CELL PART OF THE DAY

Chapter 7: Cell Structure and Function

Cell Membrane

Cell membranes are composed of two phospholipid layers.

•Cell membrane is flexible, not rigid

•The cell membrane has two major functions.

• forms a boundary between inside and outside of the cell

• controls passage of materials

Inside Cell

Outside CellCell Membrane

Cell Wall

•Found in plants, algae, fungi, and most bacteria.

•Cell membrane surrounded by cell wall

•A cell wall provides rigid support to the cell

•Gives protection, support, and shape to the cell

•Can adhere to each other to help support an entire organism

Cytoplasm vs. Cytosol

Cytoplasm: Jelly like substance that contains dissolved molecular building blocks- such

as proteins and nucleic acids. Fills the space between the nucleus and cell

membrane (includes organelles and fluid).

Cytosol: just fluid portion, not including organelles, consists of mostly water

Many chemical reactions happen in the cytoplasm, where water acts as an important solvent.

Cytoskeleton

• supports and shapes cell (Microtubules)

• helps position and transport organelles (Microtubules)

• aids in cell movement (Microtubules)

• provides strength (Intermediate filaments)

• assists in cell division (Microfilaments)

Microtubules :green

Microfilaments: red

Cytoskeleton also includes flagellum

and cilia

Have a specialized arrangement of microtubules responsible for their locomotive ability.

Flagella: long structures that function as propellers in locomotion

Cilia: short structures that work like oars

Nucleus and Nucleolus

• Storehouse for most of the genetic information (DNA)

• Two major demands on the nucleus: (1) DNA must be carefully protected and (2)

DNA must be available for use at proper times.

• Nuclear Envelope: double membrane enclosing genetic material

• Nucleolus: dense region where ribosomal RNA is assembled, processed, & packaged

with proteins into ribosomal subunits

Endoplasmic Reticulum (ER)

• Interconnected network of thin folded membranes (many creases and folds) which form a maze of enclosed spaces

• Many processes occur in the ER, a couple examples are production of proteins and lipids

• Rough ER: Ribosomes on the ER

• Smooth ER: Doesn’t have ribosomes on it. Makes lipids and performs many other specialized functions such as breaking down drugs and alcohol.

Ribosomes

• Found on the Rough ER and within the cytoplasm

• Tiny organelles that link amino acids together to form proteins.

• Ribosomes are made up of proteins and RNA , but are also responsible for protein synthesis.

• After assembly in the nucleolus, ribosomes pass through the nuclear pores into the cytoplasm, where most protein synthesis occurs.

Golgi Apparatus

• Proteins formed in the ER generally move to the Golgi Apparatus

• Golgi Apparatus consists of closely layered stacks of membrane-enclosed spaces that

process, sort, package, and deliver proteins.

• Some packaged proteins are stored within the Golgi apparatus for later use, while

other are transported to other organelles within the cell, and some are carried to the

membrane and secreted outside the cell.

Mitochondria

•Mitochondria supply energy to the cell.

•Has two membranes: inner and outer membrane

•Inner membrane has many fold to increase surface area

•Convert molecules from food eaten into useable energy known as ATP

•Has its own ribosomes and DNA

Vesicles and Lysosomes

•Vesicles: in general a small membrane bound sacs that are formed and recycled when needed.

• Proteins are packaged within vesicles which store, transport, or secrete the proteins.•Lysosomes: membrane bound organelles that contain enzymes. Defend the cell from invading bacteria and viruses and also break down worn-out cell parts.

•Numerous in animal cells. As of now, it is unknown if they are present within plants

LysosomeVesicle

Chloroplasts

•Chloroplasts carry out photosynthesis and convert solar energy to chemical energy through a series of

complex chemical reactions.

•Have both an inner and outer membrane, along with stacks of disc-shaped sac within the inner

membrane called thylakoids which contain chlorophyll.

•Chlorophyll: a light-absorbing molecule that gives plants their green color and plays a key role in

photosynthesis.

Vacuole

•A fluid filled sac used for the storage of materials

needed by a cell.

• Materials may include water, food

molecules, inorganic ions, and enzymes

•Most animal cells contain small vacuoles, however

plants contain one central large vacuole

•In plants: responsible for strengthening the cell and

helps to support the entire plant

Centrioles are tubes found in the centrosomes.

Centrioles help divide DNA.

Centrioles form cilia and flagella.

Centrosome and Centrioles