Lect 9 - nucleus

Flashcards based on lecture notes about the nucleus and ribosomes structure and function.

What are ribosomes made of?

Ribosomal RNA folded around proteins

Where are bound ribosomes found?

Rough Endoplasmic Reticulum (rER)

Where are free ribosomes found?

Cytoplasm

What is the main function of ribosomes?

Translation (protein synthesis)

What will affect the number of ribosomes a cell has?

Demand for protein synthesis

What does the nucleus contain?

Most of the cell's genes

Where else can genes be found in a cell, besides the nucleus?

Mitochondria and chloroplasts

What is the main function of the nucleus?

Stores inherited genetic information and acts as the cell's control center

What surrounds the nucleus?

Nuclear envelope

How many membranes make up the nuclear envelope?

Two (inner and outer)

What is the space between the inner and outer membranes of the nucleus called?

Perinuclear space

What is the composition of nuclear membranes?

Phospholipid bilayer

Which organelle is the outer nuclear membrane continuous with?

Endoplasmic Reticulum (ER)

What is the nuclear lamina?

A layer of cytoskeleton located just under the double membrane, composed of intermediate filaments

What protein are intermediate filaments in the nuclear lamina made of?

Lamin

What is the function of the nuclear lamina?

Maintains the shape of the nucleus, provides structural support, and helps organize DNA packing

What are nuclear pores?

Channels made of proteins that span the nuclear envelope, forming the nuclear pore complex

What is the main function of nuclear pores?

Controls the movement of substances in and out of the nucleus

What moves from the nucleus to the cytoplasm?

mRNA, tRNA, and ribosomal subunits

What moves from the cytoplasm to the nucleus?

Signals, building materials, and energy

What does the nucleolus contain high concentrations of?

Genes that make ribosomal subunits

Is the nucleolus membrane bound?

No, it is a non-membrane bound region

How long is the DNA in each human cell?

Roughly 2.5 meters

What proteins do DNA helixes interact with to pack DNA?

Histones (H2-H4)

What is a nucleosome?

Each 'bead' formed when DNA is packed by folding it around histones

What does the interaction of DNA with histone H1 cause?

The 10 nm fiber to coil to form the 30 nm fiber

During cell division, what does the 300 nm fiber coil to form?

Metaphase chromosomes

What is euchromatin?

Less electron-opaque, contains genes being used by a cell, unpacked DNA

What is heterochromatin?

More electron-opaque, contains genes not being used by the cell, packed up DNA

Why is euchromatin less tightly packed during transcription?

To allow access to specific DNA regions