[3.4] structure of eukaryotic cells

Question 1

what is the function of mitochondria?

Answer 1

aerobic respiration

Question 2

what are the key features of mitochondria? (7)

Answer 2

1. outer mitochondrial membrane
2. inner mitochondrial membrane
3. inter-membrane space
4. mitochondria DNA
5. ribosomes
6. cristae
7. mitochondrial matrix

Question 3

what is mitochondrial DNA?

Answer 3

• allows mitochondria to be self-sustaining and means they are prokaryotes,
• is the genetic material giving instructions for which proteins to make all the ribosomes

Question 4

what are ribosomes?

Answer 4

• it is where protein synthesis occurs
• produces key respiratory enzymes in mitochondria

Question 5

what are cristae?

Answer 5

• infoldings of the inner membrane to increase SA
• where ATP is produced

Question 6

what is in the mitochondrial matrix?

Answer 6

key respiratory enzymes

Question 7

what are the key features of chloroplasts? (8)

Answer 7

1.double membrane
2. ribosomes
3. thylakoid
4. granum
5. inter-granal lamella
6. stroma
7. DNA
8. starch grains

Question 8

what is the function of the double membrane in chloroplasts?

Answer 8

• it is selectively permeable
• it has proteins that determines what can enter

Question 9

what is the function of the thylakoid?

Answer 9

• it is where the 1st stage of photosynthesis occurs: light absorption by chlorophyll (light dependent stage)

small, pancake-like discs

Question 10

what is the function of the granum?

Answer 10

to increases surface area cumilatively

Question 11

what is the inter-granal lamella?

Answer 11

it is a thin rod between grana that connects them

Question 12

what is the function of the stroma?

Answer 12

• where key enzymes for photosynthesis are found
• where 2nd stage of photosynthesis occurs: glucose production (light independent stage)

(like cytoplasm if it were a cell)

Question 13

key features of the nucleus (5)

Answer 13

1. nucleoplasm
2. chromosome
3. nuclear envelope (double membrane)
4. nuclear pore
5. nucleolus

Question 14

what does the chromosome in a nucleus contain?

Answer 14

DNA wrapped around beads of ‘histone’ protein

Question 15

what is the function of the nuclear pore?

Answer 15

enables entry and exit of:

• mRNA
• tRNA
• rRNA
• proteins
• ribosomes

Question 16

what is the function of the nucleolus?

Answer 16

• produces rRNA
• assembles ribosomes

Question 17

what are the functions of the nucleus? (textbook)

Answer 17

• to act as control centre of cell by producing mRNA and tRNA and hence protein synthesis
• to store the genetic material of the cell in the form of DNA and chromosomes
• make rRNA and ribosomes

Question 18

key features of the ribosome (4)

Answer 18

1. small ribosomal subunit
2. large ribosomal subunit
3. ribosomal grooves (where mRNA binds)
4. binding sites (for tRNA and associated amino acids)

Question 19

what are ribsomes made of and what size are they?

Answer 19

• prokaryote = smaller (70s)
• eukaryote = larger (80s)
• ribosomes are made of protein and rRNA

Question 20

what is the endoplasmic reticulum?

Answer 20

an extensive network of flattened interconnected tubes within the cytoplasm

Question 21

rough ER

Answer 21

• has ribosomes embedded on the surface of the membrane
• used to store and transport proteins
• sometimes found close to nucleus

Question 22

smooth ER

Answer 22

• no ribosomes
• used to store and transport lipids and carbohydrates

Question 23

key features of golgi apparatus (2)

close to RER

Answer 23

• cisternae (membrane stacks)
• golgi vesicles

Question 24

what are golgi vesicles?

Answer 24

small membrane bound sacs that ‘bud off’ from the main membranes due to membrane fluidity

Question 25

what is the role of the golgi apparatus? (class)

Answer 25

1. modifying proteins - folding & coiling into a specific 3D shape - addition of non protein components eg. Fe for haemoglobin 2. packaging proteins - adding 'finalised' protein into golgi vesicles to be transported elsewhere in/out of cell

Question 26

what are the functions of the golgi apparatus? (textbook)

Answer 26

- add carbohydrate to proteins to form glycoproteins - produce secretory enzymes eg. in pancreas - secrete carbohydrates eg. for making cells walls in plants - transport, modify, and store lipids - form lysosomes

Question 27

what is the importance of membrane fluidity/where is it used?

Answer 27

- meiosis - mitosis - phagocytosis

Question 28

key features of lysosome (2) | (example of a vesicle)

Answer 28

- **membrane**: keeps enzymes tucked away until they are needed - **lysozymes**: powerful hydrolytic enzymes that are used in digestion

Question 29

what are lysosomes used for? (5)

Answer 29

1. **phagocytosis**: to hydrolyse pathogens 2. **apoptosis**: programmed (intentional) cell death for unwanted or damaged cells 3. **exocytosis**: release of enzymes to outside of the cell to destory material around the cell 4. **autolysis**: to completely break down cells after they have died 5. **digestion** of worn out organells so the useful chemicals they are made of can be re-used

Question 30

key features of the vacuole (2)

Answer 30

- cell sap > mostly water with dissolved sugars (eg. monosaccharides) and dissolved mineral ions - tonoplast (vacuole membrane)

Question 31

what is the role of the vacuole? (class)

Answer 31

1. **storage of the sap** 2. **structural role**: full vacuole exerts pressure ('turgidity') outwards on the cell wall so the shape of the cell is maintained

Question 32

what are the functions of the vacuole? (textbook)

Answer 32

- support herbaceous plants, and herbaceous parts of woody plants, by making cells turgid - the sugars and amino acids may act as a temporary food store - the pigments may colour petals to attract pollinating insects

Question 33

what is the cell wall made of?

Answer 33

- cellulose fibrils - microfibrils bundled together into macrofibrils that form a mesh-like network > made of multiple straight chains of beta glucose molecules

Question 34

3 versions of cell wall + vacuole

Answer 34

- **turgid** (normal) - when no more water can physically enter the cell as vacuole swells and presses cytoplasm against cell wall during osmosis - **flaccid** (soft) - when cells are no longer firm and swollen as solution surrounding plant cells is hypertonic so water will leave - **plasmolysed** - when too much water is lost by osmosis so the vacuole and cytoplasm shrink, and eventually the cell membrane pulls away from the cell wall

Question 35

properties of the cell wall (how and why)

Answer 35

- the cell wall is strong and rigid - this is so it is able to resist turgor pressure of the vacuole and maintain the cell shape - it is strong and rigid due to long, straight, unbranched chains which have hydrogen bonds between chains

Question 36

what are the functions of the cell wall? (textbook)

Answer 36

- to provide mechanical strength to prevent cell bursting under pressure created when water enters by osmosis - to give mechanical strength to the plant as a whole - to allow water to pass along it, contributing to the movement of water through the plant