Lesson 2: Cytology

Most cells are too small to be seen with our eyes alone. Biologists like ___________ and ____________ actually invented their own light microscopes to study microscopic things.

Robert Hooke and Anton van Leeuwenhoek

Magnify objects up to 1000x

Light microscopes

Magnify objects to more than 200,000x

Electron microscopes

A camera can be fitted to either type of microscope to take pictures. These pictures are called ________.

Micrographs.

Can come out as colored images

Light micrographs

Are black-and-white images, but they can be artificially colourised

Electron micrographs

Unit of life, while all of these in your body may not look the same, they all have similar parts.

Cell

Each living cell consists of living material called?

Protoplasm

The protoplasm of a cell is made up of three parts:

The cell surface membrane, cytoplasm, and nucleus

It surrounds the cytoplasm of the cell. This is made up of lipids and proteins.

Cell surface membrane, or plasma membrane

This means that it allows only some substances to pass through it. Hence, the cell surface membrane controls substances entering or leaving the cell

Partially permeable membrane

It is the part of the protoplasm between the cell surface membrane and the nucleus. It is where most cell activities occur. It contains specialized structures called organelles

Cytoplasm

Carry out many functions in the cell

Organelles

Many organelles, such as _____, _______, and _____ are not visible through the light microscope. They can only be studied under the electron microscope

Mitochondria, centrioles, and ribosomes

The nucleus consists of a small round mass of denser protoplasm called ________, surrounded by a membrane called the ________

nucleoplasm, nuclear envelope

It controls cell activities such as cell growth and the repair of worn-out parts. It its essential for cell division. Cells without a nucleus, like the red blood cells of a mammal, are unable to divide

Nucleus

The nucleus contains one or more ____ and ______

Nucleoli and chromatin

A plant cell also has a _____ that encloses the entire plant cell, surrounding the cell surface membrane.

Cell wall

This cell wall is made of ________, it protects the cell from injury and gives the plant cell a fixed shape.

Cellulose

The cell wall is ________, it is also absent in animal cells

Fully permeable

What does the nucleus contain?

Nuclear envelope

Nucleoplasm

Nucleolus

Separates the contents of the nucleus from the rest of the cytoplasm

Nuclear envelope

Is the dense material within the nucleus

Nucleoplasm

Plays a part in the making of proteins in the cell

Nucleolus

This is a mass of long threat-like structures found within the nucleus.

Chromatin

Each chromatin thread is made up of proteins and a compound called ____________________ or ___.

Deoxyribonucleic acid or DNA

Hereditary information is stored here, it also carries instructions that a cell needs for carrying out its activities

DNA

When the cell is dividing, the chromatin threads condense and become high coiled structures called ___________

Chromosomes

The cytoplasm contains tiny structures called __________.

Organelles

Each ____ is specialized for a particular function. Examples of these are rough endoplasmic reticulum, smooth endoplasmic reticulum, ribosomes, Golgi apparatus, mitochondria and chloroplasts

Organelle

Consists of a network of flattened spaces lined with a membrane.

Rough endoplasmic reticulum

Its surface appears rough when viewed under the electron microscope. This is because small particles called ribosomes are attached to its outer surface. It is continuous with the nuclear envelope

Rough endoplasmic reticulum

Endoplasm =

Within the cytoplasm

Reticulum =

Network

Are small round structures. They are either attached to the membrane of the endoplasmic reticulum (ER) or lie freely in the cytoplasm. They are needed to synthesise proteins in the cell

Ribosomes

The ribosomes attached to the ER makes ____ that are usually transported out of the cell

Proteins

The ribosomes lying freely in the ____ make proteins that are used within the cytoplasm of that cell

Cytoplasm

The ___ transports proteins made by ribosomes to the Golgi apparatus for secretion out of the cel

RER

Does not have ribosomes attached to its membrane. It is more tubular than RER

Smooth endoplasmic reticulum

Synthesise substances such as fats and steroids. Sex hormones in mammals are steroids

SER

SER converts harmful substances into harmless materials. This process is called _________.

Detoxification

It is shaped like a disc. It consists of a stack of flattened spaces surrounded by membranes.

Golgi apparatus or Golgi body

Can be seen fusing with one side of the Golgi apparatus and pinching off from the opposite side

Vesicles

Chemically modifies substances made by the ER; and stores and packages these substances in vesicles for secretion out of the cell

Golgi apparatus

Are small oval or sausage-shaped organelles. Aerobic respiration occurs in here.

Mitochondria or mitochondrion

During ____________, food substances are oxidized to release energy. This energy may be used by the cell to perform cell activities such as growth and reproduction

Aerobic respiration

Are oval structures found in the plant cells, these contain a green pigment called _____

Chloroplasts, chlorophyll

It is essential for photosynthesis, the process by which plants make food

Chlorophyll

Is a fluid-filled space enclosed by a membrane, they store substances within the cell

Vacuole

They have many small vacuoles that contain water and food substances. These vacuoles usually exist temporarily

Animal cells

They have a large central vacuole which contains a liquid called ____?

Plant cells, cell sap.

Contains dissolved substances such as sugars, mineral salts and amino acids.

Cell sap

This large vacuole is enclosed by a partially permeable membrane called the ______

Tonoplast