CELL STRUCTURE

7.2

CELL ORGANIZATIONCell divided into: Cytoplasm (found outside the

nucleus) Nucleus

ORGANELLES

•Contains the DNA (hereditary info)•Surrounded by a nuclear envelope (double membrane)• Contains nuclear pores that allow material in and out of the nucleus

NUCLEUS

INSIDE THE NUCLEUS DNA is wrapped around proteins

called chromatin. Condensed chromatin is called a chromosome.

A nucleolus is found inside the nucleus.Ribosomes are manufactured here.

ORGANELLES THAT STORE,

CLEAN UP, AND

SUPPORT

Large, saclike, membrane-enclosed structures typically found in plants.Store chemicals, absorb water to

help cells expand

VACUOLES

All eukaryotic cells contains thesesmaller, saclike, membrane-

enclosed structures.Transport materials between

organelles as well as to and from the cell surface.

VESICLES

•Small organelles filled with enzymes.•Break down macromolecules into smaller parts that the cell can use •Remove damaged organelles

LYSOSOMES

CYTOSKELETON A network of protein filaments. Maintains the cell shape Helps the cell to move and to

move organelles within the cell.

2 types Microfilaments Microtubules

CYTOSKELETON

Microfilaments

Threadlike structures made up of protein

Supports & helps the cell to move

Microtubules Hollow structures

made up of protein Maintain cell shape Make up the

mitotic spindle & centrioles (organize cell division)

Make up cilia & flagella

ORGANELLES THAT

BUILD PROTEINS

•Small particles of RNA & protein• Found throughout the

cytoplasm •Site of protein synthesis!

RIBOSOMES

ENDOPLASMIC RETICULUM

Internal membrane system where lipids for the cell membrane, proteins, & other materials are made.

ROUGH ER

Rough ER can chemically

modify proteins in vesicles & then export

them to other areas.

SMOOTH ER Responsible for the synthesis of

membrane lipids and the detoxification of drugs.

Stack of flattened membranesModifies, sorts, & packages proteins for final destination in or out of the

cell.

GOLGI APPARATUS

MAKING PROTEINS

ORGANELLES THAT

CAPTURE AND

RELEASE ENERGY

CHLOROPLASTS

•Surrounded by 2 membranes and contain chlorophyll•Photosynthetic organelles in plants that capture the sun’s light energy and convert it into food for the cell.

MITOCHONDRIA

•Contains 2 membranes with the inner membrane highly folded•“powerhouse of the cell”•Releases energy from sugars by converting them into compounds the cell can use.

CELLULAR BOUNDARI

ES

CELL WALL Support, shape, and protect the

cell Allow water, oxygen, carbon

dioxide, & other substances to pass in and out

Animal cells do not contain a cell wall.

CELL MEMBRANE All cells are surrounded by this

plasma membrane Thin, flexible lipid bilayer Regulates what enters and exits

the cellTakes in food and eliminates waste

Provides support and protection

PHOSPHOLIPID THAT

COMPOSES MEMBRANE

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PHOSPHOLIPID BILAYER

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•Forms a barrier that keeps water out.

FLUID MOSAIC MODEL Fluid-like Proteins float around freely Carbohydrates attach to the proteins Many different molecules making up a

“mosaic” Selectively permeable/semipermeable –

allows some substances to pass and others cannot.Channels or pores allow materials to pass

CELL TRANSPORT

7.3

CONCENTRATION Mass/volume

Example-12 g of salt

3 liters water

Concentration would be

4g/l

MOVEMENT ACROSS A MEMBRANE In a solution, molecules are in

constant motion. Colliding and spreading out evenly.

Diffusion - molecules moving from an area of higher concentration to an area of lower concentration.

No energy needed!

EQUILIBRIUM Once solute has spread out evenly Balance

SELECTIVELY PERMEABLE Some substances allowed to

diffuse across the membrane and others not allowed.

FACILITATED DIFFUSION Protein channels in membrane that

allow material to cross it. Still moving from low to high

concentration.

OSMOSIS (EXAMPLE OF FACILITATED DIFFUSION)

Diffusion of water through a selectively permeable membrane through protein channelsIsotonic – the amount of

solute is equal on both sides

Hypertonic - super concentrated

Hypotonic – less concentrated

FIGURE 7.18 Movement of water into or out of a cell

creates a pressure known as osmotic pressure.Can cause a cell to shrivel or expand.

HYPERTONIC CELLS Not typically a problem. Our

cells are surrounded by fluid that is equal in concentration.

Plant cells are normally safecell wall contractile vacuoles pump out the water.

CELL SURROUNDED BY FRESHWATER Cell filled with proteins, salts,

and sugars. Place the cell in a freshwater

solution

1. Cell is considered hypertonic2.Water will enter the cell3. Cell will expand

Could eventually burst

ACTIVE TRANSPORT Material moving from an area of

low concentration to high concentration.

Requires energy!

TYPES OF ACTIVE TRANSPORT

Small molecules & ions are carried across the membrane by protein channelsLike a pump

NaK pump

MOLECULAR TRANSPORT

TYPES OF ACTIVE TRANSPORT

Endocytosis-cell pinches in, creates a vacuole around the objectPhagocytosis- “cell-eating”, extensions

of cytoplasm surround large food particles

Pinocytosis – “cell-drinking”, liquid taken in

BULK TRANSPORT

TYPES OF ACTIVE TRANSPORT

Exocytosis-removal of large amounts of material from a cell, vacuole membrane joins the cell membrane

BULK TRANSPORT

TYPES OF ACTIVE TRANSPORT

BULK TRANSPORT

HOMEOSTASIS AND CELLS

7.4