eukaryotic cells - notes

Question 1

what does the cell theory state? (5 points)

Answer 1

1. the cell is the basic unit of life
2. ALL organisms are made up of cells
3. ALL cells arise from pre-existing cells by DIVISION
4. the cell contains information (DNA/hereditary materials) which is used as instructions for growth, development and functioning
5. the cell is the functional unit of life in which chemical reactions that maintain life take place within it

Question 2

a) what are eukaryotes?
b) what living organisms are eukaryotes?

Answer 2

a) the cell of eukaryotes POSSESSES a true nucleus containing genetic materials known as DNA, enclosed within the nuclear envelope
b) animals, plants

Question 3

a) what are prokaryotes?
b) what living organisms are prokaryotes?

Answer 3

a) the cell of prokaryotes LACKS a true nucleus. the genetic material is not enclosed within membranes but lies freely in the cytoplasm
b) bacteria, archaea

Question 4

what is the value of 1 Angstrom in terms of m? what is it used for?

Answer 4

1Å = 10**^(-10) **m
it is used to measure the thickness of membranes and sizes of macromolecules

Question 5

rank the following things in terms of relative sizes:
(from largest to smallest)
- ribosome
- average bacteria
- average mitochondria
- DNA molecule
- average animal cell
- hydrogen atom
- average plant cell
- nucleolus
- grana
- chloroplast
- vesicles

Answer 5

1. plant cell
2. animal cell
3. chloroplast
4. bacteria = mitochondria
5. nucleolus
6. grana
7. vesicles
8. ribosome
9. DNA molecule
10. hydrogen atom

Question 6

a) what is a protoplasm?
b) what are the 3 major structures of the protoplasm in eukaryotic cells.

Answer 6

a) living matter of the cell

b)
- cell surface membrane
- nucleus
- cytoplasm

Question 7

what makes up the cytoplasm?

Answer 7

• cytosol
• organelles
• cytoskeleton

Question 8

what is the cytosol?

Answer 8

a fluid component, and an aqueous solution of various essential ions, soluble organic compounds and soluble proteins

Question 9

what are organelles?

Answer 9

subcellular components which carry out specific functions to maintain the cell or the multicellular organism.
(they may or may not be membrane bound)

Question 10

what is a cytoskeleton?

Answer 10

a network of fine strands of globular proteins that support the cell and maintain its overall shape

Question 11

name the parts that can be found in/around nucleus

Answer 11

• nucleoplasm
• nucleolus
• nuclear envelope
• RER
• nuclear pores
• chromosomes
• DNA

Question 12

describe the structure of nucleus

Answer 12

• largest organelle, spherical / ovoid in shape
• surrounded by double-membrane known as nuclear envelope
• outer membrane of nuclear envelope is continuous with the ER
• inner membrane of nuclear envelope is in contact with contents in nucleus
• nuclear envelope is perforated with nuclear pores
• nearly all cell’s DNA is found here
• has one or more nucleolus/nucleoli within nucleoplasm

Question 13

what are the 3 main functions of the nucleus?

Answer 13

1. controls cellular activities by regulating protein and enzyme synthesis
2. responsible for nuclear division, which is the basis of cell replication
3. nucleolus is responsible for synthesis and PARTIAL assembly of ribosomes

Question 14

describe the basic structure of the cell surface membranes

Answer 14

a phospholipid bilayer with the hydrophobic tails on the interior of the membrane and hydrophilic heads on the exterior.
also contains:
- cholesterol
- glycoproteins / glycolipids
- transport proteins
(elaborated further in fluid mosaic model)

Question 15

describe a phospholipid

Answer 15

made up of a glycerol molecule attached to a phosphate group and 2 fatty acid chains

more on this in fluid mosaic model

Question 16

what are the 3 main functions of the cell surface membrane?

