Cell Structure and Function - Science with Mr...

Cell Structure and Function

Biology 12Unit 1 – Cell Structure and Function

Inquiry into Life pages 45 – 59 and 68-69

Assignments for this Unit

● Pick up the notes/worksheet for this unit and the project

● There will be test at the end of the unit composed of 3 parts:– Matching keyterms

– Multiple Choice

– Labelling Diagrams

Cell Structure

Cell Theory

Cells are the functional unit of life

They comprise the smallest living unit of any organism

All cells come from pre-existing cells

Cells have a complex structure and many specialized organelles

These organelles often work inter-relatedly

The Nucleus

can be observed as the large, centrally located control centre of the cell

surrounded by a double layered membrane with pores

contains DNA – deoxyribonucleic acid

transcription and replication of DNA occurs here

The Nucleus

Nuclear Membrane

The Nucleus

The nuclear membrane (nuclear envelope) is what separates the nuclear material from the rest of the cytoplasm

It consists of a double membrane with pores

The Nucleus

Nuclear Membrane

Nuclear Pore

The Nucleus

Nuclear pores are channels that allow the passage of protein molecules into the nucleus and ribosomal subunits out of the nucleus

The pores are ~ 100 nm in diameter, or about 1/10 000 000 metres

The Nucleus

Nuclear Membrane

Nuclear Pore

Nucleolus

The Nucleus

The nucleolus is the most prominent structure in the nucleus, seen as a dark, spherical mass

The nucleolus produces ribosomal RNA (ribonucleic acid) = rRNA

rRNA joins with proteins to form the subunits of ribosomes

The Nucleus

Nuclear Membrane

Nuclear Pore

Nucleolus

Chromatin

The Nucleus

Chromatin is DNA and associated proteins in their uncoiled state

During interphase, chromosomes are unwound and and cannot be distinguished individually

The chromatin is immersed in a semifluid medium called nucleoplasm, which is like cytoplasm in the nucleus

The Nucleus

This is an electron micrograph of a liver cell nucleus

Notice:

nuclear membranenuclear membrane

nucleolusnucleolus

chromatinchromatin

nucleoplasmnucleoplasm

nuclear pores?nuclear pores?

Ribosomes

Ribosomes are small granules that appear dark in micrographs

They are involved in protein synthesis – forming chains of amino acids to make long protein molecules

Found on the endoplasmic reticulum and free floating in the cytoplasm

Ribosomes

Cytoplasmic ribosomes are often found in small clusters called polyribosomes or polysomes

These produce proteins that are used inside the cell

Ribosomes

Most ribosomes are found attached to the surface of the endoplasmic reticulum (ER)

These produce proteins to be transported outside the cell through the ER

Endoplasmic Reticulum

A series of membranous channels and flattened vesicles that are physically connected to the nuclear membrane

The ER works with other organelles to restrict chemical reactions to particular areas


Rough endoplasmic reticulum (rough ER) is superficially covered in ribosomes

These ribosomes synthesize proteins that enter the ER


Glycoproteins can be found on the extracellular side of the cell membrane

Proteins in the ER undergo modification, often forming a glycoprotein (protein with an attached carbohydrate molecule)


The proteins are then transported to the Golgi apparatus after processing


Smooth ER is a different form where there are no ribosomes on the surface

Smooth ER is continuous with rough ER

Different functions depend on the type of cell they are in

synthesize phospholipids that are on the synthesize phospholipids that are on the surface of the cell membranesurface of the cell membrane

testosterone production in testestestosterone production in testes

detoxifying in the liverdetoxifying in the liver


Smooth ER always forms vesicles to transport proteins to the Golgi apparatus

Vesicles

Vesicles are membranous sacs used to transport compounds around the cell

often formed from the Golgi apparatus or from the infolding of the cell membrane

Vesicles

Golgi Apparatus

Also known as Golgi bodies

Appear as a series of flattened pancakes (saccules)

Golgi Apparatus

Functions to process, package, and secrete

Further processes proteins

These proteins are packaged into vesicles

The vesicles are are formed from the Golgi apparatus membrane where they will secrete their contents from the cell membrane --> exocytosis

Vesicle Secretion

Lysosomes

Lysosomes are membrane-bound vesicles of digestive enzymes produced by the Golgi appartus

Essentially “suicide sacs”

Functions:

attach to food vacuoles to digest contentsattach to food vacuoles to digest contents

destroys old or malfunctioning organelles destroys old or malfunctioning organelles

Lysosome

Vesicle Budding and Secretion

http://www.sumanasinc.com/webcontent/animations/content/vesiclebudding.html



Mitochondria

Singular is mitochondrion

Site of cellular respiration

glucose + oxygen --> carbon dioxide + water glucose + oxygen --> carbon dioxide + water + ATP (energy)+ ATP (energy)

CC66HH

1212OO

66 + 6 O + 6 O

22 --> 6 CO --> 6 CO

22 + 6 H + 6 H

22O + ATP (energy)O + ATP (energy)

Cells use ATP (adensine triphosphate) for energy

The more active the cell, the more energy it requires, the more mitochondria they have

eg. muscle cells

Mitochondria

Mitochondria

Bound by a double membrane

Inner membrane invaginates (folds in) forming cristae, creating a high surface area for chemical reactions

Inner filled spaced called the matrix, containing its own DNA, ribosomes, enzymes

Chloroplasts

Chloroplasts are the site of glucose production in autotrophs through a process called photosynthesis

They convert solar energy into chemical energy

carbon dioxide + water -----> glucose + oxygen

6 CO2 + 6 H

2O -----> C

6H

12O

6 + 6 O

2

solar energy

solar energy

Chloroplasts

Chloroplasts have a double membrane

The inner fluid-filled space is called the stroma

Within the stroma are interconnected sacs called thylakoids

Thylakoids can be stacked to form grana (sing. granum)

Chloroplasts

Chloroplasts

Chlorophyll is a green pigment found within the thylakoid membranes in grana

Photosynthesis takes place specifically within the grana in chloroplasts

Also in the stroma is DNA, ribosomes, and enzymes, just like in the matrix of mitochondria!

Vacuoles

Membrane bound sac filled with water and/or chemicals

Used in animal cells for the digestion of food and the elimination of excess water through exocytosis

Used in plant cells for storage of metabolic wastes and “pressurizing” the cell

Cell Organelles Video

http://www.teachersdomain.org/resource/tdc02.sci.life.cell.organelles/



Cell Membrane

Also known as the plasma membrane

Separates the internal environment (intracellular) with the external environment (extracellular)

Composed of a phospholipid bilayer with various partially and wholly embedded proteins

Cell Membrane

Cell Membrane

The description of the membrane is called the Fluid Mosaic Model

It has a fluid consistency, like vegetable oil

Proteins are scattered within the membrane and on the intracellular surface

Cell Membrane

Cell Membrane

The phospholipid molecule is polar – two different parts

The phosphate “head” is hydrophilic (water loving)

The lipid “tail” is hydrophobic (water fearing)

Cell Membrane

Embedded within the lipid tails are cholesterol molecules which adds strength and stiffness to the membrane

Integral proteins are those that are embedded in the phospholipid bilayer

Peripheral proteins are those that occur on one side of the bilayer or the other

Glycoproteins are only on the extracellular side of the membrane

Cytoplasm

The semifluid medium between the cell membrane and the nucleus that contains organelles

Cell Membrane, Nucleus and Cytoplasm Video

http://www.teachersdomain.org/resource/tdc02.sci.life.cell.nucleus/



Cell Wall

Found only in plant cells – two types

It is a permeable, rigid structure that adds support and protection

Primary cell walls are composed of cellulose molecules

Secondary cell walls are composed of lignin, an even stronger molecule

Cell Wall (primary)

Cytoskeleton

Composed of a network of interconnected filaments and tubules

Maintains cell shape and structure, causes cells and organelles to move

Can be assembled and disassembled very rapidly

Three components:

actin filamentsactin filaments

microtubulesmicrotubules

intermediate filamentsintermediate filaments

Cytoskeleton

Cytoskeleton

actin filaments

intermediate filaments

microtubules

Cytoskeleton Tutorial

http://www.wiley.com/college/pratt/0471393878/student/animations/actin_myosin/index.html



Flagella and Cilia

Flagella and cilia are structures composed of microtubules and are used for locomotion

http://programs.northlandcollege.edu/biology/Biology1111/animations/flagellum.html



Summary

Organelles are membrane bound structures with varied and dedicated functions

Some organelles work together, forming a network to move materials throughout the cell

rough ER and smooth ERrough ER and smooth ER

Golgi apparatusGolgi apparatus

vesiclesvesicles

cell membranecell membrane

Summary

Mitochondria and chloroplasts are double-membrane bound energy-related organelles

Photosynthesis occurs in the grana of chloroplasts

Cellular respiration occurs in the matrix of mitochondria

Probable independent origin due to the presence of extranuclear DNA

Summary

All cells maintain their structure using a dynamic cytoskeleton composed of three types of elements

Plant cells have additional means of support – a permeable cell wall and a large central vacuole that maintains turgidity

Cell Structure and Function - Science with Mr...

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