organelles part 2

Question 1

define an ultrastructure

Answer 1

depending on that function, each cell type has an internal structure that suits it for its job

Question 2

describe Eukaryotic cells

Answer 2

Eukaryotic cells have a distinct nucleus and possess membrane-bounded organelles

Question 3

describe the nuclear envelope

Answer 3

the nuclear envelope is a double membrane that surrounds the nucleus.

its outer membrane is continuous with the endoplasmic reticulum of the cell and often has ribosomes on its surface.

it controls the entry and exit of materials in and out of the nucleus and contains the reactions taking place within it

Question 4

describe Nuclear pores

Answer 4

Nuclear pores allow the passage of large molecules, such as messenger RNA, out of the nucleus.

there are typically around 3000 pores in each nucleus, each 40-100nm in diameter

Question 5

define the nucleoplasm

Answer 5

nucleoplasm is the granular, jelly like material that makes up the bulk of the nucleus

Question 6

define chromosomes

Answer 6

chromosomes consist of protein bound, linear DNA

Question 7

describe the nucleolus

Answer 7

the nucleolus is a small spherical region within the nucleoplasm.

it manufactures ribosomal RNA and assembles the ribosomes

there may be more than one nucleolus in a nucleus

Question 8

what is around the mitochondrion

Answer 8

around the organelle is a double membrane that controls the entry and exit of material.

the inner of the two membranes is folded to form extensions known as cristae

Question 9

describe the cristae

Answer 9

cristae are extensions of the inner membrance, which in some species extend across the whole width of the mitochondria to control the production of some of their own proteins

Many enzymes involved in respiration are found in the matrix

Question 10

describe the matrix

Answer 10

the matrix makes up the remainder of the mitochondrion.

it contains proteins lipids, ribosomes and DNA that allows the mitochondria to control the production of some of their own proteins.

many enzymes involved in respiration are found in the matrix

Question 11

describe the chloroplast envelope

Answer 11

the chloroplast envelope is a double plasma membrane that surrounds the organelle.

it is highly selective in what it allows to enter and leave the chloroplast

Question 12

describe the grana

Answer 12

the grana are stacks of up to 100 disc-like structures called thylakoids. within the thylakoids is the photosynthetic pigment called chlorophyll.

some thylakoids have tubular extensions that join up with thylakoids in adjacent grana.

the grana are where the first stage of photosynthesis takes place

Question 13

describe the stroma

Answer 13

the stomata is a fluid-filled matrix where the second stage of photosynthesis ( synthesis of sugars) takes place.

within the stroma are a number of other structures, such as starch grains.

Question 14

how are chloroplasts adapted to the function of harvesting sunlight and carrying out photosynthesis

Answer 14

the granal membranes provide a large surface area for the attachment of chlorophyll, electron carriers, and enzymes that carry out the first stage of photosynthesis. these chemicals are attached to the membrane in a highly ordered fashion

the fluid of the stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis

chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis

Question 15

why does am endoplasmic reticulum have ribosomes

Answer 15

provide a large surface area for the synthesis of proteins and glycoproteins

provide a pathway for the transport of materials, especially proteins, throughout the cell

Question 16

explain what happens when proteins and lipids pass through the golgi apparatus

Answer 16

it consists of a stack of membranes that make up flattened saca, or cisternae, with small rounded hollow structures called cesicles.

the proteins and lipids produced by the ER are passed through the golgi apparatus. in strict sequence. the golgi modifies these protiens often adding non-protein components such as carbohydrate. to them.

it also labels them, allowing them to be accurately sorted and sent to their correct destinations.

once sorted, the modified proteins and lipids are transported in golgi vesicles which are regularaly pinched off from the cell surface, where they fise with the membrane and release their contents to the outside

Question 17

where is the golgi apparatus especially well developed

Answer 17

the golgi apparatus is especially well developed in secretory cells, such as the epithelial cells that line the intestines

Question 18

when are lysosomes formed

Answer 18

when the vesicles produced by the golgi apparatus contain enzymes such as protease and lipases.

Question 19

what do lysosomes contain

Answer 19

they contain lysozymes, enzymes that hydrolyse the cell walls of certain bacteria.

as many as 50 enzymes may be contained in a single lysosome.

Question 20

what do the lysosomes do with these enzymes

Answer 20

up to 1.0 um in diameter, lysosomes isolate these enzymes from the rest of the cell before releasing them, either to the outside or into a phagocytic vesicle within the cell

Question 21

what features do cell walls have

Answer 21

they consist of a number of polysaccharides, such as cellulose

there is a thin layer, called the middle lamella, which marls the boundry between adjacent cell walls and cements adjacent cells together

Question 22

what is the single membrane around a vacuole called

Answer 22

the tonoplast

Question 23

what does a plant vacuole contain

Answer 23

a solution of mineral satls, sugars, amino acids, wastes and sometimes pigments such as anthocyanins