Answer 16

1. partially permeable membrane
2. acts as a barrier between cytoplasm and environment
3. prevents most water-soluble substances from entering and leaving the cell

Question 17

describe the structure of centrioles and centrosomes, and where they are found

Answer 17

centrioles: cylindrical structures composed of microtubules (a single centriole consists of 9 microtubule triplets arranged in a cylinder)

centrosome: made up of 2 centrioles

location:
(i) in pairs only in animal cells in cytoplasm outside nucleus
(ii) as single structures at the base of cilia and flagella

Question 18

what are the 2 functions of centrosomes?

Answer 18

1. produce spindle fibres which attach to chromosomes and separate them during cell division
2. involved in formation of cilia and flagella

Question 19

describe the structure of ribosome, and where they are found

Answer 19

• has no membranes
• made up of protein and ribonucleic acid (ribosomal RNA)
• comprises 2 subunits
  (a large subunit = 60s ribosome, and
  a small subunit = 40s ribosome)

location:
(i) attached to the RER
(ii) free ribosomes in cytosol

Question 20

what is the function of ribosome?

Answer 20

site of protein synthesis

Question 21

describe the structure of endoplasmic reticulum

Answer 21

• originates from outer membrane of nuclear envelope
• consists of a network of membranous tubes / sacs called cisternae (singular is cisterna)

RER:
- ribosomes bound to its surface

SER:
- lacks ribosomes
- more tubular

the membranous sacs in both ER and GA are called cisternae

Question 22

what is the function of SER and RER

Answer 22

SER: synthesis of lipids, especially membrane phospholipids and steroid hormones

RER: site where proteins are synthesised and transported

Question 23

describe the structure of Golgi apparatus

Answer 23

• consists of stacks of flattened membrane-bound sacs known as cisternae
• it is continually being formed at cis face by fusion of vesicle from ER, and continually budded off at the trans face where vesicles are pinched off

the membranous sacs in both ER and GA are called cisternae

Question 24

what are the 2 functions of the Golgi apparatus?

Answer 24

1. chemically modifies, sorts, and transports molecules within it (for secretion across the cell membrane or deliver to other parts of cell)
2. lysosome formation

Question 25

describe the struction of lysosome

Answer 25

- bound by a **single membrane** - contains concentrated mixture of **hydrolytic digestive enzymes**

Question 26

# lysosomes can carry out 3 processes what are the 3 functions of lysosomes?

Answer 26

1. **Digestion** of materials taken in by cells 2. **Autophagy**: digestion of worn-out/improperly functioning organelles 3. **Autolysis**: self-digestion of cell by releasing the lysosome contents in cell

Question 27

describe the structure of mitochondrion

Answer 27

- rod-shaped / cylindrical - bound by **double membrane**, with an outer and inner membrane separated by **inter-membrane space** - outer membrane is a smooth and continual boundary - inner membrane is extensively folded to form **cristae**, which project into the interior (aka **matrix**) - within the matrix, hereditary materials like **circular DNA** and RNA, as well as **ribosomes** can be found ## Footnote *additional point: these materials found within matrix are traits of **prokaryotic bacteria**, leading to the theory behind the origin of mitochondrion and chloroplast

Question 28

what is the function of mitochondrion?

Answer 28

involved in cellular respiration to release energy

Question 29

**describe the structure of chloroplast**

Answer 29

- large organelle, only smaller than **nucleus and large central vacuole** - contains chlorophyll (photosynthetic pigments) which make the chloroplast look green - bound by **double membrane** - outer membrane: smooth and continuous - inner membrane: gives rise to membranes called **lamallae** and **thylakoids** that extend throughout interior - interior of chloroplast: gel-like matrix called **stroma** - within stroma: thylakoids are stacked into **grana**, which are joined together by **intergranal lamallae** - has 70s ribosomes and circular DNA | lamalla (singular), lamallae (plural) granum (singular), grana (plural) ## Footnote *additional point: these materials found within matrix are traits of **prokaryotic bacteria**, leading to the theory behind the origin of mitochondrion and chloroplast

Question 30

# chloroplast extension [name the following parts in the diagram](https://drive.google.com/file/d/1pWjXR0ulEE7y-3kLB-r_GmIxDAPNLxiH/view?usp=sharing)

Answer 30

[answer](https://drive.google.com/file/d/1bY703J7nvzQbb0a-_KrgtQZUGT-tyApN/view?usp=sharing)

Question 31

what is the function of choloroplast?

Answer 31

site of photosynthesis

Question 32

describe the structure of vacuoles (and their respective names in animal and plant cells)

Answer 32

- fluid-filled structures bound by a **single membrane** animal cells: - relatively smaller and less permanent (**vesicles**) plant cells: - **large central**, permanent vacuole surrounded by a membrane called **tonoplast**, containing **cell sap** ## Footnote cell sap contains aqueous solution of dissolved materials like sugars, ions, organic acids, waste products and pigments

Question 33

what are the functions of vacuoles? (5 points)

Answer 33

1. entry of water is important during **cell expansion** during cell growth, as well as in normal water relations of plants 2. contains **pigments** in solutions 3. **hydrolytic enzymes** *may* sometimes be present, making the vacuole act as a lysosome 4. **waste products may accumulate** within vacuole 5. some of the **dissolved substances** act as **food reserves**

Question 34

describe the structure of (cellulose) cell wall

Answer 34

- consists predominantly of cellulose - cell wall materials are **strong** and **permeable** therefore allowing the free passage of substances into and out of the cell

Question 35

what are the 2 functions of cell wall?

Answer 35

1. mechanical support 2. protective layer

Question 36

group the following organelles as organelles with single membranes, double membranes, no membranes or is a membrane itself. - nucleus - cell surface membrane - centrioles - ribosomes - ER - Golgi apparatus - lysosome - mitochondrion - chloroplast - vacuole - cell wall

Answer 36

**1. single membrane** - ER - Golgi apparatus - lysosome - vacuole **2. double membrane** - nucleus - mitochondrion - chloroplast **3. no membranes** - centrioles - ribosome **4. is a membrane / layer** - cell surface membrane - cell wall

Question 37

similarities between plant and animal cells

Answer 37

1. protoplasm has **cell surface membrane, nucleus**, and cytoplasm has **ER, Golgi apparatus mitochondria and ribosomes** 2. chromosomes are composed of **linear DNA** wound around proteins

Question 38

differences between plant and animal cells (name at least 3)

Answer 38

1. **cell wall** present in plant cell but absent in animal cell 2. **lysosomes** *usually* absent in plant cell but *often* present in animal cell 3. **chloroplasts** *usually* present in plant cell but absent in animal cell 4. **vacuoles** are present, large and central in plant cell, but absent, or small and scattered in animal cell 5. **centrioles** *usually* absent in plant cell but present in animal cell

Question 39

what is protein synthesis? how are the following proteins synthesised (name/process)? a) proteins that need to be secreted out of cell b) proteins needed for use within cell

Answer 39

genetic information from nucleus directs synthesis of particular proteins using ribosomes a) **protein secretory pathway** b) synthesised by **free ribosomes**

Question 40

**ESSAY QUESTION**: describe the protein secretory pathway ## Footnote for an essay question, might also have to define protein synthesis and state the name "protein secretory parthway.

Answer 40

1. **ribosomes** bound to RER synthesise the polypeptide chain into RER 2. protein becomes enclosed in an **ER/transport vesicle**, and the ER vesicle containing the protein **buds off from ER** 3. the ER vesicle **travels and fuses** with the **cis-face** of Golgi apparatus 4. the GA chemically modifies, sorts and transports the proteins. the proteins move through the GA by **Golgi vesicles** budding off **from one cisterna and fusing with another cisterna** 5. a secretory vesicle containing the protein buds off from **trans-face** of GA, travels and fuses with cell surface membrane, thus releasing protein out of cell ## Footnote specificity might be necessary if the question named a specific protein

Question 41

[label the following cell organelles](https://drive.google.com/file/d/1aq80xlS1jtQj6I4cQoSD_NM2Hg3UwSIo/view?usp=sharing)

Answer 41

[answer](https://drive.google.com/file/d/1kztcHVJqepqq3kLfsbA4A0tyFxNYMSPR/view?usp=sharing)