cell structure

Question 1

list all ultrastructural features of an animal cell: (there’s 13)

Answer 1

• mitochondria
• nucleus
• nucleolus
• nuclear pores
• golgi apparatus
• ribosomes
• SER (smooth endoplasmic reticulum)
• RER (rough endoplasmic reticulum
• cytoskeleton
• cell membrane
• cytoplasm
• centrioles
• secretory vesicles

Question 2

what is the nucleolus?

Answer 2

it makes the ribosomes

Question 3

what does the nucleus contain?

Answer 3

large organelle surrounded by a nuclear envelope which contains pores. containing chromatin (made from dna and histones)

Question 4

the purpose of nuclear pores?

Answer 4

large complex of proteins allowing small molecules and ions in and out of the nucleus for protein synthesis

Question 5

what is a cytoskeleton?

Answer 5

network of fibres necessary for the shape, stability, and movement within the cell

Question 6

what is the purpose of the SER (smooth endoplasmic reticulum)?

Answer 6

a system of membrane-bound flattened sacs - purpose is that it is responsible for lipid and carbohydrate synthesis

Question 7

purpose of RER?

Answer 7

surface is covered with ribosomes unlike SER, proteins would enter the RER and are then folded, processed, then transported to the golgi apparatus

Question 8

purpose of the golgi apparatus?

Answer 8

they further process proteins from the RER by modifying them and packaging them into vesicles - either secretory vesicles (which leave the cell) or lysosomes (which stay in)

Question 9

purpose of centriole?

Answer 9

small hollow cylinders made of microtubules - involved in the assembly of spindle fibres during mitosis (separation) and also positioning of flagella and cilia which is important

Question 10

purpose of the cilia

Answer 10

hair like extensions which can be mobiles or stationary - stationary have an important role in sensory organs e.g. nose - mobile ones beat in a rhythmic manner creating a current e.g. in the trachea to move mucus away from the lungs

Question 11

lylosome

Answer 11

a specialised vesicle that contains digestive enzymes - they break down excess or worn-out cell parts.

Question 12

mitochondria

Answer 12

double membrane, inner one is folded to form a structure called cristae - (containing the enzymes used in aerobic respiration) - fluid interior is called the matrix - contains a small amount of DNA - which may be leftover bacteria when it was used to respire in other cells eg prokaryotic cells

Question 13

chloroplast

Answer 13

flattened membrane sacks called thylakoids - contain chlorophyll pigments, joined by lamellae - giving a large surface area for photosynthesis

Question 14

thylakoids

Answer 14

pouch-like sacs that are bound to a membrane in chloroplasts - they contain the pigment chlorophyll, that absorbs light

Question 15

crista (cristae - plural)

Answer 15

is a fold in the inner membrane of a mitochondrion - it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area for chemical reactions to occur on

Question 16

what are histones useful for?

Answer 16

a protein that provides structural support for a chromosome - each chromosome contains a long molecule of DNA, which must fit into the cell nucleus - to do that, the DNA wraps around complexes of histone proteins, giving the chromosome a more compact shape

Question 17

protein production:

Answer 17

1) proteins begin to be made by the ribosomes attached to the RER.
2) they pass along the cisternae then they are packaged into transport vesicles.
3) the golgi apparatus receives them so that they can be packaged and modified.
4) after the proteins have been structurally modified they go to the secretory vesicles.
5) some vesicles expel the proteins by exocytosis while some become lysosomes.

Question 18

what is the component of cell walls in fungi?

Answer 18

chitin

Question 19

parts of a cytoskeleton:

Answer 19

• microfilaments
• intermediate fibres
• microtubules

Question 20

whats a microfilament

Answer 20

formed from actin protein, responsible for cell movement and cell contraction during cytokinesis

Question 21

purpose of intermediate fibres?

Answer 21

they give mechanical strength to the cell

Question 22

what are microtubules

Answer 22

globular tubulin proteins that polymerise to form tubes used as a scaffold-like structure - tracks for movement of organelles around the cell

Question 23

describe protein production:

Answer 23

• proteins made from the nucleolus, attaching to RER
• proteins then pass along the cisternae then are packaged into transport vesicles
• golgi apparatus receives them so that they can be packaged and structurally modified
• go to secretory vesicles
• vesicles expel protein by exocytosis while some become lylosymes