Unit 2

Cell biology

Definition

In psychology cell biology comes into play because the brain and nervous system - which underlie all the thoughts, emotions and behaviour, are made of cells. Understanding these cells and how they work helps explain psychological processes at biological level.

Q- what is cell biology in psychology?

Cell biology, also called cytology, in psychology focuses on the study of nerve cells (neurons) and supporting cells (glial cells) in the nervous system.

It examines their structure, their function, how they communicate and change with experience

Key cell types

1. Neurons (check intro)

   • basic functional unit of nervous system.

   • specialised to transmit information via electrical impulses and chemical signals

   • parts

     • dendrites → receive signals

     • cell body (soma) → contains nucleus, integrates signals

     • axon → transmits signals to other cells

     • axon terminals → release neurotransmitters

2. Glial cells

   • support and protect neurons

   • types

     • astrocytes → regulate nutrients and maintain chemical environment.

     • oligodendrocytes (CNS) and Schwann cells (PNS) → make myelin sheath for faster impulse conduction.

     • microglia → act as immune defence in the brain.

CELL BIOLOGY

Structure and function of cell

the term cell was first used by Robert Hooke in 1664, in the —— like structure which he observed under primitive microscope. Contemporary work or Hooke and Leeuwenhoek discouraged red blood cells and variety of microorganisms using single lens microscope.

In 1831 while investigating the fertilisation mechanism of plant Robert Brown noted the existence of structure within the cell which he terms as nucleus.

In 1838 Schleiden and Schwann indicated the similarity of plant cell structure to those observed in animal tissues.

In 1830 it was proposed that all living organism are made up of cells which are the basic structural and functional units of life. This concept forms the base for cell theory proposed by Schleiden and Schwann.

Some organisms like bacteria and protozoa are unicellular while others are multicellular organisms like plant and animal cell.

Cells in all living beings show similar and some common structural features and many similar functions.

Biochemical composition of cells

1. Oxygen → 68%

2. Carbon → 18%

3. Hydrogen → 10%

4. Nitrogen → 3%

5. Calcium → 1.5%

6. Phosphorus → 1%

7. Potassium → 0.20%

8. Sodium → 0.15%

9. Chlorine → 0.15%

10. Sulphur → 0.25%

11. Magnesium → 0.05%

composition of biomolecules

*insert photo*

Domains of life

The earlier biologists believed that all life on earth belong to 2 primary cells named Eukaryotes and Prokaryotes.

Eukaryotes include animal, plant and fungi.

Prokaryotes include bacteria and all remaining microscopic organisms.

Both differ in complexities and possess some basic properties are as below →

1. Plasma membrane is common features.

2. All cells store information in genes.

3. Protein controls the structure and function in cells.

Differences →

Cell organelles and their functions

1. Cell membrane

   • All cells are bound by membrane called cell membrane or plasma membrane, it provides shape, mechanical strength to cells and protect it from external environment.

   • It is made up of lipids and proteins. There are various models proposed for plasma membrane. The most common model is the fluid mosaic model proposed by Singer and Nicolson in 1972.

   • As a major function it is a selective barrier between cell and its surroundings and it regulates various molecules in and out of the cell.

2. Nucleus

   • In all eukaryotes, nucleus represents the most prominent organelles. In leading cells, it is surrounded by double membrane with pores which allow selective passage of materials in and out of the nucleus.

   • It is the control centre of the cell, contains chromatin, composed of nucleic acids ( RNA & DNA), associated with proteins.

   • The nucleus and its associated chromosomes undergo profound changes at the time of cell division during which genetic material duplicated and identical copy is shared between 2 daughter cells.

3. Endoplasmic reticulum

   • The cytoplasm of most eukaryotic cells contain complex networks of internal membrane called Endoplasmic reticulum, which forms channels within the cells.

   • It is responsible for different synthesis of lipids and proteins

   • They are of 2 types →

     • Smooth endoplasmic reticulum

     • Rough endoplasmic reticulum

4. Golgi Body

   • The Golgi body plays a key role in modifying newly synthesised proteins and make them reach their appropriate destination.

5. Mitochondria

   • Mitochondria are membrane bound cell organelles that generate most of the cell’s energy in the form of Adenosine Triphosphate (ATP) through a process called cellular respiration.

   • Mitochondria have their own independent DNA ( mDNA/mtDNA ). These are inherited from the mother only.

6. Lysosomes

   • Membrane bound organelle that is found in all mammalian cell, except RBC. It is called the ‘suicide bag’ of the cell. It’s primary function is to breakdown cellular waste and debris by engulfing it with hydrolytic enzymes.

Cell theory

Widely accepted hypothesis of how most life on Earth operates is known as cell theory.

Three main postulates of cell theory →

1. All living beings are made up of cells.

2. Cells are basic building blocks for developing tissues, organs and fully developed living creatures.

3. All cells arise from pre-existing cells.

The modern interaction of cell theory consists of the following points →

• Energy transfer takes place through cells.

• DNA transfers from cell to cell carrying genetic information

• All cells share the same primary clinical composition

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