Biology Unit Test

Why do cells divide?

**Growth** → To increase the number of cells in the body.

**Repair** → To replace dead, damaged or old cells.

**Reproduction** → Can make exact copies (clones).

G1 Phase

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* Cell grows 
* New proteins and organelles made

S Phase:

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* Synthesis
* DNA is replicated (copied)

**G2 Phase:**

* Cell grows again and prepares for mitosis (division)

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Chromosome

**the condensed form of genetic material; composed of DNA and proteins (hereditary material)**

Chromatin

**the non-condensed form of genetic material; composed mostly of DNA and proteins**

Necrosis

Cells may die due to external factors (ex: toxins, infections, trauma).

Apoptosis

The controlled death of old cells. (ex: White blood cells divide to fight viral infections. When they’re no longer required, they undergo apoptosis).

 Normal Cells vs Cancer Cells

 Normal Cells -

Make exact copies of themselves through mitosis

Reproduce for about 50-60 cell divisions

Stick together to form masses of cells as appropriate

Self-destruct when too old or too damaged

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Cancer Cells -

Make exact copies of themselves through mitosis

Do not stop reproducing

Do not stick to other cells, behave independently

May move to another location in the body

Cell Differentiation

the process of creating a specialized cell

zygote

the cell where a sperm fertilizes the egg

embryo

unborn offspring, more cells than a zygote

**What Causes Cell Specialization?**

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1. **Cytoplasm differences**
* **Asymmetric distribution (different on each side of cell) of organelles and other factors (ie. Proteins)**
* **Produces different daughter cells**
2. **Environmental conditions**
* Differences in temperature, nutrients, stress, etc
3. **Neighboring cells**
* **Substances made by nearby cells can diffuse into the developing cell through the cell membrane (remember, the cell membrane is selectively permeable)**
* These substances then accumulate and affect change in cell development

Stem cells

**cells able to differentiate into many different types of cells**

Cell Potency

**ability for stem cells to differentiate into different cell types. The more potent the stem cell, the more types of cells it can give rise to.**

Totipotent/Omnipotent

**gives rise to all cell types, cells found only in the early stages of the embryo and placenta**

**Pluripotent**

**gives rise to all types, except placenta**

Multipotent

**limited number of cell types**

Three levels of cell potency

Totipotent/Omnipotent, **Pluripotent** and Multipotent

**Embryonic stem cells**

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* **Pluripotent** 
* Divides into any cell type
* **Research often banned due to ethical reasons**

**Umbilical stem cells**

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* **Multipotent (limited differentiation)**
* Used to **treat blood disorders, cancer,** some **immune disorders** and **bone marrow failure**
* Retrieved at birth of a child
* **Clinical trials of umbilical tissues**

Adult stem cells

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* Multipotent
* **Example – bone marrow: produces white blood cells, red blood cells and platelets**
* **Still being researched through clinical trials**

Tissue

**a collection of similar cells that perform a specific function**

Animals have **4 types of tissues**

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1. **Epithelial**
2. **Muscular**
3. **Connective**
4. **Nervous**

Tissues - Epithelial

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* **Lines the internal and external surfaces of the body**
* **Forms barriers by connecting adjoining cell membranes**

**Tissues - Muscular**

**Moves the body or organ by contracting and relaxing**

**Tissues - Connective**

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* **Many different functions**
* **Strengthens, supports, insulates, protects, fuel source, transportation**
* These **cells** are **surrounded by an extracellular matrix** (substances between cells, substance depends on the tissue but could include proteins, minerals, support molecules, etc)

**Tissues - Nervous**

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* Made of **neurons**
* Have **long projections** to **send and receive signals**
* Coordinates bodily actions

What is this? What is its general tissue type? Its Function?

columnar epithelial, epithelial tissue.

What is this? What is its general tissue type? Its Function?

Squamous epithelial, epithelial tissue

What is this? What is its general tissue type? Its Function?

Muscular tissue, Skeletal Muscle

What is this? What is its general tissue type? Its Function?

Muscular tissue, smooth muscle.

What is this? What is its general tissue type? Its Function?

muscular tissue, cardiac muscle.

What is this? What is its general tissue type? Its Function?

connective tissue, cartalige

What is this? What is its general tissue type? Its Function?

Connective tissue, bone

What is this? What is its general tissue type? Its Function?

connective tissue, adipose (fat)

What is this? What is its general tissue type? Its Function?

Connective tissue, Blood

What is this? What is its general tissue type? Its Function?

Nervous tissue, Neurons

Meristematic cells

**unspecialized stem cells in plants, divides and differentiates into different plant tissues**

Plant Tissues – Dermal (or Epidermal)

* **Outermost layer of a plant**
* **Think of dermal tissues like the skin of the plant**
* Can be specialized further
* **Epidermal root cells – form root hairs to absorb water, minerals**

**Epidermal leaf cells** – produce a **waxy waterproof cuticle** around the leaf

**Plant Tissues – Vascular**

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* For **water and nutrient delivery**, think of blood vessels
* **Xylem**
* **transports water and dissolved minerals**
* **from the roots to the leaves (transport goes one way only)**
* **Phloem**
* **transports a sugar solution (plant food)** 
* **from the leaves to the roots and vice versa (transport goes both ways)**

Xylem

* **transports water and dissolved minerals**
* **from the roots to the leaves (transport goes one way only)**

**Phloem**

* **transports a sugar solution (plant food)** 
* **from the leaves to the roots and vice versa (transport goes both ways)**

Plant Tissues – Ground Tissue

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* Many functions
* **Photosynthesis**
* **Food and water storage**
* **Structural support**

Root system

* Organs


* **Roots**

Shoot system

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* Organs
* **Stem**
* **Leaves**
* **Flowers**

Root System - Functions

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* **Absorption – water, minerals, nutrients**
* **Anchorage – hold the plant firmly in the soil**
* **Storage – food, water**
* Produces a slimy later at the tip of the root to reduce friction

Tap roots

**one main root growing downward**

Fibrous roots

**many thin, branched out roots coming from the stem**

Adventitious roots

**comes from non-root tissue**

Shoot System - Stem

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* Function
* **Supports the branches, leaves and flowers**
* **Transport substances between roots and leaves**
* Grows towards the light

Shoot System - Leaves

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* Function
* **Photosynthesis**
* Its **shape maximizes light capture and minimizes water loss (surface area)**

Cuticle

**outer layer of protection, waxy**

Epidermis

produces the waxy layer

**Palisade mesophyll**

**where most photosynthesis happens**

**Spongy** **mesophyll**

where O2 exits and CO2 enters the cells

**Vein**

**(xylem, phloem inside)**

Stoma

**a pore to let water, O2, CO2 in and out of the leaf**

**Guard** **cells**

**open and close the stoma**

Chloroplast

Air pocket

**where gases circulate**

**Shoot System - Flower**

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* Function
* **Sexual reproduction**

**Petal**:

**attract pollinators to flower**

Stamen:

the male sexual organs

**Anthers**:

produces pollen

**Filament**:

holds anther, attaches it to flower

Pistil:

**the female sexual organs**

Stigma:

**where pollen enters**

Style:

pollen travels through here to fertilize the ovule

Ovary

houses the egg (ovule) for pollination (fertilization), eventually becomes a seed

**Sepal**:

modified leaves, protect developing flowers

**Pedicel**:

connects stem to flower

\-cot” = cotyledon

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* An **embryonic leaf** in plant development, the **first to emerge from the seed**
* Plants with one cotyledon (**monocots**) and plants with two (**dicots**)