-filled matrix which contains enzymes involved in respiration

Question 8

what is the function of the mitochondria?

Answer 8

• the site of aerobie respiration
• aerobic respiration produces ATP (a common energy source in the cell)

Question 9

which cells contain mitochondria in high quantities?

Answer 9

• cells that are very active and require a lot of energy

Question 10

describe a chloroplast

Answer 10

• a small, flattened structure found in plant cells and algal cells
• they’re surrounded by a double-membrane and also have membranes inside called thylakoid membranes
• thylakoid membranes are stacked up in some parts of the organelle to form grana
• grana are linked together by lamellae (thin flat pieces of thylakoid membrane)

Question 11

what is the function of a chloroplast?

Answer 11

• the site where photosynthesis takes place
• some stages of photosynthesis take place in the grana and other stages take place in the stroma

Question 11

what is the function of a chloroplast?

Answer 11

• the site where photosynthesis takes place
• some stages of photosynthesis take place in the grana and other stages take place in the stroma

Question 12

what is the stroma?

Answer 12

a thick fluid found in chloroplasts

Question 13

describe the Golgi apparatus

Answer 13

• a group of fluid-filled, membrane-bound, flattened sacs
• vesicles are often seen at the edges of the sacs

Question 14

what is the function of the Golgi apparatus?

Answer 14

• it processes and packages new lipids and proteins
• it also makes lysosomes

Question 15

describe the Golgi vesicle

Answer 15

• a small, fluid-filled sac in the cytoplasm surrounded by a membrane and produced by the Golgi apparatus

Question 16

what is the function of the Golgi vesicle?

Answer 16

• stores lipids and proteins made by the Golgi apparatus and transports them out of the cell (via the cell membrane)

Question 17

describe a lysosome

Answer 17

• a type of Golgi vesicle
• a round organelle surrounded by a membrane with no clear internal structure

Question 18

what is the function of a lysosome?

Answer 18

• it contains the digestive enzyme, lysozyme
• these enzymes are kept separate from the cytoplasm by the membrane
• they can be used to digest invading cells or to break down worn out components of the cell

Question 19

describe a ribosome

Answer 19

• a very small organelle that floats free in the cytoplasm or is attached to the rough endoplasmic reticulum
• it’s made up of proteins and RNA
• not surrounded by a membrane

Question 20

what is the function of a ribosome?

Answer 20

• the site where proteins are made
• performs protein synthesis

Question 21

describe the rough endoplasmic reticulum

Answer 21

• a system of membranes enclosing a fluid-filled space
• the surface is covered with ribosomes

Question 22

what is the function of the rough endoplasmic reticulum?

Answer 22

• folds and processes proteins that have been made by the ribosomes

Question 23

describe the smooth endoplasmic reticulum

Answer 23

• similar to the RER but with no ribosomes

Question 24

what is the function of the smooth endoplasmic reticulum?

Answer 24

• synthesises and processes lipids

Question 25

describe the cell wall

Answer 25

• a rigid structure that surrounds cells in plants, algae and fungi
• in plants and algae it’s mainly made of cellulose
• in fungi, it’s made of chitin

Question 26

what is the function of the cell wall?

Answer 26

• supports cell
• prevents cell from changing shape

Question 27

describe the vacuole

Answer 27

• a membrane-bound organelle found in the cytoplasm
• contains cell sap (a weak solution of sugars and salts)
• the surrounding membrane is called the tonoplast

Question 28

what is the function of the vacuole?

Answer 28

• helps to maintain pressure inside the cell and keep the cell rigid which prevents the plant from wilting
• also involved in the ionisation of unwanted chemicals inside the cell