cell structures and functions (pt 1)

Question 1

cell surface membrane thickness?

Answer 1

7nm

Question 2

permeability of csm? and function

Answer 2

partially permeable and controls exchange between the cell and its environment

Question 3

what is the microvilli

Answer 3

finger-like extensions of a cell (typical of certain animal cells, such as the epithelial cells) which increase the surface area of the cell for more efficient absorption or secretion

Question 4

function of microvilli

Answer 4

(greatly) increase the surface area of the cell surface membrane

Question 5

what are the benefits (examples) of the microvilli increasing the SA of CSM?

Answer 5

useful for

• reabsorption at the proximal convoluted tubules of the kidney
• absorption of digested food into the cells lining the gut

Question 6

describe the nuclear envelope

Answer 6

surrounded by two membranes. the outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum

Question 7

what are the pores in nuclear envelope

1. called
2. their function

Answer 7

1. nuclear pores

2. allow and control exchange between the nucleus and the cytoplasm

Question 8

example of substances leaving nuclear pores?

Answer 8

• messenger RNA (mRNA)
• transfer RNA (tRNA)
• ribosomes (for protein synthesis)

Question 9

example of substances entering nuclear pores?

Answer 9

• proteins (to help make ribosomes)
• nucleotides
• ATP
• thyroid hormone T3

Question 10

describe the content found in chromosomes

Answer 10

• chromosomes contain DNA
• DNA is organised into functional units called genes
• genes control the activities of the cell and inheritance

Question 11

why do DNA molecules have to be folded?

Answer 11

• the are so long (human has around 2m of DNA).

- folded to a more compact shape to prevent the strands from becoming tangled.

Question 12

how is DNA folded?

Answer 12

• this is achieved by combining with proteins (histones)

- the combination of DNA and proteins is known as chromatin

Question 13

what are chromosomes made of?

Answer 13

• chromatin

- chromatin contain RNA

Question 14

what is the endoplasmic reticulum?

Answer 14

• a network of flattened sacs running through the cytoplasm of eukaryotic cells

Question 15

what is transported through the endoplasmic reticulum?

Answer 15

• molecules, particularly proteins can be transported through the cells inside the sacs separate from the rest of the cytoplasm

Question 16

where is nucleolus found

Answer 16

in the nucleus, one or more may be present

Question 17

function of nucleolus?

Answer 17

• to make ribosomes using the information in its own DNA

Question 18

what is the form of RNA used in manufacture of ribosomes?

Answer 18

tRNA

Question 19

which component contains tRNA for ribosomes?

Answer 19

nucleolus

• from one or more chromosomes
• nucleolus contains genes for making tRNA

Question 20

describe the components around the nucleolus core

Answer 20

• less dense region
• ribosomal subunits are assembles
• combines rRNA with ribosomal proteins imported from the cytoplasm
• the more ribosome a cell makes, the larger its nucleus

Question 21

the different parts of the nucleolus? ..

Answer 21

.. only come together during the manufacture of ribosomes

- they separate during nuclear division

Question 22

the membranes of endoplasmic reticulum form..?

Answer 22

flattened compartments called sacs or cisternae

Question 23

what happens at ribosomes?

Answer 23

protein synthesis

Question 24

why does rough er look rough?

Answer 24

covered with many tiny organelles called ribosomes

Question 25

function of smooth er?

Answer 25

• makes lipids and steroids, such as cholesterol, and oestrogen and testosterone
• storage site for calcium ions which are involved in muscle contraction

Question 26

why is smooth er abundant in muscle cells

Answer 26

• storage site for calcium ions which are involved in muscle contraction

Question 27

why smooth er present in liver?

Answer 27

• drug metabolism

Question 28

how to observe ribosomes?

Answer 28

• electron microscope (can see two subunits, one large one small)
  (LM cannot)

Question 29

units used for ribosomes

Answer 29

S units (svedberg)

• S units are a measure of how of how rapidly substances sediment in a high speed centrifuge (ultracentrifuge).
• ^ sediment, ^ s unit

Question 30

S units for ribosomes in eukaryotes and prokaryotes?

Answer 30

• Eukaryotes 80s

- Prokaryotes 70s

Question 31

why ribosomes in mitochondria and chloroplasts contain 70s ribosomes?

Answer 31

• bcs of their prokaryotic origins

Question 32

what are ribosomes made of?

Answer 32

equal parts ribosomal RNA (rRNA) and protein

Question 33

what are the interacting molecules in protein synthesis in the ribosome?

Answer 33

• mRNA
• tRNA
• amino acids
• regulatory proteins

Question 34

compare animal cell and plant cell vacuoles

Answer 34

• AC : some are phagocytic (temporary) and small, some not present at all
• PC : they are large, centralized and permanent

Question 35

why are plant cells larger in size than AC

Answer 35

presence of vacuoles

Question 36

function of nucleolus?

Answer 36

manufactures ribosomal RNA to assemble ribosome

Question 37

how are ribosome subunits formed?

Answer 37

• rRNA is synthesized from DNA
• protein assembled with rRNA form large and small subunits ribosome
• subunits exit nuclear pores to cytoplasm

Question 38

function of vacuoles?

Answer 38

• regulates osmotic properties of cells

- storage for pigments and organic compounds

Question 39

function of tonoplast?

Answer 39

• membrane which controls exchange content

enzymes, pigments , sugars / organic compunds , mineral salts , gases

Question 40

what are microtubules made of?

Answer 40

tubulin
- alpha-tubulin
- beta-tubulin
tubulins form to make a dimer
dimers join to make protofilaments
(controlled my microtubule organising centres [MTOC])

Question 41

function of microtubules

Answer 41

• structural cell component

- intracellular transport system