Cell Structure And Function

Plasma Membrane

Structure

About 45% lipid, About 50% protein, About 5% carbohydrate

Lipids are arranged in a bilayer (two layers).

Peripheral proteins attach to the membrane.

Integral proteins extend through the membrane.

Location

Envelops (surrounds) the entire cell.

Primary Function

Acts as a barrier for the cell.

Regulates what materials move into and out of the cell.

Cytoplasm

Structure

A mixture of: Water, Salts, Organic molecules

These combine to form a thick fluid and organized structures called organelles.

Location

The region between the plasma membrane and nucleus.

Primary Function

Site of cellular metabolism.

Supports other activities that help maintain the cell.

Cytoskeleton

Structure

A complex network of filaments and tubules.

Consists of: Microfilaments → made of actin filaments; Intermediate filaments Microtubules

Location

Found throughout the cytoplasm.

Suspended within the cytosol.

Primary Functions

Maintains cell shape

Helps with cell division

Helps with transport

Helps with movement

Organelles

Structure: Formed Bodies

Location: Suspended within cytosol

Function: Structures inside cells that perform different activities needed to maintain the cell.

Centrioles

Structure

Formed from nine groups of three microtubules.

These groups form a cylinder.

Location

Found near the nucleus in the centrosome.

Primary Function

Participate in cell division.

Help form spindle fibers.

Cilia

Structure

Long, slender projections of the plasma membrane of certain cells.

Location

Extend outward away from the cell surface.

Primary Function

Make rhythmic movements that propel fluids.

Microvilli

Structure

Numerous, tiny folds of the plasma membrane.

Increase the cell's surface area.

Location

Extend outward from the plasma membrane.

Primary Function

Increase plasma membrane surface area for: Absorption and

Secretion

Ribosomes

Structure

Very small, spherical structures.

Made of: 60% RNA , 40% protein

Location

Can be: Attached to the endoplasmic reticulum (ER) Unattached/free in the cytoplasm

Primary Function Site of protein synthesis.

Rough Endoplasmic Reticulum

Structure

Branching tubules that may be flattened or Tubular with ribosomes attached.

Location

Extends between the nucleus and plasma membrane.

Primary Functions

Synthesizes proteins Produces parts of the plasma membrane

Smooth Endoplasmic Reticulum

Structure

Branching tubules that may be: Flattened or Tubular

Does NOT have ribosomes attached.

Location Winds and twists throughout the cytoplasm.

Primary Functions Lipid and Carbohydrate assembly, Calcium storage and Detoxification

Golgi Apparatus

Structure

Series of flattened, disc-shaped sacs.

Location

Usually located near the nucleus.

Secretory vesicles are usually near the plasma membrane.

Primary Function

Prepares and packages cellular products for transport.

Mitochondria

Structure

Can be spherical or sausage-shaped Has an inner folded membrane.

Location

Randomly distributed throughout the cytoplasm.

Primary Function

Site where nutrients are broken down.

Produces ATP during cellular respiration.

Lysosomes

Structure

Small and spherical.

Location

Randomly distributed throughout the cytoplasm.

Primary Function

Contains hydrolytic enzymes.

These enzymes digest particles.

Peroxisomes

Structure

Small and spherical.

Location

Randomly distributed throughout the cytoplasm.

Primary Functions

Contains enzymes that break down fatty acids, neutralize free radicals, and detoxify drugs

Nucleus

Structure

A large structure surrounded by a double membrane.

Contains nucleic acids.

Location

Often located in the center of the cell.

Primary Functions Contains DNA. which regulates protien synthesis and cell division

nuclear envelope

Structure

A double membrane Contains large openings called nuclear pores.

Location

Surrounds the nucleoplasm.

Primary Function

Regulates movement of materials between:Cytoplasm

and Nucleoplasm

Nucleoplasm

Structure

Gel-like fluid. Consists of Water, Nucleic acids, and Proteins

Location

Contained inside the nuclear envelope.

Primary Function

Site of nucleic acids (DNA and RNA).

nucleoli

Structure

Small spheres containing: RNA and Proteins

Location

Grouped in an area of the nucleoplasm.

Primary Function

Site of RNA synthesis.

Chromatin

Structure

Threadlike material made of: DNA and Proteins

Location

Found throughout the nucleoplasm.

Primary Function: DNA contains the genes, which control protein synthesis.