Cell organelles and their structure

Question 1

NUCLEUS

Answer 1

Contains most of the cell’s DNA. It is surrounded by a double membrane - NUCLEAR ENVELOPE (its continuos with rough ER) - it contains nuclear pores they control what may enter.

Here the DNA is used as the template to make mRNA - contains the code to produce protein.
Because it contains genetic information - is the control centre of the cell.

CHROMATIN is the complex of DNA and protein housed in the nucleus that is formed from the chromosomes.

The nucleolus - a region where rRNA complexes with proteins to form ribosomal subunits.

Question 2

RIBOSOMES

Answer 2

protein factories

Composed of rRNA and protein. They are sites of protein synthetisis in the cell.

Each one consists a large and a small subunit.

Free ribosomes - floating in the cytosol, they generally produce proteins that are used within the cell

Bound ribosomes - attached to the ER and make proteins destined for the export from the cell

Question 3

ENDOPLASMIC RETICULUM - ER

Answer 3

ER - a network of membranes and sacs whose internal area is cisternal space.

Smooth ER - synthesis of lipids, metabolism of carbohydrates, detoxification of drug and poisons

Rough ER - it’s associated with ribosomes. Ribosomes synthesize proteins. ER bound ribosomes, the polypeptide chains travel across the ER membrane into the cisternal space - within the proteins are packaged into transport vesicles.

Question 4

GOLGI APPARATUS

Answer 4

Proteins from the transport vesicles are modified, stored, shipped.

It consists of flattened sacs of membranes called CISTERNAE.

GS - have polarity, the cis face receives vesicles, the trans face ships vesicles.

Question 5

LYSOSOMES

Answer 5

Membrane bound sacs of hydrolytic enzymes that can digest large molecules, including proteins, polysaccharides, fats, nucleic acids.

• digestive enzymes : macromolecules to organic molecules

Question 6

VACUOLES

Answer 6

Membrane-bound vesicles

Question 7

CENTRAL VACUOLES

Answer 7

in plant cell; may concentrate and contain compounds not found in the cytosol.

It can make up 80% of the cell in plants.

THE BIGGEST DIFFERENCE BETWEEN PLANT AND ANIMAL CELL.

Question 8

MITOCHONDRIA

Answer 8

The sites of cellular respiration, the metabolic process that uses oxygen to generate ATP by extracting energy from sugars, fats.

Consist of outer and inner membrane - highly folded

mitochondrial DNA in the mitochondrial mix

Question 9

CHLOROPLASTS

Answer 9

the sites of photosynthesis

Question 10

PEROXISOMES

Answer 10

A single membrane-bound compartments in the cell responsible for various metabolic functions that involve the transfer of hydrogen from compounds to oxygen, producing hydrogen peroxide

They also break down fatty acids to be sent to the mitochondria for fuel and detoxify alcohol by transferring hydrogen from the poison to oxygen.

Question 11

CYTOSKELETON

Answer 11

is a network of protein fibres that runs throughout the cytoplasm, where is responsible for support, motility and regulating some biochemical activities. Three types of fibres make up the cytoskeleton.

MICROTUBULES - made of the protein tubulin, are the largest of the cytoskeleton fibers. They shape and support the cell. They separate chromosomes during mitosis and meiosis are the structural components of cilia and flagella.

MICROFILAMENTS - composed of the protein actin.

INTERMEDIATE FILAMENTS - they are more permanent fixtures in the cell and fixing the position of the organelles.

Question 12

CENTROSOMES

Answer 12

They are a region located near the nucleus from which microtubules grow.

Centrosomes contain CENTRIOLES IN ANIMAL CELLS.

Question 13

CENTRIOLES

Answer 13

Are located within the centrosomes of the animal cells, where they replicate before cell division.

Question 14

CELL WALL

Answer 14

Of a plant protects the plant and helps maintain its shape. It is outside the plasma membrane. the primary component of cell walls is the carbohydrate cellulose.

Question 15

PLASMODESMATA

Answer 15

Are channels that perforate adjacent plant cell wall and allow the passage of some molecules from cell to cell

Question 16

EXTRACELLULAR MATRIX - ECM

Answer 16

It greatly strengthens tissue and serves as a conduit for transmitting external stimuli into the cell, which can turn genes on and modify biochemical activity.

TIGHT JUNCTIONS - are sections of the animal cell membrane where two neighbouring cell are fused, making the membranes watertight

DESMOSMES - fastens adjacent animal cells together, functioning like rivets to fasten cells into strong sheets.

GAP JUNCTIONS - provide channels between adjacent animal cells through which ions, sugar, communication molecules and other small molecules can pass.