2.1 Cell structures

Question 1

What is found in a eukaryotic cell

Answer 1

-A nucleus surrounded by a nucleus envelope which contains DNA
-Nucleolus
-Cytoplasm
-A cytoskeleton
-Membrane bound organelles(mitochondria, Golgi apparatus)
-Vesicles
-Ribosomes

Question 2

What are structures only found in plant cells?

Answer 2

-Cellulose cell wall, large permanent vacuole, chloroplasts

Question 3

What are structures only found in animal cells

Answer 3

Centrioles and microvilli

Question 4

What is the function of the nucleus

Answer 4

-It contains DNA so therefore controls protein synthesis and cell metabolic reactions(Enzymes)

Question 5

What is the function of the nucleolus

Answer 5

-It is responsible for producing ribosomes, RNA forms rRNA(ribosomal RNA) which joins with proteins to form ribosomes.

Question 6

What is the function of the nucleus envelope.

Answer 6

-Contains gaps so large molecules can move in and out.(mRNA out and hormones in)
- it has a double membrane which protects DNA from damage from cytoplasm and separates the nucleus from the rest of the cell.

Question 7

What is the function of the Rough endoplasmic reticulum

Answer 7

• Its a transport system the cisternae sends proteins made by ribosomes on its surface to the Golgi apparatus for modification and packaging

Question 8

What is the function of the smooth endoplasmic reticulum

Answer 8

-It contains enzymes which catalase reactions involved with lipid metabolism
-It is involved in lipid and carbohydrate transport, synthesis and absorption.

Question 9

What is the function of the Golgi apparatus

Answer 9

-Site where proteins are modified and transported
-Proteins can be modified by adding sugar molecules(glycoproteins) or lipid molecules (lipoproteins) and folded into 3D shapes here
-They are also packed into vesicles to be stored in the cell or taken to the plasma membrane to be exported.

Question 10

What is the function of mitochondria

Answer 10

-Site of ATP production (aerobic respiration)
-Self replicating so more can be made if a cell needs more energy
-More abundant in cells involed in metabolic activity e.g Liver cells

Question 11

What is the Function of Chloroplasts

Answer 11

-Site of photosynthesis
-The first stage occurs in the Grana (light is trapped by chloroplasts and used to make ATP and a water molecule is split)
-Second stage occurs in stroma (hydrogen ion reduces carbon dioxide to form a carbohydrate)

Question 12

What is the function of the Vacuole

Answer 12

-Filled with water and solutes so acts as a storage container
-It helps maintain the cell shape by pushing against the cell wall when the cell is turgid

Question 13

What is the function of lysosomes

Answer 13

-Help keep powerful hydrolytic enzymes away from the cell
-Can engulf old organelles and foreign matter and return digested components to cell for reuse

Question 14

What is the function of cilia and the flagella/undulipodia

Answer 14

-Airways are lined with cilia to protect from pathogens so therefore cilia is used to move substances outside the cell
-Nearly all cells have one cilium which contains receptors to detect changes in the environment
-Only human cell with a flagella is a sperm cell, this enables it to move.

Question 15

What is the function of a ribosome

Answer 15

-Ribosomes bound to rough endoplasmic reticulum are for synthesising proteins used outside the cell
-Ribosomes found free in cytoplasm are for synthesising proteins that are to be used inside the cell

Question 16

What is the function of centrioles

Answer 16

-Aid in cell division by making threads of tubulin that attach to the chromosomes, motor proteins cause the centrosomes(two centrioles at right angles) to rotate and pull the chromosomes to the opposite ends of the cell
-They are also involved in the formation of cilia and undulipodia

Question 17

What is the function of the cell wall

Answer 17

-Not in animal cells but are found in plant and bacterial cells
-Provide strength and help maintain shape
-Permeable so allow molecules through

Question 18

Cell structures

Answer 18

Revision Cards

Question 19

What is the structure of the cytoskeleton

Answer 19

-Network of protein threads running through the cytoplasm
-They contain 3 main components which have different functions(microfilaments,microtubules and intermediate fibres)
-microfilaments(7nm in diameter),intermediate fibres(10nm),microtubules(18-30nm)

Question 20

What is the function of the cytoskeleton

Answer 20

-Microfilaments made of actin are involved in phagocytosis and cytokinesis and help keep the cells strength
-Microtubules determine shape of cytoskeleton and provide tracks for vesicles and form a spindle before the cell divides to bring chromosomes apart.
-Intermediate filaments provide mechanical strength and help with cell signalling by forming special junctions between cells in some tissues

Question 21

How are proteins made and secreted

Answer 21

1.mRNA is transcribed from a gene
2.this passes out the nucleus pores to the ribosome where a protein is transcribed
3.Proteins go into cisternae of RER and vesicles with the proteins go via microtubules to Golgi apparatus
4.Vesicles fuse and proteins are modified
5.Vesicles travel and fuse to the plasma membrane and are released via excytosis (requires energy)

Question 22

What are the differences in prokaryotes and eukaryotes

Answer 22

-Prokaryotes don’t have a nucleus whereas eukaryotes do
-Prokaryotes are smaller and have smaller ribosomes
-Prokaryotes are unicellular and have no membrane bound organelles
-Cytoskeleton is less developed(Prokaryotes)
-Prokaryotes have pilli which allow them to exchange with other prokaryotes.

Question 23

What are motor proteins

Answer 23

-Motor proteins are molecular motors that can move along the cytoplasm
-They also help cell division as they are required to align chromosomes and form the spindles.