Transcript Chapter 7 Cell Structure and Function

CHAPTER 7
CELL STRUCTURE & FUNCTION
7.2 Eukaryotic Cell Structure

Objectives:
 Describe
the function of the nucleus
 Describe the functions of the major cell organelles
 Identify the main roles of the cytoskeleton
7.2 Eukaryotic Cell Structure

Cell organization
Organelles



“little organs”
the specialized
structures within the
cell that perform a
function
Cytoplasm

Description
 The
fluid that fills the entire cell
 The portion of the cell outside of the nucleus

Function
 Makes
up about 70% of the cells volume.
 Most of the cells chemical reactions occur here
The Nucleus

Function


“Control center” of the cell
Contains nearly all of the cell’s DNA (the coded
instructions for making proteins & other important
molecules)
Nuclear Envelope

Description



Envelope or layer around
nucleus
Made of 2 membranes
Function:

Allows for materials (like
RNA, proteins, & other
molecules) to come in and
out through pores
Inside the Nucleus

Chromatin
 Description:
 Looks
like granular material
 Usually spread throughout the nucleus
 Function:
 During
cell division, it condenses to form chromosomes
 Made of DNA bound to protein

Chromosomes
 Description:
Threadlike structures, often in X shape
 Function: Contain genetic information
Inside the Nucleus
Chromosome
Inside the Nucleus

Nucleolus


Description: Small, dense
area in nucleus
Function: Directs the
formation of ribosomes
Ribosomes

Description:
 Small
dots
 Found throughout cytoplasm
 Pieces of RNA & protein

Function:
 Proteins
are assembled on
these
 Build proteins based on
instructions from DNA
Endoplasmic reticulum – “ER”

Description



Function



folded membranes
Surrounds nucleus
Makes lipids for the cell
membrane
Makes proteins & other
materials that are
exported from the cell
Two types- rough and
smooth
Rough ER
 Description:
Has ribosomes on its surface
 Function:
 Modifies
proteins
 Produces proteins that will eventually be secreted out of the
cell
Smooth ER
 No
ribosomes
 Has enzymes that carry out
certain tasks, like making
membrane lipids & the
detoxification of drugs
 Liver
cells usually contain
large amounts of smooth ER
Right: rough ER; Left: smooth ER
Golgi Apparatus

Description:



Stack of flat discs
NOT surrounding nucleus
Function:

Modifies, sorts, & packages
proteins & other materials
from the ER for storage in the
cell or release outside the cell
Lysosomes
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Description:


Small balls or membrane
‘pockets’
Function:


The “clean-up crew”
Filled with enzymes that break
down




Lipids
Carbohydrates
Proteins
Cellular debris
Lysosomes (cont)



Have been linked to diseases, such as Tay Sach’s
Tay Sach’s is a disorder that is caused by a genetic
defect that prevents the formation of an essential
enzyme that breaks down lipids
These lipids build up in the body and can cause
nerve damage; prognosis is not good
Peroxisome

Description:
 Looks
like lysosomes – small balls or membrane
‘pockets’

Function:
 Contains
enzymes such as catalase
 Hydrogen peroxide is broken down here
Vacuoles

Description:


Large sac-like, membrane
enclosed structures
Function:


Store water, salts, proteins,
& carbohydrates
Pressure allows plants to
support heavy structures
Mitochondria

Description:


Oval with folded membrane
inside
Function:


“Powerplant” of the cell
Changes the chemical energy
stored in food into compounds
that are more convenient for
the cell to use (ATP)
Chloroplast

Description
2
membranes surround
the organelle
 Stacks of membranes
inside- grana
 Green
Chloroplasts

Function:


Capture energy from
the sun & convert it into
chemical energy –
photosynthesis!
Contains chlorophyllgreen pigment
Cytoskeleton

Description:


a framework of filaments
throughout the cell
Function:



Helps cells keep its shape
Helps the cell move
Made up of microfilaments
and microtubules
Cytoskeleton
Microfilaments

Description:
 Branching

threadlike structures
Function:
 Help
cell maintain shape & allow it
to move
 Assembly and disassembly cause
amoeboid movement
 Made up of a protein called actin
Microtubules

Description:
 Hollow
tubes in cytoskeleton
 made up of proteins known as tubulins

Function:
 Help
cells maintain shape
 Helps separate chromosomes in cell division
 Builds projections from the cell surface - cilia & flagella
Centrioles

Description:



Function:


Located near the nucleus
A pair of short cylinders
Help organize cell division
Only in animal cells