AP Biology chapter 4

The cell is

The simplest collection of matter that can be alive

Though cells can differ from one another they share

Common features

Most cells are

Too small to be seen by the unaided eye

Light microscope

Visible light is passed through a specimen and then through glass lenses

Lenses

Refract (bend) the light so that the image is magnified

Three important parameters of microscopy

1) Magnification

2) Resolution

3) Contrast

Magnification

The ratio of an objects image size to its real size

Resolution

The measure of the clarity of the image or the minimum distance between two distinguishable points

Contrast

The difference in tightness between the light and dark areas of the image

LMs can magnify up to

1000 times the size of the actual specimen

Various techniques

Enhance contrast and enable cell components to be strained or labeled

Scanning electron microscopes

Focus a beam of electrons onto the surface of a specimen producing images that look 3d

Transmission electron microscopes

Focus a beam of electrons through a specimen

Labeling molecules or structures with

Fluorescent markers improves tissues and cells

Confocal

And other types of microscopy have sharpened images of tissues and cells

New techniques and labeling have

Improved resolution so that structure as small as 10-20 smth can be distinguished

Cryo electron microscopy

Preserves specimens at extremely low temps

Cell fractionation

Breaks up cells and separates the components using centrifugation

Cell components separate based on their

Relative size

Cell fractionation

Enables scientists to determine functions of organelles

Biochemistry and cytology help

Correlate cell function with structure

Organisms of the domains bacteria and archaea consist of

Prokaryotic cells

Protists, fungi, animals, and plants all consist of

Eukaryotic cells

Basic features of all cells

1) plasma membrane

2) cytosol (semi fluid substance)

3) chromosomes (carry genes)

4) ribosomes (make proteins)

Prokaryotic cells (3)

1) no nucleus

2) dna in unbound region called nucleoid

3) no membrane bound organelles

Eukaryotic cells are

Larger than prokaryotic cells

Plasma membrane

Selective barrier that allows passage of oxygen nutrients and waste to service the volume of every cell

General structure of a biological membrane

double layer of phospholipids

Metabolic requirements set

Upper limits on the size of cell

Small cells have

Greater surface area to volume ratio

Eukaryotic cell has

Extensive membrane that divide cells into compartments-organelles

Plasma membrane participate directly in the

Cell’s metabolism

Nucleus

Contains most of the cell’s genes and is usually the most conspicuous organelle

Nuclear envelope

Enclosed nucleus separating it from the cytoplasm

Nuclear membrane is

Double membrane consisting of lipid bilayers

Nuclear pores

Regulate the entry and exit of molecules

Nuclear lamina

Maintains shape of nucleus and is composed of protein filaments

Chromosomes

in nucleus, the discrete units that dna is organized into

Chromosome is one long

DNA molecule associated with proteins

Chromatin

DNA and proteins of chromosomes together

Chromatin condenses to form discrete chromosomes as

A cell prepares to divide

The nucleolus

Located within the nucleus and is the site of ribosomal rna synthesis

Ribosomes

Complexes of ribosomal rna and protein

Ribosomes carry out

Protein synthesis in two locations:

1: cytosol (free ribosomes)

2: Rough ER or nuclear envelope

Components of endo membrane system

Nuclear envelope, er, Golgi apparatus, lysosomes, vacuoles, membrane

Smooth er:

1 synthesizes lipids

2 metabolizes carbs

3 detoxifies drugs and poisons

4 stores calcium ions

Rough er has ribosomes which

Secrete glycoproteins (proteins covalently bonded to carbs)

Distributes transport vesicles, protein surrounded by membranes

Is a membrane factory for the cell

Golgi apparatus

Consists of flattened membranous sacs called cisternae

Golgi apparatus

Modifies products of er

Manufactures certain macromolecules

Sores abs packages materials into transport vesicles

Lysosome

Membranous sac of hydrolytic enzymes that can digest macromolecules

Phagocytosis

Forms a food vacuole

Autophagy

Lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules

Vacuoles

Large vesicles derived from er and Golgi app

Contractile vacuoles

Found in many freshwater protists, pump excess water out of plants

Central vacuoles

Found in many mature plant cells, serve as a repository for inorganic ions, including potassium and chloride

Mitochondria

Sites of cellular respiration, a metabolic process that uses oxygen to generate atp

Chloroplasts found in plants and algae are sites of

Photosynthesis

Peroxisomes

Oxidative organelles

Endosymbiant theory

Mitochondria and chloroplasts display following similarities with bacteria

Early ancestors of eukaryotic cells

Engulfed a nonphotosynthetic prokaryotic cell which formed relationship with its host

Inner membrane has two compartments

Intermembrane space and mitochondrial matrix

Some metabolic steps of

Cellular respiration are catalyzed in the mitochondrial matrix

Cristae

Present large surface area for enzymes that synthesis atp

Chloroplasts contain the

Green pigment chlorophyll

Chloroplast structure includes:

1 thykaloids (membranous sacs stacked to form a granum)

2 stroma (internal fluid)

Plastids

The chloroplast is one of a group of plant organelles

Peroxisomes

Produce hydrogen peroxide and then convert it to water

Cytoskeleton

Network of fibers extending throughout the cytoplasm

Organizes the cell’s structures and activities

Helps support the cell and maintain its shape

Cytoskeleton

Provides anchorage for many organelles and molecules and is very dynamic

Cytoskeleton

Cytoskeleton interacts with motor proteins to produce

Motility

Three main fibers that make up cytoskeleton

Microtubules (thickest)

Micro filaments (thinnest)

Intermediate filaments (middle)

Mucrotubules

Hollow rods constructed from glubukar protein diners called tubulin

Microtubules function:

Shapes and supports cells

Guide movement of organelles

Separate chromosomes during cell division

Centrosome

Microtubules organizing center

Centrosome has pair of

Centrioles each with nine triplets of Microtubules arranged in a ring

Flagella are limited while

Cilia occur in large numbers

C and f differ in

Beating patterns

C and f share common structure

Microt sheathed by plasma membrane

Basal body that anchors

Motor protein called Dynein which drives bending movements of c and f

Microf

Thin solid rods built from molecules of globular actin subunits

Micro f structures role

Bear tension

Bundles of micro f

Make up core of microvilli of intestinal cells

Micro f that function in cellular motility interact with the

Motor protein myosin

Myosin and actin interact to cause

Muscle contraction

Intermed f

Only found in some animals (vertebrates)

Reinforce cell shape and fix organelles

More permanent cytoskeleton elements

Cell wall

Extracellular structure that distinguishes plant cells from animal cells

Cell wall protects plant cells and

Maintains its shape and prevents excessive uptake of water

Plant walls are made of

Cellulose microfibrils

Cell walls have multiple layers

Primary cell wall: relatively thin and flexible

Middle Pamella: thin layer between primary walls of adjacent cells

Secondary cell wall (in some cells): added between the membrane and primary

Animal cells lack walls but are covered by ECM

Extracellular matrix is

Made up of glycoproteins such as collagen proteoglycans and fibronectin

ECM proteins bind to

Cell surface receptor protons in the membrane called integrins

Neighboring cells in an animal or plant often adhere interact and communicate through

Direct physical contact

Plasmodesmata

In plant cells

Are channels that perforate plant cell walls

Animal cells have three cell junctions

Tight

Gap

Desmosomes

All are especially common in epithelial tissue

Cellular functions arise from

Cellular order