biology 4-5

Antibiotics

drugs that disable or kill infectious bacteria

most antibiotics are precise because

bind to structures found only in bacterial cells

Organisms are either

single-celled protists or multicellular

single celled

prokaryotes and protists

multicellular

(plants, animals, and most fungi)

Cell theory

**states that all living things are composed of cells and that all cells come from earlier cells**

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so every cell in your body was formed by division of a previously living cell

domains

Classify all life into three major groups

Bacteria & Archaea

composed of prokaryotic cells

Eukarya

include protists, plants, fungi, and animals, are composed of eukaryotic cells

Plasma membrane

separates the living cell from nonliving surroundings.

composed mostly of phospholipids arranged into a two-layer __phospholipid bilayer__ (fluid mosaic)

why are plasmas membranes fluid

because molecules can move freely past one another

why are plasma membranes mosaic

the diversity of proteins in the membrane

cellulose fibers

plant cell well

what does the plant cell wall do?

protect the cells

maintain cell shape

keep cells from absorbing too much water

extracellular matrix

most animal cells produce a sticky coat

Animal cells lack cell walls

cell junctions

structures that connect cells together into tissues, allowing the cells to function in a coordinated way

Problem

antibiotic resistance

Method

**individual soil bacteria isolated in separate compartments**

buried in the original soil

membranes allowed nutrients into each compartment but kept other bacteria species out

nucleus

the control center of the cell

nuclear envelope

**separated from the cytoplasm by a double membrane**

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on the outside

outside of the nucleus

Has pores in the envelope allow certain materials to pass between the center and the surrounding cytoplasm

chromatin

Within are long DNA molecules & associated proteins forming fibers

each form one chromosome

on inside

nucleolus

**where the components of ribosomes are made**

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on inside

Ribosomes

responsible for protein synthesis

components are

made in the nucleus then transported through the pores of the nuclear envelope into the cytoplasm, where ribosomes begin their work

some ribosomes

make proteins that remain within the cytosol

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Others make proteins that are incorporated into membranes or secreted by the cell

messenger RNA (mRNA)

DNA transfers its coded info to a molecule

how does the messenger mRNA work

exits the nucleus through pores in nuclear envelope & travels to the cytoplasm, where it binds to a ribosome

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a ribosome moves along the mRNA, translating the genetic message into a protein with a specific amino acid sequence

the endomembrane system in a cell consists of

the nuclear envelope

the endoplasmic reticulum (ER)

the Golgi apparatus

lysosomes

vacuoles

These membranous organelles are either physically connected or linked by vesicles

vesicles

sacs made of membrane

endoplasmic reticulum (ER)

**one of the main manufacturing facilities in a cell**

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produces an enormous variety of molecules is connected to the nuclear envelope

composed of interconnected rough and smooth ER that have different structures and functions

rough ER

refers to ribosomes that stud the outside of its membrane

Ribosomes attached to the rough ER produce proteins that will be

inserted into the growing ER membrane

transported to other organelles

eventually exported

transport vesicles

Some products are chemically modified & packaged that turn into this

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**made of membrane that bud off from the rough ER. dispatched to other locations in the cell**

smooth ER

lacks surface ribosomes

produces lipids, including steroids

helps liver cells detoxify circulating drugs

Golgi apparatus

works in partnership with the ER

receives, refines, stores, & distributes chemical products of the cell

lysosome

membrane-enclosed sac of digestive enzymes found in animal cells

Most plant cells do not contain it

Enzymes in a lysosome

break down large molecules such as proteins, polysaccharides, fats, and nucleic acids

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destroy harmful bacteria

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engulf and digest parts of another organelle

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sculpt tissues during embryonic development, helping to form structures such as fingers.

Two Functions of Lysosomes

digesting food

breaking down the molecules of damaged organelles

Vacuolese

large vesicles with a variety of functions

central vacuole of a plant cell

versatile compartment that may:

store organic nutrients

absorb water

contain pigments that attract pollinating insects or poisons that protect against plant-eating animals.

Central theme of biology

transformation of energy

Most of the living world runs on

energy provided by photosynthesis

Photosynthesis

**the conversion of light energy from the sun**

to: chemical energy of sugar & other organic molecules.

Chloroplasts

unique to the photosynthetic cells of plants and algae & the organelles that perform photosynthesis

Mitochondria

**produce ATP from the energy of food molecules**

*cells use ATP as the direct energy source for most of their work*

organelles in which cellular respiration takes place

are found in almost all eukaryotic cells

Chloroplasts & Mitochondria DNA

**contain their own DNA that encodes some of their own proteins made by their own ribosomes**.

Each contains a single circular DNA chromosome that resembles a prokaryotic chromosome & can grow and pinch in two, reproducing themselves

Endosymbiosis theory

evidence that mitochondria and chloroplasts evolved from ancient free-living prokaryotes that established residence within other, larger host prokaryotes

endosymbiont

living prokaryotes that established residence within other, larger host prokaryotes

Over time, mitochondria & chloroplasts

likely became increasingly interdependent within the host prokaryote, *eventually evolving into a single organism with inseparable parts*

cytoskeleton

a network of protein fibers extending throughout the cytoplasm

what does the cytoskeleton serves as

**both skeleton & “muscles” for the cell, for support & movement**

provides mechanical support to the cell

helps a cell maintain its shape

types of fibers made from different proteins in the cytoskelton

1\.Microtubules

2\. Intermediate filaments

3\. Microfilaments

Microtubes

hollow tubes of protein

microfilaments

thinner and solid.

what is the purpose of tubes

provides anchorage & reinforcement for many organelles in a cell, and some cells use them for movement

flagella & cilia

In some microtubules they are arranged

Flagella

propel cells through an undulating whiplike motion

occur singly, e.g. human sperm cells, but may also appear in groups e.g surface of protists

Cilia (singular, cilium)

generally shorter & more numerous

move in a coordinated back-and-forth motion

both cilia and flagella propel protists through water

may extend from nonmoving cells

what does human sperm want

rely on flagella for movement

cell as a machine that continuously and efficiently performs a variety of functions

movement

energy processing

production of various products

Cells control their chemical environment using

energy

enzymes

the plasma membrane

Energy

defined as the capacity to cause change

Some forms of energy are used to

perform work

Kinetic energy

energy of motion

Potential energy

s stored energy, energy that an object has because of its location or structure

Conservation of energy

explains that it is not possible to destroy or create energy

Energy can only be converted from one form to another

heat

is a type of kinetic energy contained in the random motion of atoms & molecules

all energy conversions generate it

Entropy

measure of disorder, or randomness, in a system

every time energy is converted from one form to another

entropy increases

chemical energy

The molecules of food, gasoline, and other fuels have a form of potential energy

Living cells & automobile engines use the same basic process to make the _______________ stored in their fuels available for work.

Cellular respiration

**the energy-releasing chemical breakdown of fuel molecules the storage of that energy in a form the cell can use to perform work**

Humans convert about 34% of our food energy to useful work

The rest is released by the breakdown of fuel molecules generates body heat

calorie

**is the amount of energy that can raise the temperature of 1 gram (g) of water by 1 c**

Food calories are kilocalories= 1,000 calories.

The energy of calories in food is used to fuel the activities of life.

what is used to generate molecules of ATP

Chemical energy released by the breakdown of organic molecules during cellular respiration

ATP (adenosine triphosphate)

acts like an energy shuttle

stores energy obtained from food

releases it later as needed

ATP energizes

other molecules in cells by transferring phosphate groups to those molecules

Phosphate transfer: atp energy

1\.helps cells change shape

2. enables the transport of ions and other dissolved substances across the membrane

3. drives the production of a cell’s large molecules.

Cells spend

ATP continuously

Cellular work

spends ATP

what happens when ADP is recycled?

phosphate are combined, using energy released by cellular respiration

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Up to 10 million ATPs are consumed & recycled each second in a working muscle cell

Metabolism

the total of all chemical reactions in an organism

most metabolic reactions

**require the assistance of enzymes**

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proteins that speed up chemical reactions without being consumed by the reaction

All living cells contain

thousands of different enzymes, each promoting a different chemical reaction

Activation energy

the energy that must be invested to start a reaction activating the reactants and triggering a chemical reaction

Enzymes enable metabolism to occur by

reducing the amount of activation energy required to break the bonds of reactant molecules

An enzyme is very selective in

the reaction it causes

substrate

**a certain reactant molecule**

Each enzyme recognizes as this

**induced fit**

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**The active site has a shape & chemistry that fits the substrate molecule**

the entry of the substrate induces the enzyme to change shape slightly, making the fit between the substrate and active site snugger

After the products are released from the active site, the enzyme can accept another molecule of its

substance

Structure/Function: Enzyme Activity

can function repeatedly • many are named for their substrates, but with an –ase ending

Certain molecules prevent a metabolic reaction by

binding to an enzyme &

disrupting its function

Some of these enzyme inhibitors are actually

substrate imposters that plug up the active site

In each case, an inhibitor disrupts the function of an enzyme by altering its shape

Membrane Function

Cells must also regulate the flow of materials to and from the environment

The plasma membrane consists of a double layer of fat (a phospholipid bilayer) with embedded proteins

Molecules are always

in motion

Diffusion

the movement of molecules to spread out evenly into the available space

Passive transport

is the diffusion of a substance across a membrane without the input of energy

a substance diffuses down its

concentration gradient from where the substance is more concentrated to where it is less concentrated

Substances that do not cross membranes spontaneously can be transported

via proteins that act as corridors for specific molecules

Facilitated diffusion

assisted transport, a type of passive transport

Osmosis

is the diffusion of water across a selectively permeable membrane