CELLS Structures and Functions. Basic Parts of All Cells 1.Plasma membrane – barrier between in and outside of cell 2.Cytoplasm – region inside plasma.

CELLSStructures and Functions

Basic Parts of All Cells1. Plasma membrane – barrier

between in and outside of cell

2. Cytoplasm – region inside plasma membrane

• Cytosol – includes molecules and small particles but not organelles

3. Genetic material

4. Ribosomes

Organelles!Eukaryotic Cell

Nucleus

The Nucleus1. Most obvious structure (5μm)2. Most eukaryotic cells contain a

nucleus3. Function:

• Controls most functions of cell• Houses and protects genetic

information

4. Structure:• Nuclear envelope – double membrane

layer contains genetic contents; porous – materials enter and exit

• Nucleoplasm – jelly like fluid filling nucleus

• Nucleolus – dense area where ribosomes are made

5.Processes:

• Cell Division

When cell is not dividing - DNA exists as chromatin: long, thin structures

When cell is about to divide - DNA condenses to form chromosomes: structures made of DNA and protein

• Transcription – DNA converted to RNA in the nucleus

Cell Division

Chromatin

Chromosome

Mitochondria

Mitochondria1. Size: 1-10 μm long2. Function:

• Transfer energy from organic molecules to adenosine triphosphate (ATP) – powers most cellular reactions

3. Structure: inner & outer membrane

• Outer – separates mitochondria from cytosol

• Inner – many folds (cristae) that capture and store energy

• Mitochondrial DNA – have own DNA• THEORY: mitochondria originated

from prokaryotic cells

4. Processes:• Cellular respiration – enzymes in

matrix aid in formation of ATP by extracting energy from food sources

Ribosomes

Ribosomes1. small, spherical (< 25 nanometers)2. Function:

• Build proteins• Free ribosomes – make proteins

used in cytosol (Ex: enzyme)• Bound ribosomes – make proteins

used in membranes, packaging, and elsewhere in body

3. Structure:• Manufactured partly in nucleolus

(protein & RNA), completed in cytoplasm

• Have small and large subunit

Endoplasmic Reticulum

Endoplasmic Reticulum (ER)

1. System of cisternae - membranous tubes & sacs2. Continuous with nuclear membrane3. Function – moves molecules from one part of the

cell to another4. Structure – Rough and Smooth

1. Rough ER – covered with ribosomes; involved in making proteinsa. Secretory proteins – secreted in vesicles (Ex:

digestive enzymes)b. Membrane proteins – inserted in membranes

2. Smooth ER – no ribosomes; builds lipids, produces steroid hormones, detoxifies drugs and poisons

Golgi Apparatus

Golgi Apparatus1. System of cisternae stacked up2. Function:

a. Manufacturing, warehousing, sorting, shippingb. Work with nearby vesicles coming from ER –

vesicle contents modified, given “address label (carbohydrate label),” transported to other parts of cell

3. Structure:a. Distinct polarity – membranes on opposite ends

have different thickness & molecular composition

b. Two poles: 1. Cis (same side) – receives materials from ER2. Trans (opposing side) – vesicles bud off & are

transported/exported

Vesicles

1. Small, spherical shaped sacs2. Function:

a. Migrate to and merge with cell membrane

b. Release contents outside of cell

3. Structure:a. Single membraneb. Different types (lysosomes,

peroxisomes)

Lysosomes

1. Structure – bud from Golgi, contain digestive enzymes – each vesicle is specific!

2. Function – Break down macromolecules (proteins, carbohydrates, nucleic acids)

3. Processes:1. Autophagy – Digestion of worn-out

organelles2. Autolysis – Digestion of damaged or

extra cells when time for cell to die3. Phagocytosis – Cell eating4. Receptor-mediated endocytosis

Vesicles

Peroxisomes

1. NOT produced in Golgi, contain

different enzymes, such as Catalase

2. Enzymes involved in reactions

3. Different types: Ex: Detoxify alcohol and other drugs

4. Break down fatty acids

Vacuole

1. Membrane bound storage structures, contains fluid

2. Types:– Food – stores nutrients– Contractile – contract, dispose of

excess water– Plant central vacuole much larger

than animal

Vacuoles

Centriole

Centrioles1. Animal cells ONLY!2. Organize cell structure during

division3. 2 short cylinders of microtubules

Part of cytoskeleton

Cytoskeleton• Provides shape and support

• 3 structural elements– Microfilaments (Actin)- 2 strands intertwined;

POLAR – can be used in cell movement, muscle contraction, cell division

– Intermediate fibers – NONPOLAR - anchor nucleus and other organelles in place, maintain shape

– Microtubules – hollow tubes made to maintain cell shape, hold organelles in place, POLAR – used in movement of chromosomes during division & organelles (like a railroad track) via the use of kinesins

Plastid- found in plants and algae. Contain pigments used in photosynthesis

Amyloplast- plant specific, no pigment. Function: synthesis and storage of starch

Chromoplast– responsible for carotene(orange), xanthophylls (yellow) and red pigments.