AP Biology

The Cell

AP Biology

Cell characteristics All cells:

surrounded by a plasma membrane have cytosol

semi-fluid substance within the membrane cytoplasm = cytosol + organelles

contain chromosomes which have genes in the form of DNA

have ribosomes tiny “organelles” that make proteins using

instructions contained in genes

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Cell surface area to volume

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Prokaryotebacteria cellsProkaryote

bacteria cellsTypes of cells

Eukaryoteanimal cellsEukaryote

animal cells

- no organelles

- organelles

Eukaryoteplant cellsEukaryoteplant cells

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Types of cells

Prokaryotic cell DNA in nucleoid

region, without a membrane separating it from rest of cell

Cell wall present in all

Eukaryotic cell chromosomes in

nucleus, membrane-enclosed organelle

Cell walls present in fungi and plants only

More complex Membrane bound

organelles present

Prokaryotic vs. eukaryotic cells

AP Biology2005-2006The prokaryotic cell is much simpler in structure, lacking a nucleus and the other

membrane-enclosed organelles of the eukaryotic cell.

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Why organelles? Specialized structures

specialized functions cilia or flagella for locomotion

Containers partition cell into compartments create different local environments

separate pH, or concentration of materials distinct & incompatible functions

lysosome & its digestive enzymes

Membranes as sites for chemical reactions unique combinations of lipids & proteins embedded enzymes & reaction centers

chloroplasts & mitochondria

mitochondria

chloroplast

Golgi

ER

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Cells gotta work to live! What jobs do cells have to do?

make proteins proteins control every

cell function make energy

for daily life for growth

make more cells growth repair renewal

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Building Proteins Organelles involved

nucleus ribosomes endoplasmic reticulum

(ER) Golgi apparatus vesicles

nucleus ribosome ERGolgi

apparatusvesicles

The Protein Assembly Line

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smallsubunit

largesubunitRibosomes

Function protein production

Structure rRNA & protein 2 subunits combine 0.08m

RibosomesRough

ER

SmoothER

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Synthesizing proteins

cytoplasm

cisternalspace

mRNA

ribosome

membrane ofendoplasmic reticulum

polypeptide

signalsequence

ribosome

(Free)

(Bound)

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Rough ER function Produce proteins for export out of cell

protein secreting cells packaged into transport vesicles for export

Which cellshave lot of rough ER?

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Golgi Apparatus

Which cellshave lots of Golgi?

transport vesicles

secretoryvesicles

Function finishes, sorts, tags & ships cell products

like “UPS shipping department” ships products in vesicles

membrane sacs “UPS trucks”

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proteins

transportvesicle

Golgiapparatus

vesicle

smooth ER

rough ER

nuclear porenucleus

ribosome

cellmembrane protein secreted

cytoplasm

Making proteinsPutting it together…

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Smooth ER function Membrane production Many metabolic processes

synthesis synthesize lipids

oils, phospholipids, steroids & sex hormones

hydrolysis hydrolyze glycogen into glucose

in liver

detoxify drugs & poisons in liver ex. alcohol & barbiturates

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Lysosomes Function

little “stomach” of the cell digests macromolecules

“clean up crew” of the cell cleans up broken down

organelles

Structure vesicles of digestive

enzymes

only in animal cellsonly in animal cells

synthesized by rER, transferred to Golgisynthesized by rER, transferred to Golgi

Where old organelles

go to die!

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Cellular digestion Lysosomes fuse with food vacuoles

polymers digested into monomers pass to cytosol

to become nutrients of cell vacuole

lyso– = breaking things apart –some = body

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When cells need to die… Lysosomes can be used to kill cells when

they are supposed to be destroyed some cells have to die for proper

development in an organism apoptosis

“auto-destruct” process lysosomes break open & kill cell

ex: tadpole tail gets re-absorbed when it turns into a frog

ex: loss of webbing between your fingers during fetal development

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Fetal development

15 weeks

6 weeks

syndactyly

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Making Energy Cells must convert incoming energy to

forms that they can use for work mitochondria:

from glucose to ATP chloroplasts:

from sunlight to ATP & carbohydrates ATP = active energy carbohydrates = stored energy

+

ATP

ATP

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Mitochondria & Chloroplasts Important to see the similarities

transform energy generate ATP

double membranes = 2 membranes semi-autonomous organelles

move, change shape, divide internal ribosomes, DNA & enzymes

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Mitochondria Almost all eukaryotic cells have mitochondria

there may be 1 very large mitochondrion or 100s to 1000s of individual mitochondria

number of mitochondria is correlated with aerobic metabolic activity more activity = more energy

needed = more mitochondria

What cells would have a lot of mitochondria?

active cells: • muscle cells • nerve cells

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Chloroplasts Chloroplasts are plant organelles

class of plant structures = plastids amyloplasts

store starch in roots & tubers

chromoplasts store pigments for fruits & flowers

chloroplasts store chlorophyll & function

in photosynthesis in leaves, other green

structures of plants & in eukaryotic algae

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Mitochondria & chloroplasts are different

Organelles not part of endomembrane system Grow & reproduce

semi-autonomous organelles

Proteins primarily from free ribosomes in cytosol & a few from their own ribosomes

Own circular chromosome directs synthesis of proteins produced by own

internal ribosomes ribosomes like bacterial ribosomes

Who else has a circular chromosome not bound within a nucleus?

bacteria

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Endosymbiosis theory Mitochondria & chloroplasts were once

free living bacteria engulfed by ancestral eukaryote

Endosymbiont cell that lives within another cell (host)

as a partnership evolutionary advantage

for both one supplies energy the other supplies raw materials

& protectionLynn MargulisU of M, Amherst

1981 | ??

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Endosymbiosis theoryEvolution of eukaryotes

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Food & water storage

plant cellsplant cells

central vacuole central vacuole

contractilevacuole

contractilevacuole

food vacuoles food vacuoles

animal cellsanimal cells

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Vacuoles & vesicles Function

little “transfer ships” Food vacuoles

phagocytosis, fuse with lysosomes Contractile vacuoles

in freshwater protists, pump excess H2O out of cell

Central vacuoles in many mature plant cells

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Vacuoles in plants Functions

storage stockpiling proteins or inorganic ions depositing metabolic byproducts storing pigments storing defensive

compounds against herbivores

selective membranecontrol what comes

in or goes out

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Putting it all together, try labeling..

animal cellsanimal cells plant cellsplant cells

AP Biology2005-2006

What limits cell size? Surface to volume ratio

as cell gets bigger its volume increases faster than its surface area smaller objects have greater

ratio of surface area to volume

Why is a huge single-cellcreature not possible?

What cell organelle governs this?

6:1 ~1:1 6:1s:v

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Limits to cell size Metabolic requirements set upper limit

in large cell, cannot move material in & out of cell fast enough to support life

CHO

CHO

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NH3 O2

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NH3

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What’s the solution?

What process is this?

O2

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How to get bigger? Become multi-cellular (cell divides)

O2

CHO

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CO2

NH3aa

O2

CH

But what challenges do you have to solve now?

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CO2 CO2

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NH3

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CH

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CHO

O2

AP Biology2007-2008

Any Questions??