Structure of the cell

Question 1

what is a eukaryote cell

Answer 1

cell that contains membrane bound organelles

- organelles are suspended in cytosol

Question 2

what is evidence of cellular arrangement

Answer 2

light microscope x1500 allows cells to be seen clearly

- electron microscope x50000 can see the ultrastructure of cells - confirms proposed arrangement

Question 3

What is the function of the cell membrane

Answer 3

• separates the cytoplasm from the outside environment

Question 4

structure of cell membrane

Answer 4

fluid mosaic model

• phosphate head attached to a fatty acid chain
• bilayer - tails point inwards
• cholesterol molecules
• lots of integral & peripheral proteins

Question 5

what is the function of cholesterol in the CSM

Answer 5

• help regulate fluidity and stiffens it
• prevents small water soluble molecules from passing through
• provides a suitable molecular environment for some transmembrane proteins

Question 6

what is the function of integral & peripheral proteins in the CSM

Answer 6

integral-allow different substances in and out of cells

peripheral- can act as receptors

Question 7

what is the structure of the nucleus

Answer 7

large double membrane-bound organelles that contains chromatin and the nucleolus
- nuclear envelope has pores and is selectively permeable between the nucleus and the cytoplasm

Question 8

what does the nucleolus contain

Answer 8

DNA, RNA and proteins which regulate the cell cycle

- site for rRNA synthesis

Question 9

what is the function of mitochondria?

Answer 9

generate chemical energy (ATP) necessary for biochemical reactions with aerobic stages respiration

Question 10

what do number of mitochondria indicate?

Answer 10

level of metabolism

Question 11

which cells have many mitochondria and why?

Answer 11

hepatocytes - active role in digestion
sperm cell - need ATP for motility
slow twitch skeletal muscle- high aerobic activity

Question 12

structure of endoplasmic reticulum

Answer 12

3D network of cavities, some sac like and some tubular, bounded by membranes
- two types RER AND SER

Question 13

structure and function of RER

Answer 13

• surface studded by ribosomes which are essential for protein synthesis
• packages and folds primary and secondary proteins into tertiary ones and transports in vesicles to golgi

Question 14

which cells contain lots of RER

Answer 14

pancreatic epithelial - synthesis proteins to release into the lumen
plasma cells - to produce antibodies
nerve cell bodies - to produce proteins that are used internally and transported along the axon along microtubules

Question 15

structure and function of SER

Answer 15

no ribosome on the surface
single tubular sacs
involved in lipid, glycogen and steroid synthesis and the detoxification of noxious substances

Question 16

where is lots of SER found?

Answer 16

liver cells - lipid synth and detoxification of drugs by xenobiotic degradation

Question 17

structure of Golgi apparatus

Answer 17

• stacks of parallel flattened membrane pockets (cisternae)

Question 18

function of golgi

Answer 18

modifies tertiary into quaternary or lipo/glycoproteins

• dehydrates enzyme secretions
• produce lysosomes

Question 19

lysosomes structure and functions

Answer 19

membrane bound organelles that contain hydrolytic enzymes

- decompose substances taken into the cell and destroy worn out organelles and foreign proteins

Question 20

what is glycogen

Answer 20

polymer of alpha glucose that is highly branched and absorbed from the digestive system and circulates in the blood
- can be made by most cells to allow ATP synth to take place

Question 21

why are lipid droplets found in some cells

Answer 21

store for triglycerides in the cytoplasm

Question 22

what is the structure of fat cells and why

Answer 22

nucleus pushed to the side
lack of organelles
capillaries in connective tissue between the cells
- this is because it is specialised for triglyceride storage

Question 23

what stain turns lipids black in an electron micrograph?

Answer 23

osmium

Question 24

what is the cytoskeleton

Answer 24

dynamic, 3D web like structure filling the cytoplasm that acts a framework to maintain the shape and polarity of the cell

Question 25

what are the components of the cytoskeleton

Answer 25

microfilaments
intermediate filaments
microtubules

Question 26

what are microfilaments

Answer 26

-strands of actin (contractile) so provide a dynamic framework

Question 27

where are microfilaments important

Answer 27

microvilli - act as a core through the projection to increases SA, allow motility and anchor is to the actin cortex of the cell

Question 28

what are intermediate filaments for?

Answer 28

purely structural and form assemblies inside the cell

there are 5 classes (e.g. neurofilaments)

Question 29

what are microtubules

Answer 29

largest component of cytoskeleton and made of subunits that can assemble/disassemble to provide for changes in cell shape and position of organelles

Question 30

what is the structure of centrioles

Answer 30

come in pairs

bundle of 9 tubules in star formation - one is vertical and one is flat

Question 31

what is the function of centrioles

Answer 31

maintaining cell shape in non dividing cells and tracts for transporting vesicle and organelles to move from place to place

• responsible for polymerising microtubules
• in a dividing cell centrioles replicate, separate and move to opposite sides of the cell to pull out the mitotic spindle and cause separation of the cell

Question 32

erythrocytes shape and reasoning

Answer 32

disc shaped cells
lack nucleus and organelles
can deform when passing through narrow channels and shape allows a lot of Hb

Question 33

nerve cell structure and reasoning

Answer 33

long axon as there is need to communicate to the periphery

Question 34

epithelial cell structure and reasoning

Answer 34

columnar cells and crushed together with high cell to cell contact - act as a barrier

Question 35

skeletal muscle cell structure and reasoning

Answer 35

long and thin
multinucleated
allow contraction to take place with sliding filament theory