La hidratación afecta a la autólisis.

Because both hidratación and autólisis are singular feminine nouns in Spanish, so they take the feminine singular definite article la.

• la hidratación = the hydration
• la autólisis = the autolysis

In Spanish, articles are used more often than in English, especially in general statements.

Because afectar is commonly used with a before the thing or person being affected:

• afectar a alguien
• afectar a algo

So in this sentence:

• La hidratación afecta a la autólisis

the a introduces what is being affected.

This is not exactly the same as the so-called personal a, because here a can also appear before things, not just people. It is simply a very common pattern with afectar.

Afecta is the third-person singular present indicative of afectar.

So it can mean:

• he/she/it affects
• you affect (formal usted)

In this sentence, the subject is La hidratación, which is singular, so afecta means affects.

Pattern:

• yo afecto
• tú afectas
• él/ella/usted afecta
• nosotros afectamos
• vosotros afectáis
• ellos/ellas/ustedes afectan

Because it comes before the verb and agrees with the singular verb afecta.

The structure is:

• La hidratación = subject
• afecta = verb
• a la autólisis = object/complement introduced by a

So the sentence literally works as:

• Hydration affects autolysis

Hidratación has a written accent because the stress falls on the last syllable:

• hi-dra-ta-CIÓN

Words ending in -n, -s, or a vowel are normally stressed on the second-to-last syllable unless there is a written accent. The accent mark shows that this word is stressed at the end.

It also helps you connect it with many similar nouns:

• información
• situación
• fermentación

The stress is on the second o sound:

• au-TÓ-li-sis

The accent mark on ó shows that this is the stressed syllable.

Without the accent, a learner might guess the wrong stress pattern. Spanish spelling uses accent marks very consistently to show stress when a word does not follow the normal rules.

No. In standard Spanish, h is silent.

So hidratación is pronounced roughly like:

• ee-dra-ta-see-ON (very approximate English-style guide)

The h is written but not pronounced.

Because nouns ending in -sis are generally feminine in Spanish.

Examples:

• la crisis
• la tesis
• la hipótesis
• la autólisis

So even though the ending may not look like the usual -a feminine ending, autólisis is still feminine and takes la.

You may sometimes see or hear afectar used without a, especially depending on style or region, but afectar a is very common and standard, and it is the safest choice for learners.

So for Spain-focused Spanish, La hidratación afecta a la autólisis is perfectly natural and a good model to follow.

Yes, it is a technical/scientific word and is a close cognate of English autolysis.

That is useful for learners because many scientific terms look similar in both languages. However, you still need to learn:

• its gender: la autólisis
• its stress: autólisis
• how it fits into the sentence grammatically

Yes. A common alternative would be:

• La autólisis se ve afectada por la hidratación.

This means something like:

• Autolysis is affected by hydration.

Your original sentence is more direct and active:

• La hidratación afecta a la autólisis.

The alternative version is more passive in meaning.

Not always word-for-word. Spanish uses definite articles more often than English does.

So while la literally means the, in translation English may or may not keep it depending on context. In a technical or general statement like this, English might say:

• Hydration affects autolysis

even though Spanish says:

• La hidratación afecta a la autólisis

So it is better to think about the whole sentence, not translate each word mechanically